compression

so you mean cylinder psi?

depends upon the closing point of the intake valve, do you have some camshaft info?

It depends on some factors with regard to ring sealing (blow by) and your dynamic compression not static, which can be quite different especially for a cam with any overlap.

On a new tight engine assuming ideal gas behavior you can expect pressure to equal Dynamic CR to power 1.3 at sea level e.g. for 9.5:1 dynamic CR it would be 18.7 Bara (absolute) or 17.7 Barg (gauge).

Julian

17.7 bar = 256.716729 psi

18.7 bar = 271.220499 psi

i don't understand how these seemingly arbitrary bar figures relate with no knowledge of when the intake valve closes and the actual dynamic compression stroke begins?

256.x & 271.x psi are a good 100 psi over normal cranking cylinder psi findings

This link given by 4V & Proud in another post is very interesting and indicates how to estimate the pressure in the cylinder at the cranking speed:

http://victorylibrary.com/mopar/cam-tech-c.htm

To do the math you need to know the stroke, the bore, the length of the connecting rod and the angle of the Intake Valve Closure.

But very roughly, it's between 10 and 15 bars

quote:

Originally posted by 4V & Proud:
17.7 bar = 256.716729 psi

18.7 bar = 271.220499 psi

i don't understand how these seemingly arbitrary bar figures relate with no knowledge of when the intake valve closes and the actual dynamic compression stroke begins?

256.x & 271.x psi are a good 100 psi over normal cranking cylinder psi findings

Correct I don't know the cam specs from Rene's information, nor any other internal losses (rings sealing) I simply posted an example of an ideal theoretical calculation if his dynamic compression was 9.5:1.

A leak down test provides for far more meaningful information.

thank you, already helpful. will letz you know the test result soon,
Uli