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Can you achieve greater speed / horsepower with real gas?

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Old 09-28-2011, 04:59 PM
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I think part of the problem is confusion between potential energy per unit volume and octane.

The two are not the same thing. Potential energy in the case of gasoline is measure of how much work can be done, or how much power can be made. Where octane is a measure of how much the air/fuel mixture can be compressed without detonating.
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Old 09-28-2011, 05:12 PM
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Originally Posted by fireguy View Post
I think part of the problem is confusion between potential energy per unit volume and octane.

The two are not the same thing. Potential energy in the case of gasoline is measure of how much work can be done, or how much power can be made. Where octane is a measure of how much the air/fuel mixture can be compressed without detonating.
Thanks for clearing up for us. I agree with you.

But which is better for our boats? Not sure I want to give up octane for potential energy....
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Old 09-28-2011, 05:22 PM
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Originally Posted by offshorexcursion View Post
Thanks for clearing up for us. I agree with you.

But which is better for our boats? Not sure I want to give up octane for potential energy....
Generally speaking, you should run the lowest octane possible that your engine can handle. If your engine manufacturer recommends 87, then run 87.

Octane is a measure of a fuel's stability, not energy. Higher octane gasoline actually has lower energy. All a higher octane gas provides is that it will resist premature detonation up to a higher compression ratio (that's the stability part). By doing so, it makes it possible to build an engine with higher compression and thus the potential for more power.

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Old 09-28-2011, 05:24 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)."
Agreed. Frankly, I see no reason nor benefit for mandating ethanol use for the mass public. Not only is it worse environmentally, but more energy and money go into making it, than will ever be output from it.

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Old 09-28-2011, 05:30 PM
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I can't find ANYPLACE with out this ethanel chit...
I use octane boosters as much as I can. Luckly I have SST tanks. I mix fuel when I can and avarage 89 octanes. If I can get 89 great, if not I use half 87 and half or so 91 or 93.
Didn't notice much difference however, due to this crazy Merc computer stuff.
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Old 09-28-2011, 07:58 PM
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Originally Posted by PARADOX View Post
I can't find ANYPLACE with out this ethanel chit...
I use octane boosters as much as I can. Luckly I have SST tanks. I mix fuel when I can and avarage 89 octanes. If I can get 89 great, if not I use half 87 and half or so 91 or 93.
Didn't notice much difference however, due to this crazy Merc computer stuff.


Peter

The gas station on the North west side of the Port Richey bridge has non-ethanol 91 octane.
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Old 09-28-2011, 08:15 PM
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Here - find non e gas near you:
http://pure-gas.org/index.jsp?stateprov=FL
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Old 09-28-2011, 08:59 PM
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Originally Posted by CigDaze View Post
Generally speaking, you should run the lowest octane possible that your engine can handle. If your engine manufacturer recommends 87, then run 87.

Octane is a measure of a fuel's stability, not energy. Higher octane gasoline actually has lower energy. All a higher octane gas provides is that it will resist premature detonation up to a higher compression ratio (that's the stability part). By doing so, it makes it possible to build an engine with higher compression and thus the potential for more power.
thats where my question comes in,

if the manufacturer recommends 93 oct, are you better off with 89 non eth, or 93 eth?
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Old 09-29-2011, 03:15 AM
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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
E10 has about 4% less BTU's. The HP made will thus loose about the same 4%. A 502mpi making 415hp will probably only make about 400hp on E10. That translates into about 1mph.

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Originally Posted by Boomer35 View Post
thats where my question comes in,

if the manufacturer recommends 93 oct, are you better off with 89 non eth, or 93 eth?
You must run the 93 octane E10 fuel or the engine will detonate.
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Old 09-29-2011, 07:46 AM
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Originally Posted by Boomer35 View Post
thats where my question comes in,

if the manufacturer recommends 93 oct, are you better off with 89 non eth, or 93 eth?
Like Griff said, if you're engine mfg specs 93 then you must run 93 or higher - pure gas or ethanol blend, makes no difference. In your example, 93 ethanol blend is WAY better than 89 pure gas because you're engine will survive the 93 ethanol blend fuel, but probably won't run very long with the lower octane pure gasoline.

Everything you ever wanted to know about octane ratings:
http://en.wikipedia.org/wiki/Octane_rating
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