How much more power can you make on e85?

Ethanol based fuels are common place in the automotive world and since ethanol is a renewable resource and a cleaner burning alternative to gasoline, ethanol, or mores specifically ethanol blends, have become a popular choice in many countries. Pure ethanol or E100 isn’t typically used as a fuel since its lack of volatility (compared to gasoline) can make it hard to start when the engine is cold. The most common blend we are used to is referred to as E85, consisting of 85% ethanol and 15% unleaded gasoline. It’s worth noting however that the actual ethanol content of E85 may fluctuate quite widely in pump E85 - For example it’s common to see ethanol content in a winter blend of E85 reduce to perhaps 60-70% to aid starting in very cold climates 

toyota gt86 test car on dyno high performance academy ethanol test

While E85 is great for the environment, performance enthusiasts quickly found out it’s also great for producing power. So where does the advantage come from? On the face of it ethanol actually has a slightly lower energy content than gasoline per kilogram, but it also has a much richer stoichiometric AFR (9.8:1 for E85 vs 14.7:1 for pump gas) which means we need to use more of it to mix with the same mass of air. In general when switching to E85 we will find that we need to inject around 35-40% more fuel to make the same power we saw on pump gas. E85 also contains around 30% oxygen by weight and it has a higher effective octane rating than pump gas - This is often listed as 105, however we have seen E85 perform as well as specifically blended race fuels with motor octane ratings of 116+.

MoTeC cdl3 dash display showing ethanol content

One of the key advantages of E85 over gasoline is that it has a higher latent heat of evaporation than pump gas. This means that it absorbs more heat from the combustion charge as it goes through a phase change from liquid to vapour. This draws heat out of the combustion charge and coupled with its high octane rating, makes the fuel very resistant to detonation. For those interested in performance, this means we can run more boost, more compression, more ignition advance, or all three with relative immunity from detonation. Note that contrary to popular belief, knock can still occur on E85, but it is much less likely. 

Dyno results after ethanol e85 tuning at 7psi

We recently performed some testing on our Toyota 86 fitted with a Borg Warner EFR 6758 turbo and a MoTeC M150 ECU. In stock form the 12.5:1 compression engine was heavily knock limited on pump gas, producing 198 kW at the wheels with 7 psi boost - That’s still a decent increase from the 114 kW measured when standard though. With a tank of E85 on board, we were able to optimise the ignition advance at the same 7 psi, achieving 226 kW at the wheels. This gain was achieved because we could optimise the ignition timing without encountering knock. In the end the engine took an extra 6-8 degrees of ignition advance over what it accepted on pump gas. 

Dyno results after ethanol e85 tuning at 9.5psi

Once we had achieved MBT timing (Find out in our EFI Tuning Fundamentals online course) at the minimum boost level of 7 psi, we used the MoTeC’s electronic boost control to raise the boost pressure. With an extra 2.5 psi boost (9.5 psi peak), the engine produced 266 kW at the wheels and the ignition timing could still be advanced to MBT with no sign of detonation. Note that the stock FA20 engine runs a very high 12.5:1 compression, making it a challenging task to tune when coupled with a turbocharger. Obviously we could have pushed the boost further but we would like the stock FA20 to hold together for a little longer right now. 

So E85 allows a degree of immunity from knock which obviously lends itself nicely to high boost turbo engines or high compression N/A engines. What happens if your engine is naturally aspirated and isn’t knock limited though? We have found that even in these situations you can still expect to see an additional 5% more power, making the switch to E85 a worthwhile consideration. The only downside is that you will be burning more fuel and hence your fuel economy takes a hit. On top of that you may need to rethink your fuel system with larger injectors and fuel pumps often an essential aspect of any upgrade to E85. 

If you are interested in learning more about tuning including setting up knock control, why not begin with our free 'Bare Minimum Tuning Knowledge' course. Did we mention it's free?

Also, why not check out this article on how to find out what percentage of Ethanol is in your fuel

MoTeC m1 knock control ethanol e85 tuning

MoTeC M1 Tune showing the built in knock detection system with individual knock levels from each cylinder displayed vs the knock threshold.

MoTeC M1 Ignition Map ethanol e85 tuning

MoTeC M1 Tune showing a graphical and numerical view of the ignition timing.

Want to learn more about e85 and ethanol tuning? Check out the full Ethanol and Flex Fuel Training course here.

Comments

  • Andre Simon's profile image
    Hi Vasin,

    Right now the M1 doesn't support Flex Fuel. We are using the ethanol content sensor as a display only. In the future we are intending to use M1 Build to develop flex fuel compatibility in our Toyota 86 Package. In time we expect that flex fuel compatibility will make it to the various packages already available but for now we are simply swapping between pump gas and E85 maps.
    - Andre.Simon New Zealand
    3 years ago
  •  's profile image
    In the M1 Tune. How do I setup ethanol content sensor compensate table for fuel and ignition?
    - Vasin Thailand
    3 years ago
  • Andre Simon's profile image
    A vehicle that is flex fuel capable will include a fuel composition sensor that tells the ECU how much ethanol is present in the fuel. Based on this the ECU can alter the fuel and ignition calibration to suit. Flex fuel vehicles have a fuel system designed to handle the required volume of fuel flow when operating with a high percentage of ethanol in the fuel.
    - Andre.Simon New Zealand
    3 years ago
  • MAT BOONEN's profile image
    So I have a typhoon that states on the gas cap it will accept E85. How does the ecu know it is running E85 automatically. And wouldn't the factory injectors be too small to produce the same horsepower. Or is it almost detuned to still produce the factory HP with a different lower BSFC
    - bigmat New Zealand
    3 years ago