For others and future reference here is Richard's reply
(btw Con the blue colored lines in the above are oil feed lines, not the vacuum/pressure source)

"the spray will form as designed if the vacuum hose is connected to the intake plenum, before the intake branches out to the individual runners.
It looks to me you understand the system."

Good luck.

Richard Sohn


Subject: Re: omp adapter question

Thank you for the reply Richard.

Correct me if wrong, it sounds like the nozzle needs to see a positive delta pressure from the hose connection pressure source, to the exit of the nozzle tip.

eg as long as the injector vacuum/pressure hose is connected to the intake manifold at a point far upstream of the nozzle tip, then the delta pressure will always force the spray to atomize at the tip, regardless of boost/or vacuum (ie engine load).

Sorry for the questions, but I'm sure the Mazda engineers electronic stepper motor is sophistcated, just wanted to get this right before install.

Charley V

There is some mixup in wording here that most people seem to apply because they only think they understand the metering oil system. :)

The so called "vacuum" lines are in fact fesh air lines, connected to a nipple placed before the throttle body. So that there is always higher pressure at the metering oil nozzle then in the engine.

Let me correct my self. When I said vacuum, I should of said air house/line, or air bleeding line. Excuse me !! Sometime I do, express myself incorrectly, English is my third language!!

As for the link I posed, I am not even going to argue about that one, for I already said what it is!!

But have a look at this one !! > http://www.rx7.org/Robinette/images/hoses.gif

Read !!

:)

" On FCs it should connect to one of the larger vacuum ports on the manifold by the throttle plate."

There are several ports on the plastic plate ( between throttle body and dynamic chamber ) actually I don't remember if its one of the big ports, but it should be the one that leads in front of the throttle body.

If not sure which one, it could be test by connecting hose to one of those ports and blow into it, by doing so you can hear whether it blows in to the dynamic chamber or in front of the throttle body!! That is how I did it. :)

5 heads are better than none....... : )
(ie I've gotten input from Richard Sohn, Con, Aaron and Atila)

and I apologize for an error in my reply above.

errata (my mistake)
" the blue colored lines in the above are oil feed lines, not the vacuum/pressure source"

I was wrong, the blue line is the "fresh air line" as Aaron and Con stated, and is the correct stock FD control signal input to the oil injectors..

I also checked with Atila on the forum, he had the omp adapter installed ~2 years ago on his single turbo, and uses the same "freash air" location for the oil injector connection as Con.

Richard Sohn's reply is therefore different than the stock setup. It looks like it would give a higher pressure connection to the injector, than stock, during boost (positive manifold pressure), and a lower pressure during part load and idle (vacuum).

Bottom line conclusion, my car was not connected properly (injector ports were capped). I will replumb so that it has a "fresh air line" as in the stock FD diagram from Con. This supplies fresh filtered near atmospheric pressure to the oil injectors, and helps to atomize the oil spray as the Mazda engineers originally intended.

Raises a question though for cars that are running higher than stock boost pressure.
Does this still method still give the correct spray pattern? I don't think anyone knows.
So premix is probably safer in that case?

Having a bad typing day, I meant to credit atihun for the reply (not "Atila" typo)

https://www.rx7club.com/forum/showth...hreadid=186477

posting this for all new owners. Connect the injector line to "filtered fresh air" in the stock locations. fc = upstream of the throttle plate, fd = after the air filter and upstream of turbo. Do not cap the injector nipples, and do not connect to the intake manifold.

wow lot of nice info in here1

The primary question of the subject heading has not yet been answered: Is it better to use 2-cycle oil with the OMP or by PREMIXING? Or does it not matter?

I prefer > Mod the O.M. pump to 2-cycle oil. :icon_tup:

2-Stroke was designed to be mixed with fuel, then combusted. I'm sure that premixing would be BEST, but I doubt your engine will have issues with either setup.

Random thoughts, a problem, possible solution:
(agree either system works, everything is a compromise).

For other FD owners, fyi, the Rotary Aviation Sohn omp adapter will fit if you have a stock turbo system, or a manifold similar to the single turbo setup used by FD owner atihun (very well engineered single turbo imo).

In my case, I have a longer exhaust manifold, and T04s single turbo, and the Sohn adapter creates a problem.

The adapter adds ~1" in length to the omp, and the stepper motor/position sensor almost touches the front exhaust manifold runner on my car (too much heat I am worried the sensor would fail).

So I will return the adapter to Richard for credit, I really wanted to use it : (

Here is my plan B.

Use the stock FD omp setup (engine oil).
Benefit: system works as designed by Mazda.
As an aside, I believe this system cools the rotor and seals, somewhat, similar to the oil jet "squirters" that cool the underside of the pistons on other hi performance cars (eg turbo Porsche, Saab, etc). So I like the idea of using the omp over premix.

I may also add about 0.4 oz/gallon of 2-stroke oil, in the fuel tank, for track events Benefit: added seal lubrication/insurance (this is about 40% the dosage recommended for premix without an omp, ie 1 oz/gallon in that case).

I will change the engine oil every 2.5 to 3k miles due to fuel dilution/blowby.
Benefit: I'll stick with the oem oil recommendations, improve engines life

I may consider water/alcohol injection later
Benefit: reduced carbon deposits, higher fuel octane, reduced knock

Any thoughts?

This debate has been happening as long as Mazda has been making rotary vehicles.

There are only opinions, no real facts on either side. Only anecdotal evidence that premix may be slightly better but there are too many factors to consider in a street driven vehicle. Real testing is required.

If you are tracking the car, then premix all the way as you can control the ratio.