Question in regards to SOHN/OMP & Boost
 

Hi Folks

Dunno if this has been covered before, but i have a few questions in regards to how the OMP works.

To my knowledge the OMP in stock form receives oil through the engine oil lines, which means that the oil going into the OMP has some pressure behind it. So when the OMP opens up, the oil is pushed in using the car's oil pressure and/or vacuum from engine.

My question though is apart from that pressure is there anything else that actually forces the oil through the hole into the combustion chambers?

Reason i am asking that is, by looking at the OMP i cant see anything else that is actually pushing the oil through the hole, rather from my observation the stepper motor simply opens the hole at pre determined intervals allowing the oil to go through.

Now once you introduce the SOHN adapter AND Boost, i can no longer see what is actually pushing the 2 stroke into the chambers.

You have lost the oil pressure from the engine that was pushing the oil previously before, and during boost the air is now going the other way, which means it should be actively pushing the oil back out of the hole rather then letting it in.

Unless the gravitational force from the require amount of distance from the tank holding the two stroke to the SOHN adapter will actually provide enough pressure to push the oil in?

Anyone can shed some light on this?

Regards
Jason

It runs off engine vacuum, not the oil pump.

you may want to double check that

Nobody wants to bite?

I was hoping to revive this classic thread. You have to read the whole thing to appreciate all that is both good & bad on an intrawebz forum

OMP-how it works, modification for AMECU, discussion regarding premix - RX7Club.com


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Man.

its on the internet it must be true

Someone correct me on this if I have some misconceptions, but this is how I'd set it up...

Omp pumps. The pressure it recieves is negligible.

You need vacuum to open the injectors.

One way check vavles should solve everything. One for the oil injectors to ensure they are open. (Tied into im, post tb or vacuum reserviour)

Another for the top of your 2 stroke tank (tied into wg signal) to pressurize it to max boost.

Obviously you run the risk of introducing boost/vac leaks so be careful. Make sure your 2 stroke chamber can handle the extra pressure.

Team I understand your constant need for people to research and read on their own. But you forwarded us to a post with no definitive answer.

Clearly the OMP moves oil up the lines, but how much impact does manifold vacuum have on flow? is the intake vacuum line just to pull air for atomization? Will the RX-8 injectors be negatively influenced by boost?

Just asking common questions.

The OMP is a positive displacement pump. It has a driveshaft. that has lobes and a coupple of pistons it drives.

If it worked off of vacuum then when you have the engine wide open and little if any manifold vaccum you would pull almost no oil, but for us that keep our foot on the floor we know it goes through a lot of oil at WOT.

Hydrostatic force is weight of a fluid(lb/gal) x 0.05195(hydrostatic constant) x feet of height= PSI
My 2 stroke tank is not even 1 foot above my injectors. it is just about 1 foot above the sohn adaptor
1 foot x 0.05195 x 7.6LB/per gallon(approximate)=0.39482 PSI.

In other words the hydrostatic pressure ain't doing shit.


stink, vacuum is not wanted, the injectors have a built in vacuum breaker. That is the line that runs back to your intake tube.

I have no idea how much pressure the OMP can output, so it probably couldn't hurt to pressurize your SOHN tank, but It's not needed. If you are going real high boost then it might not be a bad idea. The pressure equal on both sides should negate themselves and keep oil flow consistant.

Like I suspected it looks like the truth is always somewhere in the middle. Vacuum plays an important part in oil injection

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Those pics show exactly what i said. The valve in the injector is just a vacuuum breaker it is meant to stop the vacuum. The increased oil flow is due to increased stepper motor position which is controlled by the ecu. When the engine is off there is no vac and no injection.

I am talking about the vacuum from the intake sweep of the engine.

I suppose Mazda called it an OIL METERING PUMP (OMP) just to fool people about what they are really doing.

When the internal engine cavity has vacuum such as during Normally Aspirated intake sweep and is just basic physics at work, the vacuum will pull in more oil than the metering pump is intended to regulate. So the injector has a check valve and bleed line back to the filtered air intake tube to offset this.

Now please explain how this translates into 'vacuum plays an important role in oil injection'?

