C30A Compression test tolerances?

[jaffaz32]

I'm going to get a compression test done on a 3.0 block.

If you had to break results in to three categories for example

Anything above XXX - great!
Anything above XXX - OK!
Anything below XXX - bad!

And how much can each cylinder be out to each other compared to the highest and lowest to be considered bad?

 

[Honcho]

Based on a sea-level test:

Above 199 psi = Great (factory normal value)
Above 142 psi = OK (factory manual minimum limit)
Below 142 psi = Bad

Maximum variance per the factory manual is 28 psi.

The above are the Honda specifications. Anecdotal data suggests most C30A engines that have been serviced regularly and not abused will test at around 200 psi with a variance of 5-10 psi. Abused and poorly maintained engines usually test around 180 psi with larger variances.

 

[jaffaz32]

why thank you sir.

Perfect, exactly what i was after, much appreciated.

 

[Old Guy]

A leak-down test may be a better indicator of the condition of an engine. It is not subject to false high readings that can be caused by carbon build up in the combustion chamber of an older engine. Also, if the test shows significant leakage, a good mechanic can sometimes narrow the source of the leakage (if it is bad enough) by listening for escaping air in the intake (intake valve - although that might be iffy with the NSX variable intake), exhaust (exhaust valve ) or in the crankcase. The down side to the leak-down test is that it requires a compressor and slightly more elaborate testing equipment. I am also not aware of Honda providing any guidelines on acceptable percentage leakage (difference between the two gauges on the tester) so you may have to depend on the experience of the person doing th etest.

 

[jaffaz32]

My mechanic has just informed me my car is making 15 bar which is over 200 psi across all cylinders after a compression test.

It's making good compression, wahoo..