(Compression test) Re: Pinging or stuttering, best of two evils

[joshhignight@techography.net (joshhignight@techography.net)]

Yeah, that's what I thought. But I supose if I wind up with something like 250psi, I can probably figure that I've got a rather high c/r...

Anywho, I might give a shot just to do it. Engine is only a couple thousand miles old.

Joshua

P.S. adding 114 octane gas to a half tank of 93 helped the pinging quite a bit. But it still pings, which is making me think something is screwy with my ignition.





Well...you don't.  True compression ratio has more to do with just
squeezing air at starter crank speeds.  

Checking comp ratio is a diagnostic for ring wear, headgasket problems,
valves, etc.  What you look for is consistency between cylinders.   
While a high CR engine will give you higher psi readings than a low CR
engine, you really can't tell what the ratio is from a compression
check.

Remove all plugs, remove air intake boot, hold throttle wide open. 
Install tester, have someone crank it.  Note how many "pumps" it takes
to get to max psi, write both down.  Move to next cylinder.  After all
are done, put 1 tsp oil down a plug hole, repeat, and write those down.

You want all 4 as even as possible.  On the 2.0L 8v I built for Big
Mac, they were 210 across the board - excellent.  Highest and lowest
should not vary more than say 10% - check the Bentley.  If oil readings
are much higher than non-oil readings, you have a ring problem.

=====
Cheapass Ron
'87 Scirocco 16'Victor'

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