Hi, i'm putting a T-78 on a third gen and have a question. The oil injectors on the
top of the rotor housings have a vacuum hose and when I was pulling everything apart I did not pay attention to where it was hooked up. Do these oil injectors get regular intake manifold vacuum?

 

NO. They are supposed to go to a constant source of vacuum. The only place for this is BEFORE the turbo. If you look at the Mazda vacuum diagram, they run to the plastic elbow on the front turbo. Basically the faster the turbos spin, the more vacuum they will produce on the intake side and open the pintle inside to allow more oil into the motor. On a single turbo car I drill and tap the compressor housing where the filter mounts. I can't believe so many people do this wrong.

 

There has been debate of this a few times.
A constant vacuum souce is the best way to run them as Mazda intended,
before the turbo inlet.

 

From everything i have read on the subject:

Before turbo inlet is not a constant source of vacuum. It is atmospheric. All those things need is filtered air. Some people dont even do that. Just dont cap them or hook them to boost/vacume and you will be fine.

 

Wouldn't a constant source of vacuum be the extension manifold? Was the intention of Mazda connecting preturbo to vary the vacuum and thus injection would increase as load increased? So more load would increas vacuum (preturbo) and thus more oil would be injected.

 

+1

 

Not if the turbos are working.

 

i cant think of anywhere that would be a constant source of vacuum without a one way check valve and a vacuum chamber. FD's do come with such things to control the stock TT system, but you wouldnt want to hook up your oil lines to that or you wouldnt have your secondary turbo

Mazda uses a stepper motor controlled by the ECU to determine how much oil it is going to inject. This is not determined by some mechanical means such as the vacume lines coming off of the oil injectors. I beleive the stock ecu uses decided how much oil it is going to inject as a percentage of gasoline injected. 100:1 is what they aim for.

Just vent to atmosphere (pre turbo is atmo) with a filter (or not if you dont care, i personally decided i dont care) and go about your merry way

 

constant vacuum ?
before the turbo...?

Before the trubo is atmosphere

otherwise if you change your air filter and pipes.. they have less restriction.
THen the vacuum source would be changed.
So no nay this is vacuum.
This is just filtered atmosphere air.

 

There is a drop in pressure at the compressor inlet, someting about drawing in 50, 60 maby 80+ lbs an hour though a 2.5 to 4" hole does that

 

Really ??? so why did an undersized filter on my big single collapse everytime I reved the motor ? One of my twins actually pulled out the round metal cap thing that the put on the inverted part of the filter !!! U saying that atmospheric pressure just caused it to pop off ?? U telling me that a compressor capable of moving 30, 40 ,50 + ibs/min of air wouldn't pull a vacuum at its suction ? you're dead wrong !!!

 

you are also right...

ehm.. I think it is time to test this sometime.
I will try to fit a vacuum meter to it and see what happens

 

What about people not using any filter? where do these guy plug their oil injectors?

 

The vacuum line goes to the compressor inlet... This is ridiculous if theres going to be a debate about this. Lets think about this. The turbo pressurizes air into the engine, right? Where does this air come from? The compressor cover! Now with the air flowing into the inlet low pressure is created. What does low pressure do? Draws a vacuum. Case closed

 

i actually have them vented to the atomsphere. no caps or vacuum. its been like this for 2 years now. knock on wood, no problems at all.

 

OK so when you guys say atmosphere you mean that your letting hose on both of the nipples on the intake hanging there, and its suppose to work alright?

I'm just asking because its not the first time i've seen someone claim that this is what they've done.

 

Thats what a lot of people do , but that doesn't mean its the right thing ! the things were designed to work with a vacuum source attached to the nipple ...it up to you if you keep it like that .

 

from http://www.rotaryresurrection.com/3r...ov_nonseq.html picture #5.

"The oil injectors each have nipples on top. In stock form, these nipples draw air from the primary turbo compressor inlet. This is simply a place to draw fresh air from, which is neither boost nor vacuum. You can elect to tee them together and run the feed line to it’s original source on the primary turbo inlet, but I personally tend to leave them open (just as they are) since the amount of unfiltered air they draw in is minimal and I feel it makes for a tidier install without the extra hoses. The engine will run the same regardless of what you choose. IF you want to plumb them as they originally were, tee them together and run a length of about 10” of hose in the front."