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Discussion Starter · #1 · (Edited)
This is something HolyCrapItsFast and I have been working hard to create over the past month. Its purpose is to provide a resource for those looking to either run E85 or just wanting a better understanding. Besides clearing up common misconceptions regarding its octane rating and effect on the fuel system this thread will address availability, changes in blend, tuning, and effects on performance. Examples of members' builds and links to further information sources will also be provided.

Table of Contents:

-What is E85 and what is needed to run it (post 2)
-Effects on performance (post 3)
-Effects on fuel systems (post 4)
-Octane rating (post 5)
-Changes in blend and its effect (post 6)
-Tuning for E85 (post 7)
-Availability (post 8)
-E85 build examples (post 9)


-E85 and Ethanol Blends | Ethanol Retailers
-Growth Energy Market Development
-E85 Mustangs.com - dedicated to E85 Fuel
-Hybrid Vehicles - Alternative Fuels - Alternative Fuel and Hybrid Vehicles
-Illinois Green Fleets
-View a video clip produced by "60 Minutes" about FFVs, E85 and ethanol. The Ethanol Solution

A special thanks to George (HolyCrapItsFast). I wouldn't have been able to make this by myself.

Thank you to those who helped contribute in the planning thread.

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Discussion Starter · #2 · (Edited)
What is E85 and what is needed to run it

E85 is an alcohol and fuel mixture that contains up to 85% denatured fuel ethanol and gasoline. The ethanol is derived from corn which earns it the nick name "corn fuel." Because this fuel is comprised of mostly alcohol it has a great effect on performance (more on that in post 3).

To run E85 requires upgrading the fuel system due to the greater amount of fuel E85 requires to be used. Depending on the turbo size this can range from upgrading just the injectors and in-tank fuel pump (for a stock turbo) to a $2,000+ fuel system consisting of huge injectors, multiple fuel pumps, upgraded fuel rails, ect (for a large turbo). It is best to contact your tuner when determining the necessary fuel system upgrades for your build. The build examples in post 9 can be a great resource in determining this as well.

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Discussion Starter · #3 · (Edited)
Effects on Performance
By HolyCrapItsFast

It is strange to say that E85 produces more effective power than Gasoline when it has less energy per volume but I will attempt to explain how we can achieve more power from a fuel with less energy.

First, let’s discuss the energy contained in each fuel. Gasoline has a stored potential energy of roughly 114,000 BTU per gallon. E85 has a stored potential of roughly 81,800 BTU per gallon. This means we need to use about 30% more E85 to equate to the same energy potential of gasoline. To do this we increase our fuel injector size and adjust scaling to pump about 30% more fuel into the engine. This pretty much closes the gap regarding potential energy from one fuel to the other but there is more to it. See Item 3 below.

Power advantages and effects of using E85 over Gasoline.

1.) The most prevalent benefit is that E85 has a significantly higher octane than gasoline sold at the pump. This allows your tuner to tune aggressively in regards to timing and boost. For example when tuning boost on a 93 map, one would usually need to dial back the timing to compensate for knock. With E85, one can tune aggressively for boost and maintain the same timing level, or even increase them more. It is realistic to have no knock at boost levels exceeding 30psi coupled with an efficient turbo and still maintain high timing values. However this doesn't mean that we can just up the timing through out the load/rpm range and call it a tune. The MBT timing for E85 is about the same as gas in the low load/rpm range but is a bit more advanced in the mid and higher regions of the map. The best way to tune for this is on a dyno. Some examples below will show you just how aggressive you can get.

2.) Also the alcohol in E85 has a HUGE cooling property associated with it as well. E85 has similar cooling properties you find with Water Meth injection. A cooler charge = a denser charge. A denser charge = more Air/Fuel. More Air/Fuel = more power.

