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A Bit About Ethanol Fuels; Is E85 or Flex Fuel Right for My Hi-Power Hondacar?

  • Posted: 02-22-2019 02:47 PM
  • Engine

I had a friend who used to have a saying that alcohol was the lubrication for the ball-bearings of life. It was a fun phrase for a couple 20-somethings who knew so little about the real challenges of life that this thinking might have set them back a few brain cells unnecessarily. Irony especially being that alcohol often leads to more life-friction than less, and it should come as no surprise that the very same buddy found himself abstaining indefinitely years later. Besides, ball-bearings are fairly frictionless without much lube at all, aren't they?

If booze isn't the life-motivator it is promised to be, converting to alcohol-enhanced automotive fuel by contrast can be a great way to motivate to your car! We've been getting asked a lot of questions about E85 conversions, so we've made this post to give us a convenient place for our customers to get some answers.

Before learning about enhanced fuel, though, something important should be said about how engines make power:

How does the engine make power? It’s in the AIR.

To make power, engines pump air in, inject a little fuel at the right time, light the mix on fire. KEY: The AIR is the primary limiting factor in making power. The oxygen found in air is one of the most magical substances on Earth. If you mix just the right amount of hydrocarbons in and you have yourself a really volatile mix. Therefore, larger engines make more power; they pump more air. Therefore, boost adds more power; the pressure crams more air in. Adding air makes more power provided the right amount of fuel is added, too.

So, in case the point isn’t made clearly enough: If you aren't having a plan to add more oxygen to the engine, adding more fuel of any kind is going to be of limited benefit.

There are exceptions to this broad sweeping statement. Increasing compression and advancing timing will create conditions that can produce more power without adding oxygen. It's just that the biggest benefits to fuel changes are going to come with boost or nitrous.

What is ethanol?

Ethanol is alcohol, made from sugars. Like all alcohol, it burns when you add oxygen and an ignition source. Since it can be made from corn, and 'Merica has lots of corn, we make ethanol from corn. Since ethanol is made from plants it has been a welcome renewable addition to our favorite supply of liquified dinosaurs to make fuel. The government loves it. Our gas has about 10% ethanol in it as standard.

What is E85 or "Flex Fuel?"

From Wikipedia's E85 page:

"E85 is an abbreviation typically referring to an ethanol fuel blend of 85% ethanol fuel and 15% gasoline or other hydrocarbon by volume."

E85 is a specific kind of Flex Fuel. Flex Fuel, though, instead of being a specific 85% ethanol by volume, it can be varying ratios of ethanol to gasoline, 51% to up to around 90% depending on the station you are at, area you are in, or the time of year it is. E85 is Flex Fuel but not all Flex Fuel is E85.

What is important to know about E85/Flex Fuel?

  • It's corrosive. Fuel lines, pumps, seals, o-rings and the like all need to be designed to work with ethanol otherwise the fuel can eat away at the material and cause leaks. This is mostly a problem on older cars designed and built before ethanol was a common additive and automakers were designing components to be compatible.
  • It's hygroscopic, meaning on a chemical level it seeks out water and absorbs it (similarly to brake fluid). This is important to know because you don't want higher concentration ethanol fuel sitting in your tank for long periods of time because water will collect and enter the fuel system. The same thing can happen with gasoline, but it is more of a concern with ethanol.
  • It's got a lower energy density compared to petrol. If we light a cup of gasoline on fire, more heat is going to be given off than if we light off a cup of ethanol. In order to get the hydrocarbons in ethanol to generate the same heat as gasoline, you need more fuel than you would straight gasoline. About 25-30% more in fact. So that translates to a pretty significant increase in fuel consumption.
  • Ethanol has oxygen in it. This adds to the lower energy-density issue because in the ethanol molecule there is less "room" for hydrocarbons, and more oxygen is available in the mixture which serves to lean out the air-fuel ratio. Even MORE fuel is needed to make the air-fuel ratio work out. It's not bad for power, but it just makes the engine really thirsty. It's true there is more oxygen in ethanol and so more power can be made; just understand that it means more fuel is needed to make the chemistry work out.

