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#1
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Alcohol as a fuel
On Tue, 10 May 2005, C. E. White wrote:
> Chevron was saying that must cars will run fine on oxygenated fuel. I am > not sure what you mean when you say you get less power. If you mean you > lose engine power, I don't agree. I believe the fuel injection systems > of most modern vehicles have enough fuel delivery capacity to increase > fuel delivery to make up for the reduced energy content of the > oxygenated fuel. Doesn't work that way unless you have forced induction (supercharger or turbocharger). Yours is a common error, though, thinking that a correction in air/fuel ratio will make up for the reduced energy content of the fuel. Air is the working fluid -- fuel's just used to heat up the air so it expands and does work. Less energy in the fuel = less heat = less bang = less power. One does not trump this physical law by monkeying with the air/fuel ratio. DS |
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#2
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On Tue, 10 May 2005, dyno wrote:
> Since both ethanol and methanol have less energy per volume of fuel, one > just adds more fuel until all of the oxygen is consumed. <snip a bunch of inapplicable handwaving and ooh-ha-ha> ....and we still wind up with less work done by a given volume of fuel. Call it lower MPGs or lower power, whichever you like, it doesn't really matter. For any set of conditions, one gallon of gasoline does more work than one gallon of ethanol or methanol, straight or blended with gasoline, simply because the alcohols contain less energy. And that's just always the case. Ethanol and methanol both contain less energy than gasoline, per volume unit, period, no matter what magic modifications you do to an engine. To the degree the effective air-fuel ratio is leaned by the use of alcohol relative to gasoline, the mixture can be corrected by dumping in more fuel, but this doesn't mean you get the lost power back. Putting the effect into real-world terms, as long as you have travel left in the accelerator, you can simply push it down further with alcohol-blended fuel than with gasoline to compensate for the loss, though MPGs will continue to suffer. However, this is just *compensation*, not deletion of the loss. The extreme case illustrates this: In the extreme case (Underpowered, fully-loaded vehicle climbing a mountain highway, let's say) when the accelerator is already on the floorboard and you're climbing the hill at 35 mph in the right lane with your blinkers going -- running on gasoline -- changing to a lower-energy-content fuel means your foot will still be on the floor but you'll be doing, say, 25 or 30 mph instead of 35. (I didn't run the calculations to come up with an exact mph difference; the point is illustrative without it.) DS |
#3
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On Wed, 11 May 2005, dyno wrote:
> Since alcohols have less energy per volume and must run much richer to > maintain the same relative A/F, one increases the delivered fuel volume. Thereby getting less work (or "power", if you must) out of any given volume of fuel. Exactly. |
#4
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On Wed, 11 May 2005, dyno wrote:
> > To the degree the effective air-fuel ratio is leaned by the use of alcohol > > relative to gasoline, the mixture can be corrected by dumping in more > > fuel, but this doesn't mean you get the lost power back. > Oh really. Why not? Because there's nothing you can do to change the fact that alcohol contains less energy than gasoline. You're simply going to burn more alcohol than gasoline to do a given amount of work. > > The extreme case illustrates this: In the extreme case (Underpowered, > > fully-loaded vehicle climbing a mountain highway, let's say) when the > > accelerator is already on the floorboard and you're climbing the hill > > at 35 mph in the right lane with your blinkers going -- running on > > gasoline -- changing to a lower-energy-content fuel means your foot > > will still be on the floor but you'll be doing, say, 25 or 30 mph > > instead of 35. (I didn't run the calculations to come up with an exact > > mph difference; the point is illustrative without it.) > No it isn't. Well, ol' bean, I'm afraid I'm disinclined to put together a PowerPoint presentation for you. Perhaps if you think about it a little harder you'll catch on. > You seem to confuse power with fuel economy. For all practical purposes in street-driven cars, they are merely two means of expressing the same thing: Work done per unit of fuel consumed. It's just that talking in terms of "power" puts the emphasis on work done, while talking in terms of "fuel economy" puts the emphasis on fuel consumed. Fulminating about race cars, dyno engines and suchlike is fun and nifty, but not particularly applicable to the hordes of Chevies and Toyotas on US roads today. |
#5
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Daniel J. Stern wrote:
> On Tue, 10 May 2005, C. E. White wrote: > > >>Chevron was saying that must cars will run fine on oxygenated fuel. I am >>not sure what you mean when you say you get less power. If you mean you >>lose engine power, I don't agree. I believe the fuel injection systems >>of most modern vehicles have enough fuel delivery capacity to increase >>fuel delivery to make up for the reduced energy content of the >>oxygenated fuel. > > > Doesn't work that way unless you have forced induction (supercharger or > turbocharger). Yours is a common error, though, thinking that a correction > in air/fuel ratio will make up for the reduced energy content of the fuel. > Air is the working fluid -- fuel's just used to heat up the air so it > expands and does work. Less energy in the fuel = less heat = less bang = > less power. One does not trump this physical law by monkeying with the > air/fuel ratio. > > DS The PROPER fuel air mixture will return the power, as the proper mixture for alcohol is twice the fuel per unit of air than gasoline. IF the engine is made to sense alcohol, as in an E85 vehicle, it will restore the power, though not the milage. I doubt if non-E85 setups will recalibrate, however. My vintage racing car is set up to run alky. The main jets are bored out to approx twice the area of the stock jets. Car runs great- lots of power. I am running the stock CR, and whenever I have to rebuild engine, I will raise CR so that I will get even more power than currently. Alky powered cars are not wimpy. They sure guzzle fuel, however. Even though alky is cheaper here than gasoline, it still costs me more than if I were using gasoline. |
