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Stefan Morley
Prolific User
Username: myupctoys

Post Number: 248
Registered: 7-2009
Posted on Sunday, 20 March, 2011 - 19:16:   Edit PostDelete PostView Post/Check IP

Hi Guys,

Did a compression reading on my engine a while back and it led me to looking at where it really should be. Real issue I wanted to answer how much variation is typical. The inevitable compression ratio discussions came up, great intellectual exercise but not much real use with a compression gauge.

What I thought might be better is for people armed with a simple compression gauge to be able to compare cars of equivalent models and k's.

I'll start with mine and maybe others can contribute, 88 Bentley Turbo R 92 000kms, supposedly 8:1 ratio. Taken after car idling for 10 mins (warm not hot).

1 = 132psi 5 = 131psi
2 = 140psi 6 = 138psi
3 = 138psi 7 = 142psi
4 = 138psi 8 = 141psi

Measured at 600 meters.

Manifold vacuum at startup about 15.5 In Hg
After a 20 min run about 19.5 In Hg

That is with 10 W 40 Oil although I've since changed to slightly thicker oil. Doing so got rid of a slight amount of lifter clatter I had. Test done by removing all spark plugs, throttle about half way just so we have a level playing field.

Could be a useful reference if enough people provide stats.

Cheers
Stefan