So a local RX7 shop owner suggested that I add check valves to my OMP lines in my S5 GXL 6 port turbo because under boost I am pressurizing them hence the FDs coming with them stock.

I have no clue what the vacuum lines even do as far as operation of the OMP and can't find an explanation in the FSM in the FAQ, anyone care to explain?

 

Stock TIIs don't have check valves on the oil injector lines.

The oil injectors are connected to a metered air source (before the throttle plates), so they're supposed to see at least a bit of positive pressure. The incoming air helps force oil through them, so if anything, higher pressure air should just do a better job of forcing the oil through. People call the 4-way splitter a "vacuum spider," but it's not really connected to a vacuum source.

 

Ah, ok. The FSM doesn't show the rest of the vac diagram for the splitter but I have all four teed to the vacuum nipple on the LIM (from the block). Is there a diagram showing where they connected before I cut up my solenoid rack? lol. Kevin Lander's write-up says to run a splitter and hose and go back to it later and leaves it at that.

 

The spider's *vacuum * line attaches to the back of the throttle body. That nipple on the throttle body travels thru the body to a passage Prior to the throttle plates i.e. not vacuum but filtered and metered (by the AFM) air.

The OMP puts out Pressure. It is a oil pump itself. It does Not get that pressure from the engine oil pump. Been there, proved it to myself by blocking off the passage from the front cover to the OMP and feeding the OMP from a bottle of oil located below the oil pan (in the driveway, sitting on the gnd below the oil pan. I put a guage on the the end of a omp line and it shows pressure. More pressure at higher rpm than lower rpm. More pressure than the stock turbo puts out at high rpms.

Pull the spiders *vacuum* line off at idle. Feel the *vacuum* line with your fingers. You'll feel vacuum coming from the direction of the Spider, not from the metal nipple on the throttle body. The rotors on their Intake stroke cause the vacuum on the spiders lines.

 

yes. so vacuum generated by the OMP itself is the same as pressure on the OMP from the turbo. In both cases the air is flowing the same direction. so it doesn't matter if the OMP sees boost or not and a check valve is unnecessary. If you hook it up the way it was hooked up from the factory, the air only moves one direction: toward the OMP--whether it is pushed toward the OMP (by compressed turbo air) or pulled toward the OMP (by the OMP itself drawing vacuum, NOT manifold vacuum).

 

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Thanks, so hooking it up to a vacuum source (LIM) would be bad because under decel. and idle, manifold vacuum would reduce the amount of oil sucked into the engine by partially closing the check valve?

The only nipple on the throttle body is the one under it used for the double throttle diaphragm (auto car) and the three on the thermovalve. Did you mean the three on the back of the UIM next to the TB? Which one is it for a series 5?

 

not meaning to jack the thread but im curious also. right now all four of mine have rubber vacuum blocks on them from previous owner. is that not good? should they be open to the atmosphere or have vacuum to them? i have the engine tore down to just the block repainting and putting all new gaskets on. so now would be the perfect time to fix it.

 

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If there are no oil lines from the OMP and no *vacuum* hoses on the top of the injectors, I guess you can assume the previous owner was mixing oil with the gas to replicate the oil injectors.

If the oil hoses are connected to the injectors but no *vacuum*hoses on the injectors.......the injectors will suck on the oil lines to the omp and cause an unusually large use of oil i.e. you'll be adding oil to the pan a lot more than normal.

You should never just open the top of the injectors to atmosphere because that would not be metered air. The stock has the tops going to *atmosphere* by picking the air from the FRONT of the throttle body which is filtered/metered air.

The air enterning the top of the injectors is also a part of the air used during idle, so it they are capped off, the idle will suffer a bit due to not as much air entering the rotor chamber vs normal. Not saying air thru the injectors isn't going to the rotor chamber all the time, just saying that air is there during idle and if you cut that air off, more air will have to be added for a steady idle.

 

thanks hailers. i have the oil lines ran too the injectors just no vacuum lines. should i add vacuum lines to it? of leave it be. is a s4 engine with the mechanical omp

 

According to what he said you should hook them up to a metered source before the throttle plates.

 

LIke said above.

On the back of the throttle body are three and sometimes four metal nipples one above the other. One nipple is a larger diameter and that hose feeds what is called a *spider*. The spider has five plastic nipples. One larger one that comes from the nipple I just mentioned.