The cooling effect comes when the fuel is mixed with the incoming charge due to the evaporative relationship between the fuel and the charge and with the relationship between the dry-bulb temperature and wet-bulb temperature. The farther apart these two number are the more cooling effect occurs. Evaporative cooling is a property in which evaporation of a liquid into surrounding air cools an object or a fluid in contact with it. In this case it is the air stream itself.

You can feel this effect on a hot summer day. you can perform a little experiment to see just how this works. On a nice hot day poor a little water on your arm and blow on it. You will observe your arm to feel much cooler. Now poor a little whiskey on your arm and blow. You will now observe that the cooling effect is much greater still. This is due to the difference in evaporation rate between water and ethanol.

You might be thinking that the cooling effect can't be better than meth because the mixing of fuel and charge is so close to the combustion. This is not so much the case for two good reasons...

- The first is because the evaporation rate of Ethanol is significantly greater than the evaporation rate of Methanol and can cool the charge at a much greater rate. The cooling phenomenon is felt more with ethanol even though it has a short path to travel. These evaporative properties are greatly increase due to the air velocity and turbulence at the valve. When the charge transfers from the low volume chamber in the head to the high volume chamber of the cylinder, the cooling effect is amplified.

- When meth is injected, it's cooling effects begin immediately but are reduced as the charge absorbs heat energy along the intake path.

3.) There is a fair increase in exhaust load and energy output because you are increasing the amount of thermal energy per pound of air consumed and though a specific volume of E85 has less energy than the same volume of gasoline, you can see by the math below that the energy output of the intake charge, consisting of fuel combined with air, is greater than gasoline...

Thermal energy of Gas = 19,000 BTU/lb
Thermal energy of E85 = 13,475 BTU/lb

Lets assume a consumption of air @ 100lbs/hr

100lbs/hr / 14.7 AFR = 6.802 lbs/hr of gasoline @ 19,000 BTU/lb = 129,238 BTU @ Lambda of 1
100lbs/hr / 9.76 AFR = 10.246 lbs/hr of E85 @ 13,475 BTU/lb = 138,065 BTU @ Lambda of 1

So you can see that the final thermal energy output is greater even though E85 has less energy per volume due to the fact that we are using more of it per pound of air. Ultimately this will increase the cylinder pressure thereby increasing the exhaust load effecting the potential for quicker spool.

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Discussion Starter · #4 · (Edited)
Effects on fuel systems
By HolyCrapItsFast

For the most part, vehicles made from the late eighties and early nineties where designed with oxygenated fuels in mind because of the introduction of E10. Our vehicles use silicone and/or synthetic rubber seals which are good for ethanol use. The issue here is that it dries out natural rubber and attacks some plastics. Teflon, Silicone and synthetic rubber are good materials to use. I have yet to run into a single issue regarding corrosion of any kind or the drying of any seals. I've been running E85 for several years now and did nothing special to the fuel system other than injectors and fuel pump.

The one thing that I have observed is there is an increase in moisture inside the motor over time and can correlate to corrosion or sludge build up. With the right counter measures, you can avoid it. For example, on my car I have observed the start of sludge build up in the blow by system. By adding Catch Cans, the moisture accumulates in those now and the rest of the blow by system is clear and clean. I emptied 1 cup of clear water from the catch cans after one complete season of using E85.

Chemically, ethanol is really no more corrosive than petroleum, meaning it's not. It is a solvent and not an acid plus the oxygen atoms in it's molecule don't become interesting until the molecule is disassociated during the combustion process and that is long after the point that corrosion becomes an issue. The problem with it is that it has a high affinity for moisture and can absorb quite a bit of water. It is the moisture that is causing issues with corrosion and even vehicles designed for it are showing signs of deterioration. I guess one way to counter this is to know your source. If they have a high turnaround of E85 it will not be sitting around long enough for it to accumulate moisture and become stale.

Some things that I have employed to counter the effects of moisture and there by corrosion is...

- Know your source. Find a staion with high turnaround
- Catch cans
- Alternate from E85 to 93, I do one tank of 93 to every three tanks of E85.
- Block Heater to prevent condensation.
- Frequent Oil Changes.

