Which compression ratio is better?
9.5:1 or 10.1:1

I found these ratios on the LS1 and LS6 ...just wondering which one is better and why.


Thanx

 

Theoreticly 10.0:1 will make a little
more power than 9.5:1 on the same motor.
But there is a definate limit to how much
compression you can have on a motor with a certain octane gas. Or it will knock (ping) at heavy throttle. Different motor designs
allow some slight varience but not much.
Eg. aluminum heads generaly allow about .5
more compression ratio than cast iron heads.
They also need it to make the same power as
cast iron. Only build your motor to suit the available fuel octane in your area. If only 92 octane is available build for around 9.5:1
if 94 is available build for 10.0:1....
Higher ambient air temps will require more
octane than lower temps. A motor operated at high altitudes will require a little less octane than at sea level. and also will make less power. Don't sweat over if you have 1/2 less compression than the next guy. Overall volumetric efficentcy (breathing) is more important most of the time. Trying to operate a motor at heavy throttle loads without the required octane gas, will damage the motor in a very short time. Retarding the timing is a band-aid approach to getting around this. (reduces power to below that which could be produced with the max compression ratio that matches the available octane with optimum ignition timing.
Hope this helps...

 

Thanx for the tip...very helpful

 

Uhhh...I'm a high school dude who wants to rebuild a badass Thirdgen and I would like to know where i can purchase that LS1 Crate Engine. Will it fit?


Thanx again,
lanyabuddy

 

Hey if you have the cash for a new LS1, you may as well buy an LS6, the Z06 motor. These should be available from GM performance parts.

 

Thanx for that other tip

 

When you retard the engine on a higher compression vehicle how much hp are you taking away from the engine?

 

More than you would loose by building the
motor with the lesser compression for the available gas, that runs optimum timing.