tron@fluke.UUCP (Peter Barbee) (04/17/85)
>Howdy, all you techno-experts! (I'm not sure this applies to me) > First, what is the same about turbo- and super- chagers? They both compress the intake mixture thus supplying a more fuel-laden charge to the cylinder. Actually both types usually compress just the air and then add fuel to it but this is not an absolute rule - I've seen both types installed downstream from the carbs. The major diffeence is where they get the power to compress the air. Turbochargers use the pressure and velocity of the exhaust stream to turn a turbine which is connected via a shaft to another turbine which compress the intake. Superchargers use a belt driven by the crankshaft to drive the compressing turbine. Quickly, turbos are good because most of the energy in the exhaust steam would have been thrown away, so the performance increase is "free" (this isn't quite true because of increased back pressure, but it is nearly true), they are bad because of turbo lag. Lag is in part created because of a non-linear RPM/boost function, essentially at low RPM you have shit for boost, and because you don't have much boost it takes a while to accelerate to an RPM where you do. Superchargers have almost reversed characteristics - their power is taken directly from the crank, so all of it is power you would have used to make the car go fast. But on the other hand you can have much more low RPM boost, with virtually no lag. Now the RPM/boost function is more linear so the engine should rev more smoothly. There is a lot more to the whole question of compressing the intake charge. Things like wastegates, detonation, intercoolers, and reliability. But I think I've covered the major differences between turbos and superchargers. Peter Barbee
mike@amdcad.UUCP (Mike Parker) (04/19/85)
> because of turbo lag. Lag is in part created because of a non-linear RPM/boost > function, essentially at low RPM you have shit for boost, and because you don't > have much boost it takes a while to accelerate to an RPM where you do. > > > Peter Barbee Interesting theory... Methane powered cars? Mike @ AMDCAD