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Discussion Starter · #5 · (Edited)
E85’s octane rating:

The octane rating of E85 is subject to much debate. I never understood why some would say it is ~96 and others would say ~105 and found it to be odd that the opinions would very so greatly. After a little bit of research it became clear where these numbers are coming from.

Ethanol and gasoline both have different true octane values. When the octane rating is calculated based on ethanol’s true value it is ~96. When it is calculated based on gasoline’s true value it will be ~105. This is where the confusion comes from. The numbers I posted are just estimates the changing blends of E85 undoubtedly have an effect on the exact octane rating.

More detailed info on this can be found all over the internet. For the purpose of this sticky I wanted to keep this section short and easy to understand.

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Discussion Starter · #6 · (Edited)
Changes in blends and it's effect

It is common knowledge that E85 blends change from season to season. In the winter months more gasoline is added to the mix to aid in startup. Vehicles that are labeled “flex fuel” have built in sensors that interface with the ECU to adjust the fuel and timing tables accordingly. Because STIs do not have this feature it is important to understand the variations of E85 as well as its effect on your car.

Depending on the season and location the ethanol content may vary from minimum or 70% in the winter to 79% in the summer. It is important to note that these numbers are just guidelines and that the mixtures rarely go as low as the minimum ratings. Additionally in some locations there is a middle grade in the Spring and Fall seasons that has a minimum ethanol content of 74%. These different blends are referred to as “classes” and are labeled as follows:

Class 1 =Summer Blend (min 79% ethanol)
Class 2 = Spring/Fall Blend (min 74% ethanol)
Class 3 = Winter Blend: Class 3 (min 70% ethanol)

The classes experienced depend on area with the South generally just receiving class 1&2 while the North has class 1, 2 &3. The following link shows the classes throughout the various parts of the United States as well as the time in which they receive the blend.

E85 Blend by Location & Month

It is imperative to understand the differing blends and the amount of variation in your area because they have an effect on the car’s AFR. The exact amount of variation is hard to determine but worse case going from 70% ethanol to 85% would cause a one full point increase in AFR causing a lean condition. Keep in mind that this is a worst case scenario. It is also important to note that as the ethanol increases the car runs leaner. So since going from a Winter blend to Summer blend will make the AFR leaner the inverse is also true. Going from a Summer blend to Winter blend will make the car richer (which is not nearly as dangerous). ALWAYS consult your tuner in regards to your specific tune and the E85 blend changes. They may recommend you get different tunes for the seasons. If they feel you will be OK with one tune and you live in an area that experiences all 3 classes it may be a good idea to get tuned in the summer rather than in the winter.

It is always advised to have an ethanol content test kit to determine the exact content of your fuel. Additionally a wideband is a valuable tool for a car running E85.

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Discussion Starter · #7 · (Edited)
Tuning for E85
By HolyCrapItsFast

In this section we will discuss the basics of tuning with E85 and the reasons why several tunes may be necessary to successfully utilize E85 all year round. The following concepts are based on the three classes of fuel available and how each concentration affects the tune. This discussion assumes you have a working knowledge of tuning concepts and implementation and is in no way a guide to tuning your car for E85 consumption but to serve more as a theory of concept and workflow.

It is necessary to understand that our vehicles were not initially designed for E85 consumption and as such, lack the necessary logic to control changes effected by the changing properties of the fuel. This is the very reason it is necessary to re-tune for these different class fuels through out the year. Simply put, our ECU’s are E85 dumb. As previously mentioned, a true flexible fuel vehicle has a sensor installed that reads the ethanol content of the fuel. The ECU translates the value to a percentage of concentration and then is able to correlate that value and make compensations based on fuel composition. This allows a flex fuel vehicle to run any concentration of ethanol from 0% to 100%. We are not that lucky and, if E85 was consistent, it would not make much of a difference at all. Our only constraint would be to either run E85 all the time or Petrol all the time. Since there are three different classes of E85, the issue is slightly more complicated than just tuning for E85 or Petrol. As previously mentioned, E85 remains more consistent in the southern regions where the weather is warmer so it may not be necessary for someone living in Florida or Texas to have multiple tunes. You will need to log through out the year to determine that.

