$ per mile: high compression/high test vs. low compression/regular

Awl --

As all usenet thermodynamicists know, engine efficiency increases with
higher compression.
But high test can cost 10% more than regular. Does high compression
increase engine efficiency by at least 10% to account for the higher cost of
high test gas?

My crude PV=nRT calcs + Carnot's law indicate that it does not, not by a
long shot.
Opinions?

Somewhat related: WTF decided to make diesel more so much more expensive
than gas, when it's much cheaper to produce (comes off much earlier in the
fractionating column)??
--
EA

On Sun, 27 Jan 2013 16:40:27 -0500, "Existential Angst"
> wrote:

>Awl --
>
>As all usenet thermodynamicists know, engine efficiency increases with
>higher compression.
>But high test can cost 10% more than regular. Does high compression
>increase engine efficiency by at least 10% to account for the higher cost of
>high test gas?
>
>My crude PV=nRT calcs + Carnot's law indicate that it does not, not by a
>long shot.
>Opinions?
>
>Somewhat related: WTF decided to make diesel more so much more expensive
>than gas, when it's much cheaper to produce (comes off much earlier in the
>fractionating column)??


Supply and demand. My industry sources told me that during much of
writing of new articles about refinery capacity shortages and oil
shortages there was actually a glut of gasoline relative to other oil
products.

On Jan 27, 4:40*pm, "Existential Angst" > wrote:
> Awl --
>
> As all usenet thermodynamicists know, engine efficiency increases with
> higher compression.
> But high test can cost 10% more than regular. *Does high compression
> increase engine efficiency by at least 10% to account for the higher cost of
> high test gas?
>
> My crude PV=nRT calcs + Carnot's law indicate that it does not, not by a
> long shot.
> Opinions?
>
> Somewhat related: * WTF decided to make diesel more so much more expensive
> than gas, when it's much cheaper to produce (comes off much earlier in the
> fractionating column)??
> --
> EA

It burns hotter,but is not worth the extra money. 87 octane is what my
Dodge Van is made to run on. Its possible high test is better in the
very cold. Good to put dry gas mix in to get rid of gas tank water.
TreBert

On Sun, 27 Jan 2013 16:40:27 -0500, "Existential Angst"
> wrote:

<snip>
> WTF decided to make diesel more so much more expensive
>than gas, when it's much cheaper to produce (comes off much earlier in the
>fractionating column)??
<snip>

Short Answer: The public is getting hosed [again]

Longer answer:
A large portion of the cost difference is in taxes, in part
justified in the bureaucratic mind by the extra mileage per
gallon which reduces tax revenue. The rest is due to
legislation requiring ultra-low sulfur which costs extra to
produce using orthodox production methods.

FWIW – ultra low sulfur and ultra low wax diesel and JP4 jet
fuel can be produced by existing G/CTL [gas/ coal to liquid]
technology using the abundant (cheap) shale gas as feed
stock. There is two cost savings. The production cost of
the ultra-low sulfur/wax fuel is cheaper than that produced
by existing technology from petroleum feedstock, and it is a
totally domestic product with domestic employment,
eliminating a major portion of the current accounts trade
deficit. Naturally, we can't do it as this might upset the
major political campaign donors like the existing [tax
evading] oil companies, banks, and commodity speculators,
and upset the need for continuing wars in the Mid-East and
Africa.

http://www.synfuels.com/GTL.html

http://www.chemsystems.com/about/cs/...20Ethylene.cfm

http://www.eia.gov/oiaf/aeo/conf/pdf/cornitius.pdf

http://www.cleantechinvestor.com/por...hnologies.html

and a whole bunch more.


--
Unka' George

"Gold is the money of kings,
silver is the money of gentlemen,
barter is the money of peasants,
but debt is the money of slaves"

-Norm Franz, "Money and Wealth in the New Millenium"

"Existential Angst" > wrote in message
...
> Awl --
>
> As all usenet thermodynamicists know, engine efficiency increases
> with higher compression.
> But high test can cost 10% more than regular. Does high compression
> increase engine efficiency by at least 10% to account for the higher
> cost of high test gas?
>
> My crude PV=nRT calcs + Carnot's law indicate that it does not, not
> by a long shot.
> Opinions?
>
> Somewhat related: WTF decided to make diesel more so much more
> expensive than gas, when it's much cheaper to produce (comes off
> much earlier in the fractionating column)??
> --
> EA

If your engine has a knock sensor it will slowly advance the spark
until it senses knock, then back off and try again. This gives the
maximum advance that the fuel, temperature, humidity and load
conditions allow, and does improve the performance when you put in
hi-test. You'd have to make measurements to see if the gain is worth
the added cost.

