Yes - jet air line needs to get filtered / metered air from somewhere - if you put it pre turbo/blower you need to stop boost feeding back into the intake with a check valve .


Block this one off .


Connect to intake pre turbo/blower post maf - wants metered filtered air - must not see boost .

Connect to a catch can and then to either : intake pre turbo/blower OR vent to atmosphere .
And : Fit caps to the two nipples on the LIM .

Thanks. I have a blow through system, so I cant do anything pre blower/post maf, but the info helps and the topic has me thinking.

The OMP line could be hooked into a small filter i guess - was that the line that you were concerned about ?

or hooked up pre blower still is just fine.

To be honest I was never really concerned because drivabilty and power were good. I only got concerned when I noticed excessive oil in the intake/charge pipe.

Here is how I have had it hooked up.

Everything hooked up as stock with 2 check valves.

1-On the lower intake by the dip stick (allowing air to go towards the crankcase).

I am going to turn this around, I have been pressurizing the crank case and not letting it properly breath.

2- On the OMP line allowing filtered air to the OMP, you say it can not see boost, why? Under vacuum it works as stock and under boost, the engine is pressurized on both sides and the air flow should be stagnant. Atleast thats my thought and I think I read it somewhere.

I dont want to hook it up pre maf or open because then un-metered air is entering the engine. Yes it can be tuned for it, but its not ideal.

The Jet air and the filler neck breather are hooked up as stock.

For the breather, Instead of running a catch can, I think I am going to leave it hooked up as stock but add a check valve that will allow the engine to breath under vacuum but under boost no air will escape and pressurize the crankcase.

For the Jet air, because it is connected post blow/post maf, leaving hooked up as stock should work fine, again under vacuum it pulls in metered air and under boost both sides are pressurized.

Thoughts and opinions please and where do you think the oil has been coming in from?

so you have boost going into the crankcase , out the breather and back into the intake ?
That's how i'm reading that but without pics of your setup It is a little confusing.
Sounds like the two LIM hoses are still connected to the breather as well .

None of this sounds good and I'm not surprised you are getting oil in the intake - probably losing some power as well .



https://www.rx8club.com/attachment.p...1&d=1299485961



From the above I would conclude that i'ts not a good idea to pressurise the vac line as it may upset the operation of the check valve .

the OMP line does not feed air into the engine. so it doesn't need to be metered.

also sounds like the crankcase is the reason for your oil. you should really set it up open to atmosphere/catch can.

I am basicley thinking out loud here, so this may be full of incorrect info.

This is an 07 so the breather setup is different.

There is the oil filler neck to lower intake and the intake (charge pipe) to the bottom of the UIM by the dip stick. Both are part of the crankcase breather system.

I am pressurizing the crankcase in 2 ways.

-1st is the line from the intake (charge pipe) to the bottim of the UIM but only because I have the check valve installed the wrong way. My thought was that I wanted to keep oil from entering the intake (charge pipe), however that defeats the point of a breather. I will turn the check valve around so that the breather system can function as designed under vacuum but it will not be pressurized under boost.
2nd- The oil filler neck to the lower intake has no check valve on it, so under boost there is pressure that enters the oil filler neck and pressurizes the crank case. I will add a check valve here to allow air to flow from the ol filler neck to the lower intake manifold but under boost there is no crankcase pressurization.

However just because I am pressurizing the crank case does not mean I am loosing boost or air flow. Unless it is escaping out the dip stick tube or oil fill cap. I am probably loosing some but I think it is marginal. Either way I will fix the pressurization problem.

I am considering a catch can but my oil cant be coming from the breather system because the check valve from the bottom of the UIM is not allowing flow back to the intake (charge pipe) and the oil filler neck breather does not connect to the intake (charge pipe). So I am not sure where it is coming from.

This is the first time I am really learning about the oil meter pump and nozzles. The way I read it, the point of the vacuum line is to equalize pressure on both sides of the nozzle.

In NA form: When the housing is under vacuum (intake cycle), there will be equal pressure on both sides of the nozzle (inside the rotor housing and in the intake pipe). When the housing is in the compression, power or exhaust cycle, the pressure inside the housing will be greater then inside the intake pipe which is why there is a check valve to prevent pressure from pushing oil out the nozzle.

In FI form: During the intake cycle if the nozzle is exposed to boost, the pressure on the intake pipe side of the nozzle will be equal to the pressure inside the housing, so no air flow. During the compression and power cycle the pressure inside in housing will be greater then the intake pipe side. The only concern would be during the exhaust cycle. If the exhaust pressure is less then the pressure boost pressure from the charge pipe, air would be pushed into the housing and exhausted.

My Conclusion after doing a limited amount of research and basicly thinking out loud.

1-I do not think leaving the line to atmosphere with a filter is correct. If this is done, when the housing is under vacuum, the pressure inside the housing will be negitive and will suck in unfiltered and unmetered air.

2- Leave it the way it is. The way I see it, under intake compression and power cycles, there is no problem. My concern is during the exhaust cycle and while in boost, the boost could be pushed into the exhaust.

