I'd like to compete in NASA TT4 next year, with a WT/PWR limit of 12:1. I'm expecting a race weight of 2700 lbs with driver, so that allows me 225 average HP, or probably closer to 235 WHP. I have an 2003 F20C, and I'm putting down around 190 WHP (at Salt Lake City elevation of 4500 ft). That means I can have 45 more WHP and still be legal. I'm thinking the cheapest and most reliable way to do that is with a supercharger. I was wondering if anyone had any suggestions for a low-boost (3-4 PSI) supercharger that can take track abuse all day long?

Thanks in advance!

 

No one produces a supercharger that small for this car, 6psi is the base standard and on a weak car sees 270whp and typically its near 290-300whp, nor would the 80lb up front along with lower rpm parasitic losses from running the charger make your power gaol a practical and efficient choice. You are much better off staying NA, its not uncommon to see 225whp with good bolt ons and a tune with a factory motor, plus your not carrying around another 80lb over the nose of the car.

 

^^^ x2

Plus sc gives power up top.

You might end up slower on track with 3-4 psi

 

If he was 06+ and drive by wire, he could tune the throttle mapping to limit power to flat line at 235whp and have an extremely flat torque curve. That's essentially what the USTCC GT guys do with their s54 swaps in to E36s. They limit power production to around 250whp or so but have a super flat torque curve.

Nam, are you going to Western Nationals next week with NASA?

 

Something to keep in mind.. 225whp AVERAGE is very different than 225whp peak (for NA cars). Can't he just have a custom pulley made somewhere to drop boost a bit? I'd think that'd be the best approach.. if he's dead set on using a SC.

 

It wouldn't be the best approach since the supercharger makes its peak boost at redline, again your better off sticking to NA with bolt ons and keeping the weight of the car the same. An extremely small Turbo (something along the lines of a Greddy kit) would be the only feasible and more practical way to get this limited amount of power across most of the rpm band. The kit weighs less then a supercharger kit and Turbo's are more efficient with no parasitic losses, plus you have the ability to more effectively utilize a waste gate to control boost and power across the rpm range. It will spool fast, be responsive and I could see carry a flat trq and hp curve in the range the OP is looking for. Typically these kits at base 6-7 psi see about 250-260whp peak on the s2000 so more waste gate introduced in the upper band should be able to cap off the remaining power needed. I just hate Turbo's for tracking is all due to reliability and heat management. So up to the OP what he is willing to compromise on.

 

A custom roots supercharger at min boost is another possible option to get limited peak power with a fat power curve. 235whp is really going to be challenging to limit though without some work.

 

Building a 2.4L stroker is your best bet.

 

get a 6 psi SC kit and add a restrictor plate or vent some of the boost to atmosphere. Honestly though, it might be better to just max our your NA endeavors first.

 

This is not a common set up, the OP would be virtually on his own to construct the system to employ this approach and IF he was successful at it, the power band would be really thin, plus the added weight would negate a sizable portion of the gains made along with the detriment to the handling and breaking of the car which is just as important on the track as power. With a standard base 6psi supercharger kit, the system starts to produce positive pressure ( 1psi) at about 4000rpm and progressively doubles that pressure every 2k rpm or so, until it reaches 6psi at redline, so with a base kit there is little power produced bellow normal vtec range (ie 10whp 6trq) until about 6k rpm, at which point you are starting the need to cap it off to not exceed 235whp because the kit if left alone would make close to 300whp in that upper range, all wile adding 80lb to the car to carry throughout. Its an extremely inefficient way to go about adding 30-40whp and wont be cheap I might add. Basically what I'm saying is it will have much the same power curve as a bolt on NA car but add 80lb.