Boost Lee

iTrader: (3)

I recently did a mod to my oil metering injetors at the instruction of the person who built my engine. I replaced the injectors with bolts that have no valves in them. I'm now wondering if under boost, the pressurized intake charge will force the metered oil back to the MOP? That's only the case if the MOP doesn't pressurize the oil that it's sending to the engine. If it's purpose is just sending a volume of oil (at low pressure), then this quantity of oil could be stopped by the intake charge.

So the real question here is:

Does the MOP (OMP) pressurize the oil it sends to the engine?
If so, how much pressure are we talking about?
More than typical boost?
Same as the rest of the oil system?

patman

iTrader: (3)

it does not pressurize the oil persay, but it is a positive diplacement style pump. in other words, oil cant be pushed back thru it. The intake pressure shouldnt stop the flow.

pat

BlaCkPlaGUE

The OMP does work under oil pressure though, the oil pressure in the engine pushes oil through the pump wich in turn 'meters' it to each line. The injectors should be able to pass air through them from the vac line to the tip that goes into the engine, and not the other way around. For an NA, I really don't think that it matters if you can blow air through each end either way, cause NA's are always under a vacuum so to say. right?

patman

iTrader: (3)

wrong. the pump recieves oil at 0 guage pressure. the pickup chamber for the pump is vented into the front cover, so the pump recieves oil at atmospheric pressure.

on a n/a, there is still pressure inside the engine due to compression.

Boost Lee

iTrader: (3)

Hey... rather that state something as a fact, can you please post observations or other evidence from mazda that allowed you to arrive at your conclusions? Thanks, I don't want to be caught in a position where I accepted something as true just because someone said it is. Geroge W.'s big one is enough for this decade.

BlaCkPlaGUE

Well I thoroughly examined and took apart a mechanical S4 pump and there is nothing in there that 'pumps' oil. The only way the oil can flow through that OMP is oil pressure from the engine.

*edit*
oN another note, I never said that it recieved oil at gauge pressure either..

patman

iTrader: (3)

guage pressure just means anything above atmospheric.

got a front cover and a MOP handy? look at how they mate. there is the high pressure feed line, which goes into the inlet chamber of the MOP, and then there is a hole thru the front cover. this lets the oil vent off any pressure.

take it apart again and look closer, there is definately a pump mechanism. it is a screw style pump. like i said, it isnt much of a pump, it doesnt really make any pressure, it basically just pushes the oil thru it, but since it is a positive displacement pump, oil cant go back thru, wo it makes constant flow.

arpus im not sure what exactly information you want me to post.... ive taken apart, examined, and tested a few MOPs, im a mechanical engineering student, and I know how they work. Check this thread to see what i did with mine:

https://www.rx7club.com/rotary-car-performance-77/diy-2-stroke-mop-write-up-pics-372329/

pat

Boost Lee

iTrader: (3)

So what happens in the case of boost? Say at 15psi... the MOP doesn't produce enough pressure to counter that and enter the engine does it?

I'll accept that oil can't be pushed back into the MOP (OMP whatever), I don't understand how it still lubricates apex seals and such under boosted conditions if the OMP isn't a high pressure source.

patman

iTrader: (3)

it does push that hard. its just that pressure isnt really the right word. pressure implies 'squirting'. The MOP doesnt work that way, it just pumps the oil slowly and steadily. In other words, there is a constant stream of oil all the time, no matter what the pressure in the engine is.

pat

trochoid

iTrader: (6)

Look at it this way. Oil is basicaly a non-compressable liquid. The positive displacement pump constantly moves the oil at a metered rate. The oil injecter will see vacuum or boost, depending on the state of the intake pressure. That pressure can reflect on the oil, but will not significantly change the rate of flow, because the oil cannot be compressed, nor can it be pushed back though the system.

Positive dispalcement means just that. It only goes one way.

patman

iTrader: (3)

good explanation

HeffBoost

Thanks guys. Those were great explanations. I now understand.