When building a b18c for high boost, Which is better low or high compression?

 

If you plan on running high boost, you would want to have a low compression. Factory cars that are supercharged or turbocharged out on the market contain between a 9.1:1 through 8.5:1 compression ratio. Granted that is just a small sample of American cars (i.e. Volvo, Ford, & Jaguar), those numbers will show you what factories throw out so there is plenty of room for margin. I do believe one of the Jaguar is running 1 Bar of boost on that compression ratio range.

 

Most people go with lower compression when running a turbocharger system. My engine is 8.5:1. I run 14psi daily, on pump gas and put down 360hp on the low boost level of 14psi. Low com v/s high comp is really going to depend on the total build quality of your engine and engine control system. There are many racers that are running close to or over 11.0:1. Now they have serious engines that are purpose built to run really high cylinder pressure, and the engine management to keep all that power in check. Most street cars run between 8.5:1 to 9.5:1 and run well. The higher the compression the less boost you will need to reach a certain power point. A lower compression engine will requirer moor boost to reach the same point. (i.e. A 9.5:1 engine @ 10 psi made 250 hp, a 8.5:1 engine @ 12 psi also make 250hp.)

 

Ahh, words of wisdom if I ever heard them.

 

makes sense, thanks. So a vafc really is not enough to manage an engine build on high boost is it?

 

Exactly; it could be adequate if you were just running a wee bit of boost, but once you creep up the pressure you will need more control then that.

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by 4CFED &raquo;</TD></TR><TR><TD CLASS="quote">Most people go with lower compression when running a turbocharger system. My engine is 8.5:1. I run 14psi daily, on pump gas and put down 360hp on the low boost level of 14psi. Low com v/s high comp is really going to depend on the total build quality of your engine and engine control system. There are many racers that are running close to or over 11.0:1. Now they have serious engines that are purpose built to run really high cylinder pressure, and the engine management to keep all that power in check. Most street cars run between 8.5:1 to 9.5:1 and run well. The higher the compression the less boost you will need to reach a certain power point. A lower compression engine will requirer moor boost to reach the same point. (i.e. A 9.5:1 engine @ 10 psi made 250 hp, a 8.5:1 engine @ 12 psi also make 250hp.)</TD></TR></TABLE>

Could not have said it better.

 

What engine management did you ues on 14 psi Rocket?

 

I would have to agree with everything he said. NIce

 

Hondata if your on a budget. AEM EMS if you can spend some cash. If your serious Autronic & Motec

 

I guess Ill tell you guys what Im looking for and you can tell what you think. Im trying to hit high 12's in the 1/4. I want to do it without any engine building for now. (96 integra gsr) I have t3t4 turbo kit w/ intercooler,(7psi) clutch, and little other odds and ends. I was thinking of bumping the boost up to 9 or 10 (not sure) then dyno tuning with vafc. I already have the vafc but I may just sell it and go with hondata s200 with boost option, but do you think I need that on 10 psi? Id rather not spend that much $$, but if I have to I will. Also do any of you know about how much hondata s200 runs with boost option, obdII to obd I harness, and everything else I would need. Hondata.com the best place to get this from? Thanks guys