3rd Generation Specific (1993-2002) 1993-2002 Discussion including performance modifications and Technical Support Sections.

How much Vacuum do OMP Nozzles Need to Open?

Old 06-14-09, 11:06 PM
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How much Vacuum do OMP Nozzles Need to Open?

Does anyone know how much vacuum is required for the OMP nozzles to open? Reason I'm asking is that I have a single turbo so I plugged the OMP lines into the intake as seems to be generally accepted practice since it should always be generating vacuum. Recently I'm wondering if there really is any vacuum at idle for example. During boost it shouldn't be a problem but I really wonder at idle. So yah, anyone know how much vacuum they need to open?

I might have to hook up a boost gauge on that line and see how much vacuum is being generated at idle if any.

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Old 06-14-09, 11:47 PM
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I'm not sure I understand your question, and I feel that the question itself is based on an incomplete understanding of how the OMP injectors operate. Remember that manifold vacuum is a pulling force that acts on wherever you connect that vacuum to. A pulling force on the injector nipple moves in the exact opposite direction that it was designed for.



2nd generation OMP injectors shown here (2nd gens also inject into the manifold), operating principle is the same. The OMP nozzles are greatly misunderstood. Vacuum is applied from the engine itself, on the bottom side of the check-valve. The top port is for atomization just like the atomization port for the primary injectors. Blocking them off is a bad idea, it accomplishes absolutely nothing except potentially reducing the lubrication properties of the injector. They need to be routed to a fresh air source.



You can see in this simplified sequential vacuum routing diagram (light blue line) that the oil injectors are fed fresh air that is plumbed in with the outlet of the factory boost control vent solenoids, which are also fed fresh air.

I hope that clears up any misunderstandings.
Attached Thumbnails How much Vacuum do OMP Nozzles Need to Open?-oil_injector_operation.jpg  
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Old 06-15-09, 02:08 AM
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mine are just vented to atmosphere with little filters on them.

works fine.
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Old 06-15-09, 02:41 AM
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FYI:

From the Series 8 SAE pdf:

Apex seal lubrication has become a critical issue. In a race engine, oil supply to the rotor housing by means of injection was precisely monitored and controlled, whereas in the production unit, a larger amount is supplied, just to be on the safe side. Some of the lubricant is fed into the trochoid chamber through a metering nozzle. The previous nozzle's oil passage was 2.0 mm (0.08 in.) in diameter. Negative pressure created in the rotor chamber would cause all the oil within the nozzle to be sucked out. When the engine accelerated rapidly, oil supply could not keep up with the speed. To prevent oil starvation, the previous system supplied a larger amount of oil to be on the safe side. In the new metering nozzle, the passage diameter has been reduced to 0.08 mm (0.003 in.), halving its volume of 0.0005 L (0.03 cu. in.). A new rubber seal is also inserted to fill a gap within the nozzle body where oil used to be sidetracked. Now, there is still some oil left within the nozzle after each suction, so that the lubrication system responds to the apex seal's requirement.
Apparently, all new oil nozzles are of the Series 8 type......can't buy the older type anymore.
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Old 06-15-09, 03:33 AM
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The oil metering nozzles have an oil metering pump that supplies a certain amount of oil to them. On the top of the nozzles is the vacuum port, this port should see filtered air (preferably). The design is to keep the engine vacuum from sucking all the oil out of the lines. Instead it sucks in filtered air much like a hole in the side of a straw would prevent you from sucking up a glass of water. Inside the nozzle is also a check valve that keeps oil from shooting through the vacuum port under boost.

Some people have capped the vacuum ports and claim no increase in oil consumption or change in function, whether this is true or not I couldn't say, but the design from the factory is explained above.

So to answer your question zero vacuum is required to open the metering nozzles.
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Old 06-15-09, 07:10 AM
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You do not need engine vacuum to open the nozzles! I don't want to argue this situation either. I have my nozzles routed to a small filter and they work at all times. They just need a filtered air source. Your last resort is to tap your air filter coupler on a single turbo setup.
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Old 06-15-09, 08:25 AM
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I was under the impression that vacuum was required to open the nozzles and the oil metering pump just metered the flow oil at varying RPM's and temps.

So if my understanding is correct, having it tapped between the filter and the turbo is perfectly fine then?

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Old 06-15-09, 09:29 AM
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Question

Originally Posted by Gomez View Post
FYI:

From the Series 8 SAE pdf:



Apparently, all new oil nozzles are of the Series 8 type......can't buy the older type anymore.
Thanks for the info Gomez

Does anyone know where I can find these small rubber seals? On my new rotor housings I seem to have lost one. Ray at Malloy can't get them unfortunately.
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Old 06-15-09, 09:32 AM
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Originally Posted by thewird View Post
I was under the impression that vacuum was required to open the nozzles and the oil metering pump just metered the flow oil at varying RPM's and temps.

So if my understanding is correct, having it tapped between the filter and the turbo is perfectly fine then?

thewird

You're good to go
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Old 06-15-09, 10:06 AM
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The air lines (not vac lines) are there to make sure that the suction during the intake stroke does not pull extra oil through the OMP - rather it will pull a small amount of air. This also helps with atomization of the oil. There is a check valve in the nozzle that prevents boost from blowing oil out that line.

As noted in the hose diagram above, it should pull filtered air from before the turbo.
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Old 06-15-09, 02:56 PM
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I've seen quite a few setups where the OMP squirters are attached to a boost source on the LIM or UIM. Definitely not what you want......
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Old 06-15-09, 03:49 PM
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I would think that running the injectors air port to atmosphere (via a filter just popped on there) would only create a different injection amount during idle and conditions in which the engine is under vacuum. The only difference in the injection would then be a little bit more than usual.

Am I understanding this properly?

