Sport Compact Car - November '98
Project 200SX SE-R
By Mike Kojima
[Put into HTML format by Mike Mager]
Chasing the Type-R
Over the past 17 months we have been quite successful in our quest to extract more and more power from our 200SX SE-R while keeping emissions clean and the OBDII system happy. Now we are setting a solid horsepower goal for our engine, and it is a lofty one. To automotive engineers, the goal of 100 hp per liter in a naturally aspirated motor is a dream. One of the only affordable cars that can obtain 100 hp per liter is the Integra Type R, which extracts 195 horsepower from 1.8 liters. Our SE-R is an even more affordable car than the Type R (at least before you add up everything we've done to it), so we are setting our goals to surpass the Type R in power while still maintaining reliability and emissions compliance.
To achieve our goal we will try to get over 200 hp at the flywheel, or 170 hp at the wheels (our best estimate is that the two are the same) our of Project SE-R's SR20DE engine. Like the Type R, we have to stay emissions clean while achieving this goal. In this installment we will fiddle with the intake manifold, the header and add some underdrive accessory pulleys in our quest for more power.
Since we have ported the cylinder head, added a bigger air mass sensor and installed a less restrictive cold air intake in previous articles, we turned our attention to the only area of the intake tract left untouched -- the intake manifold. While scrutinizing the intake we noted that the stock Nissan throttle body was a huge 60-mm throttle body. This is bigger than the one on a 225 hp Mustang GT so we figured that it would not be important to modify this part.
Since the interior of the long port runners and the plenum of the intake manifold are impossible to reach with conventional porting tools, we decided to have the manifold Extrude Honed. 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 wherever it finds resistance. Extrude Honing began life as an aerospace process used primarily as a method of deburring aircraft hydraulic system couplers and lines. It is used extensively in the tool and die making business as well as in the obvious high performance applications. 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 the manifold's plenum chamber. In fact, Extrude Honing is the only practical way to port these areas.
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.
Ford has used Extrude Honing for an OEM application. On the SVT Contour, the intake manifold and the cylinder head are Extrude Honed stock from Ford! Generally most engines at a minimum see a 10 hp increase and a broader powerband with Extrude Honing. Extrude Honing generally does not affect emissions (and in some cases improves emissions) so we felt that it would fit in perfectly with our theme of clean horsepower.
The Extrude Hone people made quick work of our manifold and returned it with flow bench data. Reviewing the data showed excellent results and plenty of promise. Before Extrude Honing, the stock manifold was bench flowed. Runner-to-runner flow on the stock manifold varied by about 13-14 cfm per runner. After Extrude Honing the variance was cut down to less than 1 cfm per runner. Overall flow was increased by 16 percent.
Eyeballing the interior of the manifold we noted that the interior of the plenum and runners was now a neat smooth, satiny finish instead of the rough sand cast surface. With these excellent results we eagerly bolted on the manifold.
By a subjective seat of the pants evaluation, it was thought that the manifold improved throttle response and top end. Strangely when the manifold was dynoed, the results were a little disappointing as the engine only gained 1 peak hp while losing 1 hp below 5000 rpm. Past the power peak until the fuel cut, the engine gained 3 to 4 hp. Although these gains seem small, they were repeatable through four back-to-back dyno pulls. The manifold reduced the amount of fall off past the power peak, thus broadening the power band up on top. These results were somewhat less than we were hoping for, but the increase at the top end could certainly be put to good use. The Extrude Hone people were surprised at the results as well, telling us that every other car they have tried has gained more power than ours. A typical Integra, they say, gains 10 to 12 hp for example.
This shows that increasing the manifold's flow does not help much even on a fairly modified SR20. Obviously the manifold is not a major choke point. On an engine with bigger cams the gains would be larger as our manifold seemed to do the best at the very top end. Our computer dyno simulation software indicates that a shorter runner manifold will help quite a bit on top end above 5000 rpm with a slight loss below 3000 rpm. The Nismo racing manifold as used in the BTC touring car series has very short runners which substantiates our premise. The increased high rpm resonance of the shorter runner manifold will have a greater affect on peak power in this case than increasing the overall flow.
