ok, so I rebuilt the motor (1990 13b) with all new seals and everything was inspected prior to reassembly and the only issue is a tiny groove running all the way around one of the housings about 1/8th of an inch from the edge. Very very tiny, about 1.5mm wide and maybe .2mm deep. Put it all back together and lost the flywheel keyway so I am waiting on that part. So out of curiousity I hook up the compression tester and turn the sucker as fast as I can. I get 30psi out of one rotor and struggle to get 5psi out of the other and I am considering not even putting that motor back in the car because it seems still a little screwy. Any input would be very much appreciated!

 

Most home rebuilds can have pathetically low compression so don't loose hope. Especially when you're hand cranking it. Hand cranking it will not give you an accurate read on your tester at all. Rotaries build compression. So as it turns each cycle should "build" compression in agregate manner.

 

My motor fresh after a rebuild pulled 65psi on each rotor face and 90 cumulative.

I would think the housings no matter what should have similar compressions.

 

could it be the coolant seals got out of their slots? the TEC seals from RotaryAviation can be tricky sometimes

 

it wont have very good compression until the seals get set. which is between 500-1500 miles.

 

More than anything, yoiu can't spin it fast enough by hand to get any sort of numbers that mean anything. Minimum cranking spec is 250rpm. The fastest I can spin a motor by hand (I have a specially designed flywheel with a handle on it, like a big crankwheel) is about 150...the mazda digital tester won't even register that low. You have to have a trans and starter hooked up to get anywhere near proper numbers out of it. Go ahead and put it in.

 

adn compression is measure at 250 rpm, you are not spinngin it at 250 rpm by hand.

 

Yeah, whatever he said.

 

Is there an echo in here?

 

i would put her in afert all that work rebuilding it.. i sure your compression number will be way up when cranking it with a starter

 

The biggest thing I'd look for when turning it by hand is consistent sounding "chuffs" - if you get one chuff per half rotation alternating rotors, you should be OK.

Also, make sure the housings are seated properly. If there's no odd gap between a housing & end plate (indicating a seal out of place or such), and it sounds OK, you should be fine.

-=Russ=-

 

hook the starter up and try it that way

 

Thanks guys! I will put it in and see what happens, thanks!

 

If you didn't lubricate the tips of the apex seals, and or side plates. housings then you will have much lower compression aswell...

Sometimes so low that it wont start, squirt some oil in there before you go trying to start it, it will smoke a crapload, but it'll have much better compression