Before we continue it is good to understand the concepts of AFR as it relates to E85. Because E85 contains less energy per volume it is necessary to use more of it to achieve the same desired result. As such the stoichiometric AFR of E85 at an ethanol concentration of 85% is 9.76:1 vs Petrol at 14.7:1.

You might be thinking it is impossible to tune because our ECU’s only read up to an effective 11.2:1 AFR and can only adjust up to that point. This is not so and here is why. All ECU’s and other stand alone AFR gauges designed use a number called Lambda. That number is the same for Petrol as it is for E85 and is equivalent to 1.0 when either fuel is stoich. What this means is that for a value of 1.0 lambda, for what ever fuel you happen to be using at the moment, it will report its result as 14.7 whether it is E85 or not because the lambda is 1.0 and the gauge is calibrated for petrol. That means when running E85 and your AFR is reported to be 14.7, your real-time AFR is 9.76. This is very good news for us because all we would need to do is increase the injector pulse width till our reported AFR’s are ideal for Petrol but while running E85. With the exception of increased injector pulse width, tuning for E85 is no different than tuning for Petrol.

So why the need for several tunes? Because E85 is not at a consistent concentration. Not even with in each class of E85. Also the lack of logic within the ECU prevents the ECU from properly compensating for differences in fuel. Add on top of that the differences in altitude and weather and you escalate the effects even more so than with just petrol.

Tuning Concepts

E85 blends, Effects on Closed Loop Fueling.

Here you would expect the ECU to do its job and compensate for differences in fuel by comparing the target fuel values dictated in the Primary Fuel Tables with the real world conditions as dictated by the various sensors, and making adjustments as observed by viewing Fuel Trims Immediate and Fuel Trims Learned.

Well it does, and quite well up to a point. Your trims will compensate for errors as much as +/-25%. Though I have never personally observed fuel trims to exceed an average 12% as affected by ethanol concentration, it is possible. Many tuners will say an ideal tune is less than +/-6% when Fuel Trim Immediate and Fuel Trim Learned are combined. It is for this reason I like to dial in my closed loop fueling for the particular fuel you are running at the time.

I have observed that when utilizing E85 and running less than ideal fuel trims, the result is a slightly rougher engine idle, some hesitation and overall roughness. The closer to ideal I can make my trims the better everything runs.

These effects multiply when you change altitude or experience extreme climate changes.

E85 blends, Effects on Open Loop Fuel.

Here is where engine damage can occur. Let’s say you are running your car on a class 1 summer blend but have a tune that was derived from a class 3 winter blend. Closed loop fueling will most likely be able to compensate for the difference but when you go wide open throttle and into open loop operation, the ECU is calculating fuel that is dictated by the values set in the primary fuel table and for what ever air flow is observed at the MAF sensor but does not take into consideration readings from the O2 sensor and will mot make adjustments based on that. To put it in simple terms the ECU is deriving fuel based on look up values.

So since the ECU thinks it is calculating for Petrol, it has considered that the fuel remains constant. It thinks all is fine and continues on Fat Dumb and Happy when in actuality the ethanol content in your current actual fuel is much higher than the winter blend you are tuned for and you are now running much leaner due to the fact you are currently tuned for a fuel with higher concentrations of petrol. The risk here is a higher propensity for knock to occur depending on how aggressively you’ve tuned initially for E85. The high levels of octane offer some degree of buffer but I tend to stay on the safe side of the fence.

Overall Fueling

For closed loop operation, Fuel Trims should be maintained at the same levels of gasoline or even leaner, but for open loop fueling, there are two camps for making power and both are right. The thing to know is when one strategy is better than the other.

