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E85 fuel system requirements

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E85 fuel system requirements.

Learning from your on line classes about tuning for E85.. I'm building a new engine for my build and sized my injectors to handle either pump or E85. What I'm not clear on is the compatibility of all the components from tank to fuel injectors. Is there anything I need to consider in supporting fuel system components to switch back and forth between gas and e85.

Thank you

Hello Peter well sofar I have been tunning on e85 for like 2 years now and on pump gas back an fort .most important is to get a e85 fuel pump compatible and fuel injectors depend if it a all motor or boosted.what I have been doing so far is using ecu that have dual maps so I can run one map on pump gas and other map on e85 .

its all motor...

what is it about the fuel pump that makes them e85 compatible?

It's all about the internal materials and also pump capacity to e85 a good in tank pump is the new walbro in tank. Never had any issues with them.

thank you for the feedback... I assume normal fuel lines are compatible as well.

E85 is hygroscopic, it attracts moisture from its surrounding.

Given that you have sized the fuel system components to deliver / flow adequately, it is important to choose the components to withstand water, respectively its ill effect; Corrosion. Injector internals must be made of stainless steel or another material that does not corrode. BOSCH injectors used by Injector Dynamics, ASNU and others are made of stainless steel for example. The same rule applies for pumps etc.

Dynodom and Bellotech.. thank you both..

I'm using fuel injector clinics 525 injectors.. and spoke with the tech before ordering about the use of E-85. So I should be good on the injectors. Steel (maybe aluminum need to check with magnet) hoses from the tank to the regulator and standard OEM aluminum rails, rubber hoses and fittings.

Most of the compatibility problems come down to the smaller aspects of the fuel system such as the o-ring material and fuel lines. This was more of a problem with some older vehicles. These days most modern cars are designed with a fuel system that is capable of running on up to E10 without the need for a flex fuel system, hence some level of ethanol compatibility is essential.

As noted by others, it's the water content likely to form in the fuel system that is the other cause for concern with ethanol fuel due to its hygroscopic nature. I'm not convinced that it's smart to try building a fuel system that's tolerant of water though and even aside from your injectors and pump, you're likely to find all sorts of nasty stuff going on like the inside of your fuel tank rusting. The key is not to let the system sit with ethanol in it for long periods of time, and if that's likely then flush the system and run it on petrol.

Here's an article I wrote for Speedhunters a couple of months back that may be helpful - http://www.speedhunters.com/2015/04/everything-you-need-to-know-about-ethanol/

flushing with pump fuel would be acceptable. As part of our pre-race setup for every track session we pump the tank dry and calculate a fuel load to meet minimum weight requirements at the end of the session.

All great info thank you!


on a sidenote related to E85, I would like to point out that it is of paramount importance to run a precisely calibrated flex fuel system. Ethanol content does vary quite a bit, baby bottle tests may give you an indication of the E content, but nowhere near sufficiently accurate for my liking (and not practical in a race environment)


The e85 manufacturer that I plan on using is less than 10 miles away. And strives for by weight mixed to order batches.

I'm not sure if something has changed in the make up of E85 over the years but locally we tried the baby bottle method a few months back and it was next to useless. It took about 8 hours for separation to occur and even then the results were marginal at best.

injector dynamics confirms your view Andre... baby bottle is no longer valid, per their online comments on the subject.

I'm hoping that a personal connection with the local manufacturer ensures consistent results and mix of E85.

I think by far the biggest issue is using regular pump E85. The actual ethanol content in pump E85 can legally be as low as 51% and hence you can get wild swings in fuel consistency from tank to tank. If you're using an aftermarket fuel supplier your results 'should' be much more stable. Personally I like to include an ethanol content sensor in any install using ethanol fuel, regardless of whether I'm intending to do a flex fuel setup. It's just nice for peace of mind to know what the E% is.


would most EMS just need a sensor like this one? Then log it in the data, or would it be used to make trim compensations?

Yeah the co solvents as changed over the years (for the baby bottle method)

see the Addendum at the end ;)


Peter, just make sure the ems has flex fuel compatibility. IMO, ProEFI has the best flex fuel system of all the systems available. Might be something to look in to.

Something else, I haven't personally tested it myself, but I do know that around here most of our E85 pump stations say "Minimum 70% ethanol". Anyone know if they actually are meeting that minimum? I haven't pumped from them to see if my gauge reads out above 70 or not.

The ASTM specification states a minimum of 51% however the reason for the variable E% is to aid volatility for cold starting, so in warmer climates there may be no need to drop the E% this low. I'd personally be suspicious of a sticker on a pump but then I'm a suspicious kind of guy ;)

Am i right in thinking you only need a flex fuel sensor when theres risk of the Ethanol content varying?

Here in the UK we dont get E85 at the pump only bought in as race fuel which i believe has a pretty stable Ethanol content.

The sensor is if you're mixing. The simple explanation is that the fuel passes through the sensor and it sends a signal to the ECM which has user input parameters for how it should be adjusting fueling based on Ethanol content. So basically, you need the sensor if you fill it with drum E85 and drive half a tank and fill it with 93, or if you're pumping both from the station.

I'm going to go pump some E85 from the station next time I take the turbo bike out and see what the content reads. Would be interesting to see how true the "Minimum 70%" really is.

@heds, the ethanol content sensor is essential to a flex fuel system, however I personally recommend them just to monitor the ethanol content anyway. If you're not relying on pump E85 then you are probably in a much better situation however locally I was made aware of a 200 litre drum of E85 purchased from a race fuel supplier which was tested and found to be E100 (or probably more realistically E98). It appears someone 'forgot' to add the gasoline to mix it back to E85!

Suppose its another piece of data for piece of mind, an incorrect mix could cause all sorts of problems but without the ethanol content sensor youd never figure it out.

Could anyone advise a good sensor to go with?

Ive just bought an I/O expander so Ive got room for some extra sensors.


-13577379 (short tube) -> same as NZEFI

-13577394 (long tube) -> same as Haltech, Link, microtech & Zeitronix

- 13577429 (small body but no fixing tab) -> same as AEM

I've always used the Haltech sensor and never had a single issue.

I think it's important to note that flex/ethanol content sensors in-fact measure the conductivity of electricity in your fuel and NOT ethanol content.

If your fuel becomes contaminated with water (which we all know happens) your sensor will show a higher (false) reading.

Simply put, moisture in your fuel will give your content sensor a false reading because your sensor is actually reading conductivity and not ethanol.

The only way to have a reliable flex sensor is to have fuel that you know is not contaminated and that will not be contaminated.

Note: It's possible that there is a sensor that addresses this issue but as of now I am not aware of one.

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