AAN Compression Test – Acceptable Specifications

AAN Compression Test – Acceptable Specifications

The acceptable “Compression Pressures” are:

Specified Value: 9.0 to 13.0 Bar (131 to 189 psi) (ED: 1 BAR = about 14.5 psig)
Wear Limit: 7.0 Bar (102 psi)
Maximum permissible pressure difference between individual cylinders: 3.0 Bar (44 psi)

I do not like to see more then 10%– but that is me and does not mean that your engine might have unacceptable leakage. Perform a leak down test and see if it can be determined where the leak is coming from. If you hear it out of the CC breather or oil fill then you may have ring wear. With the hard cylinder coating and the ring design these days, I have found that cylinder leakage is not as common.

More often you hear it out of the exhaust or intake. Have a friend go back to the exhaust tip if you run it again to take a listen.

If it is the valve seating (I assume you did this at TDC) you may simply have carbon build up and a good tank of BG44 may improve your readings.

Contributors: Mark T / Dave F