E85 Basic Information
[FONT=arial, Arial, Helvetica] First of all, what is E85?:
E85 consists of 85% ethanol and 15% additives. The additives vary a lot depending on where you live and time of the year. But roughly, the 15% additives is mostly made up of gasoline, additives that helps the engine to make a complete burn, additives that helps the engine start when its cold and additives to color the fuel and the flame (so you know what substance it is, and also to help you see that it is really burning).
(Positive) facts about E85:
1. It is not corrosive to the fuel system or the engine. This is a myth and ethanol is often confused with methanol, which actually have corrosive properties. Ive run my car for well over two years on E85 without a problem. Some models before 1988 on the other hand may have some parts that are not ethanol resistant. If we are talking Volvos, then this mainly applies to the non-electronically injection systems such as K-jet etc. Most cars with electronically fuel injection (EFI) should be resistant to ethanol. Some people say it would kill your engine right away and that you should buy there race fuel instead (of course they say :eyes: )
2. It is not as harmful to the nature/environment as gasoline or any other petroleum products for that matter. Ethanol is made out of renewable energy resources such as crops and trees to name a few things. The carbon dioxide that an ethanol powered car emits is not contributing to the greenhouse effect, but is taken up by the plants and is being "re-used". The carbon dioxide then goes around in a closed loop. Gasoline on the other hand is made from oil that comes from old dinosaurs , plants and other stuff 100 000 of years ago, and it doesnt take part in the closed loop but only adds to the amount of greenhouse gasses. Ethanol is also easily bio-degradable if it should leak into our environment.
3. E85 is 104-105 octane and therefore it's more knock-resistant and can tolerate more boost or a higher CR. E98-100 is about 120 octane.
4. E85 cools the intake charge more and therefore it's more knock-resistant and can tolerate more boost or a higher CR. And it also makes the engine run cooler and to some degree, even safer.
5. E85 is in most cases at least 5% more efficient than gasoline at the same lambda value (up to 25% more efficient on some cars optimized solely for E85). Mill your heads
6. Since E85 has very good cleaning properties as well as leaving behind a rest-product of water, it is cleaning the fuel system and it will keep the injectors nice and clean. The combustion chambers, valves, ports and the exhaust will also be clean(er), almost like the car had water injection.
7. In most cases it will cost less $/mile to run on E85, and as we go into 2008 and many new plants come online we will see the price difference get even better.
(Negative) facts about E85:
1. Cars running on E85 have some trouble starting when the engine temperature drops below +5*C. Cars running E100 (not very common) have some trouble starting when the intake (the air) temperature is below +15*C. This is easily solved by using an engine heater in the winter, electrical or fuel-heated (this is recommended on all cars regardless of fuel to get better mileage, less wear on the engine and less impact on the environment etc., but that is another matter to discuss and will not be brought up here...). Some people also adds a little extra gasoline to the tank of E85 to help with cold-starts.
2. Since cars running E85 requires roughly 10 to 30% more fuel, a tank of E85 will not get you as far as a tank of gasoline and you will have to refuel more often. This is often disregarded by E85 users who learn to live with it because of the economical gains from reduced price of E85.
Technical facts about the mentioned fuels:
E85 requires 39% more fuel to reach stoich even if that is not what you may come up with when doing calculations based on the table below. This is because the injector flow is slightly different when using E85 among many other things I can't really think of at this time (will be added at a later time).
Fuel ........................ AFRst ........ FARst ....... Equivalence Ratio ... Lambda
Gas stoich ................ 14.7 .......... 0.068 ................ 1 ................... 1
Gas max power rich .... 12.5 .......... 0.08 ................. 1.176 .............. 0.8503
Gas max power lean .... 13.23 ........ 0.0755 .............. 1.111 ............. 0.900
E85 stoich .................. 9.765 ....... 0.10235 ............ 1 ................... 1
E85 max power rich ...... 6.975 ....... 0.1434 .............. 1.40 ............... 0.7143
E85 max power lean ..... 8.4687 ...... 0.118 ............... 1.153 .............. 0.8673
E100 stoich ................ 9.0078 ...... 0.111 ............... 1 .................... 1
E100 max power rich .... 6.429 ........ 0.155 .............. 1.4 .................. 0.714
E100 max power lean .... 7.8 .... ...... 0.128 .............. 1.15 ................ 0.870
Ethanol reaches max torque at richer mixtures than gasoline will.
The term AFRst refers to the Air Fuel Ratio under stoichiometric, or ideal air fuel ratio mixture conditions. FARst refers to the Fuel Air Ratio under stoichiometric conditions, and is simply the reciprocal of AFRst.
Equivalence Ratio is the ratio of actual Fuel Air Ratio to Stoichiometric Fuel Air Ratio; it provides an intuitive way to express richer mixtures. Lambda is the ratio of actual Air Fuel Ratio to Stoichiometric Air Fuel Ratio; it provides an intuitive way to express leanness conditions (i.e., less fuel, less rich) mixtures of fuel and air.
As you can see from the table shown above this section, the ideal target AFR´s under boost for both gasoline and E85 are listed. For gasoline it's 13.23-12.5, and for E85 it's 8.47-6.975. However, with E85 you will not need to richen the mixture under WOT/boost as far as 6.975 or beyond. It does not need to be proportionally richer when compared to gasoline.
Why? Again, Because the fuel has a cooling effect on the intake charge and the space in which the combustion occurs. And at such a low AFR as 9.765 (lambda=1 on E85) or lower the fuel cools pretty good, dont you think so?
Many people with some experience in mapping an ECU for use with E85 says that as high AFR as 8.5 or lambda=0.80-0.85 works well. No need to go to the extreme end of the useable scale to get safe power. It only uses a lot of fuel without giving any benefits.
E85 burns faster than gasoline at best mixtures so it is an inherently more efficient fuel. It also produces more exhaust gas for a give weight of fuel air mix giving higher average cylinder pressures in spite of lower EGT's. With straight E85 in a properly tuned car its good for about +5% power / torque increase. I suspect on a turbocharged car the benefit is larger.
Since you don't have to richen the mixture as many percent (proportionally) as you have to on gasoline, you can make more power without having to use as much fuel.
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 efficiency 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. I run my car on 8.3:1 right now. I have tried much richer mixtures but i have not compared it on a dyno yet.
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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.
I have also read that E85 burns much quicker than gas at rich mixtures so if you have your timing advanced and go WOT you could get power loss (And you might not pick up any knocks) because of the burn speed being to fast.
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Upfront, an E85 conversion is a simple electronic affair... a chip to boost injector output and a sensor for the fuel. But it's not really worth it, considering the cost of E85.
