can someone verify this info...

[SL65AMG]

http://www.automotiveforums.com/t150554.html



specifically this part



So say that you are running 8.5:1 compression pistons. To get an effective compression of 18:1, you are going to need to run approx. 16.5 psi of boost.
If you were running 9.5:1 compression pistons, then you would only need to run about 13 psi to achieve the same amount of power.

[all-mota]

it sounds like he read a few to many books. but he is right in the sense that higher compression and less boost will make the same power as lower compression and more boost but the boost does nothing to affect compression ratio it only increases the cly pressure, say cly pressure is 1000psi with 18lbs it 1018 psi.

[redrumracer]

it sounds like he read a few to many books. but he is right in the sense that higher compression and less boost will make the same power as lower compression and more boost but the boost does nothing to affect compression ratio it only increases the cly pressure, say cly pressure is 1000psi with 18lbs it 1018 psi.

i might be wrong but that doesnt sound to right. but boosting a car doesnt increase the cr

[helcat17]

it sounds like he read a few to many books. but he is right in the sense that higher compression and less boost will make the same power as lower compression and more boost but the boost does nothing to affect compression ratio it only increases the cly pressure, say cly pressure is 1000psi with 18lbs it 1018 psi.


thats not true the 18 psi would be on the intake side of the compresion stroke when your looking at boost your not looking at the pressure as much as you are the volume if you have 18 psi of pressure on the intake side then your going to get x amount more volume in the cylinder for compresion if that makes any sense and as far as the same hp on high boost/low c/p and low boost high c/p the hp will be about the same but the person with high c/p is going to have a hell of a lot more tourque especialy on takeoff and bottom end soo yea hp may be the same but ask anyone that knows anything about automotives and they will tell you that hp dont mean sh!t its the tourque that matters hp only prolongs the run just my :2cents:

[SL65AMG]

thanks for the info guys. im startin to toy with the idea of a built turbo b20 vtec..... i guess itll be more reliable than an all mota one. (both sleeved)


only problem is that it will be more expensive to turbo it than to just put high c/r pistons in it....


how much is a pretty good turbo kit? 3-4k? maybe one thats pieced together but with good parts and a pretty beefy snail...


also, correct me if im wrong, but doesnt a turbo timer keep the engine running or something to cool the system down before completely shutting down the car? or maybe keeps oil flowing through it..... someone explain it to me plz

[helcat17]

turbo timer keeps the car running to circulate the oil

[SPOOLIN]

I think it actually does raise the compression ratio during boost periods due to the fact that yes, 18 psi is gonna add up to "1018" psi BUT, think of a small 10 speed tire and a BIG truck tire. Put 5 pounds of air in both, the big tire is still really flabby at 5 psi while the small tire is about the explode. I may be talking out my ass though.

[helcat17]

^ ummmmmm NO c/r is going to be the same no matter if your boosted or not think about it under boost or not the area inside the cylinder isnt going to change therefor the c/r isnt either