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.

thewird

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.

https://www.rx7club.com/attachment.p...1&d=1245040833

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.

https://www.rx7club.com/attachment.p...2&d=1208647985

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.

mine are just vented to atmosphere with little filters on them.

works fine.

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.

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.

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.

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

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.

You're good to go :bigthumb:

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.

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 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.

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.

Thanks for the clarification guys.

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.

thewird

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.

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. :confused:

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? :icon_tup:

thewird

Yes that's correct thewird.

Word :lol:

thewird

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.

https://www.rx7club.com/attachment.p...1&d=1245198789

https://www.rx7club.com/attachment.p...1&d=1245198789

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.

https://www.rx7club.com/attachment.p...1&d=1245199372

Some help, this throws pre-turbo out of the water ^

thewird

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

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

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.

Vented is fine. The amount of unfiltered air is very small. But of course a small filter on them works too

I'm getting confused now... I thought I had this lol.

thewird

The above pic is incorrect in both ways. For one, the factory has your blue air nipple to the OMP nozzle attached to the pre turbo inlet (constant vacuum source) not after (which is both vacuum and boost). The location in your pic will subject the air line to boost. You should never have boost pressure at the OMP nozzle nipple. The only way the OMP nozzle is subjected to pressure is when the combustion chamber itself is under boost. When the combustion chamber in under pressure (I'm talking pre compression event of the rotor), everything in the intake track (except pre turbo inlet) is under boost pressure.



Edit: I just notice that you were referring to the 2nd gen setup. I don't know the routing of that set-up but your explanation of having a vacuum in a pressurised environment is wrong. You can't have pressure and a vacuum in the same location. Example... The water main to your house is under pressure. Every line it's attached to is under pressure (bathroom, kitchen, exterior line etc). When a turbo is making boost pressure, everything in the turbo outlet becomes pressurized.

arghx the FD in stock form has the oil metering injectors air line connected before the turbo. This is the source they refer to as fresh air. The amount of vacuum created by the turbo at during idle is not enough to offset the vacuum created by the engine. The only significant amount of vacuum created by the turbo would be under boost, but in this case the check valve would be closed.

I don't think the air port is for atomization. The nozzles mostly just dribble oil out much like a chainsaw blade receives lubrication. Also I never noticed the compression stroke having an effect on either the oil metering air ports, in which I had a check valve in 1 fail, or on the injector atomizing line. There is no check valve for this line and it will draw a constant vacuum when not plugged or connected to the boost pipes. There is no pulsing of air between intake and compression stroke. But under boost there is definitely pressure from the other side. Both these lines seem to behave similar to any other connection on the UIM or LIM nipples. Positive pressure generated under boost and negative pressure under deceleration and idle.

So the options available are:
Like a Stock FD: Which is right before the turbo inlet
Vented: nothing connected but could allow unfiltered air to enter under vacuum situations
Vented with small filter(s): Allows them to vent without sucking the oil out of the lines keeps air clean

Connected like T2:....? I never knew the T2 was connected to the hard pipe before the throttle body, did these models have a check valve built in? If not this might explain this method. Sounds like this is another option though mazda did away with this design for some reason?

Regarding the T2,

From the factory, the OMP lines are connected to a splitter which connects to a nipple on the UIM. That nipple is a passageway that goes before the throttle plates. It sees boost all the time. In fact, that line blew off on my car and cost me a motor. There is absolutely nothing wrong with the OMP ports seeing boost. Mazda does it from the factory.

https://www.rx7club.com/attachment.p...1&d=1243186262

On the FD under boost (according to a gauge),

Follow the green arrows from the precontrol and wastegate actuators. The air starts in the compressor outlet (boost), feeds the wastegate and precontrol actuators (there is always air passing through at least one of those actuators), and then goes into a chamber of some sort ( I've never looked at it closely ) that distributes it to the OMP injectors. The final stop is at the compressor inlet. As you can see, the air is being pushed into OMP injectors. There is no major difference among the series 4 through 8 in the atomization design.

http://i23.photobucket.com/albums/b3...d/vacrack2.jpg

a 2nd gen routing diagram. The OMP has a 4-way splitter for the 4 OMP injectors. The splitter is connected to the UIM. That port never reads vacuum, but I can attest to the boost that comes out of it as it blew off, causing a bad MAP sensor reading and serious detonation.

