Can you have too much comprssion?

S

SKiddell

Well-Known Forum User
To answer the initial question yes you can have too much compression

Compression ratio, static compression and dynamic compression are all interlinked

Sign of a good old school engine in my books. Bit like a race horse, they just want to keep running!
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Correlation doesn't not mean causality Rob... a "running on engine" is undesirable and indicates a worn, poorly adjusted or incorrectly designed engine...end Of.

The damage that can occur includes hammered bearings due to uncontrolled burn usually of residual fuel or oil "dieseling" on several of the cylinders due to hot spots, carbon build up or inappropriate compression (the rattling is usually a clue)
 
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johnymd

johnymd

Club Member
I may be wrong but consider compression ratio and compression to be different. Compression ratio is calculated as the ratio between the chamber volumes at either end of the stroke. Compression will indicate the condition of ring and valves seating plus closed valve duration amongst other things.
 
Alphabettispaghetti

Alphabettispaghetti

Club Member
johnymd said:
I may be wrong but consider compression ratio and compression to be different. Compression ratio is calculated as the ratio between the chamber volumes at either end of the stroke. Compression will indicate the condition of ring and valves seating plus closed valve duration amongst other things.
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Thats what I thought. One being a static measurement/calculation the other a dynamic one. However I was shot down in flames:D
 
johnymd

johnymd

Club Member
It's always nice when at least a couple of people are wrong together. No one want to be the village idiot but if there's a few of us we could start a club.
 
P

pmac

Well-Known Forum User
johnymd said:
It's always nice when at least a couple of people are wrong together. No one want to be the village idiot but if there's a few of us we could start a club.
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However I was shot down in flames:D
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Well i will join the village idiots club with you as I got shot down in flames for answering wrongly too.

I must try and learn not to post at all unless Im selling something.;)
 
Rob Gaskin

Rob Gaskin

Treasurer
Staff member
Site Administrator
franky said:
Thats what I thought. One being a static measurement/calculation the other a dynamic one. However I was shot down in flames:D
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No by me!

I gave the compression reading I had (200 psi) and I've no idea what other folks have but I think that's at the higher end. I was suggesting that if Mike has that or less it shouldn't be a problem.

Mike was also discussing 'running on' so again I gave my experiences of two of my cars that 'run on'. Built by different and well respected engineers, John Lloyd and Dave Jarman. Again I never had a problem.

Both cars have run really well (for what they are) so Mike can use that in his decisions.

Guys of course I know 'running on' is not in theory a good thing but my old car never suffered from it either in my ownership or afterwards (about 15 years total !!). Yes I used different plugs as advised by the builder.

Just adding my experiences.
 
MikeB

MikeB

Well-Known Forum User
Gentlemen

Thank you for the info and advice, checked 10deg at 900rpm, took it out for a run, pulled an indicated 115 and still accelerating, came back home and didn't run on, though it thought about it :)
 
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