Since the classic, or pre-'94 manifolds have longer, more curved runners, they have a greater internal scrubbing loss of flow due to the surface friction of the boundary layer. Perhaps the Extrude Hone process would be more beneficial on one of these manifolds.
So in short, if you have an SR20 engine with just the easy bolt on parts, the 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 should consider it, but it would be a finishing touch type of modification. If you have a killer high revving, full race naturally aspirated or high boosting turbo motor where the stock manifold might become flow challenged, Extrude Honing should definitely be a plus.
Since we wanted project SE-R to represent what could be done with parts available to everyone, we decided to replace our custom header with a production header made by Hotshot. Hotshot has the reputation on the Internet for having the most powerful SE-R header on the market. John Spangler of Hotshot provided us with one of his headers for evaluation.
The Hotshot header installed quite easily with a perfect fit. Its ceramic coating looked a lot better than our previous header's plasma aluminum coating. Dyno testing our production Hotshot header showed exactly the same power as our old custom header, a pleasant surprise. The OBDII system stayed cooperative with no MIL lights.
Then we had to mess things up. When looking at a parked motorcycle, we noticed that the second primary tubes of the bike's tri-y header were connected by a crossover tube. We figured that this was to broaden the powerband and increase low-end torque. If we could do the same thing on our header with good results, that would be great!
We convinced Spangler to make us a custom downpipe with a crossover tube welded in place. The results of this modified header were very interesting. Below 2000 rpm the crossover pipe gave impressive power gains of about 4 to 5 hp! The throttle response was super crisp and the off idle power was pretty spectacular. Above 2000 rpm the power was identical to the old header and above 6000, the motor lost 3 to 4 hp. As we don't really care about power in bumper to bumper traffic, the crossover pipe is somewhat detrimental to our long term power goals.
While surfing the net looking for other ways of increasing power without affecting emissions, we stumbled upon the web sight of Unorthodox Racing. Unorthodox makes underdrive pulleys for popular import vehicles. Underdrive pulleys have long been a favorite bolt on mod of domestic car fans, and there is really no difference in how or why they work on more modern engines The pulleys work by reducing the drive ration of all the accessories such as the alternator, water pump, power steering pump and air conditioning compressor. By reducing the drive ration the accessories spin slowly and have less parasitic drag on the engine, freeing up additional horsepower.
Being skeptical of the claims for big horsepower (an Unorthodox representative told to expect about 5 hp), we ordered up a set of their underdrive pulleys to do some extensive dyno testing. The pulleys were CNC machined from billet aluminum and anodized a cool shade of blue. They were significantly lighter than the stock bits, shaving a total of 3.75 lbs of rotating weight from the engine.
As a precaution, we measured the crank pulley's TDC mark in relation to the keyway to make sure that the TDC mark on the new pulley was right on. It was. Unfortunately the TDC markwas the only one on the pulley so timing the car without a dial back timing light was impossible. Not a big deal for us as we have one of these timing lights but possibly a problem for the average guy. By the time you read this, Unorthodox will be adding marks in 5 degree increments to the pulley instead of just a TDC mark. We also noted that the pulley did not have a harmonic balancer integrated into it like the stock pulley did. More on this later.
Because the new crank pulley is much smaller than the stock pulley and the water pump pulley was larger, it was necessary to run different belts. 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 part number 6PK-1000 belt to replace the stock belt which was purchased from a nearby parts house. Bando makes genuine Nissan belts so we figured the quality of this replacement belt should be good.
After running the car, our seat of the pants estimate of power gain was small, probably about 1 to 2 hp, we guessed. The engine felt more eager to rev and there was less drag when the AC compressor kicked on. Since the drive speed of the accessories was reduced we checked to see if any of the accessories were not operating correctly or if the reduced drive speed was causing any negative side effects. We plugged in a Nissan CONSULT diagnostic computer (the computer Nissan dealers use) to test for charging function and overheating. The battery output stayed above 12 volts with all electrical accessories going full blast, including our aftermarket PIAA lights and the cranking 200 watt stereo. When we made the electric windows go up and down at the same time as everything else, the voltage dipped to 11.9 volts but we don't think that is a realistic estimate of potential power demand. How often do you find yourself in a very hot, very humid, foggy rain storm at night with the engine at idle, every single light on, stereo blaring and get a bug to roll the windows up and down to the beat of the music? If you do this frequently, you may discharge your battery with the underdrive pulleys.
