Hey guys...was just sittin around today...dreaming of boosting my Camaro...and i got to thinking about how mch boost wi ould like to run etc etc...

Well, I was just curious as to how much the compression ratio raises per 1 pound of boost...I"m not sure what the other factors are...im sure there are others (i.e. what kind of turbo/supercharger you use)...or maybe there is a strict value. I hope that makes sense...just curious.

 

This gets tossed around a lot. In the strict sense, boost has no effect on CR, which a function of the engine and valvetrain geometry. But I know what youmean, and I think of it as "effective compression ratio". IOW, what static CR would the cylinder pressures under boost equate to if no combustion took place. Is that what you mean?

There's a couple of ways to get at this. The calculator at http://www.turbofast.com.au/TFcompB.html attempts to estimate it. But I doubt its' accuracy as it uses static CR in the first place. Using dynamic CR and this calculator seems to produce more reasonable numbers. If you actually knew your VE under boost, you could simply multiply your actual dynamic CR by the VE and get a number that should be pretty accurate. The actual formulas used to calculate this are beyond me, but an engineer would know where to find them.

Sorrry if that wasn't very coherent, it's been a long day.

Rich Krause

 

Rich.

what are the specs of your pistons/internals? what CR are you at? it'd be easier if you wanted to copy a list of your mods or link me to a webpage with them if its to much.

thanks
Brandon

 

Brandon: there is some general info on the shop website at www.kennedysdynotune.com but not specifics. Since it's in the context of boost and CR, here are some details re: last years setups and mods for this year.

OEM LT1 block with 4-bolt nodular caps 0.040" over
Callies forged crank 3.75" stroke
5.7" Lunati "ProMod" rods
JE "blower" pistons with -21cc dish and ceramic coated crowns
AFR 195cc LT4 heads with 76cc chambers (last year I was running these "out of the box". This year I have had some mild porting done)
LT4 intake
Vortech S-trim with 14lbs max boost (this year I will be running a Procharger F1)
water injection (in lieu of intercooling)

The static CR is ~8.5:1. Anything else you'd like to know?

Rich Krause

 

well since you asked

what would i need to run 10-12# on a P1SC. 94 Block with hotcam internals and opti swap, so far. someone mentioned a cam with higher LSA already, will the valvetrain from the Hotcam kit be ok with a blower? what kinda pistons do you recomend(Impala SS Gaskets?-are they better/thicker or am i dreaming this up?) thought about having the block studded, splayed, change the piston rings with the pistons.....but havent seen anyone concerned about the rods and crank. how much will they hold?

if you wouldnt mind, check out my other thread HERE and reply.

dont wanna hijack this thread.

thanks
Brandon