Here is the all time cheapest hop up that anyone can do. Typically most SR20DEs have the timing set to 13 degrees or less from the factory. I have seen as low as 10 degrees on a brand new factory fresh car. You can safely run up to 15 degrees on regular gas on most SR20DEs. For best performance on a stock engine, put in 92 octane and dial in between 17 to 19 degrees. This has been proven by recent dyno testing on a stock car to give up to 6 more hp at the wheels. Remeber if you have your timing turned up this high you MUST use 92 octane fuel. Do not exceed 17 degress of advance if you have a JWT ECU.
Donít tolerate any detonation though. Detonation will kill your engine quicker than lard and coconut oil will kill you! I am putting the detonation warning in here because the timing pointer on the engine can be easily bent which could cause you to accidentally over-advance your timing! It happened to me so be careful! If you have the JWT ECU, set the timing at 15 degrees. On the dyno I have not seen any difference between 15 and 17 degrees with a JWT ECU although bottom end snap might feel a little better. It is better to be safe at 15 than on the edge at 17 for only a perceived difference in throttle response. Be sure to disconnect the TPS when adjusting the timing and remember that the JWT NOS module requires that TPS terminal 1 and 2 be shorted out when setting the timing.
Synthetic Oils and Lubricants
This is a good non-envasive hop up part. I am going two open a whole can of worms here but as far as I know, Mobil 1 is the only synthetic oil to get for your engine. Not only is it the cheapest but it works the best. There is a lot of industry insider information on oil and Mobil 1 has been tested by many OEM manufacturers and found to come out on top. I donít want to start a big thing about it and cannot divulge my information's secret sources, but trust me on this one. Granted my test data did not include Valvoline, Castrol or Havoline Synthetic but it did include ALL of the famous synthetics who will remain nameless on the record. In fact, one oil that is highly regarded by list members that is sold as a direct marketed product is in fact nothing but rebottled Mobil 1 for twice the price.
Recently, my buddies at Cosworth report that Royal Purple seems to have good bearing life in the XD Indy engine but for the most part Cosworth uses Mobil One as factory fill. I have had personal good luck with Motul but have no scientific test to prove that it is super good. Adam Saruwatari tells me that Motul has cut his engine wear by 3 fold. Nismo uses Motul in their Group C LeMans car as well as the GT390R. Their testing showed that Motul was excellent.
For gear oil I have found that under racing conditions Redline MTL had superior shifting characteristics but for me has led to faster gearbox wear. On the street this may not be an issue. Nissan Motorsports has had good luck with regular Redline Shock Proof gear oil. Personally I like Motul gear oil. It seems to shift nearly as well as MTL and better than Mobil 1. It has a heavier body so it should have better shock protection for the gears than MTL. Granted this is not based on any scientific evidence, just observations and common sense.
As a non oil related note, Redline Water Wetter is legitimate and really has a reduction of water temp by about 20 degrees F, good stuff.
These super lubes can free up about 1-3 hp, have much better gearbox and engine operation in very cold weather and directly help performance by keeping your engine in top shape for longer.
In my opinion, you still need to change the engine oil at about 3000 miles for best results even with synthetics. I have noticed that the oil pressure at hot idle starts to drop at about 1500 miles with dino oil and 3000 miles with synthetics. I believe that this is caused by the oilís shearing down under hard use. Thatís where my 3000 mile opinion comes from. It is not scientific oil analysis but is based on some data. BTW, I have never had an oil-related failure in any engine I have ever built while following these rules.
The hydraulic lash adjusters on the SR20 engine do not like thick oil. Thick oil causes them to pump up and become noisy. This is especially true of 1991 year engines. For these engines you must run 5w-30 or 10w-30 oil. To get good protection under hard use with these light oils it is, in my opinion, important to run synthetics. These thinner oils provide less viscous drag which can give more hp and better fuel economy.
To my knowledge, the best oil filters are genuine Nissan. This is mostly because of the anti-drainback valve which goes a long way to reduce cold start wear. Also, the bypass valve flow rates and the particle pass through size have been determined by the factory as the best compromise between effective filtering and good flow with low pressure drop. The factory filter also has a thicker shell and better crimping that your typical aftermarket filter so it is less likely to blow off if, for instance, the bypass valve sticks or the oil is super thick on a real cold day.
Headers are probably the biggest bang for the buck item in the modification list. I have had experience with two different ones both of which offer better construction than what is typical of aftermarket headers. These headers are the Hotshot and the Stillen. Both of these headers are constructed of heavy gauge mild steel that is ceramic coated for appearance and long life. The ceramic coating may aid catalytic light off under cold start conditions which is helpful for OBD-II cars (1995 and later).
Both of these headers have been redesigned since my last update. The Hotshot header has been given larger diameter primaries of 1-3/4", up from the previous 1-5/8". This makes the primaries have less of a neckdown from the exhaust port exit. The material has been thickened to 14 gauge, up from 16 gauge used previously. This cuts down on noise and reduces the chance of the pipes cracking. The new Hotshot gives about 3-5 more wheel hp than the old one according to dyno tests on my car and another closer to stock car.
The Stillen Design has been changed to a short runner 4-1 design. Its power output is better according to Stillen but our testing resulted in nearly the same amount of power as the old design. This is surprising as 4-1 designs generally are better for top end power. The Stillen header still makes slightly more power below 3500 rpm than the Hotshot but the Hotshot outpowers it by at least about 4-5 more top end hp.
Testing on the dynojet show that the Hotshot is good for about 10-15 wheel hp, with highly built cars getting more power and stock cars getting more toward the 10 hp side of the scale, and the Stillen, 8-10. I have personally tested the Hotshot but am relying on other list members data for the Stillen unit. The hp on the Stillen unit peaks about 500 rpm lower than the Hotshot. The Stillen unit boosts bottom end, where as the Hotshot does not come into play until near the torque peak.
If you are going to keep your car pretty stock or really need bottom end torque, the Stillen is a good choice. If your car is modified with camshafts and other bits of hop up stuff the Hotshot is preferable although both perform well in either role due to the forgivingness of the tri-y design.
I have installed both headers and the fit is very good on either. However some list members have reported fitment problems on both. My own personal experience is that both designs fit well. The O2 sensor location on the Stillen unit is a little low for the 98-99 Sentra SE and requires rerouting of the sensor wire which is kinda self-explanatory. The EGR fitting on the Stillen header requires a little fudging to install. This is not a problem but can be a little hard to do for the unmechanical. First you have to loosen the two 12mm bolts that hold the EGR tube to the EGR valve. Then start the big EGR fitting nut on the header side, then tighten the EGR valve nuts a little. Then fully tighten the header fitting big EGR nut. Finally fully tighten the two 12mm nuts on the EGR valve.
The fit of the Hotshot is flawless and does not require much fiddling but if you do have a slight misalignment the above procedure will work also.
They have been some complaints of a rattle or chirping noise that both headers make at approximately 2500 rpm. To me it sounds like a cricket chirping. This is not harmful and not all cars do it. I am not sure of its root cause. The new generation Stillen and Hotshot headers do not seem to make this noise.
The intermediate pipe gasket blows out in short order on both headers. The fix is no big deal, the metal gasket from a 300ZX intermediate pipe will work or applying high temp O2 sensor safe red silicon. Either solution will work well. The Z gasket must be modified so the bolt holes line up but that can be done in seconds with a Dremel tool.
The new Hotshot header solves this problem with the addition of a copper gasket that is just about blow-out proof. You must remember to re-torque the bolts after a few days to allow the gasket to take a set. The new Stillen header has no gasket here so the problem is cured!
The have been a few new companies to come out with an SR20 header recently:
This header looks like a cheap rip off of the old style Hotshot. It also ripped off the experimental secondary crossover pipe that was featured in one of my SCC articles. Too bad they did not read the article to find out that it did not work! It has thin tubing and is painted with a cheap black paint that instantly burns off and wreaks havoc with your 02 sensor. The flex pipe is of low quality and will not last long. The generally cheesy construction won't last long either. This header produced the least amount of power of all evaluated. It is also the least expensive and does produce a good gain of about 5-7 hp so it might have some merit.