Why would you want to use ethanol-blended fuel in your hot-rod Honda?

Ethanol has a higher-octane rating than gasoline does. E85 has an octane rating around 105. This means you can run higher cylinder pressures without the risk of detonation (in a nutshell, the fuel is much less prone to "lighting itself" and causing knock).

Not only is the octane higher, but it has a high latent heat of evaporation—meaning as it atomizes it removes heat from the intake air. (In other words, when the fuel is injected and it vaporizes, it cools the intake charge. Ethanol cools more than gasoline does.)

So is my Honda is going to make more power if I change the fuel to an ethanol blend?

Yes, but there is more to it than just what you put in the tank. Your car needs to be set up for ethanol fuel to effectively use it. Plus, the fuel costs less than gasoline will but you will be using significantly more of it (nobody told you the MPGs are going to drop?). It won't make economic sense to convert if you won't reap enough of the power benefits.

A lot of Hondacar drivers have NA setups (as in—they are not using power adders such as turbo- or super-charging as a means of adding more air to the engine). If you have an NA setup and aren't running high compression—like at least 12:1 or more—the power benefit to you is going to be smaller, because 91 octane and a good tune is all you need. Sure, you'll be able to run a bunch more timing advance which will feel great, but the fuel cost is a lot to consider for that benefit. Because NA stands for "Normal Air" going into the engine. (Actually, it means Naturally Aspirated, but in lay-terms Normal Air makes the point clear than the air-charge is not boosted).

If your engine is boosted turbo- or super-charger we have more to talk about. Adding boost in this fashion adds oxygen to the mix and adding more fuel will make more power. Adding boost can be risky because if your fuel octane rating is not high enough detonation can occur and cause damage to the engine. So for higher boost, high-octane ethanol is going to hook you up! You'll be able to add more boost to the engine and have much lower detonation risk which is really going to make power.

Cooler air means more power and is safer

Also, ethanol has a greater cooling effect when it vaporizes than gasoline does, so that is a solid benefit in any case. If you are running an NA car with moderate compression but are beating the piss out of it all the time, you might find your car running a little tighter as cylinder temps are controlled just a little better.

Also since ethanol is not as volatile as gasoline the combustion is cleaner and smoother as it pushes on the pistons. Many converts say their engines run smoother and the power delivery is easier to manage with ethanol in the mix.

Ok, so I have been sold on ethanol. What do I need to know to get going?

You're getting excited—just put the wallet away for one more second, though. The first thing you need to ask yourself before buying anything is what mix of ethanol will you be using?

In California, vendors pay about 4x less tax per gallon when they sell fuel that is less than or equal to 15% gasoline, so in a round-about way suppliers are incentivized to keep it 85% Ethanol or higher. Therefore, California tends to have consistent blending of E85 that you can have a fixed "tune" for.

Other states are not consistent in this way. It is a lot more common to find Flex Fuel in various stations, wherein the ethanol content can vary between 51% and 90%. And when you take winters into account the blend really favors gasoline so you can start the engine in cold weather (because of the lower energy content in ethanol, you might find that cold-start "kick" lacking in many places that aren't California). So the region and season can play a role in the fuel mixture.

Unless you have a regular fuel source that sells consistent fuel, you might find yourself in a bit of a tuning-pickle. The AFR (air-fuel ratio) needs to be adjusted for the varying ethanol content you might encounter. Putting different blends in a car not rated as a "Flex Fuel" vehicle could have some issues.

We solve the problem with Parts and Tuning!

