Alcohol as a fuel

Brent P wrote:

> If an engine is set up for E85 as it's fuel, then it should have equal or
> better power than an otherwise equivilent engine set up for gasoline.
> Will the E85 engine consume a greater volume of fuel? Sure.

Absolutely correct.

> Just like the
> engine designed for 92 octane gasoline will consume more than the one
> designed for 87 octane gasoline.

I disagree on that one. The difference in energy content between 87 and
92 octane fuel is VERY tiny, and you can get so much better
thermodynamic efficiency if you raise the compression to take advantage
of 92 octane that the engine will probably consume LESS fuel by volume.
Of course nobody does that, because it would still be more expensive
because 92 octane costs a lot more.

"Steve" > wrote
> Brent P wrote:
>> If an engine is set up for E85 as it's fuel, then it should have equal or
>> better power than an otherwise equivilent engine set up for gasoline.
>> Will the E85 engine consume a greater volume of fuel? Sure.
>
> Absolutely correct.
>
>> Just like the engine designed for 92 octane gasoline will consume more
>> than the one designed for 87 octane gasoline.
>
> I disagree on that one. The difference in energy content between 87 and 92
> octane fuel is VERY tiny, and you can get so much better thermodynamic
> efficiency if you raise the compression to take advantage of 92 octane
> that the engine will probably consume LESS fuel by volume. Of course
> nobody does that, because it would still be more expensive because 92
> octane costs a lot more.

*NOT*. BMW, Mercedes, Toyota, etc., all have engines that
require 91+ octane (although they'll run w/o damage but with lower tune
due to knock sensors that cause spark retardation) to get best power
and mileage.

Floyd

In article .com>, N8N wrote:

> I agree with most of your points, but how do you figure that an engine
> optimized for 92 would consume more fuel than one designed to allow use
> of 87? AFAIK there's not a significant difference in the energy
> densities of gasolines with different octane ratings as there is
> between gasoline and E85.

There is a difference between them in terms of energy per unit volume.
It may be less of a difference but a difference none the less.

The extra output that a higher CR gives usually doesn't translate into
MPG. Some big blocks of the 60s had very high compression ratios for
instance...

In article >, Steve wrote:

> I disagree on that one. The difference in energy content between 87 and
> 92 octane fuel is VERY tiny, and you can get so much better
> thermodynamic efficiency if you raise the compression to take advantage
> of 92 octane that the engine will probably consume LESS fuel by volume.
> Of course nobody does that, because it would still be more expensive
> because 92 octane costs a lot more.

But the problem is that a higher CR raises the power output of the
engine, ie the thermal efficiency. Input/output. However that may not
translate into MPG. I realized this back when I took thermo and
realized that 60s big blocks could have very high CRs, yet still get
8mpg. It's not that the CR didn't give them greater thermal efficiency,
it just didn't make it into the measure of MPG.

That all aside, I was just going for the theme, and yeah yeah... this is
usenet

There is also one small problem with this -

It takes another source of energy to make Alcohol that can be burned.
You have to distill it first. To get a high enough proof of Alcohol,
you are going to have to run at least a double distillation process, if
not a triple distillation process.

So you are going to have to have another source of energy to fire a
still of some kind to produce the Alcohol to use as a motor fuel.

Using energy to produce energy is not a smart way to work. I know the
corn and grain farmers want people to think we can use Alcohol as a
fuel, but to do that we have to use another fuel first.

Small problem here.

roland

wrote:

> There is also one small problem with this -
>
> It takes another source of energy to make Alcohol that can be burned.
> You have to distill it first. To get a high enough proof of Alcohol,
> you are going to have to run at least a double distillation process, if
> not a triple distillation process.
>
> So you are going to have to have another source of energy to fire a
> still of some kind to produce the Alcohol to use as a motor fuel.
>
> Using energy to produce energy is not a smart way to work. I know the
> corn and grain farmers want people to think we can use Alcohol as a
> fuel, but to do that we have to use another fuel first.
>
> Small problem here.
>
> roland

No, not a problem at all. Utilize the resource that you have in excess
instead of converting your resources to buy from your enemies what you
don't have...or are too lazy to develop. Thats where the loss is.
Paying Arab chieftains for fuel convenience is like paying Mayan SunGod
Chieftans in Mexico for sunlight.
Anyway, last I heard, those Arabs couldn't eat their oil for substinence.

