First of all, what is E85?: E85 consists of 85% ethanol and 15% additives 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 it´s 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. Some models before 1988 on the other hand may have some parts that is not ethanol resistant. If we are talking Volvo´s, then this mainly applies to the non-electronically injection systems such as K-jet etc. Most cars with electronical fuel injection (EFI) should be resistant to ethanol.
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 doesn´t take part in the closed loop but only adds to the amount of greenhouse gasses. Ethanol is also easily bio-degradeable if it should leak into our environment.
3. E85 is 110 octane and therefore it´s more knock-resistent and can tolerate more boost or a higher CR.
4. E85 cools the intake charge more and therefore it´s more knock-resistent 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 effícient than gasoline at the same lambda value (up to 25% more efficient on some cars optimized soley for E85).
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.
(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 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.
Technical facts about the mentioned fuels:
E85 requires 42% 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
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.
When driving purely on E85 you can blend it with up to 25% gasoline in case you want to raise the AFR number used to produce max. power. In that case you can raise the boost even further since the volume of fuel needed to reach the desired lambda is decreased.
Performance application and fuel needed:
Performance application: Let´s pretend for a while that the ECU´s in our cars are pretty good at their jobs. On gasoline it will try to keep an AFR of 14.7 (lambda=1) all the time at idle, cruise and light load. It will also try to keep a good AFR at WOT/boost of 13.2-12.5, sometimes even lower than that, probably closer to 11.x.
Why? Because the fuel has a cooling effect on the intake charge and the space in which the combustion occurs.
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, don´t 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.
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. Instead you can keep the AFR´s leaner across the board and by doing so you can make room for higher boost without maxing out the injectors.
The burn rate will of course be different for different AFR's. It is a matter of tuning it right and getting the peak cylinder pressure where you want it (10 degrees after TDC). But if you are around the same ratio as on gasoline (i.e if you have installed injectors that are almost exactly 42% bigger) you are in the ballpark and do not have to worry about it. More about this later on.
Fuel needed: As you will see, both in my article as well as other places on the internet, different fuel requirements are listed. What numbers will you see and why?
1. A car converted, but not specifically mapped for E85 will consume ~30% more fuel.
2. A car running E85 will require ~42% more fuel.
3. According to your own calculations (if you have bothered to look in to it), it will not quite add up. Most people scratch their head.
Let me show you a table again:
Mode ........... Gas .... E85 ...... extra % (mass) ... extra % (flow) Stoich .......... 14.7 .... 9.765 ........ +50.5% ................ +42% Lean power ... 13.2 .... 8.47 .......... +55.8% ................ +47% Rich power .... 12.5 .... 6.975 ........ +79.2% ................ +69%
E85 has a higher density than gasoline. The change in AFR from 14.7 (lambda=1 for gasoline) to 9.765 (lambda=1 for E85) is 50.5%. But the resulting flow needed is only 42% greater.
Explanations to this: E85 will need a fuel flow that is 42% greater than the flow needed for gasoline. However, it will not use 42% more fuel since it will actually be more efficient. Generally, the engine will consume ~30% more fuel.
If I am using 46.7lb/hr injectors (45% larger than stock) which are easy to get hold of, my AFR´s should theoretically look like this:
*At idle, cruise and low load (closed loop) the AFR will be 9.56, the O2-sensor sees this and will correct it to 9.765. A very small correction, and it lies well within the adaptation limits. Not even noticeable as more than normal adaptation by the ECU.
*When at WOT/boost (open loop) the AFR will be between 8.58-8.13. This looks a little lean according to the AFR table, doesn´t it? It isn´t even in the "rich" area according to the table. No worries, the cooling properties of E85 are pretty good. But in reality I will actually get an AFR of around 8-7.5 since my ECU wants to run a slightly richer mixture than 12.5 on gasoline. It obviously does not know that it is running E85...
Efficiency:
Lets start off with some facts:
* You need 42% more flow derived from the difference in AFR at Lambda=1.
