Using Premix with OMP
 

I have searched the forums and i tried to resist making a useless post so sorry.

I have recently just bought a new engine from ray crowe and im going to swap everything over. the only concern is the omp. the old OMP seems to be working fine, its just i want to be sure.

would i be able to run the stock OMP while doing a very dilute premix? maybe like a 400:1 ratio?

any help / opinions will be appreciated.

thanks

I do it. I run 1/2 oz. per gallon, roughly. I just bought a bunch of 8 oz. bottles, and filled them up, then I keep a couple in the car and just dump it in when I fill up. Its actually just under 1/2 oz. per gallon. I use the Idemistsu Rotary Premix found here:

http://www.rx7.com/store/rx7/fdengine_maintenance.html

Also, there is a few rather large threads about running premix. That is how I came up with the ratio I use.

some good info in these:

https://www.rx7club.com/showthread.p...ghlight=premix

https://www.rx7club.com/showthread.p...ghlight=premix

https://www.rx7club.com/showthread.p...ghlight=premix

I do 1/2oz per gallon. I don't track the car. Just a couple of pulls here and there on the highway. I use protek and idemitsu premix.

so about .5 oz. per gallon with the use of an OMP is fine?

sounds good.

Also ive been reading about ash content and how some premix is bad for cat converters. as i live in california, will this significantly effect smog results? should i just burn through my gas and refill clean then smog?

ALso Qwik, you say your use protek and idemitsu. can i assume you mix both to make some sort of mega premix?

Haha no no sorry for the confusion. No mega mix..

I have both brands sitting in my shed. I alternate brands when I finish a bottle lol..

Takes about 2 months to finish a bottle of protek. Then Ill switch to idemitsu and finish that bottle.

No noticeable difference in power nor plug wear.

I just use it in hope my internals stay clean.

+1^ i do the same

Do any of the premix effect smog results at all? and is it cat friendly? that is also a concern i have as i have read some dirty the cat a lot.

I'm sure this questions has been asked many times, but since this thread is new and on subject, why is it that people do not replace the OMP when it goes bad? Is it so prone to failure, or incredibly expensive?

Are there any alternatives? I do remember reading a thread that had some special OMP system/setup from an avation rotary website...

Oilling the motor seems incredibly important, but the methods to doing it seem a bit old fashion no?

I believe an OMP is around $1500 new. I would think the added benefit would be simplifying the engine and reducing the failure points. Also, the premix should burn a lot cleaner than engine oil. I'm still on stock ECU, and occasionally my OMP will throw codes and put the car into a limp mode. Last time this happened to me I was on a 10 mile long bridge with no shoulder. I just had to trot along at about 50 mph until I could pull the codes. It was terrible. I believe I read somewhere that some aftermarket ECU's do not offer support for the OMP.

I am still rather new to the sub systems of the rotary engine, so perhaps someone else can chime in with some more info on the subject.

A used OMP is very cheap though. It's good people are wary about using used components for such a vital part of the car but I have rarely heard of people with OMP failures.

I've got a 99 spec OMP + sohn adapter and run premix off a separate tank with it and I love it. I rarely premix now even though it's still helpful.

Nice. Thanks everyone for the great advise.

The first reason is its a pain in the butt to replace with the engine in the car.

The other reason is that you need an aftermarket ECU to remove it. The power FC for example could care less if it's plugged in or not.

The RA adapter is nice, but means you need to find somewhere to mount a 2 stroke tank to feed it. The drawback is that it functions like the OEM OMP. I'm no expert but I think the premix dispersion you get using the fuel injectors to supply the premix is better than just dribbling oil onto one spot of the apex seals. Plus for me its easier to remember to put the premix in when I fill up than to have to pop the hood and keep an eye on an external tank. Course you could always put in a low tank light in the cabin or something I guess.

I've been doing both for some time now. I have a PFC and a working OMP but also pre-mix about .5 oz. per gallon.
The OMP is rpm and load dependent. It injects more as rpm goes up or load increases. And that's exactly how it works if you only pre-mix...EXCEPT that during periods of deceleration (engine braking) I noticed my injector-duty going to zero. Sometimes it lasted an uncomfortably long time, especially if I came off-throttle at high speed. So I decided to keep both. Augment the OMP with ashless 2-cycle.
I also have a boost-activated AI (water-only at this time) system which should eliminate worries over carbon build-up and hopefully reduce wear on what were new housings. I'm also running stock ignition (no amplification) but haven't had any break-up anywhere.
The other nice thing is if I run low on pre-mix I don't have to panic. Oh..and I've had friends watch during hard boost but they reported no smoke running both. :)
YRMV

You guys really need to convert to metric.

Just did some gymnastics on my calculator, and this is for my own and fellow imperial challenged reference - 0.5 oz per gallon is approximately 255:1

You bumped a three year old thread for this???

1/2 oz per gallon working out to be 255:1 sounds right. The accepted (non-OMP) premix ratio is 128:1, or 1oz/gal.

What was the point of your post? :lol:

This is the thread that comes up when you search google.
See with the metric system all you need is the Ratio, but bushells per cubit are no use to us.
Im just adding to the helpful reference, and thank you for confirming my calculation

Gonna bump this up for a discussion on the premixing with fuel cut which cuts the fuel during going down hills and sorts. I just had to get my 1 year rebuild done again and the seals had warped a bit as well as the housing scratched. I premixed at 1-1 1/2 ounce per gallon but do have a hill or bridge I go over occasionally where the fuel cut hits. How do you goes just premixing go about this, cancel the fuel cut or just pop in in neutral or something else?
Was almost thinking of just adding back the omp.

^^^

Well, that's a concern for me since my car keeps blowing oil injection nozzle check valves. It's likely still pulling oil in under vacuum even with the blown valves, but I'd be interested in pros/cons of turning decel fuel cut off. One of them, as I understand, can be fuel contamination in the oil.

You leave out a pretty important piece of information: Which apex seals?

Any pics of the seals or rotor housings? How warped, and how much housing damage? Housings new prior to the rebuild? Lots of variables here :)

On the street I don't think running on decel is enough of an issue to reinstall the OMP unless you really want the OMP.

On track like Peter's talking about it may be an issue.

Goopy apex seals, housings were not resurfaced before last year rebuild as they didn't need it. I do track every now and then which seemed to accelerate the hard hot starting when I did the oval and roadcourse at Dominion raceway. Now that I think about it, there was alot of high accelerating with fuel cutting through corners which had exhaust popping.

For now the first course of action is to remove the fuel cut in the adaptronic, but wondered what others went through being that the OMP delete is a pretty common deal now with premixing.

The oil dilution ship has already sailed if you've got big injectors, single turbo, etc. It means you need to change your oil more frequently, that's all.

remember that the carb'd rotaries mixed oil with the fuel by pumping oil into the carb. And carbs don't have deceleration fuel cut.

Is flipping the decel fuel cut off easy on a PFC or does it require a re-tune?

Just texted you back, Mr. Impatient :rofl: :blush:

Good info on your second point, but not sure I understand the reasoning behind the first point.

My 95 FD has a single turbo and bigger than stock primaries (ID725) and with nice tightly clearanced side seals I don't see much appreciable oil dilution in my opinion.

A high mileage (or poorly built) engine with loose clearances and something archaic like oem 850cc side feed secondaries being used as primaries, then I hear ya :D