This header distributed by Group 5 is a beautifully made full race 4-1 design. It is made of thick wall, ceramic coated steel with nice welds. The AEBS header features a merged collector which is a very nice, powerband-widening feature. The AEBS header produces the widest powerband of all SR20 headers and nearly as much peak hp as the power king, the Hotshot. It has produced as much as 12 wheel hp on some cars. This is surprising as 4-1 designs usually favor the top end of the powerband. In my opinion the AEBS or the Hotshot are the best headers for the SR20 currently on the market. Unfortunately the AEBS has a few minor quirks. It is one piece and more difficult to install unless you have access to a lift and it is lacking any provisions for the EGR system. There are no instructions on how to disable the EGR with the header either so many buyers of this header suffer from driveabilty problems. This is because the disconnected EGR system sucks air making the car run too lean at part throttle. It is very simple to disable the EGR so Group 5 should add the instructions to the header. If you own an ABES header simply disconnect the vacuum line to the top of the EGR valve and plug it.
The S&S header is a small diameter, long length primary tube 4-1 header. This makes it a good low end and mid range header. It gives a 6-8 hp advantage over a wide powerband. It is also painted which is a disadvantage for looks and life. It is also low in price. It is a good header for the money if you have a stockish motor.
Perhaps the most popular first piece of speed equipment is the exhaust system. On our SE-Rs, the power produced by the exhaust is not always consistent. The gains of a cat back system are not super huge and mostly at high rpm. We have seen gains of 1-3 hp on a typical SE-R although some SE-Rs have gained as much as 8 wheel hp. This is because of variance of muffler design even within one model year. Some Classics and NXen have a washer-like restrictor plate deep inside the muffler. It is impossible to spot by just looking at the car. If you have one of these restricted exhaust systems you can expect a big gain. Unfortunately I do not have a production number or VIN range of these affected cars so I cannot narrow down exactly which vehicles have these mufflers. These cars get about 6-8 hp when you upgrade the exhaust.
200SX owners can benefit from a low restriction exhaust because it will reduce the chance of getting an EGR temp sensor MIL light.
G20ís have a pretty hard to improve upon exhaust from the factory as stock.
GReddy makes one of the best exhausts tested. It has only about 2 psi back pressure and is sort of quiet. I have not tested the HKS or Borla system. The HKS system is supposed to be quiet and the Borla, Iíve heard, is loud. The Borla system also has a restrictor plate. I believe list member Ian Lyn and Shell Black have some experience with a gain in performance after removing the restrictor but the noise level went up also. Merlin Johnson has done extensive testing of different sizes and type of exhaust systems. His testing methodology is very valid and believable.
Quite a few list members have complained that the Stillen exhaust is too loud and rusts out but for the $135 price, I doubt that you could do better at the corner muffler shop. Stillen will most likely come out with a super high quality all stainless system soon.
For you do-it-your-selfers here are some general guidelines. If your engine is stock or if you are limiting yourself to bolt-ons, limit your pipe diameter to no more than 2" or you will lose some bottom end with no applicable gain on top. If you are to the point where you are getting into camshafts and headwork, 2.25"-2.5" from the cat back piping is appropriate. For turbo applications, 3" is the way to go. Try to avoid the typical muffler shop crush bends. You can buy mandrel bends from Kinsler, Burns, stainless, or Bassani. That way your local muffler shop can cut and section these for smooth, non-crush bends in your system.
Do not enlarge your header collector to bigger than 2". I have found that even with my very built 206 hp NA motor that going to a 2.25 collector lost about 6 hp through all of the powerband. After the cat, Shell Black has proved that there may be some power to be found with fairly built NA motors by going to 2.5 inch pipe.
Straight through mufflers are by far the lowest backpressure. The Walker UltraFlow, Apex'i, or Magnaflow are some common ones. Stay away from the generic louvered core glass packs. Even though those are straight through they have incredible backpressure, often more than stock. Look for a perforated core. This is a pipe with lots of small punched holes. The Walker and the Magnaflow mufflers are real loud by themselves and require a pre-silencer.
The Walker Magnum glass pack that most auto parts stores sell here is good for this. It has a perforated core. Make sure that you are truly getting a perforated core! A 24" long Walker with an UltraFlow or Magnaflow creates a system with about 2 psi back pressure that is decently quiet. Dual path, straight through, perforated core mufflers like the Edelbrock should work well also, although I have no direct experience with them. You still need a pre-silencer with them.
The common Turbo-style mufflers are not very quiet and have lots of backpressure, as do the famous Super-Trap and the Flow master, so donít bother with them.
If you are so inclined, you can do your own testing by welding a pipe bung right after the cat and running a silicon hose to a 0-20 psi gauge in your car. Then you can do 3rd gear runs through the rpm range recording backpressure. Use an old fuel filter as a surge accumulator to smooth gauge readings. Make sure all of the gas is gone! Better yet, use a new plastic one so you won't blow anything up!
Unless you are turbo or nitrous only and are going for the maximum in power, do not bother with removing or gutting your cat. Unless the cat is melted it only has about 1.5 psi of backpressure or less and only affects power by 1-2 hp if that. This is even with a built NA motor. With a turbo or NOS you will lose some power. However we did run mid 12's in Ryan's turbo car with a cat and still passing California's stringent dyno smog test. Remember, this (gutting the cat) is also a big time violation of federal law! Gutting the cat will cause a MIL light on post '95 SE-Rís which is to be avoided come registration time. There is little to be gained with aftermarket cats either, although they are priced well and if you need to replace your stock cat they can be a good value.
The most common are the JWT POP Charger (POP stands for Performance Optimized Program) and the Stillen which are almost identical. Both are washable and reusable and come with a nicely machined aluminum velocity stack base. Be sure to oil them with K&N oil after cleaning in detergent and water. Donít go crazy with the oil, a light even coating is fine. Too much oil can contaminate the hot wire in the MAF.
RS Akimoto supposedly make an intake for the Classic but I have never seen one. I think list member Justin Choi might have tested one, verifying it with MAF voltage readings and found it to flow less than the JWT POP.
The HKS powerflow does not seem to filter well. I put one on a white rag and tapped it and lots of dirt went right through it. One of my friends tested one on a flow bench and found it flowed better than the POP, but the Stillen and POP has more than enough flow capacity for our motors and personally I would rather have a filter than a boulder strainer.
I have no direct experience with the GReddy unit but it appears to be made of a fine foam which could filter better I suppose.
Justin Choi has done a lot of filter testing so he would be a good source of information.
You can expect 1-3 hp with these units. If your engine is built, they will not necessarily give you more power but will allow your engine to reach itís potential by eliminating the intake restriction of the stock air box.
If you want to test your own filters, simply use a multimeter to measure the voltage to the MAF. The higher the voltage, the more air you are flowing. Remember also that temperature and barometric pressure affect the readings so it is important to use only back to back data, not week to week.
Perhaps the most potent air intake is the JWT POP combined with the CAI or cold air intake by Place Racing. I have tested this combo and found up to an 8 hp gain with 3 more peak hp. This part is one of my bang for the buck recommendations. Hotshot is planing a CAI also. It is a nice looking chrome plated part and produces just as much power as the place unit in our testing.
To complement the CAI, I have blocked off the hot water passages in my intake manifold and throttle body. I do not recommend this to anyone who lives where it gets below freezing but for my native sunny California it is OK. The hot water prevents the manifold and throttle plate from icing up under cold conditions. The throttle may also need to be cleaned more frequently as the hot water keeps the PVC blow-by residue crap from condensing on it, as well. On real cold mornings my car has a slight hesitation for about 30 seconds but that is about the only negative effect that I have personally experienced.
Now my car consistently has the same hp, dyno pull after dyno pull. All of you who have done dyno work know that the power drops about 3hp after the first run. The manifold used to get baking hot like the valve cover but now only gets slightly warm to the touch.
The CAI stays cool to the touch even when everything else is burning hot. The CAI can reduce your 1ě4 mile time by close to 2/10ths and make your car a lot more consistent on a hot day. Look at the Mike Mager's 1ě4 mile timeslip table.
So far in my experience the only ECU worth considering at this point is the JWT unit. Without slamming anyone, to my knowledge most of the other ECUs on the market have some degree of code mistakes in them. JWT is also the only company to my knowledge at this time that can do reliable programming on Post 1995 OBD-II ECUís. Without revealing specifics, when examining the code in other companies ECUs, mistakes have been found on just about all of the other manufactures chips. In fact, one famous manufacturer did not change one single bit of code in the program! They merely socketed the PCB, and put an E-PROM WITH THE STOCK CODE IN PLACE! They charge 600 bucks for this piece of crap. They advertise in all the major magazines. I wonít name a name but their ads feature an Eclipse burning out with a sunglassed ponytail looking dude driving it.
If you want to buy another brand of ECU, ask these questions:
Can you raise the rev limit?
