im about to use cp pistons 8:5:1 thinking to low? or how much boost you think would be good because if i use to little wont i lose power...


Modified by snaileg at 5:31 PM 11/6/2006

 

Power won't be an issue of loss. it will be about the transient recovery response and dependency of the turbo that will determine when or if you will experience undesired lag. For example. If the turbo that you're using is at 2PR (2 pressure ratio) for its best efficiency, (like a 16G for example), using 8.8:1 isn't a bad idea because of the fact that you will need to run higher levels of boost (20psi) instead of say 12psi from most run-of-the mill T3/T4 hybrid turbos. Since the efficiency for a 16G is at a higher pressure ratio, running that compression is fine, though you will be very dependent upon the turbo for everything. Load and positive pressure from the turbo will be constant in order for the car to perform. on Higher static compression setups, the motor does a bit more work, and you don't need a smaller 16G with a higher 2PR in order for it to work. HORSEPOWER between lower compression and higher compression will not change. On a honda, Most stay away from 8.5:1 and below because it changes the ENTIRE characteristic of the honda engine's perfomance. You also have to look at what the car's purpose is. many road racers and those who need quick transient response b/w shifts stay about 9.5:1 and above. Drag racers, and those who want to just boast a high PSI number stay at 8.8:1 and below. The average on this site stays at about 9.0:1

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by TheShodan &raquo;</TD></TR><TR><TD CLASS="quote"> HORSEPOWER between lower compression and higher compression will not change. </TD></TR></TABLE>

Really? Would a 7:1 motor and a 10:1 motor make the same power?

 

Not if you ran more boost on the lower compression engine to make the same HP.. which you would be able to with less chance of detonation. Low CR FTW

Just teasing you tony.. I know what you mean.

 

The goal is finding the compression that works right with the fuel you're running and the boost/power you want to run.

 

I think 8.5:1 is going to be great for a pump gas street car making some good power. It makes so much more sense to compress the air with the turbo and intercooler system rather than the motors compression (within reason, 4:1 FTL ). Just pick a turbo with good boost response and have it tuned right and you will love it.

 

I think 8.5:1 on pump gas is great! There's probably a reason so many oem's use similar compression on turbo applications. On race gas, i'd go a bit higher unless you plan to run 40+psi. On alcohol i'd go even higher up to 60psi.

 

ya im planning on running a basic t3/t04e on a ls motor with simple piston/rods wanting about 20psi tuned