compression testing
 

can you use a piston engine compression tester for a rotary? what are the compression numbers supposed to be for an 84 -se?

i heard that


80 psi is shit but may run ?????

100 psi good motor

120 psi new motor

Yes you can ...........................
Make sure the car is @ normal operating temperatures
And battery fully charged
pull botht leading plugs OUt
pull the Fuses out
take the little valve stem thingy out of the compression tester
crank it w/ the throttle open(all the way)
count all three sides of each rotor
80 is OK
90 is Good(average normal)
100+ is perfect
remember when using this the reading will be about 20% lower than teh actual compression(with a mazda rotary tester) :bigthumb:

a piston tester never shows the true #'s on a rotor. but they will give you a idea of where you are at. and in the past 4 years of doing tests with my old school mazda tester i have seen very few 100 + psi motors most motors show 85-95 psi even on a 5k mile mazda reman. and when i rebuild a motor after i have done the 1st starting and warm up (while looking for leaks, and other bad things) ill let it run 10-15 min and then i do a test on it... and most new motors have 85 psi. and after 5-10k they go up a little bit

Interesting. So, what SHOULD a brand new engine (not rebuilt) engine have for compression? Is there an equation to figure out perfect compression? I know the ratio is 9.4:1 so what should be coming out as far as PSI?

Just a few thoughts on the subject.

the best #'s i have seen were on a 30k mile fd reman it was 113.5psi give or take a little on all faces... i think thats like 8 kg