Dynamic Compression Ratio vs. Cranking Cylinder Pressure ?

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Reddartowner

Reddartowner

UCF Alumni....Go Knights!
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Is there a simple relationship between calculated dynamic compression ratio for a particular engine and its cranking cylinder pressure..?? Like maybe DCR x 14.7 = CCP ?? Or is it more complex than that...?? Trying to get a feeling for what the cranking pressure will be in a 383 we're building. Dynamic cylinder pressure for that engine calculated out at 8.38. Wondering if I should go a little higher, but I'm wanting to be able to run on pump gas....

TIA....
 
I'm not up on this much, but I believe the cam selection plays a great big roll in cranking cylinder pressure.
 
Check out,Keith Black's piston website. Has the D.R .calculator,online there.
 
/6 Matt said:
As far as I know, there is no formula or direct relationship.
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I don't know of one either..........There may be some engine builders that have accumulated enough data to come close?

At 8.38 and living where you do, I was a Palm Beach county resident for 17yrs, your environment has some say also......Sea level, Hot, Humid, etc. I personally wouldn't push it much higher. Pump gas can vary in quality even at the same stations. I think i'd play it safe and just run as much timing as you can get away with and call it good.....jmo.
 
Abodybomber said:
Warm it up,pull a plug. Comp tester(lol).
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Lol good one! He probably just wants to know what it should be so when its finished he can check it and make sure its built right and sealing. I know I would If I built one cause I don't trust myself to get things right the first time! Lol
 
There's not really a direct correlation that's usable, that I would count on.

Cranking compression relies on several variables such as valve condition, ring condition, etc., while dynamic compression ratio just assumes perfect sealing and looks at the change in volume from when the cylinder is sealed up, to TDC.
 
I'd be more concerned that all cylinders were within 5% of each other and consistent over time.
 
Reddartowner said:
Is there a simple relationship between calculated dynamic compression ratio for a particular engine and its cranking cylinder pressure..?? Like maybe DCR x 14.7 = CCP ?? Or is it more complex than that...?? Trying to get a feeling for what the cranking pressure will be in a 383 we're building. Dynamic cylinder pressure for that engine calculated out at 8.38. Wondering if I should go a little higher, but I'm wanting to be able to run on pump gas....

TIA....
Click to expand...

'b' or 'rb' 383 ? head choice ?

TIA.
 
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