Buick introduced the sensor on the 1978 Turbo V-6. The company I
worked for built the test station for the sensors.

http://en.wikipedia.org/wiki/Ultra-low-sulfur_diesel
"ULSD has a lower energy content due to the heavy processing required
to remove large amounts of sulfur from oil, leading to lower fuel
economy. Using it requires more costly oil."
jsw

"G=EMC^2" > wrote in message
...
On Jan 27, 4:40 pm, "Existential Angst" > wrote:
> Awl --
>
> As all usenet thermodynamicists know, engine efficiency increases with
> higher compression.
> But high test can cost 10% more than regular. Does high compression
> increase engine efficiency by at least 10% to account for the higher cost
> of
> high test gas?
>
> My crude PV=nRT calcs + Carnot's law indicate that it does not, not by a
> long shot.
> Opinions?
>
> Somewhat related: WTF decided to make diesel more so much more expensive
> than gas, when it's much cheaper to produce (comes off much earlier in the
> fractionating column)??
> --
> EA

It burns hotter,but is not worth the extra money. 87 octane is what my
Dodge Van is made to run on. Its possible high test is better in the
very cold. Good to put dry gas mix in to get rid of gas tank water.
TreBert
================================================== ======

Dry gas, fwiw, is absolute alcohol -- or near absolute (200 proof, very
hygroscopic, bad for the skin)

Heh, and a litttle known fact-let:
The actual heat content of regular gas is higher than that of high test!!

So that right there may offset whatever advantages there are to high
test/high compression, at least in streetable cars.
The reason, btw, is due to the higher degree of branching of alkyl chains in
high test, rendering a more stable carbo-cation intermediate, ergo a lower
net release of energy. Organic Chem 101.

So I just added sci.chem.... haven't seen any rants from Uncle Al lately....
LOL
--
EA.

"Jim Wilkins" > wrote in message
...
> "Existential Angst" > wrote in message
> ...
>> Awl --
>>
>> As all usenet thermodynamicists know, engine efficiency increases with
>> higher compression.
>> But high test can cost 10% more than regular. Does high compression
>> increase engine efficiency by at least 10% to account for the higher cost
>> of high test gas?
>>
>> My crude PV=nRT calcs + Carnot's law indicate that it does not, not by a
>> long shot.
>> Opinions?
>>
>> Somewhat related: WTF decided to make diesel more so much more
>> expensive than gas, when it's much cheaper to produce (comes off much
>> earlier in the fractionating column)??
>> --
>> EA
>
> If your engine has a knock sensor it will slowly advance the spark until
> it senses knock, then back off and try again. This gives the maximum
> advance that the fuel, temperature, humidity and load conditions allow,
> and does improve the performance when you put in hi-test. You'd have to
> make measurements to see if the gain is worth the added cost.

Yeah, anti-knock is a super-cool feature.

One can also mix regular and high test, should regular gas be outside of the
engine's ability to compensate.
fwiu, 89 octane is in fact just mixed 87+ high-test, approx 50/50. So an
aware driver may find that for every 10 gals of fuel, 9 gal of regular + 1
gal of premium would do him good.
--
EA


>
> Buick introduced the sensor on the 1978 Turbo V-6. The company I worked
> for built the test station for the sensors.
>
> http://en.wikipedia.org/wiki/Ultra-low-sulfur_diesel
> "ULSD has a lower energy content due to the heavy processing required to
> remove large amounts of sulfur from oil, leading to lower fuel economy.
> Using it requires more costly oil."
> jsw
>
>

"Existential Angst" > wrote in message
...
> Awl --
>
> As all usenet thermodynamicists know, engine efficiency increases with
> higher compression.
> But high test can cost 10% more than regular. Does high compression
> increase engine efficiency by at least 10% to account for the higher cost
> of high test gas?
>
> My crude PV=nRT calcs + Carnot's law indicate that it does not, not by a
> long shot.

