compression?? odd readings

[Jeff4764]

ok, so i have an 87 n/a, ive explained this problem before... It starts fine when its cold, but once it warms up it has a hard time starting and sometimes wont even start. I was told to check compression so i bought a tester, (didnt remove schrader valve, just held in relief valve) the pulse is are very even steady pulses and all read the same. Heres the problem, its reading 50 psi every time.. But i was told if there steady and even pulses the compression is fine.. can someone give me some insight.. maybe a different problem the compression

[Phoenix7]

50 is too low. Are you sure you tested it right. That's crappy compression. Normally anything around 80psi means your motor is dying.

[Jeff4764]

im pretty sure i did, i tested both trailing, and pulled the injector and egi fuse and held pedal to floor while trying to turn it over. but if it was bad would the pulses be even

[djmtsu]

If it was tested correctly than 50psi is toast. Rebuild time.

I suggest Rotary Ressurection.

[87turbo_turtle]

sounds like its time to rebuild

[Jeff4764]

I do believe you guys, but does it sound like i did it right?? and would the pulses be even if compression was bad? could it be in the intake? I have no idea.

[Jeff4764]

and if it was 50 psi would it even start cold.

[Phoenix7]

Take a video of both rotors being tested. 50psi is too low, whether or not the pulses are even (your apex seals intact).

[djmtsu]

Just because the apex seals are there, does not mean they are efficient at sealing anymore.

Heat causes expansion, expansion lowers compression.

[Jeff4764]

ok I can do that and post it tomorrow. But does it sound like i did it right...
I tested both rotors on trailing side. the compression tester fitting screwed into the spark plug hole and i pulled both the inj. fuse and the egi. fuse. I had my girlfriend get in the car and push the pedal to the floor, and cranked it for about 10 seconds while i held the pressure relief valve in and got a steady reading of about 50 psi. I will take video, and if you guys can check it out tomorrow and give me some input that would be awesome.

[classicauto]

Originally Posted by Jeff4764

I do believe you guys, but does it sound like i did it right??

Was the engine warmed up when you did the test? Otherwise everything else sounds pretty good as far the tests execution is concerned.

Although those are low numbers even for a stone cold engien that is in decent shape....

[Phoenix7]

Plus, you can drive it until it can't hold compression. Just don't expect it to go anywhere, fast.

Some people add a bit of premix to raise compression too. If you can't get it rebuilt soon then I'm sure others will chime in with ways to help the motor last a little bit longer.

[vex]

You're doing it correctly. 50PSI is fine for checking the apex seal condition, now you need true compression value of the rotor. Do not hold the relief valve and you should get the max number on the compression. I bet you're going to be getting above 100PSI, just a guess though.


http://www.aaroncake.net/RX-7/blown.htm

[Jeff4764]

If i hold the relief valve it will just keep bouncing to 50 psi. If i let go of the relief valve it will bounce a fewtimes and stop at about 95 psi. so if what your saying is right then i am a happy camper.

[djmtsu]

Happy that you have compression, but sad that you still have hot start issues.