Can you eliminate the speed limit?
Can you compensate for larger injectors across the entire operating range?
Can you compensate for a different MAF?
Do you use a Horiba A/F monitor?
Do you understand offsets? Do you know what invalid time is?
Can you program a OBD-II box?
If they cannot answer all of these questions then go to JWT and save yourself some aggravation. I am not paid by JWT so I am not biased, but I'm amazed by their technical competence and I am very hard to impress most of the time. They are also the only tuner in this country who has pushed the limit of SR20 (and Nissan in general) development.
JWTís ECU significantly improves transient throttle response making the car feel much more lively as well as providing more total advance at WOT. The JWT ECU also leans out the A/F ratio at WOT to an optimal 12.6:1 as the SR20 tends to run rich under these conditions. Thatís a reason why the fuel pressure riser does not work too well on our cars.
The JWT ECU adds up to 8-10 hp is some parts of the power band and generally adds 3-5 hp on top. The ECU can take up to 0.3 off your quarter mile time. If you follow the same driving pattern with the JWT ECU, it has the potential for better fuel economy, as well. Premium fuel is required and 15 degrees of set timing is recommended.
For the 200SX, the JWT ECU is almost essential as this car is saddled with an annoying 109 mph speed limiter and a crappy 7100 rpm fuel cut. The ECU really adds to the driving pleasure of these cars.
On an esoteric note, under racing conditions the SR20, especially in an NX, can be subject to thermal runaway. This manifests itself when the air temp gets into the 80ís or if you are drafting in a pack (only do this on the track kids!). The temp goes up which triggers detonation which causes the knock sensor to tell the ECU to pull out timing which causes the temp to rise. This goes on in a viscous loop until the engine overheats big time. Unless you immediately drive slow for a few minutes the engine nukes. In the heat of battle you sometimes forget to check your gauges and boom! I myself blew about 3 engines like this back in my racing days.
Anyway, the JWT ECU limits the amount of knock retard and for the most part, stops this problem. If you are planning to do track events this almost makes the JWT ECU a mandatory item. JWT can also custom program the ECU for high compression and turbocharged applications for a reasonable fee. In fact, if you are going to run 11:1 compression, a JWT ECU is essential if you plan to run on pump gas.
So far, the JWT cams are about the only ones that work well on the market. One famous Honda tuner (THE MOST FAMOUS Honda tuner) came up with some cams for the SR20. I observed their mule car in action at the strip. It idled like a bridge ported rotary engine which is to say not at all, the MIL light was on and the thing was running blazingly fast 16 second 1ě4 mile times!
The JWT cams are ground on new genuine Nissan billets so the factory base circle diameter can be maintained. This is important for correct hydraulic lash adjuster function and correct valve train geometry. These are important factors for operating noise and valve train life. Other companies regrind the base circle smaller to get more lift and duration on a stock cam. To do this correctly would require an asymmetrical grind on the lobes to match valve events because of the change in the rockers angularity and motion ratio. Some custom shims under the hydraulic lash adjusters would be needed to maintain proper lash. The wear pattern on the rocker arms would not be optimal either due to their change in angularity. Most companies that do regrinds do not supply an asymmetrical grind or correction shims!
Other common aftermarket problems such as premature wear due to incompatible metals rubbing on each other are eliminated by using genuine Nissan cam billets.
JWT offers two different grinds, a street grind and a race grind. On a stock engine, the street grind is clearly superior. In my testing, the street grind lost no bottom end power (the bigger the cam generally, the less bottom end) and was good for a solid 12 hp. The gains were recorded from 4000 rpm on up and their was no penalty in fuel economy. As cams are the thing that can upset the OBD-II and emission systems the most in general, the engine was tested on a sniffer type smog machine. It put out 6ppm HC and 6 ppm CO at idle. At 3000 rpm the output was 6 ppm HC and 11 ppm CO. This is well under the limit (by almost 10 times!). Although these cams are not CARB approved, the effect upon pollution seems minimal.
I have yet to test them under the new IM240 smog dyno and plan to avoid that for as long as possible! The street cams have a reasonable idle with only a slightly detectable lope. The OBD-II system has remained happy. The race cams did not do too well on a stock engine loosing power except above 5500 rpm. Headwork and 11:1 compression are necessary for these. I have not tested the race grind on a high compression engine yet but will do so soon.
As an update, JWT has released a second generation street cam that has the same 260 degree duration of the previous grind with about 0.030" more lift and faster lobe profiles. This cam was optimized to be the most radical grind for stock springs. This cam works exceedingly well giving my car more than 6 additional wheel hp over the older grind. Shell Black also got about 5 more hp over the older grind on his motor with a stock bottom end.
Also as an update, I have passed the new stringent California dyno test with my fully built motor with flying colors. Ryan's 12 second turbo car has passed also. This proves that clean does not mean slow. It also proves that the government should not concern itself with what's under the hood if what comes out of the tailpipe is clean.
JWT also has a 264 degree and a 268 degree cam for special order only. You must have high compression and headwork to run these cams. My car has gotten about 3-5 more hp above 6500 rpm with these cams but they did cost significant bottom end hp. I have since returned to the regular street grind as this grind is much more torquey and fun to drive.
JWT will also soon release a Pro-Series cam that will have about 264 degrees duration with a whooping 12mm of lift. These will require special valve spring and titanium retainers. With their ultra fast profile, these cams should give near VTEC like top end while retaining reasonable bottom end. To exploit these cams you will need high compression and headwork. I will be testing these cams soon and will report how they work
There are a few new promising cams that have come out since I last updated these pages. All of these cams are of good quality and are pretty expensive.
I only have anecdotal information on these cams. I have heard through JWT that these cams have very poor idle characteristics and they require a custom ECU to start the car or idle. JWT has had to do custom ECU's for people with JUN cams just so they could start their cars! They are for extreme top end only and are not very streetable. They are ground on new billets. I myself do not have any experience with these. JUN parts are of very high quality and are very expensive.
These high quality cams are imported by Group 5. These have shown much promise in Group 5's initial testing with a 12 hp gain to the wheels on Chris Pinthong's bolt-ons-only NX2000. These are also a good quality billet cam but are pretty expensive. Tomei has a very good reputation in Japan like JUN. Look for more testing to be done in the near future.
Now a major maker of domestic car cams tries to get involved with the import market. Comp Cams are ground on what appears to be JUN billets. They are priced like JUN billets, almost 2X more than JWT cams. Dave Coleman of SCC has tested both the JWT and the Comp Cams and tells me that the Comp Cams feel very mild and do not feel as strong as the JWT cams. He has not dynoed the Comp Cams yet but will soon. Comp Cams has two grinds, a mild and a very mild. Dave told me the very mild is almost not any different from stock and is not worth the effort.
They are a couple of other low buck alternative grinds available for the SR20 that work to varying degrees. The first is the SR20DET "European" grind exhaust cam that Stillen and Nissan Motorsports carries. Although it is pretty inexpensive there are a few problems. The SR20DET uses a mechanical cam with no hydraulic lash adjusters. Mechanical cams require gentle acceleration ramps on the cam lobe flank. When used with the hydraulic lash adjusters in the SR20DE, these flanks keep the valve open a few thousands of an inch for about 10-20 extra degrees of crank rotation. This makes the engine think it has a real big cam at idle. Thus these cams lope like a JWT race grind or worse even though they only have about 8 degrees more effective duration.
For a classic 91-92 SE-R or NX you only use the exhaust cam as the intake cam has the same duration as the DET cam. For the other years you can use both. Supposedly these cams can give up to 6 more hp although I have never confirmed that. Our IMSA race car had the exhaust cam and I could feel a bit more power above 5000 rpm. That engine idled like a fully built motor and I was surprised that we were never protested. I donít think this cam set could pass a smog test and they would most likely freak out the OBD-II system although I have never tested either.
Another little trick is to use a 91-92 intake cam on a 95+ SE-R. This cam has 16 degrees more duration than the stocker and according to the guys at Nissan Motorsports gives 6 more hp. Ed Wolf and Kurt Sussman run these cams in their 200SXís. This cam idles fine in this application and should breeze by a smog check.
Do me a favor and DO NOT CALL JWT to debate with Jim or Clark whether these cams are better than their cams. They are not and JWT does not have the time to argue with you.
One of my SCC articles made mention of the alternative cams and JWT was flooded with calls from people wanting to argue that their cam set was not worth the money. The JWT cams have at least twice the potential power gain as the alternatives and whether you think itís worth the money is up to you as a consumer so donít waste their time on this point.
