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29 Posts
Discussion Starter #1 (Edited)
I have dug for days on this topic and not finding any real summarized answers so I have come to you guys..

Is anyone currently running E85? I understand it can work with some basic supporting mods and a great tune and some people on Ms3's and other cars seen as high as a 30% HP gain. I talked to Cobb Plano and they highly suggest not running it in a Ms3 no matter what supporting mods you have. So my questions are this. (some are ones they asked me..

I have all the supporting mods other then downpipe but it is on the way. And yes i have HPFP Internals... so here goes.

1. What will E85 do to my car in a bad way? Is it worth doing this for the pros ? (ie more HP)
2. How will I mix it? Can you not just wean off 93 slowly mixing in E85 in your tank till your at 30/70 or 50/50? Again, already having all the supporting mods.

Here is all the info I could really gather on this for Those that don't know much about E85. This came from a friend running it in a 2010 speed 3 with e-tune . Some of the info is not for MS3 but can apply the knowledge to any car.

Below are many parts to E85.
The attachment is an E85 fuel mix cheat sheet. It’s only good for E85, which is what they’re pumping now. As explained below, winter and spring/fall blends are different. In the summer it’s 85% ethanol. Winter it drops down to 70%, so the ratio changes. I have the cheat sheets for those blends somewhere too.

I’m tuned by Stratified, and highly recommend them. For you, wanting to play with ethanol a bit, something like this is an awesome option.

Stratified MazdaSpeed / Mazda MPS S-OTS+ E85 Tune [Stratified Mazda S-OTS+ E85 Tune] - $50.00CAD : Stratified Automotive Controls


Q: What is E85 / Ethanol?
(An alcohol fuel made from corn / organic matter. E85 means 85% ethanol* and 15% other hydrocarbon fuels sort of like gasoline. It's not regulated by octane rating like gasoline is, but is sufficiently badass.)

(* See summer / winter blends)

Q: Why run Ethanol?
(Suppressing knock and being able to run more boost and timing. On a 50/50 mix X hp and Y torque increase possible with a good toon.)

Ethanol has an incredibly high latent heat capacity, along with a regular octane rating of ~104 (depending on what you read). But, in a direct injection application, all of that latent heat capacity (the amount of heat used to evaporate it) is utilized in the cylinder, giving a much higher 'effective' octane rating. Pure ethanol, E100, was calculated to be ~160 octane; whereas pure methanol, M100, is ~180. As you can imagine, even small amounts of ethanol have a great affect on knock suppression.

Q: What mods do I need to run Ethanol fuels?
(No mods other than HPFP and tune)
On extremely low mixes (1-2 gallons), you can get away with no mods. When tuning for it, you may find that you have to reduce boost to sustain fuel flow without internals.

As with anything, flow mods that allow the engine to breathe will still gain power. Power comes from airflow, first and foremost, taking advantage of it without encountering knock is where E85 comes in. As you increase ethanol content, the fuel demand increases. Beyond 15-20% additional ethanol content, and you are risking dropping fuel pressure with a conservative AFR.

Q: Anything I should do before running Ethanol?
clean the pump when going above ~25% mix, just to be safe.

Set up a tune for it, just like you would when tuning any car from scratch. Start conservative, work your way up.

Q: Should I run straight ethanol or some kind of mixture?
(Mixtures of Gallons E85 / Gallons Gasoline)
3/11 yields E26 and is good for a moderate increase in power/torque.
50/50 yields E48 and is good for the standard, sneaking through the bushes rape.
Straight E85 is good for cell block rape.

Q: What was that about Winter/Summer and Seasonal Blends?
The ethanol content varies seasonally. E85 has a minimum of 70% Ethanol content during the winter, and a minimum of 79% during the summer. More ethanol = leaner mixtures. If you consider the extremes of minimum and maximum ethanol content, going from Winter (70%) to Summer (85%) will result in lean operation. Going from Summer (85%) to Winter (70%) will result in rich operation. (Requesting comment) Note, if you're running a mixture, you can compensate for the ethanol content by adding more or less E85.

Q: What's the gas mileage like on Ethanol?
This depends entirely on the tune and driving habits. Mileage can be as good if not better on 50/50 than completely stock on pump gas if tuned for it and driven non-aggressively.

Expect to lose some mileage with E85. As you increase ethanol content, the more mileage you lose. I saw an approximate loss of 25% mileage on straight E85. If you're in the boost more often (you will be), then expect significantly less.

Q: How does Ethanol fuel (E85) compare to Water Methanol Injection (WMI)?

Both are effective knock deterrents. It typically comes down to what is available, and what power you are trying to make.


29 Posts
Discussion Starter #2

Q: What about other Ethanol pump blends E30, E50, E98?
No mechanical issues demonstrated on blends up to ~E45.

Q: Will anything bad happen to my car?
(Black death at mixtures over ____ % mixture and running ___ kind of engine oil)
Frequent tire changes with even light use (lolnotraction)
Pump/spill valve cleanings over 50/50

2nd Gen MS3's sometimes see a failure of the fuel level sensor. It isn't common, but it is a known issue. Many have been covered under warranty.

Fro - I don't remember how much it was.. but MMS has it for $28, normally $45... and that sounds about what I paid for it. However, that's the only problem I've had using a 50/50 e85 mix for about a year and a half.

Q: What can I do about the black death?
(Remove and clean HPFP with naptha when pressure drops)
This might be fixable with specific types of oil used.


Q: Do I have to get the car tuned?
To take advantage of it (meaning make more power from it), yes, you need to be tuned for it. If you are planning to run >~20% ethanol content, you need a tune regardless of whether you want to make more power or not.

Q: Are there off the shelf (OTS) maps for Ethanol?
Neg. We could make some though.

Q: What do I need to change in my toon to run Ethanol?
Adjust the Fuel Specific Gravity and Injector Scalar value by Enki's calculated values. Before these options were added to AccessTuner Race, the way to do it was to scale the MAF curve.
Fuel mix cheat sheets

MAF curve is old school. FSG and IS are the new sauce, use those instead.