Because I would just run them this way since I am injecting 2 stroke straight into in anyways. A little extra can't hurt.
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Old 06-16-09, 05:09 AM
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Originally Posted by GoodfellaFD3S
Does anyone know where I can find these small rubber seals? On my new rotor housings I seem to have lost one. Ray at Malloy can't get them unfortunately.
Seeing they're selling S8 engines over your way, expect late engine gasket kits are available too, which have them included....small hole in the plastic clingwrap, presto! Otherwise they're available on their own...N3G1-14-634 (Mazdacomp(?) or offshore vendors), not entirely convinced they have an effect, unless the late oil pump and ECU is used.
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Old 06-16-09, 10:08 AM
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Thanks for the clarification guys.

Originally Posted by GoodfellaFD3S View Post
I've seen quite a few setups where the OMP squirters are attached to a boost source on the LIM or UIM. Definitely not what you want......
I also noticed this while tuning a car on a newly rebuilt motor (non-sequential conversion). At the time I had thought that vacuum was required to open the nozzles so I plugged it into the pre-turbo pipe. This was the correct thing to do but I had a different idea of how the system worked.

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Old 06-16-09, 10:47 AM
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Originally Posted by Monkman33 View Post
I would think that running the injectors air port to atmosphere (via a filter just popped on there) would only create a different injection amount during idle and conditions in which the engine is under vacuum. The only difference in the injection would then be a little bit more than usual.

Am I understanding this properly?

Because I would just run them this way since I am injecting 2 stroke straight into in anyways. A little extra can't hurt.
No the injection amount is the same. The omp is what determines how much is injected. The air port is there to keep the engine from sucking the oil out of the lines and past the omp. Whether the air port is connected to small filters or before the turbo doesnt change their opperation. The best way is to run the omp and premix a small amount like 4-8 ounces per tank.
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Old 06-16-09, 06:11 PM
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Originally Posted by Dudemaaanownsanrx7 View Post
Whether the air port is connected to small filters or before the turbo doesnt change their opperation.


This doesn't make since to me. In the above fd diagram, the OMP air ports lines are attatched to a constant vacuum source (pre turbo). How could the operaton of the OMP nozzles not change if they are vented to the atmosphere (no suction)? If vented through the atomsphere, you will loose the continous suction though the air port. With a good functioning OMP nozzle, you can blow air though it but you can't suck through it. Knowing the way the check valve operates, I'm still confused as to why the air nozzles are hooked to vacuum anyways.
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Old 06-16-09, 06:19 PM
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Originally Posted by t-von View Post
This doesn't make since to me. In the above fd diagram, the OMP air ports lines are attatched to a constant vacuum source (pre turbo). How could the operaton of the OMP nozzles not change if they are vented to the atmosphere (no suction)? If vented through the atomsphere, you will loose the continous suction though the air port. With a good functioning OMP nozzle, you can blow air though it but you can't suck through it. Knowing the way the check valve operates, I'm still confused as to why the air nozzles are hooked to vacuum anyways.
The turbo only generates significant vacuum under boost when the check valves are closed therefore nothing is being sucked. During vacuum the engine's vacuum is overcoming any possible vacuum being generated by the turbo so fresh air is getting to the nozzles.

Is that right guys?

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Old 06-16-09, 06:49 PM
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Yes that's correct thewird.
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Old 06-16-09, 06:50 PM
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Originally Posted by Dudemaaanownsanrx7 View Post
Yes that's correct thewird.
Word

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Old 06-16-09, 07:35 PM
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Don't let the terms "vacuum" and "boost" confuse you. Pressure and vacuum are all relative terms. They are forces in relation to a reference point. Draw diagrams and think about it. Venting to atmosphere is an acceptable solution, otherwise it must be routed before the throttle plates as long as it is not in the turbo inlet. From the factory, the single turbo 2nd gen cars were routed before the throttle plates but not before the compressor inlet.





Re-read Mazda's description of the operation of the OMP check valve. The OMP check valve opens and closes in relation to the 4 stroke combustion cycle. So it is opening during the intake stroke and closing during the compression stroke. This is regardless of whether your boost gauge reads vacuum or boost. The injectors should be hooked up the way Mazda did it from the factory, in the sense that there is always an absolute pressure difference between the bottom and top side of the OMP injector. From the factory, there has never been an Rx-7 that has the OMP ports tied to any kind of pulling force that opposes the force on the bottom side of the check valve.

Attached Thumbnails How much Vacuum do OMP Nozzles Need to Open?-omp_routing_1.jpg   How much Vacuum do OMP Nozzles Need to Open?-omp_routing_2.jpg   How much Vacuum do OMP Nozzles Need to Open?-vacuum_routing_3.jpg  
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Old 06-16-09, 07:47 PM
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Some help, this throws pre-turbo out of the water ^

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Old 06-16-09, 08:12 PM
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ya right now mines vented to fresh air but seeing this iam gonna hooked it up right after the turbo before my intercooler.87 TII


thats what your saying right?lol

sorry
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Old 06-16-09, 08:13 PM
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I love that handmade drawing. It would be funny if you turned it into a flash video with flashing symbols, blinking dots, more dots, more dots, more dots...

http://www.youtube.com/watch?v=HtvIYRrgZ04
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Old 06-16-09, 08:42 PM
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Originally Posted by maac0953 View Post
ya right now mines vented to fresh air but seeing this iam gonna hooked it up right after the turbo before my intercooler.87 TII


thats what your saying right?lol

sorry
Negative. Then the line would see boost, which is not what you want. Hook it up between your air filter and the compressor housing of your turbo.
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Old 06-16-09, 09:22 PM
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Vented is fine. The amount of unfiltered air is very small. But of course a small filter on them works too
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