Originally Posted by HAI-TEK7

or they both get oil at all times?

Originally Posted by DaleClark

rotor coming by on the intake stroke is what sucks the oil out of the injector.

Dale

Originally Posted by rynberg (Post 4278364)

I just learned this week about the check valve function of the oil injector nozzles (thanks Rick). The check valve is necessary to prevent boost from blowing oil right back down the vacuum lines leading to the turbos. I wonder how many people have thought their turbos were bad and blowing oil when their oil nozzles had failed instead....

Originally Posted by katit (Post 7689669)

Old post, but I'm curious.

Where those vacuum lines go?

Originally Posted by katit (Post 7690466)

Hm. So, those pipes have vacuum then. They basically suck oil into turbo. How did it happen that they got blown off the nipples? Is there any pressure there?

Originally Posted by afterburn27 (Post 7692339)

The primary turbo intake elbow shouldn't see vacuum or pressure. Well... there might be a slight vacuum, especially if the turbo is sucking air through a clogged airfilter. But I always assumed that they just used that location to source filtered air.

Originally Posted by katit (Post 7692362)

Source air? Why do they need to source air? I understand it that vacuum hoses on oil injectors is nothing but a solution to collect spit out oil (which shouldn't be spit out)

Since intake sucking air - there is enough to draw that oil into turbo.

I took turbos to rebuilder and also my primary turbo a little weak - he said that there is no way it was pushing oil. So, all oil came from OMP injectors into intake. And I got plenty of it...

Originally Posted by katit (Post 7693042)

I still wonder what is the deal with vacuum lines on injectors. What it's function?

Originally Posted by Mahjik (Post 7693078)

It's a vacuum source to keep the nozzle valves closed when they aren't needed (i.e. like at engine shut down time). Many single turbo guys eliminate the oil injection vacuum source. However, if you have the means to connect it, you should.

Originally Posted by BigIslandSevens (Post 7693081)

As to your other post about the lines being filled with oil... your injectors check valves have failed and you need to replace them. Do them both since you will be that far in anyways. Mine did this exact thing about 4 months ago. I also experienced fouled plugs every 4k miles. As well when the injectors REALLY failed completely( just started dumping oil into the intake under boost. Because the check valves were bad ;)), the ignition would break up when any boost was added. All the symptoms I had when they failed. I have a single turbo but the theory is exactly the same.

Originally Posted by afterburn27 (Post 7693364)

Do you have any documentation to back that up? I expected at least one link in your post! :lol:

Originally Posted by afterburn27 (Post 7693364)

The only time there should be a decent vacuum in the intake elbow is under boost when the turbo is really pulling air through the intake, increasing the velocity and fighting the filter. But remember that when the turbos are creating positive pressure in the manifolds and intake chamber, the check valve in the oil injector is going to be closed. No air is going to flow from the injector to the intake.

Originally Posted by afterburn27 (Post 7693364)

When the engine is pulling vacuum the check valve is open and needs to draw in filtered air, which is why I think Mazda used the primary intake elbow.

Here is something else to think about: what do the 2nd gen NA guys do? I'm pretty sure the oil injectors draw air from BEFORE the throttle body plates. Yep... no vacuum for them.

Originally Posted by Mahjik (Post 7693485)

Didn't think I needed it. However, there are lots of posts on these especially in the Single Turbo section.

Originally Posted by Mahjik (Post 7693485)

Basically, there seems to be a consenses of several ideas/functions:

1. To help meter the oil being sucked in. Without vacuum pulling in the opposite direction, the engine under vacuum would consume more oil as it would be "sucking" the oil through the lines. Thus rendering the metering sort of pointless.

2. To help ensure the oil injection lines are not empty when the valve closes (so the OMP doesn't have to fill the lines complete again to supply more oil).

Many shops cap the oil injectors when doing single turbo upgrades. So whatever the "exact" purpose of them doesn't seem to greatly effect people who remove them.

Originally Posted by afterburn27 (Post 7693710)

1: The vacuum from the intake chamber will be MUCH greater than whatever vacuum there is in the intake elbow.

Originally Posted by Mahjik (Post 7693747)

I suppose he's more creditable.

Originally Posted by HAILERS (Post 1014811)

The vacuum is coming from the rotors during their cycle. The vacuum is from the rotor chamber NOT from the throttle body. The *vacuum*hose on top of each oil injector goes to the spider. The spider runs to the large nipple on the back of the throttle body on a turbo and the large nipple on the front of a N/A. The passage in the throttle body leads to a quarter inch hole in front of the throttle plates. Therefore there is no vacuum coming from the throttle body. Its filtered air.

