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How do you find the BEST comp. ratio for a power level?

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Old Nov 7, 2006 | 04:50 PM
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Default How do you find the BEST comp. ratio for a power level?

I mean, without dropping the CR too much.
I always seem to hear lower is better, but how do you know when you're just sacrificing extra efficiency at a given power level?
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Old Dec 19, 2006 | 10:59 PM
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bump..
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Old Dec 19, 2006 | 11:05 PM
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it depends how much boost you plan on running, and from what unit. theres too many variables to sum it up in one definative answer. state your plans, them maybe we can help you out. you can also try the search function
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Old Dec 20, 2006 | 02:49 AM
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Originally Posted by Turbo LS1 SS
it depends how much boost you plan on running, and from what unit. theres too many variables to sum it up in one definative answer. state your plans, them maybe we can help you out. you can also try the search function
Couldn't say it better myself ,My buddy dropped the SCR of his 355ci LT1 to 8.2:1 while his running A P-1SC so eventually he isn't happy at all with his final results which forced him to raise the SCR again

peace
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Old Dec 20, 2006 | 04:29 AM
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Wow, I gave up on this thread.
For now this is hypothetical since I've spent all I can on the car for a while, it's time to build a garage to store it in... But I still prefer to research before making any big decisions.
But anyway, I've talked with Bob at EPP about moving from an aluminum 402 with spray, to a F1 supercharger.
I have -14cc pistons with hellfire rings. 0.007" out of deck height.
My current compression is way high for FI, so I'll have to swap to 6.0L heads.
The best I can say about power levels is, at or around 700rwhp through a 4L80 tranny. I'll consider Meth injection if necessary.

Right now I'm weighing the options between the 700rwhp capable setup I have now, and the new one.
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Old Dec 20, 2006 | 08:38 AM
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Originally Posted by V-10 Killer
Wow, I gave up on this thread.
For now this is hypothetical since I've spent all I can on the car for a while, it's time to build a garage to store it in... But I still prefer to research before making any big decisions.
But anyway, I've talked with Bob at EPP about moving from an aluminum 402 with spray, to a F1 supercharger.
I have -14cc pistons with hellfire rings. 0.007" out of deck height.
My current compression is way high for FI, so I'll have to swap to 6.0L heads.
The best I can say about power levels is, at or around 700rwhp through a 4L80 tranny. I'll consider Meth injection if necessary.

Right now I'm weighing the options between the 700rwhp capable setup I have now, and the new one.
Take your time man & if Bob involved definitely he gonna re-route ya on the right lane

peace

Last edited by bad95killer; Dec 20, 2006 at 08:46 AM.
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Old Dec 20, 2006 | 09:04 AM
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You need to pick a goal and then vendors to help you get there. I went with 8:1 compression, which some don't agree with, but Kurt from W2W reccomended it and he was one of my two key vendors for my turbo project.

I wouldn't go over 9:1 for any FI build over 700rwhp but that's just me.
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Old Dec 20, 2006 | 11:23 AM
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i say it all the time...but people are fixated on getting the highest possible CR for their FI builds, and for the life of me, i CANNOT figure out why. a little drop in compression will lose MINIMAL power, and give you 10x more breathing room to expand. Im with PSJ on this one, i went with 8.2 so i could run pretty high boost on pump. i ran the car NA for a while before i got the turbo stuff and it was not that sluggish. S/Cers usually can run a little higher CR...but the same rule applys. I wouldnt go ANY HIGHER than 9.0. thats just me
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Old Dec 20, 2006 | 12:15 PM
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im running around 8.0:1 CR for my 408 d1sc car.... it has plenty of bottom end.....

im not 100% sure but its atleast 7.9CR and no more than 8.1CR
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Old Dec 20, 2006 | 02:36 PM
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I'm at 8.6:1 CR and am driving it around right now N/A to break it in while waiting for FI kit. It is not sluggish at all! With only 364ci and that low of comp I was expecting it to be a turd but it runs damn near as good as the 346 H/C setup I had before that went mid-low 11s. Granted I have much better heads and more cubes. Personally I would stay in the 8.2-8.8:1 CR and you should be good for about any FI setup. I have heard though that around 9:1 CR works better for S/C apps. Never really had anyone explain why though.
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Old Dec 20, 2006 | 09:15 PM
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Originally Posted by SSblack98
I have heard though that around 9:1 CR works better for S/C apps. Never really had anyone explain why though.
Well here is my attempt at it then! It has to do with where the power is produced. In turbo applications they hit their torque a lot earlier normally. Therefor the lower CR doesn't impact it much. Now with a SC, they have a lot weaker lower end. They try to compensate it by keeping the CR a bit higher. Of coarse this is going to limit the max numbers before detonation, but for a mild-mid build, it is an acceptable compromise.
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