[Editor's note from Kurt Sussman. I easily passed a California smog check with the 92 cam. Since this comes up too often, I'll post the numbers here for the 91-93 intake cam, and for the 95 intake cam. In 1994 there were two different intake cams, and I'll post that when I have it in front of me rather than give out misinformation.
Year Ex. Duration In. Duration Intake Opens Intake Closes Exhaust Closes Exhaust Opens
91-93 240 248 13 55 3 57
95-97 240 232 5 47 3 57
The open and close are relative to TDC (intake open and exhaust close) and BDC (intake close and exhaust open).
This is only the cam timing; the lift is greater with the 91-93 intake cam as well (about 15%).
As far as performance, the 91-93 cam will make a difference, but Searl (with the JWT street cams) has never lost a race to me; roll-on or from a standing start. Until early 98, we had identical configurations except for his nitrous oxide kit, which was turned off for most of our races.]
Adjustable Cam Sprockets
Turbo magazine has reported huge gains in Honda and Acura engines with the addition of adjustable cam gears and dyno tuning. In my testing with JWT Street cams, the gains were inconclusive. I tried about 25 different combinations of advancing, retarding, lobe separation angle spreading and tightening with no gains worth keeping over the stock location.
JWT has gone through pains to grind their cams with the proper lobe center straight up. If I got 2-3 more bottom end hp, I would lose 5 on top and vice versa. The best alternative timing was intake cam advanced 2 degrees. This had a gain of about 3 hp in the midrange and 1-2 on bottom end with loss of only about 1-2 on top. This setting might be good for street only driving or autocross where bottom end snap is important. When I deviated by more than 8 degrees of the factory lobe center, the OBD-II system triggered a MIL light.
When building my 11:1 motor the gears were very important, allowing me to correct the cam timing despite milling 0.040 off the deck and head. When you mill things the cam timing retards and you can use adjustable gears to correct it. In fact anytime you mill your head and block like when doing a rebuild, you should use adjustable timing gears to restore proper cam timing.
Stillen claims good gains with the adjustable gears and stock cams but I havenít tested that myself. The gears are cheap and it would make a good project for someone besides me to do.
JWT and Stillen make gears. The Stillen gears are two piece and are infinitely adjustable. The JWT gears are one piece and are adjustable in 2.5 degree increments. Both are about equally easy to use. The JWT gears are safer by being impossible to slip or vibrate apart and are cheap. The Stillen gears are more expensive, but are real trick looking and can be adjusted in very fine increments which could be an advantage.
If you are going to play with your cam timing I suggest that advancing the intake cam slightly in the 2-3 degree range will most likely have a good effect on bottom end and midrange with only a slight loss of top end. This would be a good place too start.
Headwork entails enlarging the intake and exhaust passages in a head to allow for more flow. Good headwork entails subtle reshaping, not just hogging the whole port out bigger. Generally, good headwork leaves the floors of the port alone since most of the flow activity in a port is near the roof of the port. The roof is the outside radius of the bend going to and from the combustion chamber and by inertia, most of the air wants to flow up there. Good headwork usually rounds the floor hump which is the transition from the valve seat to the floor of the port.
Stock, this is usually a sharp edge which causes non-laminar (turbulent) flow separation.
The object of good porting is to increase flow as much as possible while keeping the port volume as low as possible to maintain as high of a flow velocity as possible. Big ports have low velocity at low rpm. This results in a loss of bottom end power due to the lack of energy available in the moving gas column behind the valve. The gas column has inertia which helps fill the cylinder, especially at low RPM. Generally porting your head will cause some loss of bottom end power. Good head porters might be able to increase flow in the head up to 40 percent with no loss in bottom end but that is usually for American Iron heads which are terrible to start with. Modern Japanese engines donít usually see as big gains as their design is much better to begin with. Gains of 10-20 percent are typical with a modern Japanese motor.
The other major area of headwork flow gain is in the valve job. A large percentage of gain can be in the valve job alone. The best valve jobs are called multi angle valve jobs with three or more distinct angles. The main angles are the throat cut, which is a 60-70 degree cut that blends the port wall to the seating cut. The seating cut is a 45 degree cut which is the sealing surface for the valve. This critical cut should be 0.040-0.060 wide for a multi valve engine like an SR20. Finally there is the top cut which is a 30 degree cut which blends the seating cut to the combustion chamber. The purpose of these cuts is to help the air flow smoothly around the valve, especially when the valve is starting to open or close.
Another valve job trick is to place a 30 degree back cut above the 45 degree seating cut on the valve itself. This helps the air get around the valve better especially at low lifts. A five angle valve job uses two extra cuts to make the transition even smoother. The best valve jobs are radius valve jobs which are a 3 or 5 angle valve job which is hand blended after cutting for a perfectly smooth transition. The quality of a valve job is very important because it can contribute up to 50% of the flow gains that headwork will get you.
The best valve jobs are done on a Serdi machine. The Serdi is very high precision which insures that all the valve angles and depths come out equal. Most low price shops use stones. Stones can give a good valve job but the stones must be dressed frequently and dial indicators must be used to insure that the seating surface remains concentric. Stones require a highly skilled person who is conscientious of doing a good job. A butcher can make a big mess with stones.
Unshrouding the valves is an operation where the edge of the combustion chamber is cut back by about 25% of the valve diameter so that the wall of the combustion chamber does not block the air going past the valve into the cylinder.
Polishing the combustion chamber removes sharp edges that can glow red hot and trigger detonation. It also makes it harder for carbon to stick. Polishing should be limited to the combustion chamber and exhaust port. The intake port should be no smoother than 220 grit as maintaining some boundary layer turbulence is good for good bottom end. This turbulence makes the port virtually a little smaller at low flow velocities.
Personally, my belief is that the best head porters for the SR20 head are (Dan Paramore Racing), JWT and B.C. Gerolomy. My own personnel heads are done by DPR and Nissan Motorsports uses B.C. Gerolomy. JWT requires no further introduction here!
Beware of bad headwork. Perhaps the most famous Honda builder who advertises very heavily and sponsors many 10 and 11 second Hondas does awful commercial headwork. I have seen heads from that shop that have huge, lumpy uneven ports. The valve jobs were 1 angle that were cut so deep that the valve would have to rise about 0.040 to get out of the huge crater of a seat cut! Talk about shrouding! The valves were cut so deep that I am sure that the stem tips would have to be faced off to maintain proper valvetrain geometry IF that was done! Perhaps it was the new guy that did these heads but I have seen more than one of them. This shopís work could not be all bad because of their track record, but I have yet to see a good off-the-shelf head from them. Stuff like this is why many Honda owners complain that their cars end up slower than stock!
My DPR head is a marvel of detail. The head is fully deburred to remove all sharp edges that can cut you during assembly and cause stress risers. Then it was ported by Dan Paramore, keeping an eye for increasing velocity rather than ultimate flow. My objective was to build a torquey engine with no loss of bottom end power. Dan cut down the valve guide bosses where they intrude into the port and smoothed the hydraulic lash adjuster boss where it hangs down into the intake port. This annoying feature was added to the 95 and later low port head.
The valves had the stems turned down for better flow to about 6mm below the valve guide. That way they would block less of the port's cross section area. Dan also reshaped the valves going way beyond the customary 30 degree back cut. Finally Dan swirl polished the valves. Swirl polishing is polishing putting a hurricane looking pattern on the face of the valve. This is supposed to increase flow. The shaping considerably reduced the weight of the valves which should give more rpm headspace before valves float and the classic SR20 rocker arm flies off. To my knowledge DPR is the only company that puts this much detail work into the valves.
The main advantage of the DPR head is Danís combustion chamber work. Dan welded up the edges of the chamber to increase the quench. Quench is the area where the piston top comes within 0.040 of the combustion chamber near the edge of the cylinder. The quench zone squishes the fuel air mixture to the center of the cylinder where it can be easily burned. This reduces the likelihood of detonation and increases efficiency. This feature found in all of DPRís stage 6 heads sets them apart from other tuners and is the reason that I chose them. Increasing quench does raise the compression ratio, so if you are doing pistons and stuff, this must be considered.
The DPR head has a combustion chamber volume of 43ccís down from the stock volume of 46cc. This raises the CR on stock pistons form 9.5:1 to 10:1. 10:1 is fine on pump gas with the stock or off the shelf JWT ECU. If you are running JWTís NOS 100 shot ECU the program will have to be changed a little at this CR. If you are running NOS with someone elseís kit, you will have to retard the spark a little under NOS operation. I think around 4 more degrees than you already retard for a 100 shot would be a good starting point although I have not tested that.