Q: Then what can do with my toon once I'm on Ethanol?
(Increase boost and timing by _____ ballpark figures. Split difference between timing database and your current settings?)
Timing is something people who need a guide for the fuel probably shouldn't be messing with; direct to general tuning guide.

Q: Anything to look out for when tooning?
(Knock sensor, MBT)
("When tuning timing for E, use the MAF sensor. Voltage flattens out, you're at the peak and should back it down a bit. Make sure you do the comparison runs under nearly identical conditions (temp, humidity, elevation, etc) if you can't do it on a dyno." -Enki)
If timing changes and it feels slower, you've probably gone too far.

I disagree with Enki a bit, here. For timing, be conservative and go by known good values until you are able to get on a dyno to find MBT. Very close analysis using Virtual Dyno is only good enough for the initial, broad changes. It (in my experience), is not reliable enough to report a change of 3-4hp, which is what you will see as timing gets close to MBT.

Q: Tooning differences between Winter/Summer and Seasonal Blends?
(LTFTs? Reduce boost during winter because of fuel demand?)
---- *Removed for typo.
(If you) tune during winter and it will run leaner in the summer. (Bad.) More e = more fuel has to be injected to reach targets, so you always want to tune during summer months or with your summer mix. You'll run rich in the winter. (Which is ok.)


Q: Can I store Ethanol in fuel jugs?
(Yes, keep away from moisture.)
Sealed containers are best.

Q: Should I use an additive to preserve the fuel?
(Sta-bil ethanol treatment?)

Q: How long can I keep Ethanol stored?
How good is the container at keeping moisture out?

Q: Can I test the Ethanol?
(Yes, using an Ethanol Tester kit, you can determine how much water is dissolved in the Ethanol.)

29 Posts
Discussion Starter #3
Part 1
Introduction to my experiment with E85 circa 2004

This is a summary of past posts from various forum discussions

I have been running a high ethanol fuel blend in my WRX for nearly 2 years now, with no problems traceable to the fuel. The car really likes the high alcohol blend, with an obvious improvement in performance comparable to high octane so called "race fuels".

The Stock WRX ECU can handle up to approximately 33% E-85, by volume before you get a check engine light for "too lean" due to the fuel trims being pushed to the max rich settings. Add just a bit of pump premium and the CEL will clear.

I recently shifted to STi 550 injectors without any special changes in the engine management. Due to the cars larger injectors the car now prefers a higher blend. I am now running about 95% E-85, but have run the car on blends as low as about 30% E-85 without any serious problems. At lower blends the car has some surging due to the over size injectors at higher throttle settings, but can be easily driven as a daily driver if you stay out of the >60% throttle position transition to open loop.

The one problem is that currently E-85 sites are a little difficult to find, but the more of it we use the more available it will become.

The folks backing E-85 production are pushing as hard as they can to get stations to make it available, but its a slow process. They need customers to start asking station owners if they plan on carrying it to motivate stations to add a pump/tank.
There are currently dozens of FFV's out there that are designed to run on the stuff if folks can find a place to buy it. Simple way to drastically reduce oil demand as well, and put money in our economy instead of some other countries coffers.

I currently drive 20 miles each way to get to the nearest E-85 stations, but it is still a good deal as I am paying $1.59.9 / gal for the E-85, vs about $2.05.9 / gal for premium. ( some E-85 vendors charge at a premium fuel rate of about $2.00/gal)

With the added octane of the E-85 you can actually splash blend it with mid grade gasoline with out problems.

When I suspect it will be difficult to locate E-85 from the pump I just make a point of topping off the tank before it drops below 3/4 full. This keeps the ethanol blend up to a high enough level to avoid any drivability issues with my oversize injectors.

Is the WRX warrantied to run on E85 ?
NO it is not, but my experience shows its not a major issue either.

I think it is important to note that they don't recommend greater than 10% ethanol, ie they warranty the car will run fine with up to 10% ethanol but greater than that your on your own. But they do not say you should avoid higher blends of ethanol and other tests have shown modern cars can run on upto about 30% blends with no problem.

They do specifically mention that methanol is not to be used over 5% concentration, and that is due to corrosion issues with methanol, which is Much Much more prone to corrosion than ethanol.

So far I have seen no "real" problems with the E-85. There are two minor CEL issues.

1 If your running over 35% on a stock ECU and fuel injectors you will push the fuel trims to full rich and get a "too lean" CEL.

(edit 10/02/2005 --- emission CEL has not re-appeared in quite a long time. I am beginning to suspect it was due to a loose vacuum hose resulting from the injector upgrade that got fixed as I was working on other things )

As mentioned above any "damage" should be easily remedied, ie replacing a hose, or some O rings, possibly changing to a different fuel pump. It is very difficult to predict long term corrosion, or materials compatibility so I've decided to bite the bullet and be the test dummy and see what if anything breaks.

Based on my tests, the short term conclusion is you can run concentrations of >10% fuel ethanol for periods in execess of 1 year with no detectable damage. We'll just have to see how things go in another year or so.

Hopefully this winter I'll get the time to pull the fuel pump and look over the interior of the fuel tank to see how its doing.

What is the history of large scale conversions to high ethanol fuels

When Brazil began making a wholesale conversion to high ethanol fuels back in the late 70's following the energy crisis, they made several studies on the ability of normal cars to run ethanol blends. They found that the cars of that period could run up to about 22% blends on the stock system with no problems, which is why they settled on a 20% blend as one of the fuels available. The issue was one of control authority of the ECU to compensate for the leaner mixture. Some could handle more than others. As I stated, it appears the stock ECU on the 2002 WRX is good up till about a 33% - 35% blend.

