- After 3 gallons of e85 is added, the tank must always be filled to full with pump gas.
- Do NOT use 3 gallons of e85 during a pro tune. It will skew the results and may cause the tune to be too aggressive due to the increased octane from the e85.
- Is it fine to run 3 gallons of e85 on a stock WRX tune? Yes.
- Is it fine to run 3 gallons of e85 on a Cobb OTS map? Yes.
- Is it fine to run 3 gallons of e85 after a pro tune? Yes.
- Is it fine to run 3 gallons of e85 DURING a tune? NO.
This testing was done on my personal 2015 WRX on the stock tune in April 2014.
When I first bought my 2015 WRX in April of 2014 the Cobb AP didn't exist for it yet. Luckily someone on the Romraider forum had made a logging definition for the car so i was utilizing my Tactrix cable and Romraider to log the car. My DAM was down at 0.312, I had -8 degrees of FLKC and more FBKC. The ignition timing was basically down 10-15 degrees over the whole powerband. Ultimately dumping timing like this makes cars jerky and just overall drive live shit. This is when i decided to start putting ethanol in the car. I started with 1 gallon, then 2, then 3. Ultimately 3 gallons of e85 is where i stopped....it was successfully stopping all the knock and the AFR was getting pretty lean. Adding the 3 gallons of e85 to a full tank of 91e10 makes the resultant ethanol content e24.
In the ignition timing plot below, you can see that the ethanol stopped all the knock effectively adding all the timing back to the car. At 2000rpm and 6500rpm the timing went up by 13 degrees....in the meat of the powerband it picked up 5-8 degrees of timing.
In the fueling plots below you can see that the Air Fuel Ratio (AFR) leaned out by 10-12%. This is due to the ethanol and one of the major reasons flex fuel sensors exist. An e85 tune requires 45-50% more fuel at all times than a pump gas tune. On pump gas the car was running right around 11:1 AFR at wide open throttle, with 3 gallons of ethanol it leaned out to 12.2:1.
In the Virtual Dyno plot below you can see the car picked up around 30whp. The gains are from adding all the ignition timing back in that was missing from the knock and also from the AFR leaning out from 11:1 to 12:1.
If you choose to try this, YOU MUST ALWAYS FILL THE REST OF THE GAS TANK WITH PUMP GAS AFTER PUTTNIG IN THE ETHANOL. IF YOU PUT IN 3 GALLONS OF e85 INTO AN EMPTY TANK YOU WILL BE ABOVE e70 WHICH IS VERY DIFFERENT AND WILL MAKE YOUR CAR LEAN WAY OUT.
IF YOU'RE STUCK SOMEWHERE WITH 91 OCTANE THIS IS THE EASIEST WAY TO GET RID OF ALL THE KNOCK AND MAKE SOME SOLID GAINS.
Q: Can I run 3 gallons of ethanol on my stock 2015+ WRX?
Q: Are there any downsides?
A: I did not experience any.
Q: Can I run 3gallons of ethanol on my protune or an OTS map?
A: The simple answer is to just try it. If you put the ethanol in and the car knocks worse...stop doing it. If the knock decreases and the car feels better, then you're likely fine. Remember, you must always fill the car up to full after the ethanol is added.
Q: What do you think about the MAP e30 OTS map?
A: Don't really know anything about it. I personally will NOT tune a car on ethanol without a flex fuel kit and dw300c fuel pump. Can you do it and have success? Yes. Is it risky? Yes. The whole reason running an ethanol tune without flex fuel is NOT safe is because the content varies. It's only SUPPOSED to drop to e70 at most pumps BUT there are pumps out here that say "may be as low as e52".....and there are places like AZ that only have e54 at the pump. And many shops have reported ethanol content dropping all the way into the 30's. That's when a juiced up tune without a flex fuel sensor has issues.
5 gallons of e85 and 11 gallons of 91 makes e33.
5 gallons of e54 and 11 gallons of 91 makes e23.
Q: Can this be done with 92, 93, or 94 as the base fuel?
A: Yes. Although as the base octane increases, the results are less and less drastic because the car is not knocking alot on the base octane.