I was told by the dealer that my '02 GS with L67 features a wastegate. If so I am a little confused as to what benefit a different pulley size would make, other than quicker response.
I relize this has topic has most likely been discussed to death, so my appologies.
I recently let go of my 99 SHO and the GS has vastly more power, however the handling is not as sharp, which is what I was looking for given my mostly highway driving. Note the SHO always scared me as it seemed to have little warning for the limits while cornering, fast but no communication. This was not helped any by the addition of a pair of Pilot XGT Z4.

The M-90 supercharger doesn't have a manifold pressure wastegate, no. It does, however, have a bypass valve which can open up causing the manifold pressure to reach normal air pressure.

The valve is generally open when driving around town and highways, but closes when the vacuum pressure drops (i.e. when under hard acceleration). This is in contrast to a turbo wastegate that opens to prevent turbine stalling when the throttle closes.

With a smaller pulley you can raise the manifold pressure, but the bypass valve will still operate like it did with the stock 3.8" pulley.

ferb!

Good response, I never realized that a wastegates function was to keep the turbo from stalling, makes sense now that you point it out.

Thanks

Close, but no cigar. The "blowoff valve" on a turbo keeps the pressure from backing up in the inlet piping when the throttle is closed. The "wastegate" bypasses exhaust gas around the turbo to control boost pressure. Really, about the only thing the turbo and the supercharger have in common is that they both increase the flow of air into the intake tract. More air, more fuel, more power. This is good. Smaller pulley equals even more air, even more fuel, even more power. This is even better.

Charles

Apples and oranges SC and TCs.
Wastegate is used to regulate pressure on SCs. A bypass valve or whatever will have ralatively the same function. It just regulates a little more consistantly. It will limit the amount of pressure. Some regulate according the the speed or RPM of the engine. (As I suppose this does)
Using the smaller pully will decrease the amount of time the SC gets "up to pressure"
I mentioned the wastegate before (regulator) to see if anyone had found a way to notify them when it came on. This can tell you how quickly you SC is comming up to pressure, also warn of premature release.

CR

If the smaller pulley didn't raise boost, we would NEVER have a problem with knock retard. Nor would more power be developed with a simple pulley swap.

There may be superchargers with limits on the amount of pressure, but the M90 isn't one of them. The bypass opens when cruising and at low load, and at high load the valve closes, raising manifold pressure.

Simply put, the vacuum based bypass of the M90 cares not for what the manifold pressure is, therefore smaller pullies will raise the boost.

ferb!

I have to agree with ferb.. i dont have a gtp but now the diff between sc and tc.... sc no wastegate. smaller pulley more power.....wastegate is tc....i.e. when i got stomped in my gt by a eclipse and he let off gas u hear a "woosh" noise yeah....by the way the eclipse had sev $$$$$ under the hood