How to run E85 in your car

How to run E85 in your car

The sweet-smelling, high-octane awesomeness of E85 gets us excited. It really is an awesome option for people wanting to squeeze more go out of their turbocharged or supercharged cars but it does have a few drawbacks.

Firstly, compared to regular unleaded you'll use 30% more to travel the same distance and that's down to the chemical make-up of the fuel. Secondly, ethanol is a form of alcohol and it will destroy any rubber hoses or seals not made to withstand alcohol, leading to fuel leaks, blocked fuel filters, trashed fuel pumps and injectors, and more. 

The good news is it's not impossible to set your car up to run E85 at the track, and regular unleaded for the daily drive to work, so you're not stuck carrying jerrycans of fuel around like we had to with the Suba-ute.

The secret is what is called a flex-fuel sensor, which you fit to your fuel line so it can read the ethanol content of the fuel running through it. The sensor then reports this to the ECU and the computer adjusts the engine's tune to take into account whether you're running spicy fuel for awesome boosty fun times, or you're driving Janet from Accounts to work in peak-hour traffic.

Some cars (like certain V8 Holden Commodores) actually come set-up for flex-fuel from the factory, but most cars we play with have no provision to run E85 long-term, and aren't tuned for the awesome corn sauce. This means there is a bunch of set-up required to get your nugget ready for E85 or the flex-fuel life.

Our mates at Haltech made this awesome graphic to explain how a flex fuel sensor fits into your fuel system. There are a few different ways to set it up, but the below image is the most common way to do it. 

Obviously, if you don't have a car set-up to run flex-fuel from the factory you'll also be buying an ECU which can be tuned to run on several different fuel types. The car needs to be tuned on regular fuel with no ethanol content and then with full 85% ethanol, and then the tune can be adjusted so as the ethanol content changes the ECU knows how much timing, fuel and boost to run.  

We've been mates with the legends at Haltech for years and we've set up a bunch of cars with flex-fuel on their Elite ECUs and Nexus VCUs.

Because ethanol will shred your rubber fuel lines, breaking them down internally and causing them to swell, split and generally cause you both a massive fire hazard and big problems for your fuel filter and injectors.

To fix this you need to replace all rubber hose with Teflon-lined hose, like this 200 Series hose from our mates at Raceworks. The Telfon won't break down and you can read THIS STORY HERE about how to make these types of fuel hoses.

Your in-tank fuel pump will need to be E85-rated, as will all the rubber in the hanger. This is why some cars need to have a new cradle added which can tolerate E85 fuel. 


When setting up the flex-fuel system on my 1964 Pontiac (CLICK HERE) we knew the engine was going to make a bunch of horsepower so we had to add a surge tank and two extra fuel pumps as E85 requires 30% more flow than regular unleaded. Depending on how spicy you go with the engine set-up in your car you may also need to increase the size of the fuel lines from the tank to the engine. Obviously the injectors will also need to be upgraded to suit this flow/power requirement as well. 

The elephant in the room about all of this is the expense and time required to go right through your fuel system and upgrade your ECU (if it needs it). This is why smart people recommend choosing what fuel you'll run at the very outset of the build, because this will guide what ECU and fuel plumbing solutions you'll need. 

Obviously, it is easier to just stick with only running unleaded fuel but the benefits of E85's knock-resistance on hot days makes it worthwhile alone for anyone wanting to push their car.

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