I've been reading the threads a lot just trying to soak in the information. Kicking around the idea of going FI but will probably wait until the car is paided off...


I was reading that with a SC it takes time to build up the boost. Say you wanted to stay with a stock motor so you didn't want to boost over 7 PSI. Couldn't you just put a pulley on that is capable of putting out 15 PSI, which I would assume would create more PSI at lower RPM's but then just put a relief valve on that would relieve pressure above 7 PSI so you never went over that? That way you could have 7 PSI for more of the power band instead of just 7 PSI towards the top?


Second, I always thought SC was better than turbo for low end power...but it seems that the threads here indicate the S2000 is different. What's the deal? Is turbo lag not a problem with the S2000?

Thanks

 

There are two types of superchargers. (well, there may be more, but I'm gonna keep this simple. ) Centrifugal and Positive Displacement (PD.)

Every (read: both) supercharger kit for the S2000 currently available is Centrifugal. These have a lag, similar to a turbo, but worse.

PD Superchargers do not have to "spool up" they boost almost off of idle so the low-end grunt is there.

A turbo will lag, but it can be accounted for by the size of the turbo. A tiny turbo will spool quickly, but is not capable of BIG power. A huge turbo takes longer to spool, but can make crazy power. I believe most people choose a turbo that is somewhere in between. There is some lag, but it's not as bad as a centrifugal SC.

 

So the really stupid question...

Where is the PD SC for the S2000?!???!!

 

In development.

BRP, Axialflow, Jackson Racing (sort-of.)

Honestly, I wouldn't hold my breath waiting on any of the three.

 

IMO that is the best way to do it. FI is an expensive route.

 

The lag you are referring to is not actually lag. What is being said is that centrifugal superchargers make boost that is directly related to rpm. The higher the rpm, the more boost. Hence, the boost made before 5000rpm with an SC setup is negligable. A turbo, which has true lag, runs off of exhaust. The exhaust has to be flowing enough to spool the turbo. Once there's enough flow, the turbo begins to spool and create boost. Turbos reach peak boost much lower in the rpm range than centrifugal superchargers which only see peak boost at redline (since boost is directly related to rpm).

So, there's NO lag with superchargers to speak of. Saying they lag is incorrect. They simply build boost slowly as rpms climb.

To answer your question, a smaller pulley (along with all the mods that go with it), will make more boost everywhere in the rpm range. However, top end gains are magnified far more than low end gains. For example, the low end gains from going from a 7psi pulley to a 9psi pulley (4" to ~3.5ish" for CTSC) will be negligable.

Hope this helps! GL!

 

I think what he is saying is that could you put on a smaller pulley and control the boost some how to not pass the 7lbs max on stock components, therefore build up the 7lbs earlier and keep them that way throught the rest of the powerband. for example lets say a 7lbs pulley will sees 2 lbs at 6k and go up form there to its 7lbs peek at 9k. could you install a 15lb pulley and let say it reaches 7lbs at 6k or so and have it stay there till 9k, giving you more boost throughout. hope that clarifies a little

 

In theory that's possible I guess, but how are you going to bleed off the extra pressure? Venting it though a BOV would get REALLY obnoixious in a hurry.