Strategy 1 is when using larger turbos, it is better to be richer when speaking in terms of making power provided you can burn all the fuel being injected. The reason why is because you are increasing the mass but to make successful use of the fuel you will need to reduce the timing to allow the fuel to burn more fully and also increase temperatures which will have the side effect if increasing the volume of the exhaust even more. Ultimately the exhaust load will be greater and the turbo will come alive as a result.

Strategy 2 is for smaller turbos that inherently spool quickly. In this scenario it is quite the opposite. You run leaner and make power by increasing timing.

Timing and boost

When tuning timing remember that the MBT for E85 is similar to gasoline in the lower RPM/load range of the table and more advanced for mid and higher RPM/load ranges in the WOT region. The advantage with E85 is there is a greater resistance to knock. So when increasing boost, the timing levels can remain the same and even be increased in the higher load regions. But again you need to decide your ultimate strategy as outlined above. Even though you can increase timing, you need to think about it in terms of what the setup needs to produce power and spool. You will need to experiment to find your best strategy


One other point is that when running an inappropriate tune, during start up, the initial injector pulse widths are not ideal. It will be very difficult to start the engine in the winter time if you have a summer time tune installed and perhaps vice versa.

Tuning Work Flow

These steps assume you have already installed the necessary fuel system upgrades such as bigger injectors and fuel pump as a minimum. It should also be understood that this is only to get you to a base tune status and will require further extensive tuning. Once this base is establish, the subsequent tuning steps are no different than tuning for Petrol.

1.) To start the initial E85 tune you will want to start with a known good Petrol tune that is already pre scaled for the injectors being used first. Start by logging with the petrol tune while running petrol in the tank. This is to derive a base line reference and a starting point for your E85 tune.

2.) Verify the injector scaling and record or note the fuel trim immediate + fuel trim learned while engine is at idle. Combined trims should be less then +/-6% at idle. If not then make adjustments to injector scale till trims are ideal.

3.) Verify both closed loop and open loop fueling throughout the RPM range to be ideal. Make adjustments to MAF scaling if needed and then save the tune. Repeat form step one till trims are ideal.

4.) Now save the Petrol tune as something else. This will be your new base E85 Tune.

5.) Make the switch over to E85

6.) Run the new tune and adjust Fuel Injector scaling and Boost Error Trim by applying a multiplier of 1.30 for an increase of 30% over current.

7.) Install the tune and start the vehicle. Allow it to reach operating temperature. Reset the ECU and start it again.

8.) Allow it to idle and observe the fuel trim immediate and fuel trim learned to stabilize.

9.) Observe fuel trim immediate + fuel trim learned at idle and adjust scaling till combined trims are ideal.

10.) Save your map

11.) Repeat step 7 to 10 till fuel trims are ideal.

Once you have established a base tune you can begin tuning your open loop and closed loop fueling as desired. Also changes to timing and boost can be done as desired and tip-in enrichment will most likely need to be adjusted.

Once tuning is complete, to adjust your tune to accommodate different classes of E85, all one needs to do is fill up with the desired tank of fuel and rescale the injectors till fuel trims are ideal as outlined above.

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This thread should be a model of how the work of a few can benefit many. Great work by those that put this together and to the Mods for Stickification! :tup:

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9,612 Posts
Do we want to add base maps in this thread? I'll post up my map/tune after I install my 20g and go E85. More maps sticky'd here could make the transition easier for some. Although, this applies to self-tunes as I'm sure most maps will be locked.

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Discussion Starter · #18 ·
Do we want to add base maps in this thread? I'll post up my map/tune after I install my 20g and go E85. More maps sticky'd here could make the transition easier for some. Although, this applies to self-tunes as I'm sure most maps will be locked.
I think an E85 tuning thread would be a better idea. That way you guys could chat about your tables and stuff I don't understand but wish I did. :(


I'll talk to George and see if he wants to do that. He's a self tuner. :tup:
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