A few years ago I posted this on another site, and I thought I'd bring it here. I've been running e85 for 4 years now, and can say with conviction, the shit works.
I'd spent months researching e85 before making the decision to build my SR swapped 510's fuel system to be able to run this fuel if I wanted. When I posted this in my build thread on the Realm I spent a bunch of time defending that decision. Some saw it as the black plague, others as hippy snake oil, but most saw it as a threat to their beloved tried and true gasoline. Most of the support I was getting was from guys in Australia who'd been using e85 for years.
In the interest of our new Ratsun 2.0 nonpolitical act, I'll define the conversation before it starts: This is not a tree hugging anti fossil fuel rant, this is about the search for performance. I've run into so many people who think that because ethanol is an eco-friendly renewable fuel it's somehow subversive. These same haters were saying the same thing about Datsuns a few years back. Personally if it makes my car go faster I couldn't give a flying fuck where it comes from or who it threatens.
Over the years I've read a shit ton of conflicting information about the performance advantages, and potential dangers of e85. There is a huge amount of disinformation out there, and I had no idea who or what to believe. I thought I'd dig deeper than the typical anecdotal car mag article, the over-enthusiastic crusaders in the pro renewable fuel encampments, and the wanker WAGs in the tuner crowd. With some hunting I found solid answers from scientific research studies, data sheets from NHRA, SCCA, and formula D teams who've done extensive track testing with e85. Bottom line, e85 isn't for everybody, but for modern EFI turbocharged engines, it's a very real performance fuel option. Here's what I found.
Is it an eco alternative fuel, or is it a performance fuel?
The short answer is YES. I realize there is a disconnect between the broader market's view of e85 and the performance crowd's view. It's a matter of perspective. For the average John Q Public driving a Flex fuel Ford F150, with 9.5:1 compression the only thing he's looking for is the most economical way to get to work; so with 30% less fuel efficiency, if e85's $ per mile ratio isn't on par with gas, to JQP what's the point?
It's when you raze compression that e85 starts to make real sense as a high performance fuel. With forced induction you obviously get more fuel mixture in the combustion chamber, but under higher relative compression, e85's volatility becomes more efficiently with an octane rating of 107, while at the same time it burns cooler, cleaner, and is less prone to detonation than race fuel. (more on that latter) For example, N/A drag cars are running it at 16:1 compression. Even with 112 oct race gas you'd be pinging at idle at that compression. To someone pushing the performance edge, all this adds up to a great alternative to high octane race fuel at 1/4 the price. With this in mind it's easy to see why there's a disconnect in these two viewpoints, because they are effectively comparing apples and oranges.
So what's behind e85s bad rap?
In all reality, politics, and green mania aside, e85 has it's down side; it's 25-30% less efficient, it can be hard to find, it's not as stable as gas, it's sensitive to water contamination, in cold clement it's blend ratios vary from 70 to 85%, and the biggy, it is more corrosive to rubber than gas. If you look around the internet you'll find wild claims of ethanol eating aluminum, unregulated refining methods, rampant contamination, motors blowing up and so on. Reading these claims in countless forums, I found one universal theme, it was coming from hackers who didn't know what they were talking about. Yes, If you don't do it right, as with any fuel, it will bit you in the ass. Yes ethanol is corrosive to rubber and silicon, but not to anything metal, or polypropylene/vinyl plastics.
You might recall a few years ago a sudden increase in corn based ethanol production caused a huge spike in food based corn prices, and shortly after that ethanol lost it's government subsidy of $.35 per gallon. News reports at that time were saying this spelled the end of ethanol as a viable alternative fuel. If you peel back the curtain a bit you'd find the end of the gov's ethanol subsidies was because of a preplanned end date. This subsidy was implemented years ago and was intended to get ethanol product up and running. Despite the oil companies lobbying efforts to push the gov to end it earlier these subsidies ended as scheduled. Today ethanol production has shifted to second generation non food crops and it's future is sable enough to be an A grade investment according to Standard and Poors
What's the up side?
1. Increased power:
This is a claim that has seen it's share of skepticism and controversy, so I found a reliable scientific source of information. An SAE laboratory tests actually proves that on a N/A motor ethanol provides greater engine torque, efficiency and knock tolerance than than 92 oct e10 pump gas. For example, 5 degrees of spark retard are required with E10 gasoline for each compression ratio increase, while the much less sensitive E85 requires only 2 degrees of retard for each compression ratio increase. This sounds good, but with forced induction e85 becomes a whole other beast.