If you use the Nissan Motorsports flat top pistons the CR gets close to 11:1. With the planned JWT forged big bore pistons the CR becomes 12:1 which is not streetable but the dome can be machined off to get 11:1. With 300ZX pistons the CR is close to 12:1 but it is easy to machine the domes off of these also. To run 11:1on pump gas requires a special program from JWT. The stock ECU will not work. I do not have much experience with big (100+HP) NOS units and real high compression but you must be careful! More ignition retard and richer fuel mixture are appropriate here. Detonation can result in rapid death! JWT has a 50 shot program for 11:1 available.
My DPR head resulted in a power increase of 10hp above 5000 rpm with no loss of power below that at all! That is testimony to Danís skill. The bottom end felt better but the dyno did not register that so I can not claim that. When revving the engine in neutral it was much more responsive to blipping the accelerator pedal. If Dan was to build an all out power head, I feel that their would be another 5 or so hp available at high rpmís but some low end power would be lost. Dan could have made me some bigger valves but I did not want to pay for that!
The high port classic head (91-93) is superior to the low port head (94-present). The changes to the head were done to improve hydrocarbon emissions. The high port head has long intake ports that bend smoothly around the hydraulic lash adjuster and shoot straight into the cylinder. Unfortunately for pollution's sake this long intake port necessitates having the fuel injectors farther back from the intake valve. This causes the port walls to get wetted with fuel. This fuel is sucked into the engine in-between shifts and on overrun causing the mixture to spike rich.
To eliminate this Nissan went to the current low port design with itís short intake port and close coupled injectors. Unfortunately the hydraulic lash adjuster must now hang into the intake port obstructing flow. Also the approach angle of the port no longer has such a straight shot into the cylinder either. I believe, although I have not personally tested, that the older high port head is good for about 5-10 more hp than the low port head. To substantiate my theory I have noted that when looking at Japanese Performance magazines, no Japanese tuner uses the low port head in their crazy SR20s.
If anyone has dyno results of a fully developed high port head please submit them to us so we can post them and compare them to project SE-Rís low port head.
As an update, DPR has done some R&D on the high port head and is now able to extract about 25% more flow out of them, up from the 10% increase seen with my head. Dan feels that this could result in 10-12 more hp for his latest creation. Dan has also developed a new valve spring set and new titanium retainers as well as 1 mm oversize stainless valves. George Roffe, Mike Palhs and Ben Benavides have all or some of these latest mods in their motors and we eagerly await dyno results.
There are a number of choices here. Nissan Motorsports has the European and Japanese spec pistons that are flat topped (the stockers have a slight dish) that raise the compression to 10:1. This should give about 5 more hp. Nissan Motorsports also has the SR20DET piston which lowers the compression to 8.3:1 for turbo motors. These pistons are available in the standard Nissan size grades in standard bore. This is ok for lower mileage motors but for high mileage motors you might need an oversize piston. Please donít bother Ron at Nissan Motorsports by asking him if these pistons will work in your motor at xxxxxx miles! Get a FSM and a bore gauge and figure that out for yourself first, then call him! The Nissan Motorsports pistons are cast, but they are a good quality cast piston and can take relatively high amounts of abuse. This means no real high boost levels (much above 14 psi) or huge nitrous hits (certainly not more than 100 hp).
A late model 300ZX VG30DE piston can be used with some modification to the connecting rod. This piston is 87mm up from the stock 86mm which will give you 2045cc. The small end of the connecting rod must be ground down by 0.010 on either side to give the rod enough running clearance. I did it on a belt sander being careful to mike the rod several times along the way. Be sure to put a slight chamfer on the pin bushing after you are done. I used a deburring tool and polished the edge with some 400 grit wet dry paper and some honing oil.
The VG30DE piston will give you 11:1 on a stock type combustion chamber. On a DPR stage 6 head you must mill off the dome of the piston. This can be easily done on a lathe or mill by any competent automotive machine shop. Mill the dome completely off making a flat top piston. The VG30 DE piston is a high quality cast piston.
JWT will soon release a forged 87mm piston. It will have a slight dome to give 11:1 with a stock configuration head. The dome could be removed for a lower compression. Forged pistons are much tougher and can withstand detonation and stress much better than a cast piston. The JWT piston will use a high silicon alloy which allows tight piston to wall clearances and also has a super strong, lightweight tool steel piston pin.
You might be wondering if forged or cast pistons are better. Cast pistons are made by pouring molten aluminum into a mold. Nissan cast pistons are pressure die cast in an inert gas atmosphere. Pressure casting results in a stronger, denser part with less inclusions than the low tech pour in the mold method. A genuine Nissan cast piston is dimensionally more stable than a forged piston and can run extremely tight piston to wall clearances, as little as 0.0004"! Tight piston to wall clearances help with oil consumption issues, hydrocarbon emissions and piston ring life. The bad thing is that cast pistons are more brittle and tend to crack ring lands under detonation.
Typically the number two ring land cracks on Nissan pistons. Under lots of detonation, nitrous or boost, the pin boss of the cast pistons can crack also. Usually this incident claims everything south of the intake manifold! Granted Nissan cast pistons are a high quality, strong cast piston and most list members, even you hard core ones will not get to this point.
Forged pistons are made by smashing a heated billet of aluminum into a forming die with extreme force. This results in an compressed microstructure with good grain flow in critical areas such as the pin boss. Forging alloys are also ductile and strong in nature. Forged pistons offer superior strength and toughness resisting fatigue and cracking. Forged pistons can be made thinner and lighter due to their superior strength. Forged pistons can take detonation much better than cast pistons.
Forged pistons can also handle the strain of high boost and Nitrous. All racing pistons to my knowledge are forged. The disadvantages of a forged piston are that it must run a larger piston to wall clearance than a cast piston. This is due to two reasons. The first is that forging alloys grow more with heat, the second is because of the violent nature of forging; a forged piston has more internal stress and is not as dimensionally stable.
Old school forged pistons needed to run as much as 0.009" piston to wall clearance. These pistons sound like a diesel engine, rattling like crazy. Due to recent advances in piston alloys and skirt design, modern forged pistons can be run as tight as 0.006-0.003".
Pistons that run on the high side of this scale will still rattle. Ones on the low side can be fairly quiet. Usually this has to do with the silicon content of the alloy. Low silicon pistons are the ultimate in strength and toughness but require big clearance because of the metalís high expansion rate. These are pistons used in top fuel drag racers or the real nasty turbo Hondas. High silicon pistons run tighter clearances and are slightly less ductile but are still much stronger than cast pistons.
I would not recommend a low silicon piston for street use no matter what. It would be noisy, wear rings quickly and be a oil burner after not so many miles.
JWT pistons will be high silicon and can be run at 0.003". The are almost as quiet as stock pistons. If the skirts are coated with a dry film lube like Swaintech poly moly, bringing the clearances down to 0.0015 or so, they should be as quiet as stockers.
If you are going to push the edge with turbo boost, nitrous or are going to do some real racing, forged pistons are the way to go.
By going to 11:1 CR with pistons, my engine gained at least 10 hp across the board, from off idle to the fuel cut. High compression was one of the best all around mods so far. High compression increases thermal efficiency and lowers the BSFE (Brake Specific Fuel Consumption). My car gets a consistent 29-33 mpg despite spirited driving. As I have stated before, a JWT ECU is mandatory with 11:1 to prevent engine-destroying detonation regardless of piston type.
I may be trying to build a big gun engine within the next year or so. I will sleeve the block so a 90mm bore will be possible. Forged, slightly dished pistons will be used for an 11.5:1 cr. Then a KA24 crank with a cut down snout and welded up thrust surfaces will be used to bore and stroke the engine to 2400cc. Amazingly the KA24 crank almost drops right into an SR20!
JWT pro-series race cams will be installed. More displacement can mask some of the bad characteristics of big camshafts like lack of low end power and lumpy idle. My goal is 185 wheel or 215 crank hp with even more low end torque
Crank, Rods, Bearings, Machining, Balancing, Coatings, Manifolds, etc.
The SR20 is blessed with a near bulletproof bottom end. The crank and rods are forged steel unlike the typical cast iron that most American motors run. The rod bolts are a beefy 9mm. The crank features rolled fillets, an uncommon strengthening operation used usually only for racing or heavy duty parts. The rod bolt registers are spot faced, leaving a generous amount of metal around the bolt holes, a traditional weak area in connecting rods.
