Hey, all. I figured this question deserved a separate thread since it's different enough from most questions concerning this.

With an OMP delete and turbo setup, what would you consider a healthy premix ratio? It seems 1.5 oz per gallon is typical, but I read this article, and the author seems to have a slightly different mentality, but not totally off-base.

For those of you too lazy to read (tl;dr):

(This pertains to boosted applications)Minimum Safe Amount: You should never drop below 8 oz per 10 gallons (6 oz baseline + 2 oz alcohol buffer).

Preferred Racing Rate: Many racers with similar "pure race" or boosted setups run 1 oz of premix per gallon of fuel. Some boosted applications are recommended as high as 2 oz per gallon for maximum protection.

Oil Type: For fuel blends below 50% alcohol (E30–E40), the article recommends sticking with a high-quality synthetic premix specifically designed for rotaries, such as Idemitsu, which burns cleanly and minimizes deposits.

Monitoring: Start with a "rich" mix (e.g., 1 oz per gallon) and slowly reduce it if you notice excessive oily deposits on your spark plugs.

Any thoughts on this?

 

I've tried 100% premix at 1:120 (approx. 1oz/gal) with an E20 fuel and went away from it when I saw how much carbon accumulated on the rotors. Also found a lot of sticky goo in the intake.
From there I've gone back to the OMP with 30% increased flow over stock and that seems to be working well with an 8000rpm redline. I only add (200:1) premix when I take it to the track or run at 12psi or more. Also run m/w which may be helping cool the seals and keeping them carbon free.

OMP is superior to premix due to the side exhaust ports ..... IMO

 

And the OMP, at high loads, rpm delivers something like 30:1 ratio, even at stock settings. Premix only peeps probably don’t know this…

 

Where have you heard that? I've seen that the actual limit of the OMP is around 150:1, which equates to about .85 ounces per gallon. I feel like 1.25 ounces per gallon with it deleted would be more than sufficient (and it's always flowing at that rate--not just at high RPM/load). But as Brett mentioned, if there is carbon build up even at 1 ounce per gallon, even that may be too much.

 

No, the OMP delivers a lot of oil at full throttle/rpm, or near there. Normal driving is where it sucks, and causes engine damage in my view.

Brettus is very knowledgeable, and has a lot of experience, more than I do, and I won't dispute what he says.

I will just relate my experience, which is different. In any engine, even running 1% premix 2stroke oil in a 4 stroke will not generate a bunch of carbon. In fact, if the oil is good, it will clean the chambers better than gasoline alone. You can look this up. People have tried it, so have I.

I have almost 200k miles now between 2 Renesis engines as DD, and my premix/OMP ratio for normal driving is about 40:1 and goes richer from there when given throttle/rpm. Both cars have rotors that are clean down to the metal, other than small carbon deposits in the bathtub.I have never cleaned them or used a soak, steam clean or any other. Just ran them. Stock fuel maps also(rich). They DO NOT see 4 stroke oil though. Big difference. Both have Sohns.

I will try to find some info about OMP output that I found before and posted, but I realized how much it could deliver when I had a test bench made up years ago where I could run it out of the car and measure it. My measurements were guesses because I could not correlate fuel usage and could only surmise this figure. My numbers were actually much higher than I thought, but some real-world anecdotes from racers here showed me I was conservative.

Why more oil? Because it prevents premature wear. One engine has 105k now and was put together with used housings, and still blows over 8s compression, there has been a small reduction from when newly assembled, but it is almost immeasurable, and might be only because of test conditions being different. I'm going to test that engine again, since the numbers are so close (a few psi). Many who premix at very low ratios (1% , etc or less) still report drastic compression loss at this mileage, most often failing the Mazda test. And that is with new housings, not used.

All that said, most well known engine builders recommend 1-2% premix. I will not argue with them, they have tons of experience. I believe though, that rebuilding an engine every 25 hours or so of race use, or every 70 k or less of street use is not the way. Maybe I am wrong?

 

Here you go:

From this rather epic thread that Brett started and contributed to. Team RX8 was there also, bringing the contrary view, which is welcome when done in good faith.


https://www.rx8club.com/series-i-tec...268559/page10/


See below:


For anyone interested in more examples of peak OMP output:

Quote:
Originally Posted by Steve@VersaTune
We did well over a hundred pulls over several days consuming more than 15 gallons of fuel and over a quart of oil.
Quote:
Originally Posted by Steve@VersaTune
We paid careful attention to ambient temp, intake air temp, and coolant temp so that things are repeatable. Pulls were done at 80C ECT and 20C IAT. When we came to the conclusion that any given tune was done, we did multiple pulls to confirm repeatability. We did about 10 pulls on the final tune that we published to be sure that it was repeatable. This ECU/engine is very sensitive to heat. It dumps fuel when it gets hot. It's important to keep temps under control to see consistent top performance.
Quote:
Originally Posted by Steve@VersaTune

Below is not from Steve@Versatune. It combined the quotes for some reason.

I have a series 2 and do hpde days
. I notice a huge jump in how much it consumes compared to normal drive about 1 quart a day at the track.
I also premix 8oz amsoil every tank.

[[b]QUOTE=speed7;4965078]Yeah that is about the same level as me btw. Series 2 and after every 20 minute run in an HPDE event I have to top off.. way more when compared to regular driving.

