Simplified Sequential

[afterburn27]

Glad to see you got the sequential system working David. The stock setup is really fun with a few mods. I certainly miss it and I have only driven my new setup for about 10 miles. lol

There seems to be a lot of confusion about the oil injector nipples and why they are plumbed into the primary intake elbow.

Simple answer... it was an easy place to source FILTERED air for the injectors. Under vacuum there is air being sucked into the engine through the injector nipples, and Mazda wanted to prevent dirt/dust/etc. from damaging the internals. The idea that they need vacuum to operate correctly is a MYTH. Hopefully I can explain...

First, the intake elbow is NOT a source of constant vacuum. It is atmospheric pressure. Anyone who has installed a vacuum gauge before the throttlebody on any car will know this. Under idle/light load the air in the intake elbow will be at atmospheric pressure. Under heavy load/boost there will be a VERY slight vacuum, negligible in comparison to vacuum that is seen after the throttlebody. I actually calculated the vacuum you would see under full boost and it was tiny. You would probably see slightly more vacuum if you were running a crappy air filter. But for most cases there is NO vacuum in the intake elbow. If Mazda wanted to provide a true constant source of vacuum they would have utilized a vacuum chamber.

If you take apart an oil injector you will see that it is nothing more than a banjo bolt with a check valve on top. There is nothing complicated about this check valve, it is simply there to prevent boost (and oil) from spraying back out under manifold pressure. Pics of a dissected check valve can be found here: (http://www.rx7club.com/forum/showpos...1&postcount=16). I have verified this with one of my old injectors as well.

When the engine is under vacuum it is “sucking” on the injectors. The check valve is open in this situation and allows filtered air to pass through the injector and enter the intake chamber. If the injector nipples were capped the engine would be placing excessive vacuum on the OMP lines and would quickly empty them. The OMP would not be in complete control of the amount of oil injected into the engine, the oil would be sucked out instead of letting the OMP “meter” the correct amount of oil.

DamonB has posted a great analogy of this process on the other forum:

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.

When the engine is under boost the check valve is closed and the VERY small amount of vacuum applied to the injector nipples is not affecting the injector operation in any way, shape, or form. Again, the vacuum created in the intake elbow under boost is very small and would barely read on a typical vacuum gauge. When there is positive manifold pressure the OMP must overcome the boost inside the engine, which isn’t very difficult since the diameter of the injector nozzle is so small.

So, in summary the oil injectors should be provided with a source of filtered atmospheric air. It just so happens that a convenient location for this is the turbo intake. Personally, I use a pair of leftover solenoid filters. Do not cap the injector nipples, or plumb them in to a location that sees boost pressure. If you like to gamble you can just leave the injector nipples open, but be aware that there is a slim chance for some dust or other particles to enter your engine and cause damage.

Hopefully this helps a few people.