Both the crank and rods are subjected to a severe shotpeening from the factory. Shotpeening microforges the surface of the part making it stronger and harder while leaving the interior soft and ductile. This step can improve the fatigue strength of a part by over 100% and is usually reserved for high end racing parts. The main caps are tied together with a stiff aluminum girdle which improves bottom end rigidity significantly. This feature is usually found in all out race motors. These design elements produce an engine that is nearly bulletproof. I have seen motors with over 100,000 miles on them with the factory honing marks still visible in the cylinder bores! The number of list members in the 100,000 Mile Club is a testament to the durability of the SR20.
The only catastrophic engine failures that I know of (Tom Paule and Zak Nilsson) were the result of low oil levels with spun bearings. Chuck Nibbanaís super trick engine also mysteriously disassembled itself but that might have been because of improper clearancing. I have screwed up 3 SR20ís myself but that was the result of not watching the temperature gauge while racing IMSA and SCCA. Gross overheating was an understatement. Clark Steppler of JWT has never seen a catastrophic failure that could be traced to the engines fault, either.
The same bottom end of our US model SR20DE also is used for the turbo SR20DET so we have a lot of headspace before we start to challenge the strength of the bottom end. The stock parts can be used until the hp climbs well into the 200ís. So bring on the NOS, turbo boost and compression! We have run Ryan Besterwich's turbo car (formerly Searl's) as high as 20 psi of boost which pushed the car into the low 12's with a completely stock bottom end with no harm. His car has over 80k miles on it and is still going strong. I estimate that his car is putting out over 400 hp with the stock bottom end! If detonation can be controlled the stock bottom end is pretty strong!
If you are building a hot street SR20, I recommend leaving the rods alone. By doing the traditional beam polishing you will be removing the factory tough shotpeened surface. If you reshotpeen the rods after polishing they will have to be resized and straitened as proper shotpeening distorts the parts. It is not likely that a local shotpeener can do as good of a job as the factory either. The same goes for the crank. It wonít hurt to do these traditional race prep steps but it is probably not worth the effort on the SR20.
If you do prep and re-shotpeen your rods make sure that the piston wall oil squirter hole does not get blocked or peened over. This hole sprays oil on the thrust side of the cylinder helping with lubrication and keeping the engine quiet.
In fact, I might say that no matter what you do to build a naturally aspirated motor, if you keep an 8000 rpm or less redline, you donít need special rods.
I do not have any personal experience with the well-publicized-by-Turbo-magazine, Metalax treatment process but have heard good things about them. I do have plenty of good personnel experience with shotpeening solving many parts breakage problems. Recently I have had very good luck with cryogenic treatment preventing breakage of drivetrain parts with high powered SE-Rs and I am currently building a VG30DE motor using cryogenic treating extensively.
For extreme use in killer turbo motors running near 20 psi of boost or for those of you running 100+hp NOS units, racing rods may be in order. JWT can get Crower rods. I believe these rods are machined from 4140 billet. I am using Cunninham rods in another engine. These rods are a little lighter than Crower and seem just as high quality. Carrillo makes excellent rods also but they would be a custom application and take 6-12 weeks for delivery. These racing rods do not have the oil squirter hole in them which could result in slightly shorter life of rings and pistons.
The rods and pistons should be balance to within 1ě2 gram and the crank dynamically balanced. I have found that Nissans are generally within 1 gram from the factory! A typical American car is usually off by as much as 5-12 grams! I like to polish the journal surface of the crank. You can have a local machine shop do it using the lightest grit of polishing paper belt. You donít want to remove so much material that the crank dimensions change, just reduce the RMS of the surface by knocking off the peaks of the machining marks.
The factory Nissan bearings are strong and durable. I recommend running bearing clearances in the middle of factory spec on a typical street motor. Clearances on an all out racing motor can be set on the looser side of factory. When buying bearings, Clark Steppler of JWT has told me (and I have also observed) that if an engine has any kind of mileage on it, the next tighter bearing size can be used other than the number that is stamped on each journal of the block and crank. Remember to mike and bore gauge all the journals to confirm proper dimensions before assembling. If you donít have access to these , at least use plastigauge to make sure that you are in the ball park.
When boring or honing a block, it is better to use a torque plate. A torque plate simulates the stress of a cylinder head being bolted on your block. With a block that was machined with a torque plate, the bores will remain straight when the head is bolted on. Usually the block will distort and the cylinders will become out of round accelerating wear and reducing the effectiveness of the ring seal when the head is bolted on. Granted this is a small difference but is important if you want to build a good motor. For this reason the main caps should also be bolted on and torqued when the block is being machined.
Boring and honing should be done on a Sunnan CK10 machine. This is a high precision machining center that makes the honing of a good round bore almost idiot proof. Since todayís low tension rings require a smooth surface to seat properly, plateau honing after the dimensional honing reduces the RMS of the surface for lower friction, better sealing, less oil consumption and longer life. JWT has pioneered the use of plateau honing on the SR20 and has the process figured out for a smooth bore surface that will still allow the rings to seat. When properly machined with a torque plate and plateau honed, it is possible to have an engine that leaks down at 2% or less! [Editor's note: Nissan specifies that up to 10% is acceptable; most SR20DEs leak down at close to 5% (source: senior mechanic at Falore Nissan)]
JWT is the only company in North America to my knowledge that has a torque plate for an SR20 engine. JWT is most likely the best company to machine your SR20 block. JWT can also machine your block for SR20DET piston coolers. Piston coolers are oil jets that squirt oil onto the underside of your piston dome to help lubricate the piston pin and to help keep the piston cool. As aluminum starts to lose strength above 350 degrees, piston coolers can help quiet a bit. The SR20DET uses piston coolers as does the 11:1 cr SR16VVL N-1 spec motor. This Japan market hyper motor makes 200 hp from only 1600cc!
Since Nissan feels that this 11.6:1 motor needs piston coolers it is probably a good idea to put them in yours. The piston coolers have a spring loaded valve so they only open at higher rpms to maintain good oil pressure at idle and in bumper to bumper traffic. In my motor there was a noticeable drop in water temp once the coolers were installed. To my knowledge JWT is the only company that has the fixturing to machine a block for these piston coolers. Talk to Clark Steppler at JWT for machining.
When building a killer motor it is a good idea to replace the main cap bolts with the ones found in the SR20DET. These are about 20% stronger. Nissan Motorsports stocks these.
I am a believer in special coatings. Coatings are great for adding to reliability or to help control factors such as heat so special tolerances can be used. At the advice of Nissan Motorsports I used Swain tech coatings. Unlike the other to-be-named coating houses that use off the shelf coatings, Swain develops their own in-house coatings that are much more sophisticated. Where most other companies have a one layer coating, a Swain coating might have 3-4 different functional layers. I use Swain tech gold thermal barrier coating on my pistons. This is a severe duty 3 layer thermal barrier that reduces heat transfer by about 25%. This helps protect them from detonation and Nitrous abuse. By keeping the heat out of the pistons, I can run an amazingly tight piston to wall clearance of 0.0004 inches. That is 4 ten thousandths of an inch! My engine does not burn oil at all even with water-thin 5w30 Mobil 1 oil.
I also use Swain poly moly dry film lubricant piston skirt coating. This coating uses molybdenum disulfide and tungsten disulfide for a dimensionally stable heat conducting matrix. This is better than the teflon that most other companies use because teflon distorts and creeps under load. Teflon is also a heat insulator. Since the pistons cool themselves by conducting heat through the skirts, it is not to good to insulate them. Poly Moly can help tame the clatter of forged pistons. Poly Moly also tightens your piston to wall clearance by 0.0014 or so inches so you may have to compensate in your bore machining for this added clearance.
The guys at Nissan Motorsports tell me that poly moly significantly cuts piston and cylinder wall wear. Next time I go through the motor I will probably coat the valves and combustion chamber to protect them also. One of my friends had a 20 degree drop in water temperature, 300 rpm faster turbo spool, and 300 degree higher EGT's with a fully Swain coated motor. On my hopefully 700 hp Twin Turbo Z motor, I will be using Swain coatings on just about everything from the bearings to the undersides of the pistons. I believe that these coatings are like a cheap insurance policy.
Swain also makes slippery flow improving coatings, heat dissipation coatings, wear resisting coatings and stealth coatings that are not detectable!
