MrFC3S

This has proly been asked before, but i couldnt find anything on it...
Is it a good idea to PreMix with an OMP still installed? like a Reasurence that the seals and stuff are well lubed and everything? this particular car is a stock 1979 RX7... Looking for other ways aswell to increase the longivity of the engine and more importantly the fuel economy
Thanks,
Tim

Yark79

I just started doing that this weekend. Maybe I should have asked if it was a good idea first. The only reason I'm doing it is b/c I'm pretty sure my omp isn't working. When I look at the lines, it doesn't appear that anything is running through them. I wanted to take the lines of the carb to check, but it seemed like too much trouble. I can't see too much harm in doing both.

Latin270

Its a good idea. Wont hurt the engine. It will actually prolong the life of your motor. I know premix only but I was premixing prior to removing my OMP.

Eriks85Rx7

i do it, i havent had any problems yet. I like having the feeling of reassurance that motor is protected very well.

trochoid

iTrader: (6)

At some point it is probably too much of a good thing. This can lead to fouling plugs and more carbon build up (if using the wrong pre-mix),

Floating around the forum somewhere is a paper written by Royal Purple. It states how much oil is actually used by the omp and it is much less than I ever thought it would be, 800:1 at some points, 200:1 at others.

Ideally the omp would have it's own resivoir filled with TCW-3 and the engine would be lubed with fresh, ashless oil.

I have to run pre-mix on the new bp because not only did I remove the omp, I removed the drive gear inside the front cover too. I try to keep the ratio near 128:1, 1 oz/gal. Last time I looked at my fuel filter, the gas has a green tinge to it.

I have a copy of the paper if anyone would like to read it. The link to it is in the 2nd gen sec, iirc.

lovintha7

I've read somewhere that the stocker OMP is around 100:1. Anyways, I run premix with the omp rod disconnected. Somwhere in the 100:1 range.

dbragg

iTrader: (7)

whats the best premix to use? i think ill go that rought when i start driving my SA

trochoid

iTrader: (6)

Most any oil with a TCW-3 rating. Just depends on how much you want to spend.

trochoid

iTrader: (6)

Here is a quote from the Royal Purple paper. Keep in mind that the the Technical Services Manager, David Canitz has owned and raced rotaries since '85.

"If I pre-mix my fuel for the rotary engine, do I use the same ratio as with mineral based oils? Does it burn at the same rate?

In an ideal world, the rotary engine metered oil pump should inject an ashless oil designed to burn in the combustion chamber and use a four cycle oil in the crankcase for the eccentric shaft, rotor bearings, and thrust bearings. For the street, Mazda simplified the OE system to use just one oil, that being a typical four cycle oil for both the e-shaft as well as the combustion chamber. Royal Purple recommends using our standard TCW III 2 Cycle Oil if the metered oil pump is still enabled. The two cycle oil being added to the fuel tank is in addition to what Mazda designed to inject and acts as a supplement or insurance. Depending on which engine, the level of modifications (street port, Bridgeport, peripheral port, nitrous, turbocharged) and application, the typical mix ratio could vary from 200:1 to 800:1.

For a pure racing application where the metered oil pump has been disabled or removed, again based on the actual engine and modification level, the ratio could vary from 150:1 to 600:1. For this application, we recommend our Racing 2 Cycle TCW III product or the standard 2 Cycle TCW III can also be used.

A stock FD twin turbo 13B with the MOP oil injection system can typically use about one quart per 1500 miles under hard street driving. If this vehicle is getting 15 mpg, the gasoline to oil ratio is 400:1. If the oil consumption on this vehicle reduces to 1 quart per 2500 miles and fuel efficiency increases to 20 mpg, the gasoline to oil ratio increases to 600:1. The stock metering oil pump is a great system as it varies with throttle position (load on the engine). Pre-mixing has to be calculated for the ‘worst case’ that will be seen by the engine for that fuel load. Under racing conditions, that’s wide open throttle at racing rpms. This means that at idle, the ratio may be slightly fat (rich)."

Eriks85Rx7

I have been using high performance stihl 2 cycle oil.. what are good 2 cycle oils to use while your omp still works? Where is the TCW rating on the bottle of the oil?

steve84GS TII

I dont know if it would have as big an effect on a N/A engine,but my S5 TII motor lost a HUGE chunk of power when I was premixing and running the mech. OMP at idle setting.
The reason I was doing this was because my SE front cover was being worked on to accept an electronic S5 OMP.So for the time being,I ran another SE front cover with a mechanical S4 OMP.The OMP couldnt be actuated by a S5 throttle body,so I left it at idle position and ran the recommended premix ratio in the tank,for about a month.Its been a while,but I think it was about 200:1.
I couldnt figure out why I was so slow.This was the maiden trip for my car with a full S5 control system,so I wasnt sure if I had a bad AFM or some other electronic part.I just lived with it for a few weeks until my front cover was done.When I slapped it on and hooked up the S5 OMP, I also was near empty on the tank.I filled up and skipped the premix since I now had a properly working OMP. INSTANTLY I was back to pushing 14psi and pulling hard to redline,as always.

I do a lot of work on small 2 cycle equipment and,yes you can go too heavy with pre-mix oil.Most people assume,more oil=more protection...and for the most part their right.But,more oil also affects you fuel/air mixture because in a premix,the oil displaces an equal amount of fuel.Too much premix oil will actually cause you to go lean and run hotter because there is now less fuel,but the same amount of air in your mixture.The oil doesnt burn the same as gasoline,so it doesnt contribute to power production like the fuel it replaces.I suspect this is what happened to my car because it came right back to life after the premix was gone.
If your serious about pre-mixing,I would just ditch and blockoff the OMP pad altogether.That way you can run synthetic in the crankcase with no worries,just dont forget to carry extra 2-cylce oil!

trochoid

iTrader: (6)

I would venture a guess that the extra premix lowered your octane rating too much. That will have little, if any affect on an na, but a turbo does require the higher octane, especially at your boost levels.

One thing people don't realize is, that unhooking the omp rod does not return the omp to it's lowest output. It is more of a mid-range setting by default.

MrFC3S

ok, first of all, 100:1, what does that mean? i know its a ratio, but of what?
Quote:
I try to keep the ratio near 128:1, 1 oz/gal.
Does that mean use 128oz to every 1 Gal of gas? like buying those little green bottles and filling up for say 10 gal of gas? i know its kinda a stupid question, but i have to be sure... i heard somewhere that that can mess up your seals and your corner seals and stuff if you use too much...or in this case, would it still mess it up if i did it with a Bone Stock 79 12a 1st gen
mainly looking to give reasurence so that if my OMP went, the engine would be protected anyway... im not looking to remove it... so far it works.(btw, can anyone send me some where that i can learn about the OMP, and how it works)
Thanks for the Info so far(Im trying to get the hang of it, but im a fresh mechanic...dont really know what it is to "meter" eather) the only thing i can make of it is its like a PCV Valve that pumps oil instead of "Dirty Air" and helps with lubeing and stuff.
If its safe to PreMix, whats the best brand and how much should i use in my tank every time i fill up?

trochoid

iTrader: (6)

128:1 is 1 oz of premix per gallon, i.e. 128 oz of gas to 1 oz of premix.

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