deldran

Hello everyone. I have tried searching the forum, and other places but have not found any kinda of definitive/recent thread that talks about E85 in the renesis.

I live in the land of corn so e85 is everywhere. I have been thinking over this for a while and it seems like e85 would be an excellent fuel for a rotary.

E85 Pros

• Cooler burn reducing the heat generated by combustion
• no knock/detonation - my understanding is unlike a piston motor which can handle a bit of knock without catastrophic issues. Rotary's do not like knock at all, and causes issues much faster

E85 Cons

• Worse MGP (race car - who cares)
• Possible lubrication issues? I am still learning rotary, but gas has a bit of lubricity to it, where alcohol/e85 would have less. Could be solved with higher level of premix?
• Fuel System issues? Not sure if the seals in the stock rx8 fuel system play nice with E85

The other unknown for me is what we have in the Speed3/6 community where e85 mixes with oil is the high pressure fuel pump spill valve and makes a nice black tar like substance that will gum up the pump and cause the car to not run. This is mitigated by not running more than 50% E85 content in the tank, it also appears more modern oils seem to not cause this issue when mixing with e85. For the rotary since there is no high preasure fuel pump, the concern would be this forming inside the rotor housing, but there is combustion there, so I would think it would burn off. In the Speed3/6 world the fuel will boil in the spill valve, which is what creates the black sticky death. Not sure if this would have any affect at all in the rotary.

From the bit I have learned in the last few weeks, if lubrication can be solved with the proper level of premixing, and the fuel system doesn't fail due to prolonged exposure to e85. I guess I am not sure why this isn't a more popular choice, other than worse fuel economy.
Would love to have a larger discussion around this.

Federighi

iTrader: (7)

The shortest possible answer is yes for FI rotary.

But to put it lightly, the MZR DISI is in no way comparable to any rotary engine, let alone the Renesis. Also the little fact that both 'Speed' vehicles are FI whereas the Rx8 is N/A and offers very little performance to be gained. I believe there's a member or two in the 'racer' section who've successfully retrofitted the rx8 fueling system to FLEX and realized single digit power gains while N/A compared to gasoline. I'm not sure if any cooling benefits were measurable / present.

I personally would recommend hanging out and building your knowledge + profile on the rx7club if you are seriously interested in this topic as there are very informative threads to be found there. Howard Coleman CPR and Carlos Iglesias (Spic Racer GT40R build thread) both share incredible information they've detailed over many years of working with and racing rotary. They do still have strict site restrictions iirc, so you'll need to get on it asap to get full access.

Hope this helped and best of luck in your searches!

deldran

Yea I know they are vastly different motors, just mentioning my experience with it from that platform.

I also didn’t think there would be much power gained on the rotary via e85 I was more looking at it from cooling aspect, it seems heat is the killer of these motors, and they like to run hot. Seemed logical to me to use a fuel that created less heat in general if it made sense.

I will make an account over there, thanks for the reply.

Brettus

iTrader: (2)

I ran E30-E40 in my turbo Renesis for a number of years and around 25000 kms , it wasn't a race car but it always got plenty of Jandal and was making 380whp plus. I wouldn't say there is any real comparison with a race only car but I give you my experiences anyway for reference.
I used Motul Micro 2T as a premix at 120:1 and no OMP.

My observations:
The good
1/ Detonation resistance is exceptional ... there were a couple of occasions where It ran out of fuel on high g corners and much to my amazement ... zero detonation.
2/Even when I went down to E20 for a while there didn't appear to be any need for more octane.
3/When the engine was finally pulled down it was still in good condition

The bad
1/The premix ends up getting into the sump oil so oil level goes up instead of down. Because of this I needed to change the oil often (good idea anyway). I don't think this would be such a big issue on a race car but on a street car ...having high % of premix when cruising means WAY too much oil in the combustion chamber.
2/The rotors were covered in what looked like LAVA when I pulled it down. No doubt increasing the compression ratio somewhat ...not good in a 10:1!
3/The intake manifold was full of oily goo.
4/That premix oil was freakin' expensive and I always felt like it was a waste in all circumstances other than when running high boost/rpms.


As a result of that experience I've changed my approach and for a street car this is what I do now :

1/Re attached the OMP and set it up with increased (programable) capacity.
2/When running ethanol , I add premix to the ethanol content only at 100:1. Using the logic that the main lubrication needs for petrol are covered by the OMP and any lubricity reduction from ethanol is covered by the premix.

I think this will solve the problems I mentioned above while still keeping the engine well lubricated when it needs it.
I believe this same approach would work well for a turbo race car as well.

peloponisios

Thanks for the info Brettus.
Given that deldran can access e85 very easily, on the long run would it be beneficial? You would have to change to a flex fuel pump, so that's an added cost and work. Would you need a tune also for n/a application? Add this to the prereq list.
My (ignorant) concern would be if ethanol would dry up the lines, making them brittle.
Finally, there has been some talk about this e85 friendly new premix solution.
​​​​​https://renewablelube.com/products/b...-racing-premix

Brettus

iTrader: (2)

I can't see any benefit running E85 in an N/A street car ...... there are some small gains for a racecar but you would have to weigh it all up to see if it's worth it. Yes it would definitely need a retune!
If you are turboed .... I'd still run a lower % mix rather than full E85. Re the lines ... I can't see any evidence of that and have not heard of any from others either .....but I've only run E50 at the most.

I don't know if that premix you linked is available here .... I'm sure it will become popular if it does what they claim and isn't too expensive.

deldran

I think anything to help keep these cars running cool is worth investigating. While again I am new to rotaries it seems getting them to hot is a big no no. Where on a piston car you can probably get away with over heating a motor so long as you notice it and stop. Some things I read seem to point to one instance of overheating causing coolant seals to fail. Given the primary use of my car will be for racing. Currently been street driving it a lot, because new car. It will not see winter driving and likely will be mostly weekend/AX use starting next year.

I do plan on playing around with it and seeing if it’s worth. It might not be, but it seems from what I have found so far it hasn’t been fully investigated on the rx8

darnellm

iTrader: (1)

Currently running E85 with an Adaptronic ecu.
Runs great.
Tuned by Shawn

wcs

iTrader: (2)

Funny enough I received this from HP Academy just the other day.
So fwiw here is what they have to say about E85

jcbrx8

FWIW I h/b running an ~E25-30 mix for det resistance and cooling for 2+ yrs now. I premix 5oz Micro Motul 2T, and 2oz Lucas Injector Cleaner per tank in addition to having increased my OMP injection map particularly in high load / boosted regions. Per performance #s shown in my sig...she runs well, and has experienced no instances of detonation during this time.