Yes, the flow of air is one way. Towards the rotor housing. Suction from the rotor. No air pump involvement.

Originally Posted by afterburn27 (Post 7694792)

5. NA FC's have the OMP 'vacuum' lines plumbed in before the throttle body... no vacuum there. And they use the same exact oil injectors as FD's. Oops, I guess Mazda messed up! This should be proof enough.

Originally Posted by Moejoe (Post 7696360)

If you have them off, why put stock bacl on SS is not that expensive and you know you will not have any issue with them . 14 years of heat and aging can make them brittle.

Originally Posted by Mahjik (Post 7696401)

Actually, this is what I would question. If Mazda changed them from the location of the FC's, there must be a reason. There is no denying that the FD location is a source of constant vacuum. While it might not but much all the time, it still is vacuum period. Maybe there is some use for the vacuum from that location as Mazda could have found a most easier way to get filtered air.

Originally Posted by Mahjik (Post 7696401)

It doesn't really matter as none of us are privileged to the actual Mazda technical documents about the car. So we are all just arm-chair mechanics guessing at its intended purpose.

Originally Posted by DamonB (Post 6388792)

The vacuum lines to the OMP injectors are plumbed to a filtered air source that does not see boost pressure. This means they plumb between the air filter and the compressor inlet as this is the only area that is filtered and sees vacuum 100% of the time.

Why do these vacuum lines exist? The OMP pumps oil into the motor via the injectors which really are just simple nozzles. When the manifold pressure is negative (vacuum) the engine is literally sucking on everything connected to the intake tract, this includes the oil injectors. The vacuum line provides a leak path to the oil injector so that when the engine is under vacuum and "sucks" on the injector it doesn't suck all the oil from the metering tubes. Instead the engine "sucks" filtered air through the leak path created by the vac lines and the OMP oil lines are not placed under excessive vacuum which would quickly empty them. If this happened the OMP would not be in complete control of the amount of oil ingested as whatever oil the OMP admitted into the tubes would be immediately sucked out rather than metered in small "doses". Without the leak path at the injectors the engine would merely suck as much oil through the tubes as it could get anytime the engine was under vacuum.

When positive manifold pressure is present the one way valves in front of the vacuum lines inside the oil injectors close. If there were no one way valves present inside the injectors manifold pressure would leak into the OMP system and pressurize the sump. Not only would you have a boost leak, you'd be pressurizing the sump. Both bad. When positive manifold pressure is present the OMP has to overcome the boost pressure inside the engine in order to deliver oil inside the motor but that's not very difficult since the diameter of the injector nozzles is so small.

An analogy of this would be you sucking soda through a straw. Imagine built into your straw was a pump that was supposed to control the amount of soda passing to your mouth as well as deciding how often to deliver a sip of soda to your mouth (this is what the OMP does. It decides when you get a sip and how big that sip is). If the pump were merely built inside the straw there are only two openings present; one in your mouth and the other in the drink. If you were to suck hard enough you could suck as much soda through the straw as you wished because you could suck it right through the pump, even if the pump were attempting to deliver a smaller amount of soda. If we inserted a tee into the straw between your mouth and the pump whenever you suck on the straw you'd merely suck air through the tee, allowing the pump to be in complete control of how much soda is delivered to your mouth no matter what you do at your end of the straw. We'd also install a one way valve in that tee so that when the pump is delivering soda to your mouth none of the soda goes out the tee, it all goes into your mouth.

As many have done you could eliminate the vacuum lines all together and leave the vac nipples on the oil injectors bare but that's not a good idea. This allows the engine to ingest unfiltered air anytime the engine is under vacuum. Everyone claims the OMP system works fine without the vac lines attached and they're right. The OMP system will work fine but your engine is ingesting dirty air everytime it's under vacuum. Poor choice.

My posts in this thread have further description on how the OMP works:

https://www.rx7club.com/showthread.php?t=60867

Originally Posted by afterburn27 (Post 7697167)

I'd be interested to see where the TII oil injectors draw air from. I would assume that Mazda moved it to a location that does not see boost. I'm tired of reading about oil injectors :), maybe I'll look into it this weekend.

Originally Posted by Mahjik (Post 7697282)

Uh, there are boosted TII's from the factory. :)

Originally Posted by Mahjik (Post 7697282)

However for ever post that you come up with that says it needs filtered air, there's a post just like it that says it needs a vacuum source. Other thread on the debate:

https://www.rx7club.com/showthread.p...ght=vacuum+oil

There are knowledgeable people on both side. However, none of them worked for Mazda and were also part of the team which designed the car, so you can pick and choose who you believe and who you don't.