Hi,
I have a 2002 Sunfire with a 2200sfi turbo and I want to know if the piston of the first gen of 2.2 OHV would be better because of there lowest compression ratio.
Thanks.
Pontiac Sunfire SLX-T@8PSI 2002
hpm wrote:I have a 2002 Sunfire with a 2200sfi turbo and I want to know if the piston of the first gen of 2.2 OHV would be better because of there lowest compression ratio.
[citation needed][spell check needed]I believe the only previous version with lower compression was the 1.8L, which I believe also had a smaller bore. Also, up until about '87, the pistons were significantly heavier.
And possibly most importantly, most engine builders working from factory turbo cars raise compression to increase response. So, while 9.0 might seem kinda high when compared to, say, a 7.75:1 4G63, it can actually be better.
*disclaimer: raising compression on OEM turbo-equipped vehicles is usually accompanied by a change to a forged alloy piston. While this gives them leniency in tuning, it is not necessary when the engine is properly tuned. Countless LN2-equipped vehicles have successfully boosted on factory pistons*
fortune cookie say: better a delay than a disaster
"And possibly most importantly, most engine builders working from factory turbo cars raise compression to increase response. So, while 9.0 might seem kinda high when compared to, say, a 7.75:1 4G63, it can actually be better"
this is true if its a race application when using high octane race fuel. you do this to a street motor with 93 octane your going to have some problems. if you intend to raise compression on a boosted vehicle with 93 octane your going to be limited on how much boost you can run. most likely less than 8 psi. if you lower the compression then boost pressure is no longer a limiting factor. yes, you will lose off boost power but you will gain so much more in the end.
hpm. if your only going to run ~10 psi boost then i wouldnt even bother trying to install lower compression pistons.
JOE L wrote:"And possibly most importantly, most engine builders working from factory turbo cars raise compression to increase response. So, while 9.0 might seem kinda high when compared to, say, a 7.75:1 4G63, it can actually be better"
this is true if its a race application when using high octane race fuel. you do this to a street motor with 93 octane your going to have some problems. if you intend to raise compression on a boosted vehicle with 93 octane your going to be limited on how much boost you can run. most likely less than 8 psi. if you lower the compression then boost pressure is no longer a limiting factor. yes, you will lose off boost power but you will gain so much more in the end.
hpm. if your only going to run ~10 psi boost then i wouldnt even bother trying to install lower compression pistons.
Partially agreed. I've never heard of a 7.75 DSM running
well on 87 octane, but I've heard of plenty running 8.5+ on 93.
The way I look at it is that higher compression and lower boost is more street friendly than lower compression and higher boost. Want to race it? Just throw in the high octane and turn up the boost...
fortune cookie say: better a delay than a disaster