During the 70's and 80's when oxygenated fuels and "gasahol" first saw wide use here in the U.S. there WERE fuel component compatibility problems. My 1969 VW fuel lines really didn't like the ethanol and began to leak like a sieve, some carburetor needle valves softened, some carburetor floats would soak up the ethanol and get too heavy to function as a float. There were lots of problems with clogged fuel filters on cars that had been running on gasoline only for decades and had lots of varnish build up in the fuel system. The ethanol in gasohol was a very efficient fuel system cleaner and all that crud got carried to the fuel filters. Once the fuel filters were replaced those problems disappeared.

At that time All the auto manufactures moved to ethanol compatible fuel line components, ie. o rings, rubber hose etc. They warranty that they are good to 10% but my experience shows they are satisfactory to much higher concentrations. The VW showed its compatibility problem in a matter of months after we went to ethanol blended oxygenated fuel here in Denver. Engineers typically don't solve a compatibility problem by making the new component "sorta compatible" they change compounds to materials that are not effected by the chemical in question.

The Denver area has been using ethanol oxygenated fuels (ranging from 5% - 10%) concentration for over 30 years. Every modern car works just fine with these low ethanol blended fuels. Rubber hoses and O rings last for the life of the car.

The electrical conductivity issue is not significant in the case of ethanol. It is detectable with a dialectic constant tester. It DOES become a significant issue with methanol blends which is why methanol blended fuel is so aggressively corrosive. The main issue with methanol is it aggressively attacks certain metals like magnesium and zinc. One of the reasons everyone is looking at ethanol is the 30+ years of successful use of high ethanol fuel blends in Brazil and low ethanol blends here in the U.S. with essentially zero problems after they changed fuel line and O ring and seal materials in the fuel system.

Dialectic Constants
Gasoline 2.2
Ethanol 24
Methanol 33.6
Water 48 - 88

Keep in mind that absolutely pure water is a good enough insulator it is used to cool electronic components. It does not become an effective conductor until is dissolves minerals that act as charge carriers (electrolytes).

Will my O2 sensor work with E85 and high ethanol blends?
The O2 sensor is not an issue, all it cares about is if your at stoich combustion at low throttle settings, it doesn't much care how you get there, so no need to change it.

Air-fuel ration: Air-fuel ratio - Wikipedia, the free encyclopedia
Oxygen Sensor: Oxygen sensor - Wikipedia, the free encyclopedia

What about the evaporative emissions system in my car

The higher vapor pressure of ethanol gasoline blends is not ideal for the evaporative emissions system and the vapor recovery canister. For full emissions compliance these will need to be modified. Currently there are no kits available to upgrade this part of the emissions system.

As I mentioned above the only -- real -- problem so far is simply some nusince CELs.
"too lean" if your over 30%+ on the stock injectors

If your emissions test requires no CELs present, you simply need to go to a lower ethanol fuel blend for a while to allow that nuisance CEL to clear, and the dash warning light to go off.

what would be needed for a complete conversion kit to run 100% ethanol fuel

For full conversion to alcohol fuels the change list typically looks something like:

29 Posts
Discussion Starter #4
1. Go to an compatable fuel pump (walbro 255 l/h pumps seem to work well with E85)
2. Replace fuel lines with alcohol compatible lines. (not needed on WRX based on current experience)
3. Possibly replace filter (not needed on WRX based on current experience).
4. Replace injectors with large enough ones to feed proper fueling. (+30% flow over stock)
5. Replace injector/FPR o-rings with compatible o-rings... viton maybe? (not needed on WRX based on current experience)
6. Add a spark/flash suppressor to the fuel tank inlet tube. (does not appear to be a significant hazard based on current experimenter experience)
7. Ensure the fuel tank material is completely compatible with alcohol. (not needed on WRX based on current experience)
8. Reflash or other engine management option for ideal tune to use E85's capability (optional at low to moderate boost)

With ethanol on the WRX, you only need (according to my current experience base) is numbers 4, 8.

(edited to remove comments about emissions CEL which proved to be due to other causes and has never returned)

What about fuel system corrosion?
Corrosion does not appear to be an issue with modern OBDII cars. They are all certified by the manufactures to be safe to use on 10% ethanol fuel blends, and industry insiders say they are safe for much higher percentages. You don't install components that are "sorta safe" with a chemical, you put in a fuel hose etc. that is ethanol safe for concentrations well above what you expect to use. Not to mention that folks have been talking for years about raising the ethanol level to 20% or more.

Occasional use would be no problem at all based on my experience. I have never cut open the fuel filter (still have the OEM filter in place) I'll open it when I replace it. I want to put enough time on it to have conclusive evidence if there are problems.
(edit circa 2007 I cut open a fuel line and it looked like new, not changes or damage on stock rubber fuel lines in 2002 WRX)

The engine is not an issue with either, WI using a water alcohol mix or straight alcohol injection. In those systems alcohol and water are not used in significant quantity or for long duration. The Buick GN folks and lots of folks in the DSM crowd have done it for literally decades with no problems for the engine.

Many years ago there were studies that indicated engines that ran on alcohol ALONE as a fuel, had issues with lubrication and valve seat wear. Keep in mind, those studies were done a long time ago, when engine oils were much less sophisticated than they are now, and some engine manufactures in the 1940's,1950' and 1960's made stupid engineering decisions and did not use hard valve seat inserts like stellite in the cylinder heads. This resulted in valve seat recession problems if you did not have lead additives in the fuel to protect the valve seats.

What about oil contamination?
Modern lubricants, especially the synthetic oils are much much different than the oils used during those studies, and modern engines run at higher temperatures today which will quickly boil any traces of alcohol out of the oil.
In cold weather I run an 180 deg thermostat to assist quick warmup I have left it in during this past summer and so far the engine has no heating issues with the 180 thermostat on the E85 fuel.
(edit experience shows modern synthetic oils work very well with E85)

Is Ethanol less corrosive than Methanol?
Methanol is much more corrosive than ethanol. It attacks certain soft metals that are not much used in modern fuel systems. Years ago, the carburetors were made of un-anodized aluminum and if methanol fuel was used, you had major problems with electrolytic corrosion between the aluminum and copper components used in the fuel system, since they were in continous contact.

That sort of corrosion only occurs when you have a current path between the dissimilar metals AND, a conductive path through the fluid in the system.

