The Truth About E-85 - Tech Information

With the increasing use of E-85 Ethanol based fuel and sporadic engine failures I thought it appropriate to put forward some information regarding this fuel.

The main benefit of Ethanol over gasoline is its heat of vaporization which is when the Ethanol changes state from a liquid to a gas. This change of state is endothermic, removing heat from the system to change state, which increases the density of the air/fuel mixture allowing more air (Oxygen) into the cylinder. Although Ethanol has a lower heating (BTU) value than gasoline, the charge cooling allows greater mass to be inducted which increases the total combustion mass. The charge cooling also allows increased spark timing in most applications. The net sum allows Ethanol to increase net power over gasoline.

All of this is good stuff, but with all things in life it does have some limitations. Ethanol requires more fuel mass per combustion event (stoichiometry) over gasoline. This reduces fuel efficiency per mile traveled over gasoline, so one’s fuel mileage decreases with Ethanol. Ethanol is hygroscopic (See Injector Dynamics below) so water content has caused some corrosion and chemical compatibility issues with fuel system components and rubber products, such as injectors, fuel pumps, o-rings and seals as well as tubing/fuel rails. We have seen some corrosion issues with valves and cylinder liners as well; mostly due to long term storage.

Regarding engine failures, we have seen many failures due to excess combustion temperatures and pressures such as melted pistons, cylinder heads and head gasket failures. We have also seen cracked cylinder liners from excess combustion pressure. These mechanical failures are mostly from use of pump E-85 with its questionable octane (see Injector Dynamics below) in a high output engine configuration or poor calibration (tune-up).

Another item which is in need of a separate article is spark plug heat range. We have seen numerous engine failures using pump E-85 or Race E-85 due to an incorrect heat range spark plug. As engine power output increases and duty cycle increases (mile run versus quarter mile) it is imperative to change to a colder spark plug. The increased performance of an engine is due to increase combustion heat (pressure) which increases the average spark plug temperature per combustion cycle. The spark plug must be cool prior to the next combustion cycle or the possibility for pre-ignition is greatly increased. Pre-ignition is a common failure with the increased use of forced induction in today’s street and race engines. For the forced induction Ford Modular a NGK TR6 plug is too hot above 10 lb of boost. In some 20+ boost engines a NGK BR7 is too hot. We have some folks running a NGK 10-11 heat range but the rich supercharged tune-up will cause fouling. NGK 8 and 9 seems to be a good compromise.

An interesting engine failure seen only with E-85 is wrist pin Spirolocks rotating in the groove eventually winding their way out of the groove with the end result of the wrist pin coming out of the piston causing catastrophic engine damage. We have seen many cases of an engine having all the Spirolocks (mostly left bank) halfway wound out of the groove looking like a nose hair hanging out of someone’s nostril. This phenomenon is only caused by combustion energy vibrating the piston/pin/Spirolocks. As of 2014 we have not identified the details but it does exist in hi-output E-85 applications. Round wire wrist pin locks have not shown this phenomenon to date.

Moral ----- Pump E-85 is a street fuel, so street boost and tune. Race track is race fuel and race tune and boost.

Instead of rehashing existing E-85 information, below is an excellent Ethanol fuel tech article by Paul Yaw of Injector Dynamics, put forth in detail and using the English language he excels at. Please go to Injector Dynamics for excellent technical information, particularly his Library page.

There are many papers at that are some of the best reference papers on Ethanol and other fuels as well as combustion that are well worth investigating. Don’t consider Internet discussions as valid; go to credible sources and documents for your information. Government info Production and distribution info from a production vendor.


By: Paul Yaw

The first and most important thing you need to know about alcohol is that it is hygroscopic. Hygroscopic means that it will readily absorb moisture from its surroundings. In our case, the “surroundings” would be the atmosphere, and that atmosphere contains water. The higher the humidity, the greater the amount of water, and the greater the rate of water absorption by the alcohol.

The picture below shows a typical valve from a modern ball and seat style injector. The ball shaped portion of the valve that makes contact with the seat is made from super secret alloy known only to the injector gods, but the armature is made from a fairly traditional high iron content alloy which will rust in a heartbeat if it is exposed to water.

