Quote:
Originally Posted by sw20kosh
Superchargers don't make up for altitude. Only turbo's do that because the boost that is entering the motor is tied to a turbo that is controlled by a wastegate that will keep a certain set pressure. This wastegate looks for a certain manifold pressure and tries to maintain it irregardless of what atmospheric pressure you are at.
High altitude has less pressure to begin with so a turbo will spin harder to make, say 10 psi at 6000ft. How does it work harder? The wastegate keeps shut untill manifold pressure reaches the set point. This set point is harder to reach at altitude. This set up would still make 10 psi at sea level, but the turbo wouldn't be working as hard.
A supercharger has no such mechanism to "keep the same pressure" in the manifold. A supercharged system that makes 10 psi at sea level would make, for example, 7 psi at high altitude. There is no wastegate to allow the supercharger to work harder to maintain 10 psi.
You can think about it like this:
A turbo can be made to work harder in order to maintain a set manifold pressure. A belt driven supercharger cannot. A belt driven supercharger works "X amount" and cannot work more than X amount unless you rev higher or change the pulley so that it works X + Y amount.
Ex.
X amount of work = 10 psi at sea level
X amount of work = 7 psi at 6000 ft
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Unless you have a waste gated supercharger running higher boost then what you want so it cuts you off at say 9psi that it hits at around 4k rpm, after the waste gate starts opening the back pressure on the supercharger lightens increasing mpg compared to running the supercharger without a waste gate, it also allows the ability to run boost by gear and also an actual flexfuel setup...
All the perks of a turbo with out the spool up time.
I may know someone who's doing this ass soon as he makes his fat ass fit back into his 32" jeans.