In Brazil where they have run high ethanol fuels since 1939, they found that to convert older cars designed for gasoline, long before ethanol blends were common, needed several changes to convert the cars over. This led to changes in valve materials, piston rings choices, nickel plating of the fuel tanks etc.

Modern cars in the U.S. are designed for use with ethanol up to 10% concentration in the fuel. That has led to several changes in component materials over the last 30 years that the U.S. has used ethanol enhanced fuels. All modern fuel lines and such are designed with the expectation that some ethanol will be in the fuel.

My experiment is an intentional effort to push the envelope and see what happens. Over the last 2 years I have run high ethanol fuels ( normal pump fuel here in Colorado contains up to 10% ethanol anyway) for months at a time.

At mixtures below 33% by volume of alcohol ( about 39% E-85 by volume) I had absolutely no problems of any kind. At higher mixtures > 33% alcohol, I got a nuisance CEL for too lean which could be eliminated by added gasoline to the mix or as I have recently increased the injector size. (Increasing fuel pressure would also increase the effective size of the injectors).

The only issue with near 100% E-85, is the car starts a little harder in cold weather. When it gets very cold I drop the mixture to about 80% or so to solve that by adding about 2 gallons of gasoline to the tank of E-85.

I have done no oil analysis at this point, walbro 255l/h fuel pump and 550 injectors show no signs of problems to date.


29 Posts
Discussion Starter #5
Part 2
Where can I buy E85?

Distribution is currently a problem, it is most available in the mid western states, but there is a concerted effort to get an ethanol fueling infrastructure built, it just takes time, and recognition by the gasoline vendors that there is a market. Marathon oil has already added E85 to their formal product line so things are moving in that direction.

Current high fuel prices can only help that process, as will lots of people calling up gas stations and asking them when they plan on pumping E85 for FFV's.

E85 already contains inhibitors and such to minimize corrosion, and most of the problems with ethanol usage were solved 20 years ago when most of the country moved to ethanol addition to gasoline following the oil crisis in 1973 and high oil prices that continued up until 1981.

Where can I buy E85
For information on distribution points check out:

How about fuel mixtures for E85 what is needed ?

The one interesting thing to note is that the stock pig rich mixtures at WOT on the stock ECU of the WRX are very close to max power mixtures on E85 blends. If you play with the blending ratio to find your magic number you can take advantage of this by giving the car a fuel blend that is max power rich at stock ECU WOT mixtures. *** just take your time and work up the blend slowly ***

After a few folks have dyno runs on various blends we can probably pick out a "best starting point" blend that will get you very close. We could also work out the other supporting mods to make best use of E85 for minimum cost.

It basically takes about a +30% increase in fuel flow to get the same equivalent mixture with E85 that you had with gasoline.

For example an adjustable fuel pressure regulator can increase your effective injector flow to partially compensate for the fuel changes.

As mentioned above, lean is still a bad thing, and with alcohol fuels due to the higher power levels a serious leanout is more lethal. With conservative mixtures alcohol actually burns so cool that on E85 FFV there is some concern about getting the cat to light off.

If you sneak up on a fuel blend slowly you should be just fine. I would venture to say for the near stock folks, up to 30% is probably safe as long as you give the ECU a few miles to make the major part of the fuel trim accomodation before you start beating on the car. You'll know when the ECU starts to get happy as the midrange torque is noticably better.

I also strongly suspect that a well tuned car with no cats can probably pass the emissions sniff test on high E85 blends.

How does ignition timing change on E85 ?

Timing on ethanol blends will not change very much. MBT timing for both gasoline and E85 are very nearly the same at light to moderate engine loads. At high engine load the E85 will want just slightly more advance. The big difference will be fuel/air mixture. The E85 will give improved torque with much richer mixtures than gasoline. Both gasoline and E85 will give best thermal effeciency at about 15% rich of stoich, so the equivalent of 12.78:1 on gasoline would be about 8.5:1 on E85, but E85 will continue to give better torque numbers up to about +40% rich of stoich or 7:1 mixtures, so on a utec you would want to richen up your WOT high load cells and add a tweak of timing to get the most out of E85 from what I've read.

Are you sure you don't mean that E85 will allow more advance?

Just passing on what I've found in the various sources. Logically you are correct, but one source says simply that MBT timing is the same for E85 and gasoline, and another report says at low loads the E85 and gasoline like the same MBT timing but at high loads MBT timing for the E85 is slightly more advance.

I suspect this is due to them not running ideal max power mixtures but cannot confirm it. Burn speed for E85 changes quite a bit with mixture, so if they were just a little bit lean or rich of ideal the burn rate would be lower.

Lots and lots of variables not well covered in some of the sources and in general they are focusing on emissions issues not max power torque so that would incline them to use less than best power timing advance. In a couple of the reports they also had limited control authority over timing and may not have explored the extremes very thoroughly.

what data is available on combustion speed for E85?
Just about a year ago (2003), I was finding conflicting information on alcohol fuel burn speeds and contacted The National Renewable Energy Lab here in Denver, they did a search and could only find a couple of references on it, one that showed ethanol fuels burn faster, so the literature is not very rich in data on the subject. Most reports are not entirely applicable to our needs like tests on lawnmower engines and alcohol fuels have some significant limitations

Still digging for info but that is my best information at the present time.

The report that mentioned the slight increased advance requirement on heavy load E85 fuels was :

"Final Report Control of Exhaust Emissions from Small Engines Using E-10 and E-85 Fuels"
LARA - MI Department of Licensing and Regulatory Affairs

On page 12 it says :
"Tests were conducted to assess the impact of MBT ignition timing on fuel economy and exhaust emissions. The spark timing was varied until the least advanced timing was achieved for the maximum torque for a given setting of the engine throttle. The A/F ratio was adjusted to achieve near stoichiometric operation. ... " The MBT timing for E-85 fuel was a few crank angle degrees advances compared to E-0 fuel when the engine was delivering high loads, typically 100 - 75%. Not much difference was observed at lower engine loads."

