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Re: [Healeys] 4 Cyl Compression Measurement

To: Bob Spidell <bspidell@comcast.net>
Subject: Re: [Healeys] 4 Cyl Compression Measurement
From: Oudesluys <coudesluijs@chello.nl>
Date: Wed, 02 Dec 2009 23:28:25 +0100
Allthough there are ways to compute the final pressure, it is very 
complicated and probably not very accurate.
You have to take into account pressure loss through leakage, heat 
exchange air/cilinder/piston, engine and ambient temperature, cranking 
speed, valve timing and overlap etc.
Most important is that all cilinders show the same pressure within ca. 
5% of each other and that there is no significant oil burning or 
crankcase pressure.
Kees Oudesluijs
NL

Bob Spidell schreef:
> Found a link: 
>
> http://en.wikipedia.org/wiki/Compression_ratio 
>
> Look at: " Fault finding and diagnosis" 
>
>
> bs 
> -------------------------------- 
> Bob Spidell - San Jose, CA 
>
>
> Compressing a gas causes it to heat and (try to) expand, raising pressure 
>beyond nominal. 
>
> There are formulas for computing the total compression, but I'm to lazy to 
>google it right now. 
>
>
> bs 
>
> -------------------------------- 
> Bob Spidell - San Jose, CA 
>
>
>
> Sorry, but I'm not following the math here. Atmospheric pressure is 14.7 psi 
> (at sea level) so a compression ratio of 8.5 should yeild appx. 125 psi. 
> Assuming I'm missing something, can anyone splain what it is? 
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