-------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
And this from Eric Meyer (way back when), which speaks to the output properties of the OMP. I assume its the standard 1.5 quart tank that was ( is still ) in popular use. This correlates well with the output ability I have seen myself. I believe he went to 1oz per gallon on OMP elimination later. I have not found out why. Again, this is about the pump output.

Also, I will add to this. I have seen ALL oil injection pumps on motorcycles and watercraft, and my old FB, produce gobs of oil consumption at their max settings. The RX8 is no different.

The info in the last sentence below, assuming 14 gallons gas, and 1.5 quarts oil, equates to 36:1. From what he is saying, that is not the maximum output either. If its just a quart in the tank, its still 56:1.

Note: We feed our OMP with the rotary aviation remote feed (which blocks off the pull of crankcase motor oil) and allows us to use a two stroke product. The OMP is not connected to any map and runs mechanically. Current rate of use is approx 1 qt per hour of WOT operation (give or take 10%). Turning up the manual dial on the OMP increases the rate of oil consumption and lowers the EGT by about 25F but limits car operation to about 1/2 hour (not long enough for us to run a full tank of fuel for an enduro or our 50 minute World Challenge races (plus parade and cool down laps). We have our OMP set so it runs approx a full tank of fuel at .89 Lambda.
__________________

Also, I will add this in here from Racing Beat also. I know a lot of us are aware of it, but it hasn't been posted here and may be useful. I believe from how the article is written, that the engine in question was also using the OMP in addition to the stated ratio of premix (77:1).

RX-8 - Race Tips

While undertaking development work on the RX-8 Renesis engine for SCCA T2/T3 use, we decided to introduce extra oil into the fuel to monitor the effect. To our surprise, this additional oil increased power! Further dyno testing found that by adding 10 oz. of Royal Purple 2-Stroke Oil to 6 gallons of fuel, we gained an average of 1.7 HP from 2000-9000 RPM, along with an increase in peak power of 4 HP. We validated this increase by changing back to a "non-oiled" fuel - and the power returned to the previous level. Later, we tried the same test with another brand of synthetic oil with nearly the same results.

For racing applications, the addition of a high quality synthetic oil increases power and most certainly decreases wear. The only negatives are the cost of the oil and an increase in the tendency to foul the spark plugs. (Note: We have not performed these tests on non-RX-8 engines yet, these results are unknown.)

 

So the OMP can provide a flow rate of 3.5+ ounces per gallon??

 

https://www.rx8club.com/series-i-tec...9/#post4872214

 

And when we had this discussion, I didn't dispute your calcs, since I measured it a different way, dynamically. I actually got more than this on the test bench, which I estimated at the time IIRC to be somewhere better than 40:1 capability at redline. I measured myself in a running car and got close to 30:1, with a lot of full throttle 7-8.5k running over short period, which is also "close" to the racer's anecdotes posted, and others I've run across since that I would never be able to find again. Regardless, it's a lot more than 1%, it's tough to measure 100% accurately, but the answer is MORE.
Now, with the OMP mods, VT map changes, etc. its more than that. And I'm happy about it. Burn oil or burn engines. Welcome to Rotary Land!

 

Also this from I-Rotary: ( Dr. Iannetti)

https://i-rotary.com/pages/apexseal-faq

His seals last longer under power/racing than stock. He also recommends much more oil than most. Could be a factor, hmm? (Can't screenshot above).
Racing-
Gas: 1.5-2.0oz with or without OMP
Street-
Gas: 1.25oz + with OMP


https://i-rotary.com/pages/i-rotary-renesis-apex-seal

 

^^ That’s for running their specific steel (non-ceramic) material seals. Not for OE seals.
.

 

You might want to read more on that site. So that much oil is "too much" for the Mazda seals? Not needed?

"The IRAS can be treated just like the Mazda OEM apex seal in all applications. We strongly recommend the additional use of a high quality 2 stroke oil in the fuel to improve the longevity of the apex seal (Mazda's, or I-Rotary, or any other aftermarket apex seal)."
"Importantly, the premixing of a high-quality oil in the fuel will also help lubricate the rest of the sealing grid components and all the other internal wear surfaces of the engine."

Then it goes on to give you a table of premix ratios I stated above with OMP function. Definitely not the 1% premix only that has become rotary lore for all these years.

 

This was a good read, thanks guys for all the useful info.

 

you can always run more premix, but on a street car that’s going to potentially cause issues

spark plug fouling
cat converter fouling

they were only running 1 oz. per gal fuel on the Mazda Formula Renesis engine race cars per Daryl Drummond, but that was using full RX7 depth Iannetti ceramic seals. I don’t consider Iannetti to be the end-all source of wisdom for factory seals; especially for long term street use, but if you do, then OK.
.

 

At 1% how long were those engines lasting before losing measurable power? I’ve never seen anything on this other than some anecdotes here and there. Did you have any information on this in your talks with DD— What did he expect to see? Very curious to know…

 

Whats a gallon? I use 235ml oil to 20L of fuel for a mix 85:1. No OMP. I didn't have any buildup inside my motor when it came apart. But that motor did have a stock OMP on it for the first 50,000ishkm(history unclear) & then 10k no omp + turbo. I do wonder about my wideband, but haven't had any issues so far.