  1. Buy a tuning computer to give you engine management ability.

Before you get started, you will need some kind of fuel tuning, engine management, or programming tool to calibrate the computer to tell it how to handle the mods you will be doing. In most common Hondacar cases, this means a reflash tool from popular brands Hondata or KTuner. These modules can re-write the stock computer mapping to make your setup run correctly. You can also use great AEM computers which completely replace the stock computer for tuning in more aggressive applications. Of course, all the above are available from Heeltoe. We can help you determine what is right for your build.

  1. Buy larger fuel injectors.

After you have your engine management figured out you need to handle the increased volume of fuel you need (to make up for the lower energy content, additional oxygen molecules, and the presumed increase in overall air to the engine with power adders). To add more fuel to the cylinders you will need larger fuel injectors. The injectors aren't physically bigger, but they will inject more fuel needed to overcome the extra oxygen you are adding and the reduced energy density of the ethanol fuel. Because of the extra capacity we say they are "bigger." There are a few brands that Heeltoe promotes—Deatschwerks (just say DW if you want), Injector Dynamics (or ID), and Fuel Injector Clinic (or FIC), even factory Honda RDX (doesn't stand for anything afaik) injectors may work great for milder NA builds—and can set you up with the necessary plugs to get them installed in your engine.

  1. Buy a larger fuel pump.

The fuel system needs to maintain pressure, and since adding larger injectors will flow more fuel from the system the factory pump may not be able to "keep up" with your engine's fuel demands. You will need a higher capacity fuel pump to make sure the fuel system has enough flow when those injectors open to keep fuel at a steady pressure when the injectors open. Many direct-replacement in-tank and in-line fuel pumps are available from Heeltoe, from DW, Walbro, Radium Engineering, and AEM. (AEM is nice because they have one especially for E85 applications, aside from just being "compatible")

  1. Buy a flex-fuel sensor (especially if your ethanol fuel-days are not going to be consistent).

And if your ethanol content is going to be varying then it is a good idea to add a flex-fuel senor to more-or-less convert your car to a Flex Fuel vehicle. A flex fuel sensor will detect the amount of ethanol in the fuel, which you may want if you won't be tuning for a specific ethanol mix. These sensors can talk to whatever tuning module you are using and adjust the computer's parameters accordingly to give you the most performance for the amount of ethanol in the fuel. This is pretty cool because it means that you don't have to worry so much about what fuel you put in the car because it might be incompatible with your tune; the tune will fix itself! Heeltoe has components from KTuner, AEM, and others that really help your custom setup but also offer brands like PRL which have direct drop-in PnP setups for some applications.

  1. Go get a tune to make all the above work right!

And last to mention but probably the most important thing you need is a professional tuner! Someone who can calibrate your ECU program to handle the different fuel and power mods you are adding. We listed a tuner last but really, we recommend researching this facet of the job first. Someone local with access to a dyno is the best, but you can also arrange an e-tune or remote-tune. If you are planning to raise boost significantly, we strongly urge a dyno visit even it is a bit of pilgrimage to get it done.

In conclusion:

E85 and Flex Fuel can be really great friends to have in the tank when you are after making the most of your mods. They can allow you more creative freedom with your ignition and cam timing and allow you to cram more boost into your engine, all of which will result in noticeably more power. The fuel will help the performance engine run smoother and cleaner overall. There is a cost to the benefits in the form of added fuel consumption and investing in a few parts but at least the bits you buy it aren't too costly (assuming your car's factory fuel system does not need to be completely redone to the ethanol doesn't turn your hoses to goo).

Looking for more power? You'll get it with ethanol! How much will depend on your total setup. Heeltoe is in your corner to make sure you do it right.

Time for a beer! Cheers for reading and remember, Heeltoe is In Your Corner!


Special thanks to David Walker who provided a lot of info and editorial help to polish a lot of the swirls out of this article.

About the Author

Marcus di Sabella Marcus is the founder of Heeltoe Automotive. He's been working with cars (mostly Honda cars) since 1996, and has been providing enthusiasts with excellent products, services, and web experiences since 2002. He's been published in Honda Tuning, and holds a degree in Engineering Technology.


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