Compression ratio for built engine?

Neo187H · 08-07-2014, 11:20 PM

What compression ratios are people with high HP built engine turbo builds running and more importantly, why that ratio? Speaking with a tuner they recommend 9:1 going down that road but from what I've seen most everyone seems to be running 10:1 and getting in the upper 500HP all the way to 600HP range. Is there an advantage to the lower compression at those power levels? The car would be running 93 octane gas.

DEpointfive0 · 08-07-2014, 11:29 PM

Lower compression allows for more power
Higher compression allows for better response

Most chose the happy medium of 10:1

Super Werty · 08-07-2014, 11:56 PM

Quote:

Originally Posted by DEpointfive0

Lower compression allows for more power (with boost)
Higher compression allows for better response (typically seen on high revving Naturally aspirated engines)

Most chose the happy medium of 10:1

fixed for you

The reason you would want lower compression for a boosted engine is to lower your chances of detonation..aka engine knock, so you can push in more boost

Neo187H · 08-08-2014, 12:32 AM

I should specify, I know the general reasons behind going one way or the other but was curious about it more specifically in regards to our engine. As in, what kind of response or power might be lost by lowering the CR, how much higher might the ceiling be with a lower CR setup?

Hopefully that clarifies what I'm asking a little better.

theDreamer · 08-08-2014, 08:35 AM

Other factors will come into play with headroom of power/response along with CR. What fuel are you planning to run, any additional cooling adders (meth?), what is the plan for the power?

TopgunZ · 08-08-2014, 09:19 AM

I know we are not a fan of GTM at this point. But Sam recommends 11:1 even on a built engine shooting for lots of boost. Especially if you are running E85 to ward off knock.

The higher compression will get you that better low end power and will also get your turbo spooling up quicker. We all want faster spool!

Neo187H · 08-08-2014, 12:36 PM

Quote:

Originally Posted by theDreamer

Other factors will come into play with headroom of power/response along with CR. What fuel are you planning to run, any additional cooling adders (meth?), what is the plan for the power?

I'll be running 93 octane exclusively and currently have no plans for anything like meth. The car will be driven at least a few times a week on a lower than max power setting likely in the range of upper 400-lower 500HP possibly turned down a little more.

theDreamer · 08-08-2014, 01:35 PM

Quote:

Originally Posted by Neo187H

I'll be running 93 octane exclusively and currently have no plans for anything like meth. The car will be driven at least a few times a week on a lower than max power setting likely in the range of upper 400-lower 500HP possibly turned down a little more.

And what are your goals for full power?

Neo187H · 08-09-2014, 09:49 AM

Sorry for the slow response, work got the best of me.

I'm shooting to break 600 on high boost and daily it likely high 400s, maybe a little more or less depending how that feels. I'm used to the 425ish my Stillen puts down so we'll see where exactly it's settled.

08-07-2014, 11:20 PM	#1 (permalink)
Neo187H Enthusiast Member Join Date: Jan 2009 Location: Albany, NY Posts: 302 Drives: PW 370Z Rep Power: 16	Compression ratio for built engine? What compression ratios are people with high HP built engine turbo builds running and more importantly, why that ratio? Speaking with a tuner they recommend 9:1 going down that road but from what I've seen most everyone seems to be running 10:1 and getting in the upper 500HP all the way to 600HP range. Is there an advantage to the lower compression at those power levels? The car would be running 93 octane gas.

08-07-2014, 11:29 PM	#2 (permalink)
DEpointfive0 Premium Member Bitches Join Date: Jan 2012 Location: SoCal Posts: 14,824 Drives: a lot Rep Power: 17151	Lower compression allows for more power Higher compression allows for better response Most chose the happy medium of 10:1 gbrettin likes this. __________________ Do YOU want to know what/where I got my username from? ( Click to show/hide ) NSFW due to language:

08-08-2014, 08:35 AM	#5 (permalink)
theDreamer A True Z Fanatic Join Date: Feb 2009 Location: Texas Posts: 30,879 Drives: 370z Rep Power: 4210	Other factors will come into play with headroom of power/response along with CR. What fuel are you planning to run, any additional cooling adders (meth?), what is the plan for the power? __________________ theDreamer's Z // Fast Intentions // Uprev // GTM // HKS // TEIN theDreamer's Silvia // URAS // GREDDY Houston Zs // Facebook // Twitter // Instagram

08-08-2014, 09:19 AM	#6 (permalink)
TopgunZ A True Z Fanatic Join Date: Jun 2012 Location: Minneapolis Posts: 2,651 Drives: 06 350Z , 09 370Z MT Rep Power: 6833	I know we are not a fan of GTM at this point. But Sam recommends 11:1 even on a built engine shooting for lots of boost. Especially if you are running E85 to ward off knock. The higher compression will get you that better low end power and will also get your turbo spooling up quicker. We all want faster spool! __________________ ROTREX SUPERCHARGER TUNER KITS - $6799/ CUSTOM STILLEN AIR TO AIR KITS -$2100/ 700+ WHP!! WWW.TOPGUNSPEEDWORKS.COM

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08-08-2014, 12:32 AM	#4 (permalink)
Neo187H Enthusiast Member Join Date: Jan 2009 Location: Albany, NY Posts: 302 Drives: PW 370Z Rep Power: 16	I should specify, I know the general reasons behind going one way or the other but was curious about it more specifically in regards to our engine. As in, what kind of response or power might be lost by lowering the CR, how much higher might the ceiling be with a lower CR setup? Hopefully that clarifies what I'm asking a little better.

08-09-2014, 09:49 AM	#9 (permalink)
Neo187H Enthusiast Member Join Date: Jan 2009 Location: Albany, NY Posts: 302 Drives: PW 370Z Rep Power: 16	Sorry for the slow response, work got the best of me. I'm shooting to break 600 on high boost and daily it likely high 400s, maybe a little more or less depending how that feels. I'm used to the 425ish my Stillen puts down so we'll see where exactly it's settled.