Oil injector air bleed questions
 

Background: Single turbo FD that has a Cosmo upper & lower intake manifold, and a GM LS3 DBW throttle body, managed by a Link G4+ ECU. I'm in the process of returning the factory OMP back to the car (the Link ECU can manage it, and I'm building a new harness to support the extra I/O), with the RA OMP adapter so I can run premix to it from a tank just like I did on my FC.

Anyway, since it's not a stock FD UIM/LIM, and there's no factory throttle body, the air bleed ports that would be there to plumb the oil injectors into don't exist. Doing some reading here, it looks like the solution to my problem is to; (1) Put a bung somewhere on the IC plumbing before the DBW throttle plate, and plumb that to the injector air bleeds, or (2) Just plumb them to atmosphere with a little filter.

The question is which is better? If I understand the FSM diagrams correctly, it looks like Mazda is doing what amounts to method #1.

The Cosmo LIM has a little 4 port manifold on its underside that I may be able to utilize to keep the plumbing clean. See picture - those 2 larger nipples and 2 smaller ones do not connect to the LIM itself; it's like a manifold on a manifold. So I'm thinking I can plug one of the larger nipples, connect each of the smaller ones to the oil injectors, and the open larger one would go to the IC piping to provide the filtered air source. BTW, that 3rd small nipple is blocked off - it goes nowhere, not sure if that is by design or the work of a PO.



https://cimg5.ibsrv.net/gimg/www.rx7...11da28f736.jpg

While we're on the subject of LIMs, the LIM gasket came out literally reusable which was a big surprise!


https://cimg8.ibsrv.net/gimg/www.rx7...a0f69b986a.jpg

The FD has the 2 oil injectors in the rotor housings. The vacuum lines from them stock go to the rat's nest, then to the "barrel" that's in front of the stock boost control solenoids which is finally plumbed down to the primary turbo inlet duct.

Basically they are just fed filtered atmospheric pressure air. You don't want them going somewhere where they would see vacuum or boost, just filtered atmospheric air.

I don't know if they actually put anything out as far as oil vapors or anything. In other words I don't know if they can just be left open to atmosphere or if they need to be plumbed somewhere so they don't make a mess on top of the engine.

Dale

That's pretty easy then, I'll pick up a little air filter (like MAC valve little) and plumb it to atmosphere with those handy Cosmo LIM ports. No worries of oil vapor blowing out of them - per the FSM oil injector test procedure, they work just like check valves - you can blow air thru the port, but can't suck air thru if they are working.

Yep, I bet that line on the Cosmo was probably for the oil injectors, it's a similar set up to the FD. That should do the trick nicely and will be very clean.

Dale

It's been discussed here before I'm sure, the primary turbo face develops a small depression. When the crappy oil injectors fail, which they all inevitably do, even out of the box, the pressure through the one way valve from the engine, pushes the oil back to the turbo elbow and delivers lubrication through the inlet tract....however inefficiently. If no premix in the equation, I wouldn't recommend running to atmosphere, the old method of sticking a hose/filter off the end, assumes a level of reliability, that's not present in those bits of rubbish.

FYI oil injector failure results in puking oil out of those lines, so it's not a bad idea to plumb them someplace where you could see that happen.

I've owned and have been wrenching on rotaries since the mid-'80s, and I've never had an oil injector failure. Maybe I'm lucky. Anyway, this FD OMP will be getting its oil supply from an external tank - which makes it super easy to see if something is going wrong; it will be obvious if the tank is emptying either too quickly or too slowly than the normal rate I'd expect to see.

First rx7 here was 1981, but that's neither here nor there on FD oil injectors. I'd expect most people are blissfully unaware when they fail, other than when they're plumbed back in front of the compressor and the telltale pool of oil is in evidence - if they happen to pull the intake. Excepting blockage or break in a line, external tank level won't tell you much short of pump failure.