How to figure optimum DCR?

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Mar 10, 2006 | 01:36 PM

LOnSLO

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From: Gainesville, GA

How to figure optimum DCR?

This is for an engine running 15.5:1 SCR using C25 fuel. Is there a target I need to be shooting for? What parameters need to be known to figure this out?

Mar 10, 2006 | 01:50 PM

DAPSUPRSLO

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From: Salisbury,MD

Quote:

Originally Posted by LOnSLO

This is for an engine running 15.5:1 SCR using C25 fuel. Is there a target I need to be shooting for? What parameters need to be known to figure this out?

http://www.chevelles.com/forums/show...t=97864&page=2

I think reply 17 summs it up pretty well.

http://speedtalk.com/forum/viewtopic.php?t=2495

Take a look here as well. These should give you a good idea of some theories that exist out there on all this stuff. As for my opinion well it would seem the cam choice should come prior to picking your SCR but I know it doesn't always work that way so i'd say base your IVC on what rpm range you intend the motor to work it's best in. I know it's a very broad response but I don't think there is any absolute answer to this question either. Good luck man!!! Look forward to hearing of the results of that monster.

Mar 10, 2006 | 01:56 PM

LOnSLO

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Yep, I know it's a trial and error deal, but there has to be some sort of starting point. Should I start at like a 10:1 DCR and work up, or start at a 15:1 DCR? This motor should be pulling plenty of rpm with the heads and intake and extremely light bottom end.

Mar 10, 2006 | 02:03 PM

DAPSUPRSLO

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I think you have two choices here in my opinion. One is call an expert with his own software and/or many years of experience with similar combinations, or two try things yourself with some software that is available to the public or just through trial and error. If I was going to use software myself i'd look into some of Larry Meaux's Pipe Max software found at http://www.maxracesoftware.com/pipemax_win.htm

It tells you alot of things and appears to be very accurate after looking at guesses the software makes and real world outcomes on speedtalk. The only thing though is you will have to enter the cam specs in yourself and try different things but it should give you an idea of plus and minuses in your intended power band. Good luck!

Mar 10, 2006 | 02:08 PM

SStrokerAce

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From: NY

If you have 15:1 you better be spinning the snot out of that motor.

You really don't pick a DCR you want, you pick a cam that has the right valve events.

What is this motor anyways?

Bret

Mar 10, 2006 | 02:10 PM

gun5l1ng3r

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From: Laguna Niguel, CA

I have always loved high compression motors, only thing is they wont run on the 91 octane I get here in socal

Mar 10, 2006 | 02:12 PM

LOnSLO

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From: Gainesville, GA

I've looked at that program before, and it does look good. I don't like to give too much faith in the "experts". Three cam companies will tell you three totally different things. I like to get a ballpark first, for my combo, then talk with a grinder. I usually buy 2 or 3 cams at a time for the same motor, and see what works best.