List member Kurt Sussman is planning to build, test and manufacture a short runner intake manifold. When running computer simulations with Dynomationís software, gains of up to 15 hp above 5000 rpm with losses of only 2-3 hp below 3000 were noted. This seems to indicate that Nissan sacrificed lots of top end power to gain a little below when designing the manifold. I noted that Nismoís race manifold as well as GReddy and JUNís race manifolds have short runners. The 196hp SR20VVL also has a short runner manifold. As these manifolds are designed for the RWD S13 and S14 chassis, Kurt took it upon himself to design one for the FWD cars. Yeah Kurt! We will be posting the results of this manifold as Kurt get around to it. However, he just had a baby girl which should postpone his manifold development for quite a while. If anyone else wants to do it, let me know
Extrude Honing is a process where an abrasive putty is forced through your manifold or other difficult to port areas at a high velocity, removing material. Extrude Honing is great because it can port areas where it is otherwise impossible to do so, like in the middle of your very long runner manifold or deep inside your manifold's plenum chamber. Extrude honing is also very good at equalizing manifold runner flow.
Smaller more restrictive areas in the head act like a venturi so the putty flows faster there. Faster flow equals more cutting action and thus the Extrude Honing process by nature removes material where it's needed the most. This cutting mechanism is very good at producing runners that flow equally.
We tried Extrude Honing the manifold on project SE-R. This is the shorter runner manifold for the low port, post '93 head. The end results were mixed. Although the Extrude Honing performed extremely well on the flow bench, as the folks at Extrude Hone said it would, the dyno tested power increase was minimal.
On the flow bench the Extrude Honed manifold flowed a whopping 15% more than the stock manifold. Runner to runner flow which varied by about 13-14 cfm per runner stock had the variance cut down to less than 1 cfm per runner. With these excellent results we eagerly bolted on the manifold. By a SOTP evaluation, it was thought that the manifold improved throttle response and top end power. When the manifold was dynoed, the results were disappointing as the motor only gained one peak hp while losing one hp below 5000 rpm. Past the power peak until the fuel cut, the motor gained 3-4 hp. Although these gains seem small, they were repeatable through 4 back to back dyno pulls.
This shows that increasing the intake manifold's flow does not help too much even on a fairly modified SR20. Obviously the manifold is not a major choke point in the induction system. On an engine with race cams the gains would be larger as our manifold seemed to do the best at the very top end. Our computer simulation still indicates that a shorter runner manifold will help quite a bit. This is because the shorter runners will resonate at a higher rpm, improving cylinder filling through passive supercharging. This resonance tuning does not rely on pure steady state flow gains like extrude honing does. We are eagerly waiting for Kurt Sussman's short runner manifold, though we may have to wait until his baby graduates from high school!
Since the classic or pre-94 manifolds have longer, more curved runners, they have greater internal scrubbing losses due to the increased surface friction of the longer, deeper boundary layer (the still air near the runner's walls that does not contribute to flow). Perhaps this process would be more beneficial on one of these manifolds.
So in short, if you have an engine with just the easy bolt on parts, the Extrude Hone process most likely will not help much if at all. If your engine is really built with cams, headwork, compression, etc. and you are interested in getting every bit of power, you might consider it, but it would be a finishing touch type of modification.
If you have a killer high revving NA or high boosting turbo motor it might definitely be a plus.
Unorthodox Racing Underdrive Pulleys
Being skeptical of the claims for big horsepower on the Unorthodox Racing web site, we ordered up a set of their underdrive pulleys to do some extensive dyno testing. Joe at Unorthodox told us via a phone conversation that he felt that the pulleys would be good for about 5 hp on the SE-R.
When received, the pulleys were obviously CNC machined from billet aluminum and anodized a nice shade of blue. They were significantly lighter than the stock bits. We measured the TDC mark in relation to the keyway to make sure that the TDC mark was right on. It was. Unfortunately the TDC mark is the only one on the pulley so timing the car without a dial back timing light is impossible. Not a big deal for us as we have one of these timing lights but possibly a problem for the average joe. We suggest that Unorthodox add marks in 5-degree increments to the pulley instead of just a TDC mark.
To install the pulleys, we removed the passenger side wheel and wheelwell splash shield, exposing the front of the engine. An air impact was then used to remove the main pulley nut. The 10mm bolts holding the water pump pulley were removed with the belt still in place to prevent them from spinning. Two 6mm bolts were used in the existing holes to lever the stock main pulley off the crank. I don't really recommend doing this as it is real easy to punch a hole in the front cover this way. Use a puller or back up the bolts with a peice of thick metal to prevent damaging the cover. To get enough clearance to completely remove the main pulley, the passenger side motor mount had to be loosened and a jack placed under the motor to lift it slightly shifting the engine enough to get the pulley off. The new pulleys were installed in reverse order.
The stock belt for the water pump and AC compressor could be retained but a shorter belt was necessary for the alternator and power steering. We used a Bando p/n 6PK-1000 belt to replace the stock belt which was purchased from World Pack, a nearby parts house (1-800-733-2277). Bando makes genuine Nissan belts so I figured the quality of this replacement belt should be good.
After running the car, my SOTP estimate of power gain was small, about 1-2 hp. The engine felt more eager to rev and there was less drag when the AC compressor kicked on. I plugged in a CONSULT to test for charging function and overheating. The battery output stayed above 12 volts with all electrical accessories going full blast, including my aftermarket PIAA lights and 200-watt stereo cranking. When I made the electric windows go up and down at the same time the voltage dipped to 11.9 volts but I seriously donít think that is a realistic estimate of potential power demand. I donít think you would be caught in a very hot, very humid, foggy rain storm at night while broken down on the side of the road, engine at idle with every single light on, fogging up the windows while making out with your girl (or guy) stereo blaring and get a bug to roll the windows up and down to the beat of the music while waiting for the tow truck! If you do this frequently you may discharge your battery with the underdrive pulleys.
I tried to make the car overheat in bumper to bumper traffic on an 80-degree day, plus high speed cruising and free revving the motor to 7000 rpm for a few minutes. The coolant temp never went above 94 degrees C. I also did some violent slalom maneuvers to test the power steering. There was no sign of power steering pump up. The AC was perhaps a little less effective but it was hardly noticeable. After all this testing I conclude that the pulleys are at least safe. I think that under racing conditions the car may even run cooler as the stock water pump is prone to cavitate at over 6500 rpm.
Some list members have been concerned that the underdrive pulleys lack of an inertia ring as the one in the stock pulley could have some negative effects on motor life. I believe that this is not true. The SR20, unlike most domestic motors, has a fully counterweighted crankshaft and is internally balanced. It does not rely on a counterweight on the front pulley and flywheel to give dynamic balance like Ford or Chevy engines. Highly modified domestic motors are internally balanced at a great cost but us Nissan owners get that stock! I believe that the damper on the stock pulley is mostly to damp out accessory drive noise. With the underdrive pulley in place there actually seems to be less idle and high rpm vibration. I could not detect any increase in accessory drive noise but my car is sort of loud.
The next step was the acid test on DPRís Dynojet chassis dynamometer. Amazingly the pulleys were good for a maximum of 6 hp over stock! The increase was about 2 hp at 2000 rpm rising in proportion with rpm to 5 hp at the power peak to 6 hp at the rev limit. The smooth gradual increase of power deceptively made the SOTP feel less. Normally most mods put a hump somewhere in the powerband that is easy to feel. Not so for the underdrive pulleys. Their seamless addition of power was very hard to feel. Being a skeptic we ran the car three more times to see if it was a fluke. All three runs yielded the same results.
At $189 list price these pulleys get our bang for the buck award! There are often group deals for less on the se-r mailing list.
Unorthodox has introduced a 4 piece pulley set that includes the power steering and alternator pulleys also. I have tested these and found perhaps a small 1 hp gain over the old 2 piece set. Shell Black has found a larger about 2-3 hp gain in his testing. Surprisingly I can feel a larger SOTP difference with the 4 piece set. Taking our suggestions, Unorthodox has improved the pulleys by adding a steel sleeve under the front main seal for longer life and is now adding all of the correct timing marks. The new product is even better.
We have also tested the pulleys extensively on the racetrack at temperatures over 100 degrees and found that the pulleys significantly reduce water pump cavitation induced overheating. Despite thrashing on a road course which is much harder on a motor than drag racing, we have yet to see any increase in wear on the motor.
