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Can you achieve greater speed / horsepower with real gas?

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Old 09-28-2011, 03:35 PM
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Originally Posted by THEJOKER View Post
I've never run ethanol in my boat. If you travel with your boat plan ahead and I think you can always find non ethanol fuel.
Not in the northeast you can't, I dont know of anyone that carries nonethanol gas in CT...
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Old 09-28-2011, 03:38 PM
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The stuff I have been running is 90 octane non ethanol. Most of the local marinas have switched to it, but there is only one station in the area that carries it at the pump. I bought some bulk last year, but with the price over 4 bucks this year I just filled at the pump as needed.
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Old 09-28-2011, 03:38 PM
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I am sure this has probably been answered somewhere before. But, if your fuel pump and injectors can only flow X amount of volume at full throttle, will a boat go faster using real gas of the same octane vs. fuel that has ethanol?

Along with all of the other ethanol related documented issues, I have read that real gas has more usable energy per volume than ethanol. So is thinking correct that at max. capable fuel flow that you will get more performance out of your boat with real gas?

Thanks in advance for your help.
Gasoline contains 115,400 BTU/gal of potential energy.
Ethanol contains 75,700 BTU/gal of potential energy.

That's 34% less energy. You'd need 50% more fuel flow using pure ethanol versus gasoline to yield the same power output.

E10 (10% Ethanol / 90% gasoline) contains 111,430 BTU/gal, 4% less than pure gasoline.

On an older, conventional engine set-up your available power will decrease.
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Old 09-28-2011, 03:42 PM
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would you rather run 93 octane with ethynol or 89 non ethynol?
I think that's the real question here. At least all the marinas in michigan carry non ethonal 89 or 90 octane. So I wonder if that's better or 93 with ethonal?

I also heard E85 was higher in octane then 93 so maybe fresh ethonal fuel is better but stale is worse
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Old 09-28-2011, 03:54 PM
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A quick google shows many results for ethonal being 115 octane and e85 at 105. Dyno results show e85 MAKING MORE POWER then 93 and equal to race fuel. Also did find where ethonal has less energy.

IMO there are to many variables and not a big enough difference between gas and ethonal blended gas to worry.
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Old 09-28-2011, 03:59 PM
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...On an older, conventional engine set-up your available power will decrease.
Without a tune-up adjustment, true. The engine could be running slightly too lean with a 10% fuel blend.

However, the ideal air/fuel ratio for ethanol is much lower than gasoline. In theory, you should richen up the engine and it would yield slightly more power.

Given that most marine engines are tuned to the rich side, I would suppose that there is a better-than-even chance that 10% ethanol fuels may actually add power by leaning the engine out just slightly.

Engine builders with alcohol experience - want to weigh in on this?
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Old 09-28-2011, 04:20 PM
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You're absolutely right Chuck. You can certainly take advantage of ethanol's inherently higher octane and F/A ratio benefits with a purpose-built and specially tuned engine and eventually make more power.

But that notwithstanding, in older engines that is not the case, and power output will suffer. My boat is one of those. I detest ethanol fuel on the water so I avoid it like the plague, but there was one occasion where I was away from my marina and left with no choice, so I put in some E10 to get me home. I lost rpms and thus speed, plain and simple.
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Old 09-28-2011, 04:28 PM
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I'm no fan of it as a substitute for gas. It has some nasty emissions side effects, too. From Wikipedia:

"Ethanol combustion in an internal combustion engine yields many of the products of incomplete combustion produced by gasoline and significantly larger amounts of formaldehyde and related species such as acetaldehyde. This leads to a significantly larger photochemical reactivity that generates much more ground level ozone. These data have been assembled into The Clean Fuels Report comparison of fuel emissions and show that ethanol exhaust generates 2.14 times as much ozone as does gasoline exhaust. When this is added into the custom Localised Pollution Index (LPI) of The Clean Fuels Report the local pollution (pollution that contributes to smog) is 1.7 on a scale where gasoline is 1.0 and higher numbers signify greater pollution. The California Air Resources Board formalized this issue in 2008 by recognizing control standards for formaldehydes as an emissions control group, much like the conventional NOx and Reactive Organic Gases (ROGs)."
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Old 09-28-2011, 04:35 PM
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I dont think the two equate eg., 93 with ethanol vs. 89 real gas. Some motors like a 496 HO or 525 are happiest with the lower 89 octane.

My question stems around whether there are any notable horsepower / top speed differences with an apple to apple comparison whether it be 89 with E to 89 without E, or 93eth. to 93 octane real gas.

There seems to be a consenses building that the fuel burn actual volume is potentially 20% more with ethanol (seems kind of big if it is really that much!)

But if you can only flow X = max. amount of fuel at WOT. Would'nt the boat perform substancially better if real gas can provide that much mor energy to burn?

Just trying quantify and decide if it is worth the extra effort for the pure gas search.

Thanks
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Old 09-28-2011, 04:38 PM
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Looks like some of the answers are above.......Thanks

Last edited by SWW17; 09-28-2011 at 04:48 PM.
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