why is lower compresion better?

[lucki17]

why is lower compression better for turbo cars? and wouldnt lower compression make it rev quicker?

[drdisque]

compression has nothing to do with revs, bore and stroke does.

in simple terms, lower compression is better because you can run more boost without detonating given a certain octane level.

[lucki17]

okay cool thanks, what happens when a non turbo car has lower compresion?

[drdisque]

it makes less power

[theflinger]

As far as I understand:
More compression = more power but higher detonation requiring higher octane gas. Forced Induction also creates heat and pressure so if you are running a 10.5:1 CR, you wont be able to make much boost, unless you want to run race gas, which has a high high octane and will prevent detonation.

[SaabJohan]

High compression ratio = higher efficiency = lower fuel consumption + more power but also a larger risk for knocking.

[Zgringo]

Originally Posted by drdisque

compression has nothing to do with revs, bore and stroke does.

in simple terms, lower compression is better because you can run more boost without detonating given a certain octane level.

True revs have nothing to do with compression. Neather does bore and stroke. The area in the combustion chamber caused by the piston shape, dished, flat or domed determines the compression ratio.

in simple tearms, you have to run more boost to raise the compression ratio high enough so your engine makes power.
A engine's power is created by it's compression ratio. With no compression it would be like pouring gas on the ground, it would just burn, but confining the gas and compressing it, now you developing energy. The more you compress it the more power you develop. This compressing is the compression ratio or multiplication factor.
Let's say you have gas with high enough octane rating, your engine won't detonate till it reaches a compression ratio of 16:1.
Now well use 3 engines being the same except as follows:

#1 engine has 16:1 pistons
#2 engine has 10:1 pistons and 10lbs boost
#3 engine has 8:1 pistons and 16lbs boost

What's difference in power output in these engines?

http://www.goodvibesracing.com/Compression%20Ratio.htm

Nada, zip there all just about the same give or take a couple HP'

Albert

[Zgringo]

Originally Posted by SaabJohan

High compression ratio = higher efficiency = lower fuel consumption + more power but also a larger risk for knocking.

No truer statement has been said....simple and very accurate.
With proper fuel management, timing and the use of a computer you can make unreal amounts of power.