After feeling like my car was getting a little doggy durring the last part of the summer I decided to finally do a compression test today.



Results are with throttle open all the way.



On a cold engine, front and rear bounce 80-85psi pretty evenly with check valve removed from compression gauge.

A tad higher than 90psi with the check valve in the gauge.

After I warmed up the engine the reading were almost identical.



I then poured a little atf in the plug holes and got 110 front and 105psi rear.



Are these numbers a little low or ok for a 13b-re stock port?



Thanks

Cam

 

first off you should always do a compression check with the engine at full operating temp. cold motors tend to not seal properly. second at what rpm was the compression checked at, ie the higher the rpm the more compression you may see. so if you are cranking the car over at 150rpm the compression numbers will be slightly lower then if it was being cranked at 250 rpm. how much oil is the mop pumping into the motor, due the the nature of the motor the mop has a vast affect i have recently found out on the compression numbers at lower rpm. and lastly yes by adding atf to the chambers the numbers will go up, thats a givin.



i noticed when i cranked my re over at normal operating temp i was getting 7.2 , 7.3 , 7.3 bar both frount and rear @ 154 rpm,,,,,,,,,, bat was gettin low. i added a charger to the mix and retested the compression and was getting 7.8, 7.9 , 7.8 bar @ 183 rpm on the re motor. i was using the mazda rotary compression tester that my work forgot they gave me 3 years ago hahah. anyways do the convertion as that was on a 500 mile motor with hella hp untill the faitel ping took out 2 rear apex seals.

 

Just about time for a freshining up.

 

I stated in my first post that the compression numbers were almost identical hot vs cold.

Cranking rpm was at about 200rpm according the the haltech.

This tank of gas has premix 200:1, I was told I should try premixing a little richer. I'll do that next year.

I knew that adding atf would artificially raise my compresson numbers but I'm wondering how much it should raise them?



Also I don't have any hot start issues like I've read about when the compression is too low.



Thanks

 

i think its ok, you're looking more for even bounces than the peak number anyways

 

Agreed. Just drive her into the ground. THat is what I'm doing with my 235,000 km original motor, original turbo S5TII. I have a spare engine I'm building up. But as long as she runs the original engine can stay.

 

Dosent look too bad. Similar readings on front and back cant be too bad. Its the major inconsistency that you need to worry about...for the most part.

 

A regular comp tester isnt a great way to judge your engine under alot of scrutiny.



The best thing you can do with that is use it with the shrader valve in place to get the highest pressure in that rotor, lets say you get 90 psi. Take the shrader out and see if you get 3 even spikes. Now you know your in the 90 psi ballpark on all 3 sides of the rotor.

 

Thanks for the replies guys.



I'll run it one more season and see how it looks after that. If she still starts she'll still get run

 

yep basically