Run Pre-mix or run RA OMP?

[dr.occa]

What are your opinions/insights/experiences on the subject? Is there a difference as far as purpose in your view? What are the pro & cons between the two methods? Which will provide enough "coverage" for better engine health/performance?

[NYCGPS]

premix in ur tank, best u can do.

and best of all, it's free (minus the cost of premix)

[FDguy]

delete OMP, run premix.

[TitaniumTT]

NO NO NO NO!!!!!!!!! Premix in the tank and keep the OMP and get the RA kit and inject premix. Decel Fuel Cut is such a wonderful thing.

My OMP dies a few days ago so I had to turn the Decel fuel cut off (even though it's a pump and it will continue to pump even when the stepper motor is @ 0, and ironically will pump as much as it would when the throttle is closed, I'm just not taking any chances) The original plan was to wait 4-6 weeks to tear the car apart to do the OMP and the turbo's, but after literally 13 miles of driving, 9 of which were on the highway, I'm wanting to tear it apart tomorrow. Decel fuel cut is a beautiful thing

[NYCGPS]

premix does not burn off right away, it will stay on the housing surface for a while, so decel will not kill your engine in any way.

The engine will run even without any kind of premix/oil, it has been proven in labs, it will shorten it's lifespan, sure, but just decel alone will not effect anything.

if your OMP is working, just leave it and add 1/2 oz per gallon to ur tankful of gas. best of both worlds

[GySgtFrank]

Depends on what you want to do. Racing I'd say delete the OMP and premix. Street, I'd have to vote for the RA unit so that you can inject two cycle oil rather than burning engine oil. Either way works though, the OMP delete is more reliable if you can remember to put the oil in everytime you fill up. I'm not that trusting of my own competence so I plan to use the RA kit.

[Chad D.]

Do both. OMP adapter + premix.

[Pete_89T2]

I'm using the RA adapter and running premix through the stock OMP only at this point. I used to add a little premix to the tank for extra insurance (about 1/4~1/2 oz per gallon of gas), but I'm finding that for street driving that may be a little too rich and unnecessary given the premix smoke and aroma in the exhaust.

I've been closely monitoring premix consumption against both fuel consumed and miles driven, taking into account the type of miles driven (i.e., highway cruises vs. serious floggings), and my average oil consumption rate is running at about 200:1 overall, fuel to premix. This is with the stock S5T2 OMP (electronic) fed premix via the RA adapter. Looking at just the hard miles, and my data says it burns at about 80:1; an easy cruise on the highway and it's only about 325:1

[TitaniumTT]

Originally Posted by NYCGPS

premix does not burn off right away, it will stay on the housing surface for a while, so decel will not kill your engine in any way.

How long is a while? How many revolutions? Even on decel EGT's can get 1200* so it will burn.

Originally Posted by NYCGPS

The engine will run even without any kind of premix/oil, it has been proven in labs, it will shorten it's lifespan, sure, but just decel alone will not effect anything.

So you're aware that not premixing or removing the OMP will shorten the lifespan of the engine, yet you're willing to do it?

Originally Posted by NYCGPS

if your OMP is working, just leave it and add 1/2 oz per gallon to ur tankful of gas. best of both worlds

Actually the best of both worlds would be an OMP adapter and premix in the tank.

[infernosg]

What advice would you guys give for the following application:

S5 engine (electronic OMP)
Custom intake manifold (no provision for oil injectors)
Haltech Sprint RE (can't control electronic OMP)

Changing/modifying the intake manifold and/or changing the ECU are not options at this time, unfortunately. Aside from living with pre-mixing and no decel fuel cut the only option I can think of is to switch to a S4 front cover (clearance issues with S5 rotating assembly) and use the S4 mechnical OMP, which requires rigging some kind of OMP-throttle linkage (running TWM ITB's) and utilizing only two of the stock four oil injectors.

[Pete_89T2]

Originally Posted by infernosg

What advice would you guys give for the following application:

S5 engine (electronic OMP)
Custom intake manifold (no provision for oil injectors)
Haltech Sprint RE (can't control electronic OMP)

Changing/modifying the intake manifold and/or changing the ECU are not options at this time, unfortunately. Aside from living with pre-mixing and no decel fuel cut the only option I can think of is to switch to a S4 front cover (clearance issues with S5 rotating assembly) and use the S4 mechnical OMP, which requires rigging some kind of OMP-throttle linkage (running TWM ITB's) and utilizing only two of the stock four oil injectors.

The S5 electronic OMP is basically a 4 position stepper motor, perhaps you can use a spare output from the Haltech to run it at one of those four fixed positions (suggest the one that corresponds to "pig rich" oil delivery)? Or you can electrically hardwire it to do the same whenever the engine is running. The 2 extra OMP ports going to the intake mani would be blocked off on the OMP, but you would retain the 2 injector lines you have going to the housings.

Not the greatest solution, and you'll still have to live with premixing with the fuel, but it should be good enough to allow you to enable decel fuel cut as those 2 remaining OMP injectors will be functional.

[NYCGPS]

Originally Posted by TitaniumTT

How long is a while? How many revolutions? Even on decel EGT's can get 1200* so it will burn.

So you're aware that not premixing or removing the OMP will shorten the lifespan of the engine, yet you're willing to do it?

I don't remember the exact hours, but Mazda did test running the engine without any sort of premix about 10-20 years ago, it was in either SAE papers or the book about Rx-8. I have to look it up

reason why Premix does not burn off as fast is because it's staying on the wall, which is much cooler and that's the reason why it will stay for a while. As for how many revolutions? if the engine can last hundreds of hours without any sort of premix, I think it will be fine for a while. Will it cause extra wear? a bit. but Rotary Engine have other problems that might kill it before this "Extra wear" happens.

off the top of my head, when Mazda first test Rotary Engines, their sample actually last about 200 hours before it failed from chatter marks, and that's lmore than 40 years ago.

Actually the best of both worlds would be an OMP adapter and premix in the tank.

if I can get rid of OMP without modifying the ECU in my FC and FE, I would. you can be on the safe side, but I would take it out without a 2nd thought.

[Supernaut]

I run both. At the very least though you should premix IMO. The work to do both isn't really that much more anyway so you might as well.