I disagree.

https://www.rx7club.com/attachment.p...1&d=1245216564


Also, I am hesistant to use the terms "vacuum" and "boost" because it leads to confusion. I don't want to get caught up in semantics and terminology. If the way I explained some of that seems contradictory, just ignore it or don't otherwise let it obscure my point.

Do you know if the T2 OM nozzles have a check valve built into them?

Okay I wasn't sure if that was a description for the FD or the T2. I wonder why they changed the design on the FD and gave it just filtered air rather then pressurized air like it's predecessor. Maybe they were kinda learning as they went too. Which is why everyone is now so confused. lol

Screw it, just hook them up to something....... anything, including nothing haha.

Just make sure the check valve works or you will have a mess.

They do receive pressurized air, that's what I pointed out when I edited my last post which you may have missed. The OMP atomization ports are connected after the precontrol and wastegate actuators in terms of the flow of air. The pressurized air flows from the compressor outlet to the wastegate/precontrol actuators, to the wastegate/precontrol solenoids, and then either to the OMP injectors or back to the intake. It's no different than the charge relief valve venting pressurized air back to the intake. If anything were to be hooked in with the charge relief recirculation it would also be receiving pressure.

The overall design is the same between the 2nd and 3rd generation cars. But like everything on the FD, it's just more... confusing.

My car hasn't been stock for awhile but i'm fairly certain it connects to the plastic elbow on the front of the primary turbo, which would be filtered but not pressurized air

Yes even in the diagram you can clearly see the teal colored line connects to the plastic elbow on the primary turbo, this elbow doesn't have pressure the filter connects to this elbow. I don't know what the turbo control solenoids are doing on that line, either they vent back here somehow or the labeling is not clear, but I clearly remember the oil metering lines going to that plastic elbow which definitely does not have positive pressure.

^^Correct.

nevermind.

Ok good. arghx was confusing me lol. Thanks.

thewird

I read this and am confused. I just installed single turbo. I want to keep my omp. Do I route these lines to the turbo filter? Open to air with filter? Or just connect it to one of the unused ports on the UIM? or..other?

From the factory, these OMP 'breather' lines get filtered air from the turbo filter. Running a new line to the turbo filter on your new setup should be fine.
Many people, myself included, have connected them to atmosphere using small breather filters. Doing this should be fine also.

Routing them to the intake manifold will cause problems, don't do that.

I know this is resurrecting an old thread, one thing missing from the check valve, vacuum, boost, conversation is that the nozzles see the same oil pressure the engine is generating. So you must consider the differential pressure between the air and the oil pressure. As long as you're not generating more boost than you are oil pressure you should have a positive gauge pressure at the nozzle so oil is going IN the nozzles.

I don't think that's correct. The oil pressure that the rest of the motor sees is regulated by the OMP (literally the metered part).

The job of the vacuum line to the nozzle is to allow the motor to suck air in at low load when there's no oil being metered in by the OMP, otherwise, the motor would suck oil out of the lines, which would then be empty for a moment under load, when it occurs, before the OMP could refill them.

The nozzles have a super low crack pressure, like less than 1 PSI. But vacuum/boost aren't used to activate or trigger oil injection. The nozzle is just a banjo fitting with a check valve on top of it.

Final thought: If a nozzle becomes blocked, or the check valve fails, you'll get oil wherever its routed to, and it can be a mess, but it's nowhere near the mess you'd get if it was a constant 90psi oil.

I’m not so sure on the FD, but the Renesis S1 OMP is a positive displacement metering pump driven off the e-shaft that has no engine oil pressure at all

so I’m going to speculate that the engine oil pressure statement is possibly not correct.
.

Good point. The plastic OMP lines certainly don't look like they are built to experience engine oil at 100psi pressure.

Being a non-engineer I probably said it incorrectly, but its what I meant to imply. Any oil in the OMP lines is put in there by the OMP, and not under engine oil pressure. I'm not sure if the OMP sees any pressurized input, but whatever comes out of it is not engine oil pressure.

