Lets talk some about the affects of compression..
Thread Starter
Joined: Nov 2001
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From: Valrico, Florida
Lets talk some about the affects of compression.. I know too much compression is not good for FI, but I see the Ford camp using more and more compression for a lot of thier setups and they are getting good results. I was wondering the possibilities of running 9.5:1 compression on a 408ci combo with a 88mm turbo for a street application. I am sure the combo would be boost limited on pump gas unless alchy/meth is used, but I hear turbo response would be quick and gas mileage would be better than with lower compression. I am starting to see all these high #'s on pump gas, 700 to 800rwhp.. I am amazed at how well these combo's are holding up. I would like to get some input from you guys on how well a pump gas 408ci setup would perform with 9.5:1 compression and if I decided to run C16 will I still be boost limited? Also, I am trying to decide on what LSA to run.. 114 to 117 is the norm.. Which would stretch my powerband out to 7krpm??
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For any street motor that'll see pump gas in a fairly hot climate I would run 8.0:1 compression.
With a 408 motor and good heads/cam selection you'll still make 430-450RWHP on 8.0:1 all motor.
With a T88 and 12-15#s boost on pump gas you'll be in the 750-850RWHP easily.
With a 408 motor and good heads/cam selection you'll still make 430-450RWHP on 8.0:1 all motor.
With a T88 and 12-15#s boost on pump gas you'll be in the 750-850RWHP easily.
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i think a lot of people are scared of compresion. it brings back memories of the old ford cosworth day when you have to run around 7.0-1 if you wanted big boost!
people are running stock motors (over 10-1) at 15psi! now ok these motor might not last a lifetime but they do work well! now if you drop forged internals in there then it should last till the end of time!
also the extra cc and higher comp would make a big turbo spool quick! if you only need 15psi to get to your goal then why not use high compresion??? plus the biiger turbos wil be more efficent and thus cooler meaning you will need a little less bost for the same power.
i would want to run wate rinjection or meth just to be safe. but i recon it could be done no problems!
Chris.
people are running stock motors (over 10-1) at 15psi! now ok these motor might not last a lifetime but they do work well! now if you drop forged internals in there then it should last till the end of time!
also the extra cc and higher comp would make a big turbo spool quick! if you only need 15psi to get to your goal then why not use high compresion??? plus the biiger turbos wil be more efficent and thus cooler meaning you will need a little less bost for the same power.
i would want to run wate rinjection or meth just to be safe. but i recon it could be done no problems!
Chris.
TECH Senior Member
Joined: Nov 2001
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Originally Posted by chuntington101
i think a lot of people are scared of compresion. it brings back memories of the old ford cosworth day when you have to run around 7.0-1 if you wanted big boost!
people are running stock motors (over 10-1) at 15psi! now ok these motor might not last a lifetime but they do work well! now if you drop forged internals in there then it should last till the end of time!
also the extra cc and higher comp would make a big turbo spool quick! if you only need 15psi to get to your goal then why not use high compresion??? plus the biiger turbos wil be more efficent and thus cooler meaning you will need a little less bost for the same power.
i would want to run wate rinjection or meth just to be safe. but i recon it could be done no problems!
Chris.
people are running stock motors (over 10-1) at 15psi! now ok these motor might not last a lifetime but they do work well! now if you drop forged internals in there then it should last till the end of time!
also the extra cc and higher comp would make a big turbo spool quick! if you only need 15psi to get to your goal then why not use high compresion??? plus the biiger turbos wil be more efficent and thus cooler meaning you will need a little less bost for the same power.
i would want to run wate rinjection or meth just to be safe. but i recon it could be done no problems!
Chris.
jmo of course
Thread Starter
Joined: Nov 2001
Posts: 8,259
Likes: 4
From: Valrico, Florida
Originally Posted by CHRISPY
For any street motor that'll see pump gas in a fairly hot climate I would run 8.0:1 compression.