* A car straight converted to E85 without any other modifications will use 30 to a little over 35% more fuel. Since 42% bigger injectors are actually needed, but the fuel consumption is not 42% higher, you can see that the efficiency goes up.
* If a car tuned for gasoline use and high power is converted straight to E85, it will use more E85 at part throttle and less E85 at WOT than a car tuned for running only on E85.
* A car tuned only for E85 use and high power will use less E85 at part throttle and more E85 at WOT than the car that was initially tuned for gas and then converted to E85.
* An efficient engine can take advantage of a good tune and only use ~20-25% more fuel when running on E85 than on gasoline. That doesn't just have to do with energy content, but also the other properties of E85, like burn rate (which can use a more efficient ignition setting), octane number (can also use a more efficient ignition setting), and cooling properties (ultimately leads to a cooler combustion chamber and the possibility of a more efficient ignition setting).
Then you ask why?
Let's start with this...
Energy content by weight: Gasoline: 46.4 MJ/Kg E85: 33.1 MJ/Kg
Weight per volume: Gasoline: 0.7329 Kg/L E85: 0.7806 Kg/L
Energy content by volume: Gasoline: 34 MJ/L E85: 25.84 MJ/L
Some of the numbers here will be recognised from the previous statement:
You need 42% more volume of E85 to reach Lambda=1.
At Lambda=1 on E85, the energy content is 7.92% higher than on gasoline.
That is why a car that is converted straight to E85 doesn't consume 42% more fuel. You get more energy from E85 at the same Lambda. The cooling properties and slightly different burn rate also adds a positive effect on the fuel consumption here.
If you then tune the car to use all the properties of E85, it will be a lot more efficient and use even less fuel that a car converted straight to E85 (aka: a car tuned for gasoline, but equipped with bigger injectors to run E85).
When it comes to power:
This is basically just repeating what I said previously in the same post, but to clarify I will say it again.
On E85 you can use much richer mixtures when aiming for very high power. One of the advantages of E85 is the cooling properties since a lot more is injected. Because of that, you can run a much more advanced ignition setting.
Since the octane number is higher, you can also run a much more advanced ignition setting.
And the car will also develop more power because E85 will contain more energy at the same Lambda.
Why stock engine management systems can't adapt to E85:
Even if the stock engine management systems had bigger injectors to be able to run E85, they would never pull it off in a safe way, and this is why...
Any modern EFI can, and if you let it, it will adapt to any fuel regardless of what AFR it takes to reach Lambda=1. But they are not programmed that way.
You can extremely easy program it do run on gas, then on E85 without even doing anything else than just filling up with E85 at the pump. The programming is the easy bit. The EFI just reads the O2-sensor and corrects the base fuel mixture and stores how much is needed to get to Lambda=1. Then it uses that base line to run the fuel in question, whichever fuel it may be.
But... all modern EFI's have a built-in adaptation already. Not as big as the step between gas and E85, but big enough to fix the car if any error with the fueling should occur.
What that means when it comes to practical use is this: An EFI that is suppose to be fail safe, and at the same time have the possibility of running another fuel type, can not operate if something goes wrong in the system. It can not differentiate between a fault and a different fuel.
We could easily instruct both LH, Motronic, Megasquirt or any other self-learning computer to do this, but they would never be fail-safe. They would simply have a too big span in fuel adaptation (fuel-trim) that the car would break very easy if something went wrong.
Example 1: On a normal car when an injector only can spray half of its rated capacity, the O2-sensor picks this up and instructs the ECU to increase the fueling. Since it is increasing the fueling much more than it is suppose to in order to get to the right mixture again, it thinks that something is wrong, goes into limp-home mode and lights the CEL.
Example 2: On a car with a great span in adaptability, this would instead be interpreted as a different fuel, ultimately creating a dangerous situation for the engine, never goes into limp-home mode, and it also never tells the driver that something is wrong.
