BruceSAllen

My Lotary 7, a custom third gen stuffed into a Lotus Super 7 replica, is showing a strange low oil pressure symptom (verified with a precise analog gage). On cold startup I read 20 psi, pretty much independent of rpm. After warm-up it reads 10-20 psi at idle and as I slowly raise RPM it will go up to 50 psi at 1500 rpm and then drop gradually to 20 psi or lower as rpm is increased up to 5,000 and As I drop rpm, somewhere around 1500 the pressure will jump up to 40 and drop with a further drop in rpm. Does it sound like the front pressure release that is supposed to operate at 150 psi or the rear oil pressure regulator that is supposed to open at 110 psi is sticking opens at too low a pressure? Dropping the oil pan is a big pain because I have a full car undertray pop riveted on but maybe that is what I need to do. Car still runs great! Ideas? I hope it is only a regulator spring. 5W50 Syntec as always. Remote oil filter. www.greasedshadow.com

Gadd

It's likely that front cover oil cross over o ring has blown out. It's fairly common when the front cover has been install with out the oem gasket but the oem o ring was used. A fix is to replace the o ring with the one Rotary Avation sells with there kit, sorry I don't know the size but if you call Tracy at RA I'm sure he can help.


Buy the way, nice car. How much does it weight?

BruceSAllen

thanks. Maybe I can remove the front cover without pulling the engine.

weighs 1800 lbs. 330 hp. Check Web site.

GTRay

If the belly pan is rivitted on you might have some issues getting to the bolts on the bottom of the front cover.

Ray

alexdimen

iTrader: (13)

make sure you take the proper precautions if you're removing the front pulley/cover

this explains what i'm talking about:

http://www.mazdatrix.com/faq/pulley.htm

nice car! looks like alot of fun.

silverTRD

iTrader: (37)

looks like fun indeed

BruceSAllen

Gadd,
Is that an oil channel built into the front cover?
This engine has never been apart since I bought my 94 FD new.

Gadd

Yes, it's a passage directly from the oil pump to the banjo bolt on the front cover to the oil cooler. If the motor has never been apart, it less likely to be the problem. Are you having any other symptom, like knocking noises? I'd cut the oil filter open and see if there is any bearing material inside.

Gadd

You might take a look at the RX7 Service Highlights Manual section D. It shows the oil flow of the stock 13BREW.

https://www.rx7club.com/3rd-generation-specific-1993-2002-16/94-fsms-available-download-449950/

BruceSAllen

Thanks, GADD. This SHM is easier to read than the little shop manual I was using.

BruceSAllen

GADD,
I have pulled the pan as well as investigated the symptom you describe at
http://www.mazdatrix.com/faq/oring.htm
With the help of a mirror I am able to look around the periphery of the original gasket that surrrounds the O ring and the gasket does not seem to be blown out.
The front oil pressue control valve spring is only 1 mm short. The rear oil pressure regulator doesn't want to come apart so I'll buy a new assembly.
Any other ideas?

alexdimen

iTrader: (13)

isn't that o-ring problem only on 2nd gen engines that have been re-assembled improperly?

BruceSAllen

Dunno, but I owned my third gen from new and it has never been dissasembled and still has the front cover gasket surrounding the O ring.

mdpalmer

iTrader: (24)

Are you sure about the front pressure release and rear oil pressure regulator operate/open at 150 psi/110 psi (respectively)? Reason I ask is because I watched this and he's claiming a stock pressure regulator is ~68 psi...

increasing oil pressure video

Also see this (help visualize ):

rotary engine lubrication

Gadd

The only other thing you can check from the pan is to make sure the oil pickup screen is clear and the tube sealed well to the front housing. The relief valve spring the pressure regulator are fairly cheap so you could replace them, but it is rare for them to fail. I'd pull the front cover, check/replace the thermal pellet in the e shaft, check the front cover o ring, and if there was no obvious sign of it blowing out, I'd remove the oil pump and spec it as per the FSM. After all that, the only other thing is worn main and/or rotor bearings.

edit:

Oh, What are you using for an oil cooler? It would a good idea to check the remote filter, cooler, and hoses for any restrictions. It's a long shot, but it's worth a look.

BruceSAllen

I took those pressures from the shop manual.
I have ordered new front oil pressure control valve spring (only 1 mm short) and rear pressure regulator. When these come, if the problem is not resolved I will check the oil pressure right where it exits the engine in front on the way to the aftermarket oil cooler.

mdpalmer

iTrader: (24)

gotcha. in the "specifications" table. thanks.

Gadd

Ahh. great idea. Please keep us posted.

White94RX

5W-50 oil seems a little thin. Something thicker might increase your pressure some. I run 20W-50.

To each his own, but generally, most people don't run synthetic oils. Rotaries inject oil in with the air fuel mix, and I've heard synthetic may not burn as well, or may leave ash deposits or some crap. But i doubt you'd have any problems with it, just thought i'd mention it.

BruceSAllen

I replaced the spring in the oil pressure relief valve (front of engine). It was .1 inches short. And I replaced the rear pressure regulator assembly (I could not dissassemble the old one). I replaced the oil pan and filled up with the Idemetsu 20w-50. I knew I was in heaven when as soon as I started the engine, cold pressure read 115 psi on the test pressure gage. With car fully warmed pressure is 30 psi at idle and 115 at 3000 and above.
And I never had to pull the front engine cover!
Thanks all, especially GADD.

mdpalmer

iTrader: (24)

^^ Congrats That must feel great for you to know the fix didn't involve a lot more work.

But holy hell, your oil pressure is sky high (esp with revs)! What have you done to increase the oil pressure (I've seen the trick with compressing the rear regulator a bit... but I thought that would give you about 80 psi @ 3k RPM)?

Get out and drive your car now

EDIT: where did you measure the pressure?

BruceSAllen

The pressure is no higher than the shop manual says for the rear pressure regulator release. I seem to remember the new car (94) would read 110- but admittedly on the stock RX7 gage.
Must be that the new pressure regulator from Mazdatrix is set to 115. Of course I am using heavier oil too. Maybe if I got it really hot with some warm weather track driving instead of idling in the garage the pressure would come down. I gotta bolt up the engine, clean things up and pop rivet the bottom pan back on to get it on the road.
Pressure gage is T-ed into the oil line coming from the front housing before the remote oil filter and oil cooler.