When was your 21 built? Any 2021 built after December 2020 good luck getting a tune. EVO they have to crack open your ECU. There are none available that you can just flash with Dynojet.

If you plan on doing long desert rides stick with 91.

 

If you want maximum reliability then an aftermarket tune is likely going the wrong direction.

 

I have 3K miles on my RR with an Evo 3R 93 octane tune. Never a single issue at all ever. Not even a check engine light ever. I get 12 MPG racing through the desert and can do 130 mile rides without getting a low fuel light.

 

My car is a 2019 XRS Turbo R and I run a Evo E85 tune for the last 3 years. I'm lucky to get 50-75 miles on a tank of fuel. Now I do run my car wide open most of the time. I ride mostly dunes (real fast sand trails) and fast drit road, like a rally car.
I'm always filling my car up when most of my buddy still have 1/2to 3/4 tank of fuel in there cars. E85 will burn 2 to 1 over a pump gas tune. But I do like the power it makes.

I would stay with a pump gas tune if I was running fast desert riding. I've been looking to go with a bigger turbo setup so I can go back to pump gas and make around the same HP I making now. But that's like $5-7k to run that setup. I can't justify that yet.

Now I can't get E85 at the pump where I live. So I have to buy it by 55gal drum. I run Renegade ProE85 and that cost me $540 a drum right now (thanks Biden). Last year it was $406 a drum. And I will use 3/4 of a drum on 1 dunes trip.

 

Yeah I’m up in the air now between the two how many miles are on your car?

 

FYI, you shouldn't be using that much more e85 over pump gas. Around 30% is pretty typical from my experience.

 

Just remember that an E85 ran car will need much more often oil changes, fuel tank draining if stored at all especially in humid environments. Lack of readily available fuel especially in the desert. You can build a car that can switch back and forth between the two with just a reflash BUT 7-10K is a reasonable range.

 

unlikely your 21 can be flashed (cheaply)
e85 needs a big injector tune
do you have access to e85 at the pump
most places out west sell flex fuel...that is usually only e70 or less
and is why most west riders buy e85 by the can
here in the mid west we get e85 in the summer
but winter we get flex
if you buy e85 at the pump always check it before you fill up
all e85 users need a cheapo tester...simple and fast

https://a.co/d/blhwGtV

https://a.co/d/c7DRqPX

 

yes 30% is the average
but at max boost its about 50%

 

I shifted my fuel 30% up across the map on a turbo subaru. It ran perfect. I don't buy the 50% comments. You will use more fuel if you twisted the boost up going from gas to ethanol.

 

30% more then 91 just driving normal, prob 50% if you race a lot