That is why there are no cars with this kind of adaptive EFI.
Other kinds of EFI systems exists though, like the SAAB Trionic system in the bio-power cars (and the GM system of course), or the Volvo system in the flexi-fuel cars. They do it differently. They have a sensor in the fuel line that tells the EFI what fuel is being used. Then the EFI switches tables in the computer.
Economical gains:
My car usually use 11.0L (average) of gasoline per 100km of driving (mixed, pretty normal driving). E85 is supposed to use up 30% more fuel, so my consumption should be 14.3L of E85 per 100km of normal driving.
I have driven the car a lot on E85, and I am going through just a little over 57L of E85 in 400km. WOW! That is 14.3L per 100km, just like calculated.
I am impressed!
This also means that my usual cost of 154sek/100km has gone down to 116sek/100km, even though I drive like a maniac .
And of course, the power and driveability is much better.
My experience with E85:
1. Better power (cooler intake charge, higher octane and the fact that it is cleaning the engine pretty good).
2. Smoother power and better stability at part-load.
3. I can run a tremendous amount of boost, and it keeps pulling harder and harder all the way to redline without any problems.
4. After only 50 miles the tail-pipe began to get a lighter color. It was black inside before, now it´s brown and very transparent. My pipe is chromed and now you can see the chrome on the inside as well.
5. The sound from the engine is different. It sounds more powerful.
6. The smell from the exhaust is much nicer.
Thoughts about E85 for those who like to go one step further:
Since E85 is more knock-resistent you can modify your engine to make better use of the properties of the fuel and thereby gain both power and mileage at the same time. You can benefit from: * Advancing the timing (statically or dynamically). * Raising the compression ratio by milling the head down. * Still maintain a high boost level in conjuction with high CR. * In some cases you can run a slightly leaner mixture under part-load or WOT that will benefit the mileage and give head-room for more boost.
* If you have an aftermarket EMS you can get a lot out of E85 with careful mapping. * For those of you that have looked in to Somender Singh´s groove theory, this may be very interesting for you (think: 12:1 CR or more, very advanced timing and high boost...).
Tuning spark maps with E85:
With ethanol you can advance the timing pretty much because of two things:
* Burn rate at different rpm's.
* Octane rating.
Thoughts on LH2.2 and LH2.4:
The stock chips are not very good to run ethanol (E85) on. The spark map is f-ed up even for gasoline use, and even more f-ed up for ethanol. It doesn´t look very good when you view it graphically (think roller coaster). Don´t get me wrong. I am not saying that the stock chips are bad in anyway when it comes to running E85, they are just inefficient. Pinging is definitely not an issue since the spark map is very conservative.
Thoughts on programmable EMS:
Let the piston pass TDC with at least 10 degrees before the peak pressure occurs.
Richer mixture will burn quicker, but... a richer mixture will also raise the threshold of knock.
Follow this rule: MBT = "Minimum ignition for Best Torque". Use the least/smallest possible ignition advance that gives maximum torque.
So... how much advance can you actually run? Since knocking is not the greatest problem with ethanol you should worry about other things, namely the headgasket and other things! You can advance the ignition a lot across the range but how much pressure can the headgasket take? How much pressure can the head bolts take before they stretch? How much force can the rods withstand before bending/breaking?
I ran +3 degrees across the board on my chipped LH2.4 system for a while. It gave me a lot better low end torque but made my engine sound "hard" above 5000rpm at 20psi of boost. The reason it sounded "hard" was that the cylinder pressure was so great at a very early stage of the combustion cycle. It made me gain low end torque but robbed me of horsepower up top.
It is more a rule than an exception that you will have over-advanced the ignition (and thereby loosing power again) before knock occurs on ethanol. The cylinder pressures will therefore become very high so watch the rods/headgasket.
Knock is not proceeded by the rods making a window in the block when running ethanol. The rods will pop out to say hello much earlier than that...