Big Bore Throttle Bodies and MAFs
I recently tested the RC engineering big bore throttle body. This throttle body is 64mm vs the stock 60mm. The workmanship and attention to detail are superb. The throttle body casting is honed to tight tolerances so a good idle can be maintained and the throttle shaft is aerodynamically profiled with streamlined button head bolts that are staked, much like OEM. Although it felt like it was giving a lot more power in my SOTP evaluation, on the Dyno no power increase at all was registered just as I had previously predicted. My theory is that it improved throttle response so much that the engine seemed a lot more powerful. However, I think this mod is worth while just because of the vast improvement in feel and response. Perhaps with more mods, the engine will need the additional flow and the TB will actually help.
I also tested using a big 80mm MAF from a late model Maxima using a custom programmed JWT ECU. My engine is getting close to the point where it can top out the stock ECU but not quite yet. Even through the Maxima unit is nearly 45mm larger than the tiny stock MAF, I did not gain any power except for about 2-3 below 4000 rpm! My theory on this is that the larger hole helped the CAI resonate better at lower rpm. I don't think bigger or bored out MAF's like Stillen sells are worth it unless you are turboed or your engines are modified to the point where they can pull more than 5.15 volts on the airflow meter. This is the point where the stock MAF is maxed out.
Spark plugs and Ignition systems
There is a lot of controversy on the list on what is the best, most appropriate sparkplug for our cars. My opinion is yet another one but at least it is backed by years of racing experience and recent dyno testing.
Heat Range of plugs
Sparkplugs come in many heat ranges. This is so the plug can be matched to the type of use an engine receives. For low speed, short hop driving, the plugs electrodes must stay hot enough to burn away and self-clean fouling carbon deposits. For this type of driving a hot plug is needed. For high speed racing at high rpm, the plug can become too hot and glow like a diesel glowplug causing pre-ignition and detonation. This can quickly destroy an engine. To prevent this a cold heat range plug is needed.
The length of the insulator of the center electrode determines a plugs heat range. You can tell a cold plug from a hot plug by looking at the center electrodeís insulator. If the porcelain insulator is short, it is a cold plug. If it is long and extends deeply into the steel shell of the plug, it is a hot plug. This is because a cold plugs short center electrode has a short path to conduct heat out of the electrode. A hotter plug has a longer path and dissipates heat more slowly.
Most listmembers seem like they are unaware of matching the spark plugs heat range to the type of driving that they do. I wince when I think that many are squeezing nos or pumping turbo boost with the stock hot plugs.
In my opinion the best spark plugs for the SR20DE and DET are the stock Genuine Nissan NGK platinum plugs. I like a decent platinum plug. Platinum is a noble metal with a high melting point. Being almost inert, it is highly corrosion resistant even at high temperatures. That is why a platinum plug lasts about 3 times longer than a conventional plug. When used in the plug's electrode it resists erosion much better than steel.
Stock Nissan plugs have platinum in both the center and ground electrode for really long life. Most aftermarket platinum plugs only use platinum in the center electrode. I prefer for most engines, even the stock ones, to run the PFR6B-11 spark plug. This is the middle heat range for the NGK plugs. SR20 powered cars come with PFR5B-11 plugs, which are one heat range warmer. Originally when the SR20 was first introduced, the cars came with PFR6B-11s but they were fouling out during port storage where the cars are continuously being started, moved a few feet, and shut off. The countermeasure to high warranty on low mile sparkplugs was the switch to the hot plug.
The PFR6B-11 works well on high compression, turbocharged or NOS powered cars. For running extreme boost (more than 18 psi), a big shot of nos (more than 100 hp) or really high compression (more than 11:1) the cold PFR7B-11 plug is necessary. This plug will be on the edge of fouling during regular day to day driving so it can be considered a race only plug.
The SR20 has a shallow included angle of the combustion chamber. This makes for a quick burning, detonation-resistant chamber. I have also found that shallow included angle chambers for the most part do not like extended tip plugs. When experimenting with extended tip plugs I have found that the engine loses about 3-4 hp across the board. Many aftermarket plugs are extended tip. The theory behind extended tip plugs is that the extended tip puts the electrodes in a more turbulent section of the combustion chamber, thus helping them stay clean of fouling.
In the SR20 an extended tip plug puts the electrode too close to the piston dome screwing up flame propagation, thus losing power. This is important to consider if your are deviating from the Stock Nissan recommendation. Make sure that the tip of the plug that you are buying does not extend further than the stock plugís tip. If you are running flat top or domed pistons, this is even more critical as the tip of the plug is even closer to the piston dome.
The SR20 has a powerful stock ignition that can fire through turbo boost and NOS. Gap the plugs at 0.045". If you experience misfire under squeeze or high boost (and the rest of the ignition system is in good condition, like the cap, rotor and wires) you can close the gap down to as small as 0.020" to prevent it. Go down in 0.005" increments until the misfire stops. Higher cylinder pressures cause by big NOS or high boost requires smaller gaps with the stock ignition. The smaller gap loses a little power but this trick can tide you over until you can get that snazzy turkey roaster ignition.
High Power Ignition
I havenít run across a SE-R that has needed this yet but I suppose that over a 100 shot of nos or 18 psi of boost might need a high power ignition. Jacobs ignitions are crap. I would not bother with them. I prefer an MSD 6A or better unit. I have never needed an MSD on an SR20 yet but I have had very good luck with them on other cars including racecars. The Crane Hi 6 has gotten rave reviews also but they seem prone to burning out (two of my friends have been stranded because of a burnt out Hi-6). These ignitions are very powerful, capable of firing the spark plugs for over 30 degrees of crank rotation. Just the thing for high cylinder pressures.
I have a Nology coil booster on my SE-R. It seemed kind of hokey but I installed it. It has allowed my car to run smoothly even with the plug's electrodes completely burned off. When the coil booster was unplugged the car would barely run so I guess it works well. The Nology coil booster is the only easy way to hop up a 200SXís ignition as the coil is an integral part of the distributor.
I believe I have found the limits of the stock SR20 ignition system. On Ryan's turbo car, when exceeding 10 psi of boost we developed a misfire which required that the plug gap be closed to 0.020". Even this was only good to 14 psi before misfire started again.
On my 11:1 compression NA motor misfire was happening until I closed the gap also.
So on really built cars I now recommend the MSD 6A or SCI ignition system. On 95 and later cars with an internal coil, MSD makes an external coil conversion kit for Hondas that also works on our cars. Just be sure to cut the primary conductor from the stock coil and fill the resulting hole in the distributor cap up with silicone or some of the extra power from your new coil will be wasted.
As a note, these ignition systems don't seem to work too well with Nology wires. I use either stock or NGK wires.
These high power ignitions will not give you much more power but they will eliminate frustrating misfire and help starting and low speed driveabilty.
I hate these plugs. They have a weird center electrode that is flush with the insulating porcelain. What happens is that this electrode quickly erodes so it ends up being a depression in the porcelain, making the spark shoot out of a hole. Sparks like to propagate from sharp edges so I think they have a hard time getting out of this hole.
These plugs will absolutely not work for long in high compression, high rpm, boosted or NOS applications. The are marginal on a stock engine. In my experience they work OK for a few thousand miles then start to idle roughly and on modified engines misfire under load. It amazes me that an OEM level supplier like Bosch can make pieces of crap like these.
Some listmembers have recently dyno tested these plugs on stockish engines and have found them to be OK. This included some used plugs that were at least 20k miles old. My personal opinion is that these are pretty bad for most stock motors. The VG30 in my Pathfinder will barely run with these plugs. Kit Wetzler also experienced poor driveabilty in his NX2000 with these plugs.
[ Ed note: This is Mike's opinion of these plugs based on his personal experience. ]
Bosch Plus 4
Although I have not had any experience with them, Chris Pinthong and Dave Coleman have tested them and found them to work well. These plugs have an unusual design with 4 ground electrodes much like a rotary engine plug. Hopefully they are much better than the regular Bosch Platinum.
NGK V plugs
These work fine, just change them frequently. Be sure that the tip does not extend further than the stock plugs.Split Fire
I call these Miss Fires. They have an extended tip that the SR20 hates. The dual ground electrodes may have some merit by creating more sharp edges for spark propagation but this is moot when the extended tip causes hp loss.
Champion, AC and others
I donít have any experience with these. Make sure the heat range and tip length is appropriate for our motors. I think that these brands have some premium labels that have unique electrode configurations to have more sharp edges for spark propagation. Some list members have had good luck with these.
The main thing to remember with SR20s is that the plugís tip length must be close to the stock plugs or power loss will result and the heat range must be appropriate for the intended end use or engine-destroying detonation may occur.