Taranis

First off, sorry in advance for the long read. I've posted this question before, but this one's a little more detailed than the last post.

The suspect: My 87 RX-7 N/A.

This past weekend, I installed a K&N intake and RP 50mm catback. The only prior mod is a bonez superflo kit, installed about a year ago.

Up until this weekend, the car runs fine. Actually, it still runs fine, but I have one thing that' nagging the hell outta me.

After I put on the catback and intake, I've noticed a 10-15 psi drop in oil pressure. I use Castrol 10W-40 on a white NAPA filter.

First, I checked all over the place for loose lines or leaks. Nothing. Not one drop leaks anywhere, from the oil cooler to the oil pan gasket. So I pulled off the oil pressure sensor wire - and it was gunked up. Cleaned it thoroughly, slapped it back on, and bingo - my pressure's back up to 60psi @ 3000 RPM. Cool. Ran it all day, off and on, yesterday and it stayed the same - 30psi @ idle and 60 @ 3000.

This morning, I warm the car up for about 5 min and take off. I notice the pressure is sitting around 40psi @ 2500.

As the car warms up and the temp needle starts to move, I get on the freeway and get it up to 75 mph (which is about 3000 RPM), and the pressure stays around 45 psi. WTF?? So I ease off and keep an eye on it. Eventually, about 40 minutes later, it's up around 55psi. I pull in to work and park and it's 20psi @ idle.

I'm baffled.

The car idles, runs and pulls fine - very smooth operation (especially after the intake and exhaust changeover). The motor does not smoke, not even on start-up. It uses about 1 qt for every 500-600 miles. I've looked repeatedly for leaks and found nothing.

Before the intake and exhaust changeover this weekend (meaning it had the superflo kit on already), the pressure was consistently 55-60 psi @ 3000 RPM and 30-35 psi @ idle.

Any one of the experts around here, or anyone else have any ideas? The last thing I need is ground up bearings because of oil starvation. I was thinking the small filter on the airpump (comes with the kit) is responsible for the pressure drop (?).

RETed, if you read this - HELP? What the HELL is going on? Should I change my username to Mr. Paranoid?

Thanks for your patience in reading all that, but I wanted to provide as much detail as possible.

Any and all insight is much appreciated. Thanx.

- Jim
(Mr. Paranoid)

Edit: I'm taking this week to have a mechanical gauge put on to see if the stock gauge is faulty. Could the connection of the sensor wire on the other end be at fault?

Josepi

-It uses about 1 qt for every 500-600 miles.

Something is not right there, should be closer to 2000 miles.

-No smoke...

Do you still have cats (one/both)?

How many miles on the motor? Has it been rebuilt?

Factory gauge?

Taranis

Motor was rebuilt about 40K ago. No smoke, have one cat that comes with the bonez superflo which is working fine. The gauge is factory.

Vroomaster

I've noticed that my '86 7 doesn't run at full oil psi until fully warmed up. Then runs at the prescribed psi. Doesn't sound like a problem.

RETed

I would verify oil pressure readings with a good known mechanical oil pressure gauge first before pulling hairs.&nbsp It could be the oil pressure sensors is failing intermittently...



-Ted

Cameljoe

Sounds to me that the problem is either with the sender or the connection.

von

At idle my car runs just under 30 psi.. Like 28 or something. I run 10w-30 GTX.. At 3000 rpm the pressure is just abuve 30psi like mabey 35-38 and I have streight pipe and intake with 15,000 on rebuild.

copandengr

Do you know if the eccentric shaft oil bypass valve was disabled when the engine was rebuilt? Sorry to give you one more thing to worry about.

Mazda designed this valve to bypass cooling oil flow to the rotors for a speedier engine warm up. This was done for the same reason as the 3K idle feature. The engine is "dirty" as far as emissions until it is warmed up to operating temp. The bypass valve acts like the thermostat in the cooling system. It allows the rotors to reach operating temps more quickly.

The problem with this valve it that if it fails and allows oil to bypass the rotors you will quickly overheat them and roast the seals.

It is really easy to defeat this valve. All you need do to get to it is remove the e-shaft hub bolt. The valve will either come out with the bolt or be in the front of the shaft. The valve can then be disabled by wither replacing the pin with a piece of bolt or by buying a manufactured plug replacement from Mazdatrix, Atkins or somewhere else.

Taranis

I do not know if the oil bypass was disabled when the motor was rebuilt. If it was, I would assume the pressure would be close to the same regardless of the intake and exhaust setup being changed. I did think about that tho. Judging by the way it acts when cold vs. when it's warmed up, I think the oil bypass is stock and not modified.

RETed - that's what I'm starting to think too. One day good, another day bad? Bad electrical connection somewhere... maybe a ground?

von - THAT scares me. Your PSI is lower than mine! If you decide to check into it, could ya lemme know what you find out?

The factory owners manual says at 3000 RPM, it should be between 45 and 60 psi. I think I'm within spec, but barely. Time to find a mechanical gauge, I think.

Thanks for all the replies so far. Add more if you think of anything...

- Jim

copandengr

Racking my brain as much as I can still leaves me with no other ideas than the timing of your oil pressure problem is a coincidence. I can't imagine how the work you did could possibly affect the pressure. As Ted said it may be electrical. I would not panic untill the pressure is verified with a know good mechanical gauge.