I am thinking about selling the car pretty soon, so I had the compression checked at a local Rotary specialist. Results are:

Front: 77 / 80 / 75 @ 243 rpm
Rear: 78 / 78/ 78 @ 253 rpm

From reading I know that these results are at the very low end of acceptable. The car does not smoke at all, does not use coolant, and starts without issue hot or cold.

Just wondering if I should rebuild now before risking more damage or wear. The car is barely driven, maybe twice in the last 4 months. Opinions welcome, thanks!

 

What are your vacuum readings at idle for both rotors? Anything lower than 15 inHg is a sign of a tired motor. Assuming stock ports

 

Yes stock ports. Only mods are Power FC, Apexi intakes and catback exhaust.

Here is a video I took of the car idling about a month ago. I've been struggling with getting it to idle without hunting for 10 seconds.

The commander read -414mmhg which i guess is a little over 16 inhg

The vac source was off the upper intake that is usually capped.

 

Stay on top of your regular maintenance(new antifreeze every 3 years!) and it should last you a good long while. That engine seems fine, and your Power FC probably just needs to relearn its idle.

 

That oil gauge looks wacky to me at the beginning...

 

Are you sure about that?

My engine has:

Front rotor: 7.7, 7.6, 7.6

Rear rotor: 8.0, 8.0, 8.0

which I consider to be a very healthy motor and I average between 50-60 kPa at idle, or about 14.5-17.7 inHg. So, sometimes I see figures below 15 inHg but I'm sure my engine is in pretty good shape.

 

Cib, what units are your pressure readings? I forgot to put my measurements in psi.

 

that's pretty low, how many miles are on the car? with it that low your housing are probably worn beyond use, so if anything at best your saving a rotor by rebuilding it now

 

My compression results are in Bar but converted to PSI it would be:

Front rotor: 111.7, 110.2, 110.2

Rear rotor: 116, 116, 116

All at 250 RPM.

 

keep up with regular maintenance, premix and just drive it.

 

Yes, I mean your results are very low but really even and as long as the car starts hot and cold and isn't using coolant I would just drive it until it doesn't start anymore.

 

At 83k your housings are not worn out unless you drive the **** out of it all the time or you run around with no air filter. I would do the water steam clean method to help clean some carbon out of the engine and exhaust. These engines will maintain compression for well into the 100k range as long as the internals are clean.

 

You cannot get/give an accurate idle vacuum unless your idle is stable.

'Stock' idle is very low, like 720 rpm. Most 'street' ported engines will idle at 900-1000 rpm.

Who checked the compression? Was it done with the engine completely warmed up, and did they open the throttle fully?

 

The car only has issues idling at zero load, so I think it may be a power fc issue. If I turn on just the running lights it settles perfectly about 800 rpms if memory serves. I will try get another clip tomorrow.

The compression test was done by MER in Cresson, Tx. They are a race shop, they advertise rotary work and they had lots of cars, parts and torn down engines in their shop. I found them trustworthy and I believe they did the test correctly.

 

Your idle issues seem to be tune related. I would take it to a competent tuner to sort out the idle before you bite the bullet on a rebuild. Did you try the idle relearn procedure?

 

That is how mine works with the pfc. At startup it revs up higher than idle but if I turn the lights on it will settle to the idle rpm. Throughout the driving cycle at stopping it can idle around 100-300 rpms higher then the set idle until I hit the lights and it would settle back down. The idle is set the same in the options for no load/load/ac load.