what should the comp be at

 

Compression test using a piston engine tester :

1) note battery strength. A weak battery will yield low compression results.

2) Remove both lower plugs and wires.

3) remove EGI fuse from engine fusebox.

4) have a friend floor the accelerator pedal, opening the throttle for more airflow

5) insert your tester into the leading hole

6) hold the valve on the side of the tester open

7) have your friend crank the car over for 5+ seconds.

8) observe the needle bounces. You should see 3 in succession without skips, even bounces, in roughly the 30-35psi range.

9) let out on the valve now, and let the tester reach an overall compression value for all 3 faces(highest of 3 will be displayed). 115+ is like new, 100-115 is healthy, 90-100 is getting weak(1 year or less in most cases) below 90 could blow at any moment.

10) repeat for opposite rotor. Note difference in overall compression between rotors, which should be no more than 20psi max.

 

alright bro thanks

 

do it with a warm engine too.

 

i just did it with it being cold and it was at 90 psi on bolth rotors why do it with a warm engen

 

You are supposed to run the engine and get it up to normal opperating temps before doing the test. Also, If the engine is ported (large port) it will effect the compression reading.

The info given above is a little misleading. A freshly built motor will read 100+. But I have seen motors with 60psi push 25psi of boost for two years. Ask J-Rat. He had about 400Hp.

Re-do the test with a warm motor. IF you have 90 all the way around, your fine. You can re-do the test periodically to see that you arent loosing compression after a few months. That would be a good indicator that your engine is on the way out.

 

my motor is an N/A with a street port

 

http://www.aaroncake.net/RX-7/buy1.htm

85 or greater is good on a NA. How large is the port?

 

Dammm, I just did mine a week ago and it looks like I did it wrong. First I did a cold compression test, did not warm the car up. The person that was starting the car did not press the gas pedal at all down, and to finish doing this incorrect I did it on the trailing plugs. I got 95 on both rotors and I got even bounces. What do you guys think? Shoud I do it again or is this a good enogh indicator that the engine is ok?

 

I would say 95 from a cold engine, and not on the throttle is more than fine.

 

Everytime I've done a test, i've held it WOT.

 

i pulled the motor out of another car so im not sure