ranger306ci

What is the purpose of the vacuum lines on my metering oil injectors on my '85 13b?
I know the answer will probably be pretty simple, and I will end up beating my head against the wall..................

ranger306ci

equalize pressure among the oil injectors?I know that the vacuum lines don't supply a vacuum, they let air in. The lower pressure is inside the engine.

RotorMotorDriver

iTrader: (1)

There are no vacuum lines that I know of, are you sure youre not thinking the oil lines are vacuum lines? As far as I know, the oil is pumped from the oil metering pump (OMP) up to where it gets injected into the housings on the 13B and the intake on the 12A. No vacuum lines anywhere.

~T.J.

ranger306ci

13b's are different, dude. You have 4 clear lines(oil) that run to 4 oil injectors. On the end of each injector a vacuum hose is hooked up, that runs to the inlet side of the throttle body.
So, each injector has 2 lines to it; an oil line, and a hose line. Like I said, the vacuum line is not actually a vacuum source, the vacuum source is the engine. It sucks through the oil injector, and fresh air is drawn in through the vacuum line.

RotorMotorDriver

iTrader: (1)

Gotcha, didnt know that, thanks .

~T.J.

EDIT: So if you havent figured it out then, I would say youre right they equalize the pressure so the engine doesnt just suck oil in through a straw, this way the pressure is released and it can truly be metered into the engine. Right?

gsl-se addict

iTrader: (3)

The purpose of the lines, as I understand it, is

1. To better atomize the oil

2. To equalize pressure as you and T.J. have already mentioned

As you said, the pressure is lower (higher vacuum) at the base of the injector than at the other end of the vacuum line, so the air flows into the oil injector. In addition there is a check valve in the top of each injector that only allows air to flow in that direction. The oil is pumped into the center of the injector via the OMP, while the air flow from the vacuum line pulls the oil into the engine and breaks the oil up into finer droplets in the process.

If you didn't have the lines the vacuum would pul the oil up the OMP lines, as T.J. said. With the check vavle and the air line, as vacuum is generated, air is allowed to enter through the top of the injector, eliminating the vacuum draw on the OMP lines. It could just as well have the vacuum lines removed with atmospheric pressure on the other side. But Mazda chose the route becuase the area before the throttle plates, which is basically at atmosphric pressure, but the air has been passed through the air filter, so it is clean.

Kent

ranger306ci

Beating my head against the wall now.............................

ranger306ci

So how is it different in a turbo application, where the air may not be at atmospheric pressure, but boosted?

gsl-se addict

iTrader: (3)

I am not real familiar with the turbo system, but it appears to be the same. The actual pressure doesn't really matter, it is the pressure difference that is important. On a turbo setup, both the vacuum reference line (before the throttle plates) and the injection end of the oil injector should both see boost so it is the pressure difference between the two points that allows for the flow of air through the injector.

The only real difference I can see is that the OMP will have to overcome the boost pressure to deliver the oil to the injector. I did take a look at the FSM for the second gens and the turbo OMP does have a higher output.

Hyper4mance2k

iTrader: (40)

thats why when you go turbo you start premixin'

LongDuck

Something that has not been mentioned above is that the oil vacuum lines coming from the Dynamic Chamber go through a 'spider' to split the single DC vacuum line into the 4 oil injectors. This spider also contains the one-way valve so that oil cannot be drawn back up the lines into the intake, as might occur if an oil injector clogged, or if the oil metering pump line to the injector broke.

My understanding of the vacuum source being applied to the injector is that the opposite pulses of vacuum, combined with the one-way valve, will result in oil being 'squirted' from the oil injector into the intake air path (for the intake manifold mounted injectors), and into the top of the rotor housings (for the apex seal injectors). As mentioned above, this helps to atomize, or break up, the oil flow into smaller particles, allowing it to cover more surface area and provide better lubrication.

It's the action of the 'pulsing' of the two vacuum sources at 1) the Dynamic Chamber, and 2) the intake stroke of the rotor that result in the metering of oil through the injector. HTH,