Ethanol is not in and of itself a high performance fuel, but it does let you push compression far beyond the normal detonation limitations of pump gas and even straight race fuel. Detonation occurs when excessive heat and pressure in the combustion chamber cause the air/fuel mixture to auto-ignite. e85 is not as volatile in that respect, but that has nothing to do with the stored potential energy of each fuel. In all reality gas has more PE than e85, but there are limitations to how much, or how efficiently you can get that energy out of gasoline. It is that lower sensitivity, and natural cooling effect of ethanol during atomization that keeps auto-ignition from happening. This allows for higher compression which releases greater potential energy, thus producing more power. Greater access to it's PE is also one of the reasons why e85 burns cleaner, because more of it's energy is converted during combustion.
"Because Ethanol contains oxygen, it has a very low power stoichiometric
when compared to gasoline fuels (6.5 compared to 12.5). Ethanol must be run at much richer
mixtures than gasoline, more than offsetting the lower energy per unit volume. The net
energy released per cycle is higher and this results in more horsepower."
If you want to really geek out on this there are lot's of peer reviewed research studies out there that show very detailed data on the performance characteristics of e85 Heres an abstract below of one covering this very topic.
An Experimental and Modeling Investigation into the Comparative Knock and Performance Characteristics of E85, Gasohol [E10] and Regular Unleaded Gasoline [87 (R+M)/2]
Publisher: SAE International
2. Cooler combustion:
Test studies report an average difference of 218 deg F lower peak exhaust gas temp than 87 oct E10 pump gas. I must admit, I have no idea how they defined base optimal tune for each fuel, or I should say I couldn't understand how they did it. Still, with a peak EGT of 1650 F on an average turbo charged motor, 200 deg is significant. As any turbo guy will tell you, heat is the number one barrier in getting the densest air/fuel mixture into the combustion chamber. To that end we use bigger inter coolers, water spray, ducted fans, heat shields, on and on. Take 200 degrees right of the top and you can see the benefit.
Ethanol has a very high MON octane rating, allowing engine
builders to run higher compression ratios without fears of destructive detonation. It also has
a very high Latent Heat of Vaporization, so the engine is cooled far better than one running
on gasoline. This lowers bottom end and oiling system temperatures substantially.
3. Zero carbon build up.
Shit, that ones self expiatory.
4. Average price per gallon is still around $3.50
OK it is 30% less milage, but 105 oct race fuel is $12 per where I live. you do the math.
And 5. last but not least it is better for the environment.
What is required to convert to e85?
Honestly it's not for the faint of wallet, or the average weekend warrior. A list of fuel system upgrades are:
Teflon fuel lines
Bigger fuel pump, maybe two ethanol approved
Silica tank vent
Bigger high quality injectors (see calc below)
Adjustable fuel pressure regulator
REALLY GOOD DYNO TUNER WHO KNOW E85
Tuning for e85 is not as easy as simply upping the fuel delivery by 30%. It requires different timing and fuel curves, and the O2 levels need to be monitored by the ECU. plotting these curves is not something you can DIY by data-logging hard accelerations. It requires a dyno and a tuner that knows his shit.
When selecting injectors it's a good idea to select a slightly smaller injector than needed. You can make up the difference with higher pressure, but you will also get better dead time results with smaller sprayers. A good rule of thumb to select an injector than will run peak hp at no more than 85% duty cycle.
For instance, say I determined that I would need 1250cc injectors to produce 450hp on e85. I could get 1000cc injectors and push fuel pressure to 57psi to get 1250. That way I will get a much better dead time response than I'd get with a 1650, or 2000cc injector.
Here's a quick calculation to determine the correct injector size for the amount of hp you'd like to produce.
HP (1) X BFSC (2) Number of cylinders X duty Cycle (3)
* Brake Specific Fuel Consumption: This is the amount of fuel consumed (in lbs. per hour) for each horsepower made. This should be .45 to .50 for naturally aspirated engines and for Turbocharged engines .60 to .65
To calculate the injector size for E85 use a multiplying factor of 1.47 . The 1.47 number represents the difference between the stoiciometric fuel ratio of gasoline and E85. Gasoline is 14.7 and E85 is 10.0
Keep in mind, all these numbers are averages and can depend on tuning, boost, and so on, but this will get you in the ball park.
A new development in the market are electro-voltaic sensors that can monitor ethanol levels and average it to an O2 sensor so your ECU can adjust it's map accordingly; basically turning any motor into a flex-fuel system. Again not a job for the average tuner/programer,
Measuring Ethanol Content Vai O2 Sensor
Cheers, and I hope this comes in handy for anyone interested.