Supercharger & Lower Compression

[Stallion]

How come a supercharger needs a lower compression? I have the general idea how a supercharger (blower) works, but I don't understand the need for LC.

Thanks!

Stallion

[MaineShark]

If you put pressurized air into the cylinder, then compress it, you end up with excessive pressure, leading to detonation (or worse).

Lowering the compression eliminates this, but it does reduce the efficiency of the engine. Of course, the supercharger more than makes up for the reduction

Joe

[Stallion]

Oh I see. The compression of the bare engine has to be lower because the blower raises it immensely.

Thanks!

[gooney0]

On a related note, I heard turbo chargers require more backpressue. Is this true? if so why?

-Gooney0

[MaineShark]

Originally posted by gooney0
On a related note, I heard turbo chargers require more backpressue. Is this true? if so why?

-Gooney0

Turbos don't require more backpressure, but they spool up quicker (less lag) with slightly higher backpressure. Not humongous backpressure, but slightly more than one might run to actually obtain peak power. While the power is diminished slightly, the lag is also reduced, and makes the car perform better in cases where the throttle must go up and down. If you were building a land-speed car, where you care only about top end, then you wouldn't car about the lag, so you'd run as little backpressure as possible.

Joe