The OMP receives the same pressure as the engine sees, it does nothing in controlling the engine oil pressure. The engine oil pressure is regulated by the regulator valve on the rear iron.

Semantically speaking, "metered" in this sense is not pressure, it's volume. It is metering a volume of oil to the engine combustion chamber. If it was pressure, then it would be called a regulator. But the combustion chamber doesn't care about the pressure of the oil, it's the volume of oil.

What I meant on the differential pressure is the difference between the pressure inside the chamber and the pressure on the air inlet of the nozzle. If the pressure in the chamber is lower than the nozzle inlet, oil and air will be sucked into the chamber. If the pressure in the chamber is equal to or greater than nozzle inlet, the check valves are closed. In which case, the positive displacement of the OMP will push oil into the chamber.

At low load, the cam in the OMP has no movement, and thus no positive displacement. The spool (sector valve) takes in oil at current engine pressure, and then the spool bleeds the pressure off into the OMP line. So it's more like a dribble at low load. (shown in the 1800ohm position in the graph below). At low loads (no boost), the engine vacuum sucks out the oil and uses the air to atomize the oil.

At high load the cam in the OMP has about 2.5mm of movement, and that changes it to a positive displacement pump. So, like before, the spool takes in engine oil pressure, and then when the spool is aligned with the outlet ports you bleed the oil into the line. But now, you also drive the cam forward and push more oil volume through the line, and forcing oil into the combustion chamber. (shown at the right on the graph). Under boost, the check valves prevent air being forced out of the nozzle air port and into the oil line.

So the oil pressure in the spool is at engine oil pressure, then it closes off and that pressure is stored in the spool. When the spool is aligned with the outlet port the spool pressure gets bled into the line.

And the plastic lines are really small OD/ID so they can take a lot of pressure. Commercially available nylon lines the same size can easily take ~200-300psi. Think of a road bike bicycle tire, You pump those things up to 80-90psi, but a drag tire is like 3psi. It's all about the volume. But I digress, the plastic lines aren't a limiting factor in the OMP's operation.

from the omp declassified thread.
https://www.rx7club.com/3rd-generati...art-ii-895388/


https://cimg0.ibsrv.net/gimg/www.rx7...d68fe81a78.png
https://cimg0.ibsrv.net/gimg/www.rx7...37b424986c.png

I don't think that disagrees with what I said, save for one point. I don't think the oil in the OMP lines is at engine oil pressure. I've had the check valve in the nozzle let go several times, and while it's a mess, it's not a 100psi of oil mess.

I think we are kind of saying the same thing, but maybe coming at it from different ways. So you're right in saying the oil pressure in the omp line at the nozzle is basically nil. I don't disagree with that.

Here are some simplified pictures of the operation.

1. When the spool is rotated and aligns with the engine oil pressure port, (p1) the body of the omp is filled with engine oil pressure (p2=p1).
2. The spool rotates, trapping the engine oil pressure. So p2 is still equal to p1.
3. The spool rotates to the omp line port. At the instant the port is uncovered the body pressure (p2) is still at engine oil pressure. And then the pressure is bled off to the line pressure (p3) because the volume of the line is much greater than that of the body, and the line pressure is at or below ambient because of the check valve direction.

So for a very very short instant, and a very very short distance the omp line pressure at the omp is at engine oil pressure, at the nozzle, it's definitely negligible. Is it going to build up to engine oil pressure if the check valve is blocked? Under low load/rpm? No, there's no pumping action. Under high rpm/load? Maybe? I haven't tested how much pressure the pump is capable of producing.

And even with that said, the OEM lines have way more pressure holding capability than required. They are in no way a weak point of the system. The only reason to upgrade them is because you can't find the OEM ones or just want bling.


https://cimg3.ibsrv.net/gimg/www.rx7...041af50c65.png
https://cimg4.ibsrv.net/gimg/www.rx7...8a1e62e246.png
https://cimg5.ibsrv.net/gimg/www.rx7...1ebb95ec61.png

100% agree, aftermarket lines aren't necessary, the factory are quite adequate. Maybe even preferred, since you can see what's happening in them.