I'm assuming that this explains the timing change as they were using what would be closed loop fuel mixtures on the WRX. So in load cells that would continue to use closed loop fueling you would want to have slightly more ignition timing than you would with gasoline. In the case of WOT open loop fueling where your running a max power rich fuel mixture, I very strongly suspect the fuel burn speed would be noticably faster, and you would use less ignition advance than on gasoline and reap the benefit of less negative work on the late stages of the compression / early period of combustion prior to TDC.

In a power point presentation presented by the EPA at the SAE Government and Industry Meeting in Washington D.C. on May 13, 2003 titled:

"Ethanol-Gasoline Blends: Fuel Economy and Emissions Benefits"


On page 9 of the presentation is a nice chart comparing laminar burn speeds of gasoline and Ethanol.

It shows the following burn speeds:

Mixture fuel/air---- 1:1 ------------ 1.1:1

Gasoline --------- 26 cm/sec ------- 30 cm/sec (max about 31 cm/sec)
Ethanol ---------- 41 cm/sec ------- 45 cm/sec (max value)

Clearly at +10% - +15% rich mixtures where ethanol shows max thermal efficiency it burns significantly faster than gasoline. Which could be quite important to a very over square bore engine like ours!!

what is the ideal fuel air mixture for E85

If you are tuning with a wideband O2 sensor you will want to switch it to Lambda mode to get valid fuel air mixtures with blended fuels. If you can only get gasoline AFR's, simply divide the gasoline AFR's by 1.5 to get the true AFR for 100% E85. If running a partial mixture you can make proportional changes based on the percentage of E85 in the mix.

Here are some comparisons of stoichiometric fuel mixtures for different fuel blends:
======== stoichiometric AFR ===== max power rich AFR
Gasoline ---------- 14.7:1 -------------------12.5
100% E-85 ------- 9.73-9.8:1 ------------- ~ 9:1 - 8:1
100% fuel ethanol - 9:1 ------------------- ~ 7.2:1

One source specifies that the proper fuel tune (stoich) for a VW Golf running 22% ethanol was 12.7:1 (this reference was probably from the Brazil tests)

Ethanol reaches max torque at richer mixtures than gasoline will.
Using a 99% ethanol mixture MEP increases with mixtures up to 40% excess fuel where with gasoline MEP is reached near 20% excess fuel. Over all thermal efficiency for both gasoline and ethanol is reached near 15% excess fuel.

E85 burns faster than gasoline at best mixtures so it is an inherently more effecient fuel. It also produces more exhaust gas for a give weight of fuel air mix giving higher average cylinder pressures inspite of lower EGT's. With streight E85 in a properly tuned car its good for about +5% power / torque increase. I suspect on a turbocharged car the benefit is larger.

My source lists stoich for E85 as 9.8:1 ( "Burn rates and emissions from ethanol gasoline blends" )

Detail discussion of E85 tuning can be found at specialty E85 web forums such as www.e85forum.net • Index page where they have assembled people with lots of first hand experience tuning with E85 in high performance situations.

E85 fuel ethanol content seasonal changes

E85 fuel blends change content seasonally just like all gasolines blends change with the seasons. This seasonal change in blend for E85 is primarily to improve cold weather starting, where the changes in gasoline during cold weather is to improve cold weather starting. In the summer months, gasoline must be blended to reduce vapor lock and to reduce evaporative emissions.

The recommended dates for changing E85 fuel blends are listed in a chart in the E85 handbook on page 22, which is in the "E85 Fuel Specification" tab.
The Volatility class specifications are broken down on page 10.

Volatility class 1 --- minimum ethanol 79%
Volatility class 2 --- minimum ethanol 74%
Volatility class 3 --- minimum ethanol 70%

As you can see each region has a different start date and recommendation for seasonal blends depending on local weather climate.

Here on the high plains east of the rockies in Colorado we run the class 1 fuel blend from mid June -- mid Sept, run class 2 fuel from mid Sept -- mid Oct and run the class 3 fuel blend from Mid Oct -- mid April, then back to the class 2 blend from mid April to mid June. The standard only specifies a minimum ethanol content, vendors can run higher ethanol content if it is economical. If it is cheaper for the fuel blender to add more he can. Ethanol content is bottom line driven by local weather conditions, and cold starting problems for local drivers just a gasoline blends are modified to give easier starting in cold weather.

In the Southern part of Texas they would never go to a class 3 blend, and in Wisconsin, they would only have the class 1 blend for about 2 months in the summer. In Florida they would be on class 1 almost all year long and in North Dakota and Wyoming and Montana, they would be on class 3 almost all year long.

29 Posts
Discussion Starter #6
Power available on E85

Many sources make a big deal about E85 having less thermal energy per gallon that a gallon of gas. They frequently draw the false conclusion that you cannot make more power on E85 than you can on gasoline. E85 actually has a higher specific energy at stoichiometric fuel air mixtures than gasoline, and at proper max power mixtures releases more thermal energy in the cylinder for a given amount of air to burn. Since an internal combustion engines power output is primarily air supply limited this means you can make 5% to nearly 30% more power on E85 than you can on gasoline.

(edit 6/10/08) Current experience shows turbocharged cars like the WRX and DSM families can run upwards of 30 psi boost on E85 tunes without knock. The only case I know of where knock was logged was on a 500+ whp DSM running 35-39 psi boost!

Ethanol specific energy at stoichiometric fuel air mixtures is actually higher than gasoline allowing a higher release of energy per lb of air burned than gasoline.