You didn't understand because you don't understand.


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Team the check valve seems to operate in the other direction. Where chamber vacuum is higher than the intake vacuum it looks like it helps pull in more oil.

You are right I don't fully understand; so I read the entire thread you told everyone to read; and here I am with the two conflicting ideas trying to figure it out because you are more concerned with telling people they are wrong then just saying who was right in the rx7club argument. I get it you want to make people find the information on their own, but your guidance rarely sets anyone up for success, rather your own narcissism.

I guess my main issue is with my lack of fluid dynamics knowledge is how the sucking of air from the intake and oil interacts inside the injector.

Does it help increase the flow of oil by adding more pressure, or does it displace the oil and inject less?

Either way I think my statement that vacuum plays an important part in the system is on point.

The vacuum will suck in additional oil if it is not relieved. So there is a vacuum breaker in the top of the injectors to stop this from happening.

There is some people who have installed restrictors in that line to cause additional oil injection, but that is not necessarily the best solution since it only increases oil when the engine has high vacuum

That's no more accurate than what you think of the person that went out of his way to try and explain it to you in simple terms. I didn't say you were stupid, I said you don't understand.

If vacuum dilutes oil injection at low load as you suggest, then why does Mazda use an expensive, complex PCM-controlled electric pumping system to regulate the output flow relative to engine load, rpm, & throttle position? Every iteration of the system has moved further and further in that direction.

Think about it this way. Pumps push fluid and vacuum pulls fluid. If you push & pull at the same time then what is the end result? Bleeding the vacuum off with a filtered supply source eliminates the pulling effect so that the pump is only pushing.

Hoping that you may understand now.

Got it. So the check valve and hose to the intake is only there so the engine vacuum is negated and doesn't pull too much oil.

Team I know you are one of the most knowledgeable people on here, and I also have seen you steer people in the right direction rather than spoon feed them, but it gets to a point where you seem to be pushing them around. It can get abrasive. So excuse my frustration, but sometimes going on the goose chase can feed people just as much bad information from uninformed people as the truth.

Being stupid and not making the effort is not the same thing. There's no narcism in having paid your dues and expecting the same of anyone else. While there are people who genuinely deserve to be on welfare, there are also a bunch of mooches taking advantage of a free hand out rather than experience the *frustration* of earning their own existence. This forum is no different.

From another view, what if I hadn't posted that you "don't understand"? Where would your understanding be now? I see things posted often that IMO aren't correct, yet sit back quietly. If the harmony of something being wrong or someone blowing smoke up your @ss yet going unchallenged appeals to you more than so be it. You won't be alone here.

Blast from the past
 

'sup Wankers.

The guy talking about the OMP being a cam driven positive displacement pump? lol, wrong. The shaft with the cam lobes has about 70° of angular travel, and it's controlled by the stepper motor. For you illiterate types, that means it does not really "spin". It only serves to position spring loaded needle valves that can increase oil flow.

The driven portion of the OMP is also not a pump. It's just a shaft with two worm gears on it that spin a pair of brass sleeves. They somewhat resemble valve guides with holes drilled in them perpendicular to the axis a valve stem (or in the OMP, it's a needle valve/needle jet if you like carbs #MikuniBoyz) would normally travel.

As they spin, the holes in the sleeve will line up with the ports in the section of the OMP valve body that feed the lines. There are two "banjo outs" on either side of the spinning sleeves. This means that the "injector banks"? (2 sets of 2) are fed pulses of oil 180° out of phase? with each other lol.

IMPO, I don't think gravity feed is sufficient for a Sohn adapter.

I have an S1 OMP completely stripped down right now. I'll post nudes if anyone asks.

:lol:

It ends now.

That's the only warning you'll get from me I promise.

Travis

Maybe he didn't recognize the prior comments were already self-chilled from 3 years ago? Otherwise he seemed to totally misunderstand the intent of your post. There's already a thread on the forum detailing all the internals and electrical testing of the S1 oil metering pump.

Needless to say, I clearly foresaw the future that we're now experiencing here in the USA ....



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Damn it what did I miss, :lol: