I am trying to make heads or tails of my compression numbers , and thought a few insightful minds here may be able to help me!

I bought a 93 R1 , with a "new" Excellent Performance Inc / Pettit Racing engine. Street Ported with 3MM seals , new housings ( Possibly Rotors ) and everything else. With a little over 2K miles on the a compression test was run hot on the engine by a local Mazda dealer and it pulled a solid 93-100 PSI on all faces.

I know these numbers vary greatly depending on the porting done / seals used etc , but does this sound about right to you guys? Thanks in advance!

 

Sounds healthy. Identical to my 8000 mile reman.

 

Sounds about right, if a little low. the 3 mil seals are probably the culprit. I wouldn't worry, the motor is healthy.

My engine that I ported and built pulled right around 104 psi on all faces with 9k on the rebuild, but 50k on the rotor housings. Nice to know that I build motors as stout as Pettit does

 

Goodfella are you on aim? Add me - pr0dr1v3

 

ok, i will next time i get on. I dont use aim on this computer, I only use it when I visit my parents on my old man's computer. If you want to chat you can always PM me.

 

Ok, well I got MEPS this whole weekend, so I'll talk to you when I get home!

 

do a cold compression check. the numbers are always lower on a heatsoaked motor for some reason

 

The check is supposed to be done with a warmed-up engine, at 250 cranking rpm. A cold engine will yield inaccurate numbers

 

Thanks for the input guys!

 

Wow. I build motors from 100k mile used housings and get numbers as good or better than that. The last engine I built with new housings made 110psi with 5 miles on it. Another new housing motor with 3mm seals and solid cornerseals made 118psi with 1000 hard miles on it. 93-100 is okay, but honestly anything under 100 is less than stellar, especially for a rebuild. I usually look for 105+psi from a rebuild with many miles at all on the breakin.

 

yes, they are. however, his engine is fine, but if he wants some peace of mind and some slightly higher numbers he should do it with a colder engine