Quote:
Originally Posted by BlackJack
While that may be true on some of the newer setups, boost is achieved incrementally by RPM's on a supercharger, unless you're using one with a bypass valve where you can push maximum boost in the lower range because the boost levels are low.
I've been using older model S/C's on V8's during many of my earlier days, but that was pre-Vortec style, such as the original GMC, Weiand, etc, so my tech might be a little out dated on newer setups, but I usually don't mess with low-boost applications (below 15psi).
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What you are saying is true, but the increment of change between, say 3600 and 5600 rpm in my case is very small (about 11-13 lb at sea level) and I suspect if boost is lowered by using a smaller drive ratio, or absence of the bypass valve, that affects how large the increment of change is.
The bypass valve I'm talking about here is the type that opens under vacuum. It can also be adjusted and "tuned" to affect throttle response.
One thing I noticed when going to the 2.0 (and the 1.9) inch pulleys on the M62 was not only was the max boost level higher, but the time to reach near-maximum boost level decreased. I'm guessing that since it is now spinning faster at idle and in bypass mode, it has more momentum when the bypass closes and boost kicks in.
At this point, it is probably necessary to step up to an M90 to get all the potential out of this format, though there are still some technical advantages with the M62.