Typical gasoline Thermal energy 19,000 BTU/lb max power fuel air mixture 12.5:1
Typical E85 Thermal energy 13,475 BTU/lb max power fuel air mixture 6.975:1
Typical ethanol Thermal energy 12,500 BTU/lb 6.429:1

If you are consuming 100 lbs of air, lets see how much fuel energy you release for each of these fuels using gasoline as the base 100% reference.
100/12.5 = 8 lbs of gasoline @ 19,000 BTU/lb = 152,000 BTU = 100%
100/6.975 = 14.337 lbs of E85 @ 13,475 BTU/lb = 193,189.9 BTU = 127% more heat energy
100/6.429 = 15.555 lbs of Ethanol @ 12,500 BTU/lb = 194431.5 BTU = 128.9% more heat energy

Typical fuel energy contents:
gallon of gasoline = 125,000 Btu
1 gallon of ethanol = 84,400 Btu
1 gallon methanol = 62,800 Btu
1 gallon of gasohol
(10% ethanol, 90% gasoline) = 120,900 Btu
1 gallon of E-85
(85% ethanol, 15% gasoline) = 90,500 Btu
1 gallon of kerosene or light distillate oil = 135,000 Btu
1 gallon of middle distillate or diesel fuel oil = 138,690 Btu

My long term average on gasoline was 24 mpg, my mileage on the same setup on E85 was 22 mpg, my current mileage on gasoline is about 22 current mileage on E85 is 18 mpg.

Current setup upgraded turbo-
gasoline mileage 22 mpg = 5682 BTU/mi
E85 90,500 Btu /gallon / 18 mpg = 5028 BTU/mile (daily driving with periodic high boost acceleration)
E85 90,500 BTU/gallon/ 19.3 mpg = 4689 BTU/mile (driving mostly off boost as daily commuter)

Old setup stock turbo -
gasoline mileage Gasoline 125,000 Btu/ gallon / 24 = 5208 BTU/mile
My old setup, @ 92% of gasoline milage or 22 mpg
E85 90,500 BTU/gallon/22 = 4114 BTU/mile

A 5% increase in engine power is common on NA engines with minimal conversion changes, and much higher numbers are possible if compression or boost is used to take advantage of E85's higher fuel octane.

Testing ethanol content with the water test
The proper way to do the water test is specified on page 27 of the handbook.

Handbook method:


2.1 + 1.94 x (total vol - lower meniscus) = hydrocarbon
ethanol = 100 - hydrocarbon

Ethanol bonds very strongly with water so the percentage is not a direct relationship as seen above in the formula.
For example, If you add 10 ml of water to 100 ml of standard pump gasoline, and end up with 17ml of phase separation -- you have a full E10. (yes I know the math does not work but this is due to ethanol's bonding properties) In this case 10 ml of water and 10 ml of alcohol bond to form a mixture of 17 ml of water alcohol mix.

Choosing proper injector size for Subaru WRX E85 conversions

E85 fuel FAQ - Page 57 - NASIOC

Simplified formula:

(turbo max air flow CFM at target boost) x 1.38 ~= static injector flow cc/min each injector on E85

(assumes a 4 cylinder engine with similar fuel needs to the Subaru WRX)

What is your test history to date (6/2005) with E85 ?

I just tallied up my usage over the last 2 years, (the first year I was very cautious and did not use very much). I've put about 500 gallons of E85 and 100% fuel grade ethanol through the cars tank --- that's some where around 40 fill ups, or around 9,000 miles or so on high ethanol (ie greater than 10%) blend fuels.

I am intentionally running the E85 with no special fuel system modifications. In a few years or when ever problems crop up, I'll pull things apart and see what has happened. So far I have absolutely no evidence of ANY kind of degradation on my 2002 WRX. The only non-stock component I'm running in the fuel system at the current time is a walbro 255 L/hr pump, so I cannot absolutely tell you how the stock pump likes the stuff.

Update ( Jan-Nov 2007)
I made a full conversion over the winter bringing the car back on the road with decapitated OEM injectors flow tested at 810 cc/min, an Aeromotive adjustable fuel pressure regulator which gives me the ability to dial in any fuel pressure I want from 35 psi to 70 psi with the turn of an allen wrench. A slightly improved ECUtek reflash, and the Mistubishi 16G turbo off a 96 Australian WRX. At 17 psi I produce 281 AWHP compared to 240 AWHP I was hitting on 100 octane Sunoco GT100 and 250 AWHP I could hit on Sunoco GT+ 104 octane race gasoline at higher boost pressures.

I have successfully tuned a usable home made FFV setup by optimizing the tune for a 50/50 blend of E85 and gasoline. At moderate boost levels the ECU is capable of making the necessary adjustments and open loop fueling is acceptable (see detail notes in the FFV segment below).

I have currently moved to a 100% E85 tune since I now have adequate availability of E85 and can run it all the time with little difficulty. In a cost per mile basis my current tune is equivalent to getting 30.5 mpg on pump premium (20 mpg on E85 at $2.19 vs pump premium at $3.35/gallon). On a cost basis the car is consistently cheaper to drive on E85 than it is on gasoline.

Why is E85 a better fuel ?

Ethanol and is a very turbo friendly fuel for many reasons.
1. It has a much higher evaporative cooling power than gasoline so the intake air charge in the cylinder is significantly cooler that it is with a comparable mixture of gasoline --- that means higher VE.

2. Its octane as blended in E85 is about 100, its blending octane when added to gasoline is rated at 118, so it is a very cost effective octane booster.

3. Ethanol burns faster than gasoline but has a slightly longer ignition delay during the slow burn phase of combustion so the engine does not do as much negative work fighting rising cylinder pressures due to large ignition advances. The total ignition advance for E85 is almost identical to the ideal advance for gasoline so it does not cause the ECU problems when you mix them.

4. At proper mixture you actually are releasing more energy in the cylinder due to the higher quantity of fuel you can burn. ( Ethanol can burn effeciently at much richer mixtures than gasoline can) That means about a 5% increase in energy release all by itself.

5. Peak combustion pressures are actually lower for ethanol than for gasoline but the cylinder pressures stay higher longer, so you have more (longer) crank angle that is usable by the engine. This lower peak cylinder pressure also helps with detonaton control.

6. It will, at proper mixtures lower EGT's by around 200 deg F, but due to the higher quantity of exhaust gas products it produces you do not lose any spool up (in fact I would wager spool up is better).

