Compression test
 

Purchased my 94 FD approx. 9 months ago. I've installed a downpipe, catback, intake and the normal gages to monitor engine parameters. I've always had the problem of the engine stalling at a stoplight with the AC on and it would take several attempts to start the engine after warm up. Needless to say, I continued to drive the vehicle because I still had decent gas mileage (17/18 mpg), every now and then I would remind other drivers on the road that we rule and finally I just enjoyed driving it. After several months of research on the boards I decided to take a compression reading and these were the results: Front rotor - 2.5, 2.5 2.0. Rear rotor - 2.5 across the boards. With these readings I thought I missed a step. I checked everything and performed the test several times and came up with the same results. I have 84K with no history of any rebuild. Boost is normal and the engine still pulls hard. I plan on a rebuild in the near future but will continue to drive it but with less stress on the engine. Any comments, suggestions or recommendations for rebuilds would be appreciated.

That seems way too low to even be running? Are you sure the throttle was wide-open when you did the test?

yea that seems low. wat kind of compression tester are u using?

What units are those in? Who did the test?

Dave

Yes, it seems extremely low. Throttle was held wide open. Went ahead and tried another gauge. I borrowed the compression tester from autozone. The gauge reads PSI and KpaX100. I got the same results on this test. My max pressure from either rotor was 70 PSI. I got the 2.5 Kpa with the relief valve removed or held open.

84k isn't high for a rotary to loose that kind of compression(provided everything is functional). Since all your readings are close in numbers I would assume all you need is a good carbon cleaning to loosten up the seals. Stuck seals will give you low compression readings making you think the engine needs a rebuild.


https://www.rx7club.com/showthread.p...ht=water+de%2A


I would do this and retest later down the road. You need to give the seals time to loosten before retesting. There are other methods you can use but this is the cheapest way to do it. I do it 3 times a year and have 98k with excellent compression on my original engine. Bottom line keep the internal seals loose and the engine will run better for a longer period of time.

Thanks for the help! I'll try the carbon cleaning and retest for compression later. If this works or even helps a little I'll continue to do as part of my routine maintenance.