Ethanol's Effect

[RV7ator]

E10 91 mogas slows my -7 around 4-5 mph at cruise.

For the grins of it, I A/B compared 100LL from one tank to 91 mogas ruined with 10% ethanol from the other tank. The lower energy density of ethanol through a volumetric measuring device like a carburetor assures you can't make the same horsepower. In my case it's about 12-13 hp or so lost to the corn lobby. The numbers at 8,500 ft/21.5 in/2400 rpm/100 ROP: 100LL = 198 mph, E10 = 193-4 mph. Nothing calibrated, it's all wet-thumb-to-the-wind rigorous, but the trend is right.

When MTBE was the Greenies darling, my 172 lost ~2 mph.

What was more interesting is the time it took for the different fuel to make it from the selector to the engine: 3 1/2 minutes! I couldn't believe there was that much volume in the system to keep the mill turning at cruise power for so long. Think about that if you ever start sucking contaminated fuel. Changing tanks may not help before you run out of airspeed/altitude/ideas.

John Siebold
Boise, ID

[N1593Y]

Thanks for the data. Wish others who have experience would contribute their observations.

[rv6ejguy]

I was reading an article in Aviation Week recently where Embraer converted a Lycoming IO-540 over to run on E96 ethanol for their EMB 202A AG plane. Resulted in 20 more hp but a 40% reduction in range. Price of the fuel there is 1/4 that of avgas. This is the only production aircraft to use alcohol fuel and over 60 have been produced now. Initial tests indicate cooler running and very clean chambers, valves plus very lower carbon contamination rates on the oil. (Pierre, this thing has a 2094 lb. hopper capacity and electrostatic spray system).

Some of the new studies and pilot plants producing ethanol from discarded bio mass, algae and sugar cane show great promise. A new plant in Ontario is now producing 1 million gallons of cellulose ethanol from non crop sources per year with plans to be even bigger in the future.

Brazil has massive sugar cane crops (more efficient than corn by far) to power their ethanol industry and the majority of vehicles there are either flex fuel or ethanol fueled. It shows it can easily be done on a very large scale- people just have to get off their butts and do it.

[Mike S]

Alcohol is capable of making more HP than gasoline, provided the rest of the engine is optimized for it.

Look at the difference at the drag strip.

IIRC, it has to do with octane----resistance to detonation. But, to actually get the improvement, a lot of things have to be done to the engine. Compression, timing, and fuel flow the main ones. Also, cut back on cooling capacity.

Oh, by the way-----fuel flow goes up a bunch----40% seems to stick in my mind.

To just switch tanks as John did, the results could be expected. If he had been running more than just 10% etoh, then the loss would have been greater.

[Randy Walls]

Did you richen the mixture when switching to the tank with ethanol? Ethanol is use as an oxygenator in auto fuel, if you did not richen the mixture you would have been way below peak power. The engine should make the same horse power but burn about 8% more fuel. So the speed shouldn't change.

[rv6ejguy]

Engine guys often argue about why alcohols make more power than gasoline in engines. One thing not often mentioned is that as ethanol or methanol is vaporized, it gets very cold, absorbing heat from the intake charge and increasing its density. This is clearly evident if you have ever run alcohol in race engines on a humid day, frost can form on the intake runners downstream of the injectors- even when the ambient temp is well above 70F.

In Porsche's Indy car program, engineers measured intake charge temperature drops of up to 80C!

Another thing to consider in the power equation is that the sheer mass of alcohol decreases the amount of air than can be inducted as a percentage of the charge mass. This may be offset by released oxygen.

One thing is clear from dyno testing and track use of alcohol, engines make 5-15% more power than on gasoline and it is a wonderful fuel for high compression or turbo engines. I ran a couple of turbo street cars on M85 for two years. The range sucked but you could run full boost without any ignition retard. Great fun.

[frankh]

LOP opearations seems to cost me about 5mph but I can't lean to 7gph at 2400 sq like i could with 100LL..&.5 GPH seems to be the minimum with E10.

I when I get some time I will do a side by side test.

mind you at mogas at less than $3 and 100LL at over $5, I'm not too dissappointed with the performance loss.

Frank

[RScott]

A little OT: My auto mechanic races dragsters & we were talking about alcohol a couple days ago. He runs a 500 HP engine, gets about 7 seconds in the quarter mile, peaking at 197 mph, using 4.5 gallons in those 7 seconds! Carb jet is over .200 in diameter to get that fuel flow. He says he use about twice as much alcohol as he would gas, but wouldn't go as fast with gas.

[az_gila]

Originally Posted by RV7ator

.....
What was more interesting is the time it took for the different fuel to make it from the selector to the engine: 3 1/2 minutes! I couldn't believe there was that much volume in the system to keep the mill turning at cruise power for so long. Think about that if you ever start sucking contaminated fuel. Changing tanks may not help before you run out of airspeed/altitude/ideas.

John Siebold
Boise, ID

...should not switch tanks just before take-off...

Use the fuel that worked in the taxi and run-up phase for take-off....

[robpar]

One of the main reasons that Alcohol produces more power is that you can burn more of it. As Ross said it cools the intake charge but you can run a much richer mixture. I can not remember the exact number but I think it is around 9.5 lb air to a lb of alcohol. Gasoline's richest mixture is around 12 :1.
Nitro-methane is even more drastic at about 2 lb air to 1 lb of nitro. This more than makes up for the lower heating value of alcohol and nitro-methane.

I read a paper on some research done by the EPA on a pure alcohol engine. They were running a compression ratio of 18 : 1 using port injection and spark ignition. They were able to get the same volumetric (ie mpg) as gasoline. The engine produced approximately the same power as gasoline. They were not trying for more power but the same fuel economy with equivalent emissions. Their reasoning that E85 at higher cost and more fuel consumption would be a hard sell to consumers seems logical.

The high compression ratio produced a more efficient engine and recovered the power loss from alcohol. Yes there is a power loss if running at stoic but it looks like you maybe able to run richer and still meet emission standards so some alcohol blends can make more power than gasoline. I thought when I read it that the engine would be an interesting aircraft engine.

I will try and find the paper and post the link, it is an interesting read.

Bob Parry