Well, there is a lot of knowledge ot there.
Here, in writing, just a few things to confirm what others have been writing before. This time, from real experience, real test labs etc... So this time (for a change) i know what I am writing about.
I work for a company that produces lawn and garden equipment.
I work only with the problems (after-sales and service...), or, in my twisted mind, the fun bits!
This means that I have some real life experiences, not only from one or two engines, but from about 1000 engines over the past 4 years...
We have been modifying B&S 5,5 Hp Intek engines to run on Ethanol for a few years now.
Only problem has been jetting the carb correctly. We ended up fitting an adjustable main jet, and that problem is gone.
The modification is fully our responsibility, since B&S are not willing to support this in any way.
Our risk, our customers, our warranties in other words...
Here in northern Europe, environmental concerns are high, and we always try to look into the future.
Right now, future for us is renewable fuels, spelled Ethanol.
Now, we have our own engines built (far east), ready for Ethanol straight from the factory!
Looking at our specific market, 16% of all new cars sold today is so called "flexi-fuel" cars (pump gas or E85, or any mixes in between).
Reason for this high figure is mainly lower tax, free parking in some cities etc.
Readily availible (+500 filling stations in a small country with a population of 9 million!), and cheaper than normal gas (-30%), the E85 is a success. (85% ethanol, 15% normal unleaded gas).
E85 in modern cars: My wife is driving a Ford Focus (-02). Reasonably modern, according to my standard.
To run that car on 50% E85 is no problem what so ever. No modification, no changes in MPG. Nothing that I can measure anyway.
This is also the experience from others. Older cars (carb. engines) just need higher fuel pressure to get more fuel (10-20% into the engine.
E85 in small engines: Ethanol is more corrosive. I have seen float bowl cups perforated, main jests plugged etc. but it is all because of one thing, and one thing only: Storage.
Ethanol will absorb water. Water will corrode just about anything...
Store the carb. DRY during winter storage (over 4 weeks storage time).
Modifications: Two things needed to make the engine run perfect on E85.
-Raise compression. Normal lawnmower engine is typically around 8,5:1. Shoot for 10:1.
-More fuel. Approx 15-25% (by volume) is typically enough, given that you run E85.
I know, theoretically you need 46% (by weight) more, but because of density of Ethanol, that equals 36% more by volume to reach lambda=1.
The 15-25% I refer to is however real life experience values, not theoretical. Yes, sometimes it is hard to know if the real world or the map is correct. That is when it is handy to have an engine lab...
Given that the price of E85 is (today) about 30% lower than pump gas, the main reason why people choose to run on Ethanol is because of taxes (on cars) and environmental concerns.
You cannot really save a ton of money running on E85, but it makes you sleep better at night, knowing that at least it is renewable resources...
Note: A modified small engine will not be 100% flexi-fuel, since it will be running very rich on pump-gas.
Change the main jet, and you are however back to pump gas specification again.
Starting: The starting problem that you all are referring to is mainly because of the low compression. Run higher compression, and most of those problems will go away, since you have almost a "diesel preheating", because of the higher compression.
You also need a good ignition system.
Old B&S systems were typically a little "weak" in the start-up range compared to some of the more modern systems found today.
But honestly, I would not run Ethanol in my snowblower, or any other "critical winter machinery".
On other words, in the winter, no tests with alternative fuels in the car...
Lawnmovers are ideal test animals. Relatively cheap, simple designs and only (mainly...) used in non freezing temperatures.
Emissions, start up Emissions are mainly unburnt Ethanol. We all know ethanol can be dangerous, especially if you drink it...
No, but seriously, since the E85 contains smaller volumes of nasty (cancerogenus) hydrocarbons, the startup emissions have been found not to be as bad as the startup emissions from gas powered engines.
Ecological?Well, depends on how you calculate.
Some say you need more energy to produce then you will ever get out of the fuel, some say the opposite.
That is all up to you.
Oil:Maintain your regular intervals. On a small lawnmower engine, that typically means...never...
Seriously, oil is cheap, engines are not. Your call...
/Bikerbob