Care to guess what happens when the alcohol in your fuel system is contaminated with water?

The armature rusts, and sticks the assembly shut. At least that’s what has happened to the injectors that get sent back to us when the car doesn’t start after sitting for a month. Worse are the cases where the injector is left on the engine because it continues to function, but the valve lift is reduced by the layer of rust on the mating end of the armature.

Considering that total valve lift varies from a high of ten thousandths of an inch, to a low of three thousandths of an inch, it doesn’t take much rust to substantially change the flow rate of the injector.

Inconsistent Ethanol Content

By: Paul Yaw

The whole point of running E85 is to take advantage of the superior properties of ethanol, right? And E85 means 85% ethanol, 15% gasoline right?

Not exactly.

Referring to “ASTM D5798-11 Standard Specification for Ethanol Fuel Blends for Flexible-Fuel Automotive Spark-Ignition Engines” we see that the 85 in E85 signifies a maximum ethanol content of 85% with the remainder being “unleaded gasoline, gasoline blend stocks for oxygenate blending (BOB), natural gasoline, or other hydrocarbons in the gasoline boiling range.”

Clear enough. 85% Ethanol and 15% WTF-ever, right?

Not exactly.

The 85 percent doesn’t refer to pure ethanol, but to denatured fuel ethanol which already contains 2% hydrocarbons to make it “unsuitable for beverage use under a formula approved by a regulatory agency to prevent the imposition of beverage alcohol tax.”

The real meaning of that bit of lawyer-speak horseshit is that E85 has a maximum ethanol content of 83%.

And that defines our maximum – so what about our minimum?

Are you sitting down?

The original specification set the minimum ethanol content at 75% which was lowered to 68% in June of 2010, and lowered again to 51% in June of 2011. As of February 2012, this is the current specification and E85 purchased from the pump could have an ethanol content as low as 51% and still be within spec.

So now that you know the what, you’re probably interested in the why. At least I hope you are. You didn’t come here with a blank stare and drool running down your face expecting to see how many people “liked” E85 did you?


By: Paul Yaw

Here’s the why. Like gasoline, E85 is blended to meet government mandated volatility levels that ensure – in theory at least – compliance with evaporative and cold start emissions requirements. These requirements vary with location and season, with the highest volatility requirements occurring in the coldest parts of the country, during the coldest part of the year.

The standard measure of volatility (a measure of a fuels ability to be readily vaporized) is Reid Vapor Pressure, typically stated in units of pounds per square inch (psi). A higher numerical value indicates higher volatility.

As of Feb 2012, there are four volatility classes defined for ethanol fuel blends. These classes define a volatility range, and the specification is as follows:

Class 1 (RVP = 5.5-8.5)
Class 2 (RVP = 7.0-9.5)
Class 3 (RVP = 8.5-12.0)
Class 4 (RVP = 9.5-15.0)

The class requirements change throughout the year as the average temperature changes. Areas like the North Coast of California, which have mild seasonal changes, switch back and forth between Class 1 and Class 2 as the seasons change. Other regions with more extreme seasonal temperature changes cover the entire range from Class 4 in the winter, to Class 1 in the summer, with classes 2 and 3 used in between. As a point of interest, Hawaii is unique in being the only state with the same volatility spec all year round. (Class 1).

Pure ethanol has a Reid Vapor Pressure of 2.3 psi and needs the addition of gasoline, or “hydrocarbons in the gasoline boiling range” as mentioned above to meet these volatility requirements. The higher the volatility requirement, the higher the gasoline content which of course means less ethanol.

So what does that mean to you, the end-users and tuners?

It means that the ethanol content will vary dramatically with season, as will the “hydrocarbons in the gasoline boiling range” used to meet the volatility requirement. In practical terms, it means that you may not get the same tank of fuel twice.


By: Paul Yaw

To be more specific, let’s consider how this variation in ethanol content affects the two critical parameters of the fuel (Stoichiometric Air Fuel Ratio and Octane Rating) using the extremes of 83% ethanol, and 51% ethanol.