7. It is much cheaper ( if you go to a station that is not trying to price gouge).


How much will my miles per gallon of fuel drop with E85?

The only negative to E85 is that it gives a lower fuel milage on a gallon for gallon basis to gasoline. The actual difference in energy content between straight gasoline and E85 is about 27%.

The drop in mileage is not as significant as you would think based on that difference due to the higher efficiency of the ethanol as a high performance fuel. This winter I was getting about 92% of the fuel milage I would get on gasoline on 100% E85.

The lower mileage is not really a big deal, ethanol has lower energy per gallon but your reduction in milage is not nearly as large as that difference would imply. Due to the higher torque,you use slightly smaller throttle openings to get the same level of performance, and due to the greater quantity of combustion products (more moles of gas) per lb of fuel the engine efficiency actually goes up slightly. My long term fuel mileage average is in the vicinity of 24.5 mpg, with pump gas, and with 75% ethanol blend, I was getting just over 23 mpg driven normally. Recently I have been flogging the crap out of the car to sort out new boost controller settings for my new turbo (went from a 13T to a 16G). Given I now have a larger turbo and all that is hardly a noticeable fuel mileage drop. I have gotten around 300 -345 miles/tank on straight gasoline when I was bone stock, and I expect to get from 280 - 310 miles per tank on the E-85 based on my notes of fuel consumption and accounting for the unusually hard driving I have been doing the last week working on the boost controller settings.

In very cold weather <20deg F I don't go above about 90% E85 to improve cold starting and speed up engine warm up a bit. Other than that the car loves E85 and so does my wallet ---- $1.89/gallon (6/2005) for 100 octane fuel is hard to argue with. It only drops my fuel mileage a small amount. I get 93.76% of my gasoline milage when driving conservatively in my WRX with the larger injectors and high ethanol fuel blends.

will a wide band O2 sensor accurately read fuel air mixtures with E85 blends ?

To get an accurate AFR reading you need to switch the meter to Lambda or equivalence ratio setting rather than AFR. Most O2 sensors assume you are running gasoline and will report a stoichiometric mixture as 14.7:1 which is the proper value for gasoline. E85 has a Stoichiometric mixture of between 9.7 - 10:1 and a max power mixture of about 6.98-8.5:1 or so, where with gasoline it is 12.5:1-to 13.1.

If you must use an O2 sensor that only reports gasoline AFR information simply divide the numbers it reports by 1.47 - 1.50.

On gasoline, my ECU is supposed to give a mixture of 11.5:1 and on 100% E85 the dyno's wide band reported an AFR of 11.6:1. That means that my true AFR on the E85 was about 7.8:1 which is right in the middle of max power mixtures for E85.

The energy balance question

Some sources say that fuel ethanol requires more energy than it returns is this true?

No not really based on recent studies using very detailed analysis of actual energy inputs currentlyused, in modern farming and state of the art ethanol plants the numbers come out as below. Note that gasoline actually delivers less energy than was expended getting it into your tank.
It has a negative energy balance. Which is exactly the claim the anti-ethanol lobby is blaming fuel ethanol with as a good reason not to use it.

Fuel ethanol returns:
+31% (Wang - 2002)
+34% (Shapouri - 2002)
+21% (Graboski - 2002)
Fuel ethanol with state of the art production techniques can return +68% (Wang - 2002)

Gasoline energy balance (GREET V1.6)

Conventional gasoline -19%
Reformulated Gasoline -20%
MTBE -33%


Page Not Found

A USDA study released in 2004 found that ethanol may net as much as 67% more energy than it takes to produce. Argonne is one of the US Department of Energy's largest research centers.



Report on the new study :

National Corn Growers Association

Is ethanol energy-efficient?: Journey to Forever

The cellulose based ethanol production will actually return nearly 100% energy because it will use its own waste product stream for process energy.

Using the cellulose based process also eliminates the argument that more land will be required to grow corn than is available. Fact is many crops can be used to brew ethanol.

A list of common production sources of the above include.

sugar cane
Sugar beets

It can also be commercially prepared from cellulose treated by enzymes. Sources include:

waste paper
scrap rags
grasses (switch grass)
crop waste


We're not talking about the total substitution of ethanol for gasoline, but a concerted effort to displace as much as possible. The U. S. is already the worlds second highest consumer of fuel ethanol behind Brazil. Every barrel of fuel ethanol burned replaces 3/4 of a barrel of petroleum on a energy content basis. At current oil prices nearing $70 per barrel that is a significant amount of money payed out to U.S. suppliers for a commodity instead of to foreign suppliers. Given that money rolls over 5-6 times in an economy before it get sequestered in a long term capital investment, that means $350 dollars of net benefit to our economy for each barrel of fuel ethanol consumed vs a negative $50 of loss of revenue to the overseas supplier.

Yes I know that much of that money gets passed through the hands of U.S. companies but the end point is still the overseas oil producer.

Even more important, the energy inputs for fuel ethanol production are in large measure low quality heat requirements that can be met with domestic sources of energy which we have in great abundance, like Coal or waste heat from other processes.

How does fuel ethanol rank on Green house gas production ?

Using E85 you have a very favorable green house gas production picture. The CO2 produced when burning the ethanol portion of the fuel is totally recovered by the next seasons crop. This is the definition of a renewable fuel.

In short your "Net" green house gas production is only 15% of what it would be on straight gasoline. That is the equivalent of getting 6.7 times your normal gas mileage.

