What mods do I need to run full e85 on stock turbo?

[razorlab]

This is not true. All modern fuel lines are ethanol-rated, because all gas has ethanol unless otherwise noted.

This. I can't believe this myth is still rampant. It's almost 2025.

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[tenkyouken]

This. I can't believe this myth is still rampant. It's almost 2025.

So I don't have to do anything...?

 

[kern417]

So I don't have to do anything...?

Correct. I along with many others have been running E85 on stock fuel lines for years.

And PI is a completely separate item. It taps into your stock fuel line to add a second set of 6 injectors that run in parallel to the stock ones. It Doesn't make sense why upgraded fuel lines would require PI or vice versa.

Really it just depends on your goals. If you just want to run E85 and have fun, you can do that now with an E85 tune. If you want to run E85 and make XXX horsepower, that's a better starting point. Because then we can advise you what fuel setup, turbo options, etc you should run to hit your goals. But I've seen many people make around ~450whp on full E85 with stock fueling. Still more than stock and more convenient than mixing.

 

[tenkyouken]

Correct. I along with many others have been running E85 on stock fuel lines for years.

And PI is a completely separate item. It taps into your stock fuel line to add a second set of 6 injectors that run in parallel to the stock ones. It Doesn't make sense why upgraded fuel lines would require PI or vice versa.

Really it just depends on your goals. If you just want to run E85 and have fun, you can do that now with an E85 tune. If you want to run E85 and make XXX horsepower, that's a better starting point. Because then we can advise you what fuel setup, turbo options, etc you should run to hit your goals. But I've seen many people make around ~450whp on full E85 with stock fueling. Still more than stock and more convenient than mixing.

I'm making about 480whp on e50 and am on a flex fuel tune. I am happy with the power but I am currently mixing to do so. I do want the convenience of not mixing.

1. Do I need to get a retune to account for full e85 while still making what I make on e50 or is that unnecessary because I'm on flex?

2. Is there a concern or negatives of just running e85?

3. While my area is great and filled with e85 stations, I might not always have access to it. If I'm on an e85 tune, would it be harmful to fill with 91? (This is why I people are on flex tunes, right?)

Thanks for the feedback, this is super helpful!

 

[Thraxbert]

1. If you have a flex tune, going up to 85% ethanol concentration will be fine without re-tune. Not totally optimal, but fine.

2. Gasoline has lubricating properties not found in e85. Occasionally putting through a blended tank, or a tank full of gasoline, could help keep certain seals in good condition. This is not imperative, but it's one of those "unknown longterm benefits."

3. If you are on a flex tune, you can fill up with anything between the base octane of the tune (I assume 91 in your area) up to full e85. For example, my tune is 93 Flex, meaning I can run a full tank of 93 Octane or any mixture of ethanol above that including full e85.

 

[tenkyouken]

1. If you have a flex tune, going up to 85% ethanol concentration will be fine without re-tune. Not totally optimal, but fine.

What do you mean by not optimal?

 

[Thraxbert]

What do you mean by not optimal?

Flex fuel works on a concept called "scaling timing."

Timing is when the spark plug fires before top dead center (BTDC) of the compression stroke. If, for example, you are "advancing timing" by 9 degrees, it means that the spark plug fires 9 degrees of crank rotation BTDC. The more timing advance your fuel lets you run, the more power you will make.

If you've ever looked at a US gas pump and seen the acronym "AKI," that's anti-knock index, where a higher number indicates more resistance to knock. 93 octane is 93 AKI. Pure e85 is (by most estimates) 105 AKI. Ethanol is valuable because it is harder to ignite, and is therefore less prone to self-igniting or incomplete ignition. You see that reflected in the higher AKI number.

Now, when you "scale timing" in a tune, it means that the tuner makes the timing more aggressive as more ethanol is added to the car. Most tuners can only fully dial-in the tune when you're actually sitting there with the most aggressive setup you plan to run, then scale back from there. So if you are currently sitting on an E50 tune, then it's probable that the scaling in your map is less tuned/less performant/less "dialed in" than it would be if you retuned the same map with full E.

This is not every tuner, but it's common. Generally speaking: if you're tuned up to X fuel, going beyond that will be less good than if you re-tuned to your new maximum and dialed back.

 

[tenkyouken]

This is not every tuner, but it's common. Generally speaking: if you're tuned up to X fuel, going beyond that will be less good than if you re-tuned to your new maximum and dialed back.

Amazing information. Thank you again.

I understand the whole idea of my tune being e50 and going beyond will be less good now.

I am going to retune it. I brought it up to the tuner about using e85. They said maximum power is e50, so going beyond that, it will lose power. Again I understand if you maximize the tune to be at e85 and dial back from there, it won't reduce power. But am I giving up power by not just keeping it at e50? The tuner is making it seem like it's a bell curve where e50 is the cap without PI.

How should I approach this?

 

[Thraxbert]

Yes, e50 is the cap, unless:

You turn down boost PSI until it matches the fuel system flow rate with e85

Add PI to raise the cap

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