I've noticed this with quite a few boosted cars. Why lower the compression from, say 10.1:1 to 9:1?

newbie to the turbo thing, please forgive me.....

 

lower compression is safer on the motor compared to running higher compression...sorry for the short answer gotta run to work

 

ok..here's the deal on high compression and boosted cars:

High compression engines produce more power, but they also produce more heat...so essentially you will need a good consistent air/fuel combination to avoid detonation.

Detonation is usally caused by excessive heat in the combustion chamber that cause the a/f mixure toignite prematurely (usually during the compression cycle)..severe damage to the piston and or rods and maybe even the crank can result.

In boosted cars, the turbine is sending compressed air into the cylinders. This alone can raise the air temperature causing the engine to detonate. So as a safety measure lowererin the compression a point reduces the chaces of detonation and raises the threshold for boost. Having said that, if you have access to good fuel (95+ octanes - which is harder to detonate a relatively lower temperatures), you can theoretically boost a very high compression engine with good tuning.

 

Also with lower compression you give your tuner a wider window for tuning. With a high c/r there is little room for mistake when tuning.

 

i run 10.2:1comp but am trying to make
350-400whp @15psi

 

other than lowering the compression, what else can be done to help prevent detonation?

 

a nicely done fuel system, along with an ignition system and the correct amount of tuning.

jB

 

Intercooler

 

Is the J & S Safeguard an example of part that can help?

 

yes.. the j&s senses detonation and retards the timing in each cylinder accordingly. I would love to pick one up but they are expensive...it almost covers the cost of a standalone like hondata.

 

The J&S is expensive, but it is so worth it. IMO it is an essential piece for a boosted motor.

 

just make sure you find yourself a good tuner...tuning is the key and i think is the biggest factor w/ boost. find a tuner "good" tuner and see what he suggest for your set-up, after all...he'll be the one working on it.

 

i've used both version of the J&S and would NOT recommend either. Save the cash for a programmable ECU. The J&S often misses clearly audible knock even at max sensitivity. A big waste of cash in my book and thats from someone that got stung twice.

 

then what would you suggest? i keep seeing this Hondata ECU thing posted often. What's the word on that?

 

Hondata is the ****!

http://www.hondata.com

do some reading!

 

Yeah, J&S is a reactive system. You need to proactively prevent detonation. Only good tuning and the use of suitable parts will prevent detonation.

 

I agree 100%

 

how can there be any truth to this. i was always under the impression that air + fuel = power. the lower compression you run the more air you can force into your engine including fuel. now the draw back to this is the time it takes to put air into your motor causing lag. now someone please tell me if i am right or wrong.