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Hello all,
I'm posting this here because I believe it's a general rotary issue as opposed to just a first-gen specific kind of problem. I have a full bridge-ported 12A in my 1982 RX7 race car. I bought the motor from an RX7 specialist shop who said that the motor came out of a first-get RX7 racer that had been rolled and parted out, but as far as the shop owner was aware it was a functional motor. Aside form believing it would run, collectively we know noting about the motor otherwise. The engine looks to have been rebuilt before and I can't tell what year 12A it is. I didn't take the flywheel off to check it's art number to establish what internals it's running before i installed it in the car; all I know is that it doesn't have the eyebrows cast in the housings over the spark plugs.
The engine seems to run well, except that it has really low oil pressure. The bridge-port idles at around 2000 rpm and it seems to hold 20 PSI at warm idle. As the RPMs increase the oil pressure keeps up at a ratio of 10 PSI per 1000 RPM before it drops off massive at 3500 RPM. At around 4000 rpm it has only about 20 PSI and it stays about that way until the shift light comes on at 7200. Coming from mainly small block chevys, 10 psi per 1000 rpm is generally acceptable. With rotaries I have no clue, but I know its way below factory spec (I checked my 1982 service manual and it should be between 68-74 PSI at 3000 rpm) and it falls off that ratio pretty quickly anyway.
I'm very familiar piston engines, but I need some rotary experts to help guide me on this. What do y'all think it could be? Is it a failing pump? Failing oil seals? Could the oil pressure regulator be going bad? I'm very certain it isn't my gauge that's failing, it seemed to read appropriately on the 12A engine I had in the car before. Anyone have any ideas? Also how hard is it to change the oil pump on a rotary? I've heard horror stories about the Torrington bearings on the front of the E-shaft falling into the engine if the clutch isn't depressed while removing the front cover plate. Can anyone way in on that swap also??
here's a link to what the oil pressure gauge is reading as the RPMs increase
I neglected to mention I've had the pan off and I checked the pickup screen; it was debris free upon inspection. I also gave i a little wiggle up in the car and it seems to be properly secured, but I'm not sure how good a test that is.
I also neglected to mention, the oil pressure gauge is a mechanical Autometer Pro Comp gauge that gets its readings from an adapter of unknown make that sits below the oil filter, much like the racing beat adapter.
its very abnormal that pressure drops wth rpm, as the pump is fixed isplacement and is very small on a 12A engine, so its unlikely it would cavitate at just 7000 rpm. bearing clearance is also unlikely as this would be most present at idle and at high rpm the increased volume of the pump should increase pressure linearly.
if you have sump of I would inspect the pressure regulator on the rear iron, maybe it is going not smooth or has dirt in between. also the front relief could be partitally stuck. Still all of this one would expect it would be most present at low rpms.
I haven't yet checked the pressure regulators; I should look at those next. I've been debating replacing the oil pump with the larger 17mm pumps found in the early 13Bs so it may just be time to pull the engine anyway.
On a similar note, I've been scouring the internet looking for answers to my oil pressure problem and I found this on Mazdatrix's website in a how-to section describing the front cover o-rings:
"What you are trying to prevent is having the gasket and O-ring squeezing out of place and blowing the oil (under pressure) into the front cover instead of through the engine. SYMPTOMS of this problem are lower oil pressure at all times, but especially when the engine is hot. A slight “squeeze-out” can give 10-20 lbs at idle, 40-55 at 3500rpm, and drop to 35lbs at 5000rpm. A large “squeeze-out” can give almost zero at idle, and maybe 35-40lbs above 2000rpm."
That seems to describe my engine's symptoms pretty well. I've also noticed a small oil leak where the front cover joins the keg. It's less a leak, and more a constant oily wetness at the point where the cover meets the iron. Has anyone had any experience with this sort of "squeeze-out" issue?
It can happen yes, especially on early enginees that dont have the teflon washer around the oring. Although i would see it as a fixed leak path and would not expect the pressure to go back down at hogher rpm.
if you have sump off you can blow compressed air into the oil outlet at the front cover and then watch from below of you see a leak at the oring.
if it leaks you must take front cover off and could at same time replace oilpump with a wider one. Be carefull for the trust bearing when re assembling
I'm definitely worried about the thrust bearing falling of of its shoulder! I've read some horror stories of front cover repairs gone wrong and bearings ending up in engines. I'll probably stand the engine on its flywheel and work on the oiling system that way. It'll also give me a chance to put my oil baffle on this engine. The engine that's coming off needs a full rebuild so its not gonna miss it! I'll keep you guys posted on how this whole thing goes.
Hello all! I know its frowned upon to bring threads back from the dead, but I wanted to cap the thread off by explaining how I fixed the oil pressure problem.
I pulled the engine and removed the front cover and lo and behold the O-ring that is meant to seal the oil passageway had completely blown! The Mazdatrix page I'd read (mentioned earlier in the thread) clued me in to begin looking into the o-ring, and the oil leak that developed between the front cover and the engine keg really reinforced my suspicions. I installed a nw o-ring and resealed the front cover with silicone instead of a gasket and the engine has been running great ever since. Th oil pressure is holding steady at 80 PSI cold and drops to 60 when warmed up.