[edit 02/11/07 - 06/03/07]
how to make a simple conversion to a FFV with your Subaru see posts
#806, 809, 819, 821 ( page 33), post 828,(page 34), post 869 (page 35) post 918 (pg 37)

post 944 (page 37 cold start problems due to summer/winter blend switch over.

post 946 (page 38 -- emissions test on E85)

discussion regarding walbro fuel pumps and E85
E85 fuel FAQ - Page 43 - NASIOC

IMPORTANT update on FFV auto tune
post 950 ( page 38 very lean on open loop running Autotune if you turn down fuel pressure )

The Jan 2008 HotRod Magazine has an article on E85 that is quite positive on its use as a performance fuel.
(although nothing new in the article that has not known for several years by E85 experimenters)

They have the results of a back to back dyno test of 100 octane race gasoline vs E85 on a 402 CID LS2 , 10.2:1 compression ratio, crate engine, done by Wheel to Wheel Powertrain in Madison Heights Michigan.
Gasoline (100 octane race gas) 540 hp @ 6000 rpm, 509 ft-lb torque @ 5200
E85 ------------------------ 546 hp @ 6000 rpm, 524 ft-lb torque @ 5200

With a turbocharger kit installed fueled on E85 :
13 psi boost -- 850 hp @ 5900 rpm, 833 ft-lb torque @ 5000 rpm
no comparison to gasoline you can't run that kind of boost on it with this engine.

752 Posts
where were you when I had a technical writing class?
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29 Posts
Discussion Starter #9
Thanks for compiling all that info. People love adding 3 gallons of E85 to their tank and getting tuned for it. I've never considered it because I didn't want to deal with the Black Death that seems to follow at some point. Also, E85 is scarce in my area.
Im not very sure what black death is but it does scare me . I have E85 all over Dallas. Do you think this is worth the extra gains?

5,636 Posts
Do you think this is worth the extra gains?
If you like power it is. The engine screams with as little as 25% E85 in the mix. 325 hp is pretty easily attained with 25% e85. You absolutely have to get tooned by someone that knows how to do it. Stratified and ATVfreek on MSF know how to do it safely There are a lot of parameters that need to be changed in order to keep it safe. AFR's, Maf curve wastgate Dc's, boost psi max, boost and fuel psi cut off points, engine load parameters, throttle settings, specific fuel gravity, timing, etc, etc, etc. Black death isn't a problem until you mix in more than 50% E85. The only down side to 25% E85 for me was the wild torque steer from so much power. The car was constantly trying to throw me into a ditch when I got on it hard (FWD FTL). Poor gas mileage was a lesser issue. 170 miles to the tank was rude, but whatever.

Your posts are so long and contain so many questions i can't answer them in any detail. All I'll say is that to run up to a 50% mix all you have to do is be fully bolted and have someone that knows how to tune E85 on your MS3 do it. You be fine. Fuel pumps, fuel lines, injectors and black death are all non issues until you exceed the 50% mix ratio. There are absolutely a shit ton of people that run 25% long term without issue. I was one of them. I was self E85 tuned. If you research thoroughly you can do it yourself safely.

What is black death? The high pressure fuel pump (hpfp) in the MS3 uses a plunger that the cam follower pushes to elevate the fuel pressure. A tiny amount of engine oil seeps through that plunger. When the tiny bit of engine oil mixes with more than 50% E85 in the fuel pump (hpfp not the tank pump) it turns the fuel in the hpfp pump into a gooey black mix that clogs some of the tiny passages in the fuel pump over time (a couple of tank fulls). It only happens with more than 50% E85 mix.

Links to the two guys i mentioned that are gurus at tuning MS3's with E85. Pay one of them the $250 they ask to tune you and you won't be disappointed.
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410 Posts
Sorry I just glossed through the posts at the top. I am just wondering though, why are you adamant about using E85 on your MS3?

29 Posts
Discussion Starter #12
If you like power it is. The engine screams with as little as 25% E85 in the mix. 325 hp is pretty easily attained with 25% e85. You absolutely have to get tooned by someone that knows how to do it. Stratified and ATVfreek on MSF know how to do it safely There are a lot of parameters that need to be changed in order to keep it safe. AFR's, Maf curve wastgate Dc's, boost psi max, boost and fuel psi cut off points, engine load parameters, throttle settings, specific fuel gravity, timing, etc, etc, etc. Black death isn't a problem until you mix in more than 50% E85. The only down side to 25% E85 for me was the wild torque steer from so much power. The car was constantly trying to throw me into a ditch when I got on it hard (FWD FTL). Poor gas mileage was a lesser issue. 170 miles to the tank was rude, but whatever.

Your posts are so long and contain so many questions i can't answer them in any detail. All I'll say is that to run up to a 50% mix all you have to do is be fully bolted and have someone that knows how to tune E85 on your MS3 do it. You be fine. Fuel pumps, fuel lines, injectors and black death are all non issues until you exceed the 50% mix ratio. There are absolutely a shit ton of people that run 25% long term without issue. I was one of them. I was self E85 tuned. If you research thoroughly you can do it yourself safely.

What is black death? The high pressure fuel pump (hpfp) in the MS3 uses a plunger that the cam follower pushes to elevate the fuel pressure. A tiny amount of engine oil seeps through that plunger. When the tiny bit of engine oil mixes with more than 50% E85 in the fuel pump (hpfp not the tank pump) it turns the fuel in the hpfp pump into a gooey black mix that clogs some of the tiny passages in the fuel pump over time (a couple of tank fulls). It only happens with more than 50% E85 mix.

Links to the two guys i mentioned that are gurus at tuning MS3's with E85. Pay one of them the $250 they ask to tune you and you won't be disappointed.
Mazda DISI Tuning : Stratified Automotive Controls
Freektune - Freektune
Thank you for all this. true life saver. I plan on doing a 30% mix but I have to get the down pipe. I don't care about exhaust as its a daily driver and don't want that annoying drone and sound like a 17 year old with is ricer .. Even with 30% people say they got tremendous gains. Very exciting. I plan to take it to Cobb Plano for a protune. I will see about getting an E85 map but they don't rec in a speed3, even in low mixes. Ill post info as I get it . Thanks for the help

OH also. is it really 170 miles per tank? at 30%?? damn i spend $50 a week and i live 9 miles from work =( . I get 300+ on full tank now..

29 Posts
Discussion Starter #13
Sorry I just glossed through the posts at the top. I am just wondering though, why are you adamant about using E85 on your MS3?
Just the power gains on something so simple. I have all supporting mods for it really. just need a tune..
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