#6
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Daniel J. Stern wrote:
> > Because there's nothing you can do to change the fact that alcohol > contains less energy than gasoline. You're simply going to burn more > alcohol than gasoline to do a given amount of work. > The exception would be if the octane rating of the low energy fuel were high enough to greatly increase the CR. However, I don't think the octane of ethanol (I believe it is about 125) is high enough to allow that increase in CR. Yeah, fuel economy is a strong function of CR, but you'd have to increase it a LOT to get a 50% increase in efficiency. I tend to agree with Daniel that alcohol will never deliver the mpg that gasoline does, though it can deliver the same HP/CI. |
#7
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"Daniel J. Stern" > wrote in
n.umich.edu: > On Wed, 11 May 2005, dyno wrote: > >> > To the degree the effective air-fuel ratio is leaned by the use of >> > alcohol relative to gasoline, the mixture can be corrected by >> > dumping in more fuel, but this doesn't mean you get the lost power >> > back. > >> Oh really. Why not? > > Because there's nothing you can do to change the fact that alcohol > contains less energy than gasoline. You're simply going to burn more > alcohol than gasoline to do a given amount of work. your still not getting it!!! only less per "volume" add the proper volume of alcohol back (as in richer mix) you add the total power, btu, any measure you want to use, and your power is returned to the same level. the only thing changed is the vol efficiency of the fuel. > >> > The extreme case illustrates this: In the extreme case >> > (Underpowered, fully-loaded vehicle climbing a mountain highway, >> > let's say) when the accelerator is already on the floorboard and >> > you're climbing the hill at 35 mph in the right lane with your >> > blinkers going -- running on gasoline -- changing to a >> > lower-energy-content fuel means your foot will still be on the >> > floor but you'll be doing, say, 25 or 30 mph instead of 35. (I >> > didn't run the calculations to come up with an exact mph >> > difference; the point is illustrative without it.) this will not happen unless you do not have the correct a/f ratio. If the ratio is changed to accout for the alcohol the power at WOT will not change. no speed reduction, only lower MPG. KB > >> No it isn't. > > Well, ol' bean, I'm afraid I'm disinclined to put together a > PowerPoint presentation for you. Perhaps if you think about it a > little harder you'll catch on. > >> You seem to confuse power with fuel economy. > > For all practical purposes in street-driven cars, they are merely two > means of expressing the same thing: Work done per unit of fuel > consumed. It's just that talking in terms of "power" puts the emphasis > on work done, while talking in terms of "fuel economy" puts the > emphasis on fuel consumed. > > Fulminating about race cars, dyno engines and suchlike is fun and > nifty, but not particularly applicable to the hordes of Chevies and > Toyotas on US roads today. > -- ThunderSnake #9 Warn once, shoot twice 460 in the pkup, 460 on the stand for another pkup and one in the shed for a fun project to yet be decided on |
#8
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Don Stauffer wrote:
> > My vintage racing car is set up to run alky. The main jets are bored > out to approx twice the area of the stock jets. Car runs great- lots of > power. I am running the stock CR, and whenever I have to rebuild > engine, I will raise CR so that I will get even more power than > currently. Alky powered cars are not wimpy. They sure guzzle fuel, > however. Even though alky is cheaper here than gasoline, it still costs > me more than if I were using gasoline. Was talking to a local sprint car guy that runs alky... in a 25 lap race on a 4/10 mile track, they'll use almost 30 gallons. Yikes. |
#9
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On Wed, 11 May 2005, Kevin Bottorff wrote:
> > there's nothing you can do to change the fact that alcohol > > contains less energy than gasoline. You're simply going to burn more > > alcohol than gasoline to do a given amount of work. > > your still not getting it!!! only less per "volume" Yes. Less work per volume unit of fuel burned. I'm not sure what you imagine I'm "not getting". |
#10
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Daniel J. Stern wrote:
> On Wed, 11 May 2005, dyno wrote: > > >>Since alcohols have less energy per volume and must run much richer to >>maintain the same relative A/F, one increases the delivered fuel volume. > > > Thereby getting less work (or "power", if you must) out of any given > volume of fuel. Exactly. Your point was that one could NOT get the power back. And all I have stated (as have others) is that by adjusting the fuel quantity back to the same equivalence ratio the total energy in the cylinder will be the same (or slightly better) and therefore the power will be at least as good as it was on pure gasoline. This is really pretty basic chemistry and thermo. If you don't want to believe me, look in Heywood's, Obert's or the Taylor and Tayor IC engine text books. No disagrees that more fuel mass is needed. |
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