1. Stoichiometric Air Fuel Ratio – Pure ethanol has a stoichiometric air fuel ratio of 9.003. The stoichiometric air fuel ratio of gasoline ranges from approximately 14.5 to 15.0 but is generally considered to be 14.7. Accordingly, the stoichiometric air fuel ratio of a mix of 85% ethanol and 15% gasoline is 9.972:1, while the ratio for a mix of 51% ethanol, 49% gasoline is 12.15:1. Based on these numbers, if we tuned our engine to a lambda value of .85 in the middle of winter, we could expect a lambda value of 1.036 when we switch to our summer mix.

It is!

I did say specific, so let’s include the density of the two fuels to make our numbers more accurate. Performing the same calculation, but accounting for ethanols high specific gravity of .79, and using a value of .72 for gasoline, we get a summer mix lambda of 1.006. Not quite as extreme, but still off in left field, and likely to rattle itself to death, or turn a piston into swiss cheese.

Fortunately the summer mix will have better detonation resistance, and better cylinder cooling due to its higher ethanol content, but if the tune was anywhere near optimized before, it sure isn’t now.

2. Octane – There are two considerations here. The first and most obvious is that as the ethanol content is decreased, the octane rating, or detonation resistance of the fuel, will also be decreased. The second, and not so obvious, is based on the ridiculously vague definition of what hydrocarbons may be used to “tune” the volatility of the blend. Note that this definition is not at all specific about which hydrocarbons should be used, and makes no mention of the octane rating of those hydrocarbons.

In case you forgot I will post it here again:

“Unleaded gasoline, gasoline blendstocks for oxygenate blending (BOB), natural gasoline, or other hydrocarbons in the gasoline boiling range.”

Since the overall octane rating or detonation resistance of the blend is dependent on all the components that make up the fuel, we have no way to estimate the octane rating of the final blend even if the ethanol content remains constant.


By: Paul Yaw

In the real world, the broad flammability range, excellent cylinder cooling, and outstanding detonation resistance of ethanol make these issues less problematic than the numbers might suggest. But that doesn’t change the fact that injectors get stuck, and engines blow up because of the facts stated above.

How to deal with it? As with most things, knowledge is power. Just knowing that your opponent has a big left hook is half the solution.

1. Do not let your E85 or methanol-powered car sit for extended periods of time. In hot humid weather, the alcohol can absorb enough water to rust injectors in less than a week. If the car is going to sit, “pickle” the fuel system by emptying the tank and flushing the system by running the engine on gasoline for a few minutes.

2. Monitor the ethanol content of your fuel. This can be done one of two ways. Either install a fuel composition sensor, or measure it directly using the “baby bottle method” which is detailed at the end of this article.

3. Tune conservatively. Knowing that the octane value of the fuel can change even if the ethanol content remains constant, you will be wise to leave a few hp on the table by keeping that final 2 degrees of advance to yourself.

4. Eliminate the consistency issues altogether by purchasing “racing” E85 by the drum. Not exactly practical for the average street car, but if you’re racing I wouldn’t even consider running E85 from the pump. In addition to having a consistent ethanol content, E85 from a race fuel blender should insure that the “other hydrocarbons in the gasoline boiling range” used to make up the remaining 15% are of high quality with a reasonable octane rating.

Better yet, buy E98. The car may be a bit hard to start on a cold morning, but it is a race car right?

5. Don’t be stupid. This should cover anything I forgot.

Thanks for reading.

Paul Yaw
Injector Dynamics

Bottom Line

We have seen some folks use the water solution test and claim 90% Ethanol in their E-85. This obviously is a faulty test. Maybe someday I will conduct a fractional distillation of various E-85 samples versus the water test to validate the accuracy of the water test. Not a high priority for my business model.

We have seen some Flex-Fuel vehicles report varying E-85 compositions with the same fuel tank load of E-85. Stratification (Gasoline and Ethanol separating) of the E-85 comes to mind which may be worth investigating.

Bottom Line --- E-85 has its place as a fuel but use your head instead of the guy’s down the street or the Internet guy.

Michael Rauscher
L&M Engines