We tried to make the car overheat in bumper to bumper traffic on an 80 degree day, plus high speed cruising and free revving the engine to 7000 rpm for a few minutes. The coolant temp never went above 94 degrees C. Stock SE-R's often have the coolent temp run up to 100 C. Maybe much of this cool running is due to the Swain Thermal coatings and the JWT piston coolers but we don't think overheating will be a problem even on stock vehicles. We 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 at idle on a hot day but it was hardly noticeable.
After all this testing we concluded that the pulleys were at least safe. We think that under racing conditions the car may even run cooler as the stock water pump is prone to cavitate at over 6500 rpm. The pulleys will reduce the pump's shaft speed to a point where it will not cavitate even at redline.
Some observers to this process were concerned that the underdrive pulley's lack of an inertia ring balancer as featured in the stock pulley could have some negative effects on engine life. We believe that this is not a serious concern. The SR20, unlike most Domestic engines has a fully counterweighted crankshaft and is internally balanced. It does not rely on large balance weights on the front pulley and flywheel to give dynamic balance like Ford or Chevy engines. Highly-modified domestic engines are often internally balanced by racing engine buiders at a great cost, but Nissan owners get that stock! The damper on the stock pulley is probably primarily intended to reduce accessory drive noise. With the underdrive pulley in place there actually seems to be less idle and high rpm vibration. We could not detect any increase in accessory drive noise ether. Only time will tell, but we are not overly concerned.
The next step was the acid test on DPR's 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, and rose in proportion with rpm to 5 hp at the power peak and to 6 hp at the rev limit. The smooth gradual increase of power deceptively made the seat-of-the-pants feel like less power. Normaly most mods put a hump somewhere in the powerband that is easy to feel. Not so for the underdrive pulleys. Theire seamless addition of power was very hard to feel. Being skeptics, we ran the car three more times on the dyno to see if it was a fluke. All three runs yielded the same results. We definitely are impressed with the performance of these underdrive pulleys.
On a less performance-related note, Enkei just released its neat looking five spoke Wun-Gun wheel in a 18 x 7.5 inch size with the correct 40-mm offset and 4 x 100 bolt pattern for the SE-R. Since we love the BTCC touring car look (the touring cars actually use huge 19-inch wheels), we just had to get these on the car. Since the increased diameter of these wheels affects the gearing and the slightly increased weight affects acceleration, we will be using these rims for street driving and shows while keeping our shocking yellow, superlight 17" Enkei RPO-1's for performance applications only. Don't get us wrong, the Wun-Gun is very light for an 18-inch wheel, but the 17-inch RPO-1's are about 5 lbs per wheel less.
For tires we used Toyo Proxes FZ4 tires in 215/35-18. Toyo is one of the only companies that produces tires in this ultra-low profile size. The FZ4 is unusual because it is an all season rated high performance tire. Although they are not quite as sticky as the ultra-high performance Proxes T-1's that are mounted on our 17-inch RPO-1's, they do offer surprising grip considering their mud and snow rating. The tires had excellent wet grip as we found through many an El Nino downpour! They also have a tread wear rating of 300, and unheard of level of wear resistance for a high performance tire. Surprisingly, the ultra-low profile 18-inch FZ4s seemed to ride a bit smoother than the 17-inch T1 Pluses. We speculate that the FZ4 may have slightly softer sidewalls. All things considered we were pretty pleased with this tire's performance. It's hard to believe that it has an all season rating!
The FZ4's super short sidewalls require lots of skill during mounting to avoid damaging the rim and tire. At the advice of Toyo Tires, we had our tires mounted and balanced at Wheel Zone, a local Toyo Dealer with plenty of high performance tire experience. Having our rims or tires damaged by a gas station hack would have been very vexing.
We are now stuck at about 165 wheel hp, nearly 200 crank hp, just knocking at the door of our goal. Although the Type R Intergra matches us on peak hp, our SR20 make quite a bit more low end and midrange horsepower and torque. Our engine cranks out up to 30 more hp in some parts of the powerband! We will try different header designs and maybe some different camshaft profiles in later issues in our quest to get a solid 100 hp per liter with good emissions. Stay tuned!
Reprinted with Permission