With a 408 motor and good heads/cam selection you'll still make 430-450RWHP on 8.0:1 all motor.
With a T88 and 12-15#s boost on pump gas you'll be in the 750-850RWHP easily.
With a 408 motor and good heads/cam selection you'll still make 430-450RWHP on 8.0:1 all motor.
With a T88 and 12-15#s boost on pump gas you'll be in the 750-850RWHP easily.
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I plan to run just under 9:1 on my setup (probably forged 347) with #317 6.0L heads. Plan to run 15# boost. Didn't want to drop down to 8.25:1 and lose power out of boost, and take longer to spool.
Originally Posted by CHRISPY
Kev from W2w is running 8:1 on his 385 D1SC car. He makes 675RWHP on 100% pump gas.
I am going for a 8.7:1 for a street driven meth injected 370. The nice thing is that you can play with the heads a little up and down to see the effects.
What are folks using to monitor the knock vs: compression ratio? Has anyone been able to actully compare the effect of Octane, Compression and Knock?
What are folks using to monitor the knock vs: compression ratio? Has anyone been able to actully compare the effect of Octane, Compression and Knock?
I am also curious to hear of tests and results on this topic... Old motors vs modern are completely different when it comes to detonation. I know I could get away with 10.25:1 with edelbrock aluminum heads and that big solid roller in my 464ci pontiac in my 67 on 91 octane (california bs gas) without detonation, any higher and I'd be pushing it on those hot summer days.
The facts that folks should keep in mind:
-Stock LS1 is 10.1:1 compression
-Power goes down 3% for every full drop in compression
-125F IAT's would be safe, 150F and over is getting hot
-Aluminum blocks and heads disperse heat faster than steel
-Aluminum blocks warp easier (the bores), and you can lose ring seal on a highly blown aluminum shortblock a lot faster than you might realize
-Some FI shops shoot for 8:1 simply to have more headroom, they don't see the power trade-off as a big deal.
-Stock LS1 is 10.1:1 compression
-Power goes down 3% for every full drop in compression
-125F IAT's would be safe, 150F and over is getting hot
-Aluminum blocks and heads disperse heat faster than steel
-Aluminum blocks warp easier (the bores), and you can lose ring seal on a highly blown aluminum shortblock a lot faster than you might realize
-Some FI shops shoot for 8:1 simply to have more headroom, they don't see the power trade-off as a big deal.
guy comes out 2 the car meets sometimes. with an s2000 w/ turbo/AEM EMS/ 1000cc injectors, full exhaust runs 17psi and 455whp. dynosheets and all. hes on stock block @ 11:0 compression i guess it just takes AIT's, and fuel to keep you from blowing up
Originally Posted by Pro Stock John
The facts that folks should keep in mind:
-Stock LS1 is 10.1:1 compression
-Power goes down 3% for every full drop in compression
-125F IAT's would be safe, 150F and over is getting hot
-Aluminum blocks and heads disperse heat faster than steel
-Aluminum blocks warp easier (the bores), and you can lose ring seal on a highly blown aluminum shortblock a lot faster than you might realize
-Some FI shops shoot for 8:1 simply to have more headroom, they don't see the power trade-off as a big deal.
-Stock LS1 is 10.1:1 compression
-Power goes down 3% for every full drop in compression
-125F IAT's would be safe, 150F and over is getting hot
-Aluminum blocks and heads disperse heat faster than steel
-Aluminum blocks warp easier (the bores), and you can lose ring seal on a highly blown aluminum shortblock a lot faster than you might realize
-Some FI shops shoot for 8:1 simply to have more headroom, they don't see the power trade-off as a big deal.
TECH Senior Member
Joined: Nov 2001
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Originally Posted by longrange4u
John... thought it was 10.4:1 for a stock LS1. Ok so the CR directly effects the IAT's? What is the purpose of the thicker heads and headgaskets? I thought that was a CR thing... keep the heads from lifting?
Thicker headgaskets affect quench and squish.