The other four go to the injectors top nipple.

Spider can be seen on the Mazdatrix forum somewhere. Or you can somehow buy some plastic nipples from the auto store and rig something up.

If you leave it as is, the injectors will suck a lot more oil from the omp than anybody would want. You'll be filling the pan up on a regular bases.

OF the four nipples on the back of the throttle body, only one is vacuum and you don't want to use that for this application. That would be the bottom one that is vacuum. The other three all come from Prior to the throttle plates and are not vacuum. One of those goes to the air bleed nipple located b/t the two oil injectors on the intake manifold. One is not used for anything at all.

If you just leave the upper nipple of the injector open to atmosphere, you'll have the equiv of a air leak and the idle will be crummy because it's not Metered air i.e. air that has gone past the AFM.

The attached jpg shows the four nipples I mentioned. Pay no attention to the hand written numbers, they were for something else.

 

i'm not sure I understand how not having the oil injector air bleeds hooked to the UIM would increase oil consumption. What part of Mazda's design makes the air bleeds necessary?

slightly off topic but still related: doesn't the middle nipple on the front of the UIM go before the throttle plates? I thought it was to recirculate the crankcase vapors from the PCV, which I have removed and replaced with a catch can. I was thinking of running my primary injector air bleeds to that middle nipple, and my secondary injector air bleeds to the rear one (s5 has secondary air bleed nipples)

Another weird thing. I looked very closely at my S4 and s5 turbo UIMs and I cannot see how those nipples draw air from before the throttle plates. It looks like the air passages just go into the the plastic gasket/spacer thing between the UIM and TB.

 

I'm still not sure how the entire air bleed thing works...either way I'm still looking for an answer if anyone knows. I have the air bleeds all tee'd and hooked up to a nipple on the LIM (extention mani.? w/ the aux ports) close to the block. My builder told me this was OK, will this create a vacuum/boost leak?

 

Your builder is ignorant. Not stupid, but ignorant of how thing work. Ther'es a huge difference b/t stupid and ignorant. I'm ignorant on how a number of things work. Like my 401K (along with my Fidelity account mannager).

The upper nipple on the oil injectors does NOT not NOT not reciever vacuum. It gets AIR that comes from the front of the throttle body. NOT an area of VACUUM.

The last thing in the wide world of sports, is for the upper nipple on the oil injectors to get VACUUM. For one thing, if the check valve internal to the oil injector fails open, then the VACUUM that would be put on the upper nipple would suck the oil out of the OMP rapidly and go to the place called NOT WHERE THE OMP OIL IS SUPPOSED TO GO.

The only SUCTION (read vacuum) that the oil injector sees, comes from the rotor inside the engine on its intake stroke. That vacuum pulls oil from the OMP and the air from the upper nipple , into the combustion chamber.

I probably shouldn't have written the above, but I"m torqued. The pages out of the training manual should have explained things a bit. Better than I, I'm sure. But in the end, when all is said and done, the upper nipple on the oil injectors gets fed from the large diameter nipple on the back of the throttle body. The large nipple that is in the row of nipples I posted in a jpg earlier. That IS NOT A SOURCE OF VACUUM. I LIKE ALL CAPS MYSELF. AGAIN IT IS not A SOURCE OF VACUUM.

I'LL NEVER VISIT THIS POST EVER AGAIN , SO HAVE AT IT.

 

On the S5 NA ATX TB and UIM there is no large diameter nipple for pre-TB air...all three are the same sizes, guess I'll remove the TB and see where each one goes. Either way from the info in your post, vacuum would be fine for the oil injectors to receive since there is a check valve that keeps the oil from being sucked into the manifold...but I'll go ahead and stick with the stock routing.

 

^ re-read what he said. The oil injectors should never receive vacuum.

 

here is quick diagram in case anybody is still confused



as you can see, if vacuum is connected or if the ports are capped, excessive oil will be injected. you want atmospheric pressure before the throttle plates. In a boosted motor it does not matter if there are external check valves, the injector check valve should still work like normal

and the bit in the training manual that says during the compression period, the check valve closes to prevent backflow isnt completely correct, since the oil injectors never see pressure from rotor compression, only from intake compression from boost