-Bill

Brent P wrote:

> In article >, Steve wrote:
>
>
>>I disagree on that one. The difference in energy content between 87 and
>>92 octane fuel is VERY tiny, and you can get so much better
>>thermodynamic efficiency if you raise the compression to take advantage
>>of 92 octane that the engine will probably consume LESS fuel by volume.
>>Of course nobody does that, because it would still be more expensive
>>because 92 octane costs a lot more.
>
>
> But the problem is that a higher CR raises the power output of the
> engine, ie the thermal efficiency. Input/output. However that may not
> translate into MPG. I realized this back when I took thermo and
> realized that 60s big blocks could have very high CRs, yet still get
> 8mpg. It's not that the CR didn't give them greater thermal efficiency,
> it just didn't make it into the measure of MPG.
>
> That all aside, I was just going for the theme, and yeah yeah... this is
> usenet
>

I would suggest that the poor fuel economy might have been caused by a)
cam timing that makes the idle sound like the drum intro of "Hot For
Teacher" b) running the engine waaaay outside the sweet spot on the BSFC
curve (due to a) that's going to be at a fairly high RPM)

Most "big blocks," at least the ones that required premium gas, were
tuned for maximum power, not maximum efficiency - now today those things
go hand in hand, but back in the day, before mfgrs. had to worry about
emissions, there were a few power tricks that cost a little in
efficiency but drivers were willing to accept that tradeoff...

nate


--
replace "fly" with "com" to reply.
http://home.comcast.net/~njnagel

Brent P wrote:
> In article >, Steve wrote:
>
>
>>I disagree on that one. The difference in energy content between 87 and
>>92 octane fuel is VERY tiny, and you can get so much better
>>thermodynamic efficiency if you raise the compression to take advantage
>>of 92 octane that the engine will probably consume LESS fuel by volume.
>>Of course nobody does that, because it would still be more expensive
>>because 92 octane costs a lot more.
>
>
> But the problem is that a higher CR raises the power output of the
> engine, ie the thermal efficiency. Input/output. However that may not
> translate into MPG. I realized this back when I took thermo and
> realized that 60s big blocks could have very high CRs, yet still get
> 8mpg. It's not that the CR didn't give them greater thermal efficiency,
> it just didn't make it into the measure of MPG.
>
> That all aside, I was just going for the theme, and yeah yeah... this is
> usenet
>
>
Big thing here is that CR effect on efficiency is for FULL THROTTLE.
The efficiency really depends on the ratios of actual pressures, not the
geometric compression ratio. Large engines usually run at very
restricted throttle for most of time. The result is inefficiency.
Smaller engine runs larger throttle opening to deliver same horsepower,
with increase in thermal efficiency. Of course, there are many other
factors, but if everything else is the same, running at larger throttle
opening results in lower specific fuel consumption. (disregard onset of
power enrichening) So two engines putting out same power will give
efficiency edge to smaller one with higher throttle opening.

I believe this is the idea behind some of these fancy new variable cycle
engines, as well as ones that cut out some cylinders depending on load
and TP.

"Don Stauffer" > wrote
> Big thing here is that CR effect on efficiency is for FULL THROTTLE.
> The efficiency really depends on the ratios of actual pressures, not the
> geometric compression ratio. Large engines usually run at very
> restricted throttle for most of time. The result is inefficiency.
> Smaller engine runs larger throttle opening to deliver same horsepower,
> with increase in thermal efficiency. Of course, there are many other
> factors, but if everything else is the same, running at larger throttle
> opening results in lower specific fuel consumption. (disregard onset of
> power enrichening) So two engines putting out same power will give
> efficiency edge to smaller one with higher throttle opening.
>
> I believe this is the idea behind some of these fancy new variable cycle
> engines, as well as ones that cut out some cylinders depending on load
> and TP.

Your "explanation" is not very right, either because you can't write
clearly or because you are unclear on the concepts and science/engineering.
I'm not going to attempt to re-cast your explanation, as it would take
too much time, and all that stuff is readily available on the www.

BMW's Valvetronic engines are un-throttled (variable lift valves)
and appear to be about10% more efficient and 20% more powerful
than the ones they replaced.

Floyd

On Sat, 14 May 2005 08:51:53 -0700, Scott en Aztlán > wrote:


>On 13 May 2005 21:05:44 -0700, wrote:

>>There is also one small problem with this -
>>
>>It takes another source of energy to make Alcohol that can be burned.
>>You have to distill it first. To get a high enough proof of Alcohol,
>>you are going to have to run at least a double distillation process, if
>>not a triple distillation process.
>>
>>So you are going to have to have another source of energy to fire a
>>still of some kind to produce the Alcohol to use as a motor fuel.
>>
>>Using energy to produce energy is not a smart way to work.

>We use energy to produce energy all the time. Oil needs pumps,
>refineries, ships, trucks, etc. etc. etc. to be converted into
>gasoline and made available for consumers to purchase. If natural gas
>isn't coming out of a particular well with enough pressure to be sent
>down the pipeline, they run it through a compressor. And so on.

>Why is this OK for petroleum fuels but not for alcohol fuels?

Probably because with alcohol, you end up with less than you started with.