Specific E10 questions

HIFI

HIFI

Member
TECHNICAL Contributor
Oct 5, 2006
555
Rio Grande, TX
Boat Info
1998 400EC
Engines
Merc 454 Horizon
E10 questions . . .

My engines are 7.4 MPI Mercruiser with 385 HP. I review the specifications and I am expected to turn 4200 RPM WOT. Back in 1998 those specifications were rated/tested without E10 gasoline. Now I burn E10 and I would not expect 385 HP or 4200 RPM WOT.

Is there any science/math that would help me rate my performance expectations with E10?
Would you pitch props for the rated WOT to compensate for the E10 Gas performance drop?
 
Octane is octane and as long as E10 has it, I seriously doubt that it would affect horsepower if the engine is properly tuned and maintained. However it will affect gas mileage since ethanol has less energy content than normal gasoline blending components. I used to work for a major oil company and they blend to an octane specification and a vapor pressure specification depending on the time of year and altitude.
 
Your engine is an air pump. Fixed displacement. Alchohal(sp) requires less air for compustion. Therefore more alchohal for the same amount of air. Alchohal funny cars make lots of HP because of this. There is some math around on the net if you look. Nitromethane is something like 2.5:1 compared to gasoline. Pound for pound makes less power but the 2.5X more than makes up for it. Your fuely engine will adjust its trim cells for the lean condition the E-10 will cause. I believe you will make more HP.

Now a carb job like mine, I would have to fatten up my main jets and richen my idle circuit some. Hope that all made sence. ...Ron
 
I can't find the link, but I read a good report about E10 (may have been E85) vs Regular Gasoline (MTBE). Maybe it was done by Car & Driver, Edmunds... it was someone reputable, anyways. They did a test using the same vehicle (car) on the same roads - keeping as many variables out of the equation as humanly possible, except for completely emptying and filling the tank with the two gas's. The regular gasoline provided slightly higher mileage.

I think this finding is pretty much the norm in every report I've seen about E vs Regular.

Let me say that I am no where near an expert on gas. I'm only relaying info I've heard and read about. I do look at sources, though, and consider the various things I've read to be credible.

All that being said, I would think that the very slight performance loss from E10 would be extremely negligible in the context of your question. Meaning, I don't think it's worth the time to change anything because you're using E10. However, a normal tune-up would probably be a good idea.
 
OK, a quick Google search for the comparison of BTU's between regular gasoline and E10 provided a number of links showing that E10 has approximately 3% less BTU's than straight gas. I would think that E85 would be even worse as straight Ethanol has significantly less BTU's than straight gas.

Does 3% equate to needing to make changes to your engine or props? I don't know. If it was me, I don't think I'd worry about it. As mentioned above, wouldn't the engine computer adjust for it, anyway?

I'm not really disagreeing with what Bon is saying... From the few sentences he wrote, he obviously knows more about this than me. I just don't understand how less BTU's = more HP?
 
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Did alot of screwing around at a 1/4 mile track with a 99 firebird. I seen my fuel trims keep the injectors open longer as I used alcohol doped fuel. Didnt really drop my ET enough to say it was a mod.

I hope I didnt lead any one to think there would be a big hp gain. Like Dennis said there is 3% less BTU content, but you get to burn more. gasoline has a air to fuel ratio around 14:1 and alcohol is around 9:1. And your only dealing with 10% of your fuel.

So I believe the 10% alcohol in the pump gas would only increase a 7.4 385 hp by 10hp. (somebody check my math). Thats not enough to change a prop. Probably wouldn't even see a rpm increase. ...Ron
 
I should have clarified what I meant in my first post regarding octane equivalency. Even though E10 has less energy per gallon than normal gasoline it has the same octane rating. Octane is not a measure of energy content but rather a measure of the fuel's resistance to early detonation or pinging. Most modern cars have an octane sensor that if lower octane gasoline is present, it retards the spark, thereby reducing efficiency ergo horsepower.

Ron has explained quite well that engine controls compensate for the lower energy content of E10 by putting more of it into the cylinder. It is this increased volume that leads to slightly less mileage per gallon. The reason for this is gasoline is sold by liquid volume so a gallon of E10 is priced the same as a gallon of normal gasoline but really is slightly more expensive on an equivalent energy basis.
 
I am not a gas expert (although my wife would disagree...), but my opinion is that E10 SUCKS!

And later generations (along with smarter people today) will think we were fools to use it.:smt021

The energy that is put into manufacturing and distibuting ethanol negates any positive impact. Plus, adding 10% alcohol leads to about a 5% reduction in fuel economy. That is not really helping our dependency on foreign oil. (but the farmers should do love it!).
 
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