3- Attach the line pre blower/pre maf because I have a blow through system but post air filter. In the configuration with no boost, it will be identical to stock . While in boost the pressure inside the housing will be positive and the pressure from the line will be negative. Will there be a downside to this? Will this effect the proper operation of the oil metering valve?

I believe that when functioning properly the oil is only injected during the intake cycle when the pressure on both sides of the valve are identical.

With configuration #1 the pressure on the housing side will be negitive while in vacuum or positive while in boost, but never neutral which defeats the point of having the stock line attached to the intake pipe.

With configuration#2 the pressures will be identical and the oil nozzle will function properly.

With Configuration #3 while in vacuum the pressures will be identical but while in boost the housing side will have positive pressure while the line is under vacuum.

Yes you are ..................................don't do that ! Do you really think that 10psi of boost inside your crankcase is a good thing ?
Block off both the LIM and UIM holes and connect the oil fill breather to a catch can vented to atmosphere .
This is how practically every other FI owner does it and it works great. Just because you have some extra hoses on the later model does not mean they have to be hooked up to something . If you don't pick up 5-10whp by fixing this i'll eat my hat .

What about from your omp vac pipe install?


Do you realise that the oil nozzle does not follow the rotor around the housing ?
It is always in the suction part of the intake stroke and therefore should always be under vacuum in an NA car . Plus : as NGO mentioned earlier there is no actual air flow through the nozzles so a simple filter on the line will be fine .

I have a 07 as well..i just capped the lines to the intake manifold and ran a breather at the oil filler neck.

Also Highway : make sure you log AFRs after fixing this - you may find it will run leaner than previously . Another member was doing the a similar thing to you and his AFRs went way lean after fixing it , so has to retune now .

No I do not think my 12 psi in the crankcase is a good thing. I am going to fix this.


What is OMP vac pipe?

I have a check valve on the line to the OMP that will only allow air to the OMP and not back to the intake pipe, I did this to make sure no oil could enter the intake pipe.


HAHA I do now. Just a bad habit of thinking of it like a piston motor.

Its allways in the intake cycle so no matter what, the pressure will always be identical on both sides, both in vacuum or boost. Come to think of it, I remember reading about this on another thread and the concensious was that it can be left as stock.

To quote your diagram posted earlier, " the oil nozzle receives barametric pressure from the air hose to prevent negaitive pressure from the engine being applied to the oil inlet." This line MUST be connected to the intake pipe so that the pressure on both sides of the oil nozzle remain the same while under vacuum.

Fixing the breather issue, placing the OMP line pre turbo or letting the OMP line go to atmospher?

This is the thread I was refering too. https://www.rx8club.com/showthread.p...&highlight=omp

Sounds like I could leave it the way I have it now or hook it up to the LIM. I am leaning toward the LIM.

Good - please block off those excess holes and fit a catch can as suggested earlier.

....The vac hose going to the omp injector
Ditch all that and fit a filter like we said earlier.


Did you realise that the in the stock NA location it is at ATMOSPHERIC pressure (=Barometric ..........it's the same thing) or just a very slight vacuum at WOT.

The ONLY reason to connect it to the intake is because that air has been FILTERED !

Fixing the breather issue .....

Every time you go into boost you are filling up a very large reservoir with METERED boosted air . Feed that into the engine instead and your tune goes off . Still the same amount of air through the MAF but more of it now going into the engine .


OH - and guess where all that oily pressurised air is going to go when you back off the throttle ? If you guessed into the engine you are only 1/2 right ;)

I managed to get some parts diagrams (thanks to ASH8) for the 2006 -2008 models so have updated my first post to better show what to do with the extra hoses on those models .

this is a great Thread Brettus!!!!!!!!!!!

How did the factory turbo rx7's have there OMP plumbed?

Don't know . Unless the design is identical I'm not sure that info is relevant .

Update : It has come to my attention (heard of it happening 3 times now to different people) that the jet air hose WILL blow off at the point it connects to the steel pipe beside the thermostat unless it is FIRMLY ziptied .
The connection is shown in the red circle although the tie is obscured by the electrical wire in this pic . If you still have the air pump valve and tubing in place (I don't) then it will be harder to see from the angle shown .

https://www.rx8club.com/attachment.p...1&d=1299523538

Important : If you find that this hose has blown off and you suspect that the engine was tuned with it like this , your tune may lean out to a point where detonation could occur . Be very carefull going into boost after you fix this .

Zip tying it TODAY... Still curious as to if I should attempt to zip tie the other end or wait until I am doing some work that will make it easier to reach it

pic added

Have not heard of it blowing off there - i guess the hose is short and has to physically bend to come off so it is less likely .
Still , I'm glad mine is ziptied :)

Don't zip-tie it.
The JAB is directly above the exhaust manifold and zip-ties disintegrate very, very quickly in that location.
Use a small worm-gear hose clamp or a spring-type clamp.

/\ good point . Although mine has been ziptied for 2 yrs now ....