Correction:

The Carnot efficiency just BARELY keeps up with compression ratio, but it IS
close -- or closer than I thought. But still proly futile.

Here's how it works.

Carnot Eff = 1 - Tlow/Thot
Going from a compression ratio of, say, 7 to 9, gas laws will predict a
temp rise of the same ratio.
Using temp ratios that give an approx effic for IC engines of 67%, use 1 -
1/3.
Now increase Thot by about 30% (like the CR increase), and your effic goes
up to .75, for a 8% improvement in efficiency.

But, considering that, in thermo, nothing EVER turns out in your favor, it
is almost a guar-own-tee that the payoff for high test does not keep up with
the expense.

Combine that with the fact-let that I posted to Jim, that regular gas
ALREADY has more energy content than high-test, and f'sure (well, almost
f'sure) itsa losing proposition.

Along these same lines, #6 heating oil has RADICALLY more heat content than
#2 heating oil, AND is substantially cheaper. So the home-moaner gets effed
butt again.....
--
EA







> Opinions?
>
> Somewhat related: WTF decided to make diesel more so much more expensive
> than gas, when it's much cheaper to produce (comes off much earlier in the
> fractionating column)??
> --
> EA
>
>

On Sun, 27 Jan 2013 14:08:55 -0800 (PST), "G=EMC^2"
> wrote:

>On Jan 27, 4:40*pm, "Existential Angst" > wrote:
>> Awl --
>>
>> As all usenet thermodynamicists know, engine efficiency increases with
>> higher compression.
>> But high test can cost 10% more than regular. *Does high compression
>> increase engine efficiency by at least 10% to account for the higher cost of
>> high test gas?
>>
>> My crude PV=nRT calcs + Carnot's law indicate that it does not, not by a
>> long shot.
>> Opinions?
>>
>> Somewhat related: * WTF decided to make diesel more so much more expensive
>> than gas, when it's much cheaper to produce (comes off much earlier in the
>> fractionating column)??
>> --
>> EA
>
>It burns hotter,but is not worth the extra money. 87 octane is what my
>Dodge Van is made to run on. Its possible high test is better in the
>very cold. Good to put dry gas mix in to get rid of gas tank water.
>TreBert

Lower octane = higher volatility, and is therefore better in cold
weather. Higher octane fuel can cause hard starting.

On Jan 27, 2:40*pm, "Existential Angst" > wrote:
> Awl --
>
> As all usenet thermodynamicists know, engine efficiency increases with
> higher compression.
> But high test can cost 10% more than regular. *Does high compression
> increase engine efficiency by at least 10% to account for the higher cost of
> high test gas?
>
> My crude PV=nRT calcs + Carnot's law indicate that it does not, not by a
> long shot.
> Opinions?
>
> Somewhat related: * WTF decided to make diesel more so much more expensive
> than gas, when it's much cheaper to produce (comes off much earlier in the
> fractionating column)??
> --
> EA

Your engine's compression ratio is fixed and anything with an engine
management system(like in the last 3 decades) is going to adapt to
whatever you stick in there. Your compression ratio is designed for
the lowest common denominator and the timing is adjusted automatically
so it doesn't ping. My old van had a built-in mileage computer, 91
octane didn't do any better than 85. Alcohol-free gas got like 10-15%
better mileage, though. Now the air-cooled VW is a different deal,
only has an open-loop injection system and needs the extra octane to
keep from getting holes in pistons from knock. Runs like crap with
the ignition retarded.

Sulfur is the reason on the diesel, EPA decided to mandate a much
lower sulfur content. Sulfur gets removed anyway in processing, just
that below a certain point it starts costing a LOT extra to do. Some
diesels relied on that sulfur to keep injection parts from galling and
binding, I can remember guys with VW Rabbits haunting the boneyards
looking for pumps after the changeover. On the other hand, you aren't
breathing as much sulfuric acid in urban areas.

Stan