What is the max compression I can run with 8 psi
What is the max compression I can run with 8 psi I see a lot of these stock cars running small amounts of boost with 10.5:1 motors! I only want to run 8 psi! How much compression can I get away with? I am building a 427. Need to decide on cr at this point! I have ls6 heads with a stage 3 port! Thanks in advance for your info!
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Joined: Jun 2002
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From: Deer Park
I'm no FI guru, but last I read- the rule of thumb is 1lb of boost = 1/2 CR point. So if you are running 8lbs of boost, that's equal to about 4 CR points so almost 14.5:1.
This is old school roots style/ Carb'd application- so I don't know how relevant it is to FI/ Centrifugal setups.
I do know that boost is only a measure of the engines inefficency (more or less), so this must be taken into account.
also- if you are going FI, you want the CR to be as low as possible and make it up with boost. 10.5:1 is really too high IMHO for a 427 build. You should have 8.5:1 adn get a bigger blower. If you are in the process of building a motor- and want to SC it, then you need to drop the CR to about 8.5:1.
I'm sure there are a ton of people in the FI section that can elaborate on this.
This is old school roots style/ Carb'd application- so I don't know how relevant it is to FI/ Centrifugal setups.
I do know that boost is only a measure of the engines inefficency (more or less), so this must be taken into account.
also- if you are going FI, you want the CR to be as low as possible and make it up with boost. 10.5:1 is really too high IMHO for a 427 build. You should have 8.5:1 adn get a bigger blower. If you are in the process of building a motor- and want to SC it, then you need to drop the CR to about 8.5:1.
I'm sure there are a ton of people in the FI section that can elaborate on this.
No I want to do 8 psi only and spray at the track! I see a lot of stock cars or cam and heads cars with 10.5 or 11.1 cr running 5-8 psi and these cars are making around 500 rwhp with little mods. So I was thinking about a 450-500 rwhp N/A and 8 psi would get me close to 700 rwhp! Is this correct?
how much spray? With a lower compression you're not gonna make more power, you're just gonna have a more reliable setup.
Depending on how much nitrous is used I would say I'm assuming around 100-150 shot around 600 rwhp with nitrous. probably around 450 give or take some without.
Depending on how much nitrous is used I would say I'm assuming around 100-150 shot around 600 rwhp with nitrous. probably around 450 give or take some without.
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I really couldn't tell you exact numbers, I can only approximate. You might make more or less. Hopefully more. It really boils down to your combination (heads, cam, headers, exhaust) and then having it all tuned in right.
It should run like a raped ape either way.
It should run like a raped ape either way.
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Verdad Gallardo TECH Enthusiast
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From: Deer Park
Originally Posted by indianaa
Btw I'm running a 408 or a 427 motor not stock! The n2o will be from 100-250 shot!
Why? I can't see what you are trying to accomplish with this setup. You want boost and dope- the result being high hp/ fast times.
Why not get a good FI motor built, the right way, and maybe use a little dope to help it out. It seems like you are a little over zealous on the FI/ N2O mix thing. If a little good, then alot is better.
Why not just spend the money on a hardcore FI setup that will give you what you want? I don't see where the 200 shot of N2O is necessary. But hey- it's your dollar.
I have a d1sc and heard of a lot of problems with fuel / ignition problems with big boost applications! So I figured run 10.5:1 cr with motor making about 475 rw would give me roughly 700 rw with no belt issues or ignition / fuel related issues. And I would be able to spray 100-250 Ultimately being 800-900 rw
Staging Lane
Joined: Oct 2003
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Originally Posted by indianaa
I have a d1sc and heard of a lot of problems with fuel / ignition problems with big boost applications! So I figured run 10.5:1 cr with motor making about 475 rw would give me roughly 700 rw with no belt issues or ignition / fuel related issues. And I would be able to spray 100-250 Ultimately being 800-900 rw
