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

"Stanley Schaefer" > wrote in message
...
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.
================================================== ======

"A little sulfuric acid never killed anyone...."
lol
--
EA



Stan

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?
>
The trick with high-octane gas is it allows the ignition to be advanced
quite a bit before knocking develops. If you did that on old engines
with mechanical distributors, you could actually see the difference in
gas mileage. Whether it paid for the price difference was not so clear.

Today this advance could be done by the engine computer, but for the most
part it WON'T, due to the increased production of nitrogen oxide.

Jon

"Jim Wilkins" > wrote in news:ke4bln$5ml$1@dont-
email.me:

> "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

Sorry but your not quite right. the comp will only adv the timing up to
the ign map in the comp.not untill ping unless it is within the map range
already. high test in an eng not rated for it will just waste the hi
test because the fuel map is not optimized for the higher octaine gas.
some of the newer eng with a higher comp ratio will do it but the run of
the mill car will not. KB


>
> 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
>
>

On 01/29/2013 02:31 PM, Kevin Bottorff wrote:
> "Jim Wilkins" > wrote in news:ke4bln$5ml$1@dont-
> email.me:
>
>> "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
>
> Sorry but your not quite right. the comp will only adv the timing up to
> the ign map in the comp.not untill ping unless it is within the map range
> already. high test in an eng not rated for it will just waste the hi
> test because the fuel map is not optimized for the higher octaine gas.
> some of the newer eng with a higher comp ratio will do it but the run of
> the mill car will not. KB
>

This is quite true.

But one factor you are all forgetting is how much better the exhaust
sounds on a high-compression engine vs. a similar engine with less
compression

nate


--
replace "roosters" with "cox" to reply.
http://members.cox.net/njnagel

On 1/30/2013 7:08 PM, Nate Nagel wrote:
> On 01/29/2013 02:31 PM, Kevin Bottorff wrote:
>> "Jim Wilkins" > wrote in
>> news:ke4bln$5ml$1@dont-
>> email.me:
>>
>>> "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
>>
>> Sorry but your not quite right. the comp will only adv
>> the timing up to
>> the ign map in the comp.not untill ping unless it is
>> within the map range
>> already. high test in an eng not rated for it will just
>> waste the hi
>> test because the fuel map is not optimized for the higher
>> octaine gas.
>> some of the newer eng with a higher comp ratio will do it
>> but the run of
>> the mill car will not. KB
>>
>
> This is quite true.
>
> But one factor you are all forgetting is how much better the
> exhaust sounds on a high-compression engine vs. a similar
> engine with less compression


To you, maybe.
All your modern cars can't run dual glass packs

--
Andrew Muzi
<www.yellowjersey.org/>
Open every day since 1 April, 1971

On 01/31/2013 01:23 PM, Ed Huntress wrote:
>
>
> "AMuzi" wrote in message ...
>
> On 1/30/2013 7:08 PM, Nate Nagel wrote:
>> On 01/29/2013 02:31 PM, Kevin Bottorff wrote:
>>> "Jim Wilkins" > wrote in
>>> news:ke4bln$5ml$1@dont-
>>> email.me:
>>>
>>>> "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
>>>
>>> Sorry but your not quite right. the comp will only adv
>>> the timing up to
>>> the ign map in the comp.not untill ping unless it is
>>> within the map range
>>> already. high test in an eng not rated for it will just
>>> waste the hi
>>> test because the fuel map is not optimized for the higher
>>> octaine gas.
>>> some of the newer eng with a higher comp ratio will do it
>>> but the run of
>>> the mill car will not. KB
>>>
>>
>> This is quite true.
>>
>> But one factor you are all forgetting is how much better the
>> exhaust sounds on a high-compression engine vs. a similar
>> engine with less compression
>
>
> To you, maybe.
> All your modern cars can't run dual glass packs
>
>
> Andrew Muzi
> <www.yellowjersey.org/>
> Open every day since 1 April, 1971
>
> ================================================== ======
>
> I can't access the original post, but EA, I think your premise is wrong.
> You thinking is good, though. <g>
>
> Octane ratings originally were done in the lab with mixtures of octane,
> pentane, and heptane. The ratings were based on *percentages* of octane
> in the mix. I don't think there was a straight-line ratio between octane
> rating and potential compression ratio.
>
> I could be wrong about that, since it's based on reading some book from
> MIT Sloan Automotive Labs many years ago. But I think that's right. Of
> course, to get ratings over 100 required projecting what it *would* be,
> based on whatever formula they worked out at the time.
>
> In fact, IIRC, the compression ratios were slightly *higher* than the
> octane percentages would indicate. So, if I'm guessing right about how
> you ran the relationship to the Carnot cycle, you may have started with
> an incorrect assumption that octane rating should translate directly to
> relative compression ratios.
>
> --
> Ed Huntress

the relationship between compression ratio and octane is much more
complicated than that. the japanese discovered that combustion chamber
shape and its internal sonic characteristics have a significant impact
on whether an engine knocks or not - it's not simply a function of
compression ratio. you will therefore observe that many [modern]
japanese engines go to great lengths to keep cylinder head combustion
chamber features rounded, and to make sure that flame paths are as
non-convoluted as possible - so they can use higher compression ratios
with lower octane gas.

furthermore, not only did this engine research change compression/octane
thinking, combustion chamber design has also proven to help
significantly with cleaner combustion and thus emissions.

bottom line, this is a highly technical subject on which billions have
been spent in research over the years. as research has advanced, old
presumptions about octane and compression have had to be all but abandoned.


--
fact check required

On 01/30/2013 05:08 PM, Nate Nagel wrote:
> On 01/29/2013 02:31 PM, Kevin Bottorff wrote:
>> "Jim Wilkins" > wrote in news:ke4bln$5ml$1@dont-
>> email.me:
>>
>>> "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
>>
>> Sorry but your not quite right. the comp will only adv the timing
>> up to
>> the ign map in the comp.not untill ping unless it is within the map range
>> already. high test in an eng not rated for it will just waste the hi
>> test because the fuel map is not optimized for the higher octaine gas.
>> some of the newer eng with a higher comp ratio will do it but the run of
>> the mill car will not. KB
>>
>
> This is quite true.
>
> But one factor you are all forgetting is how much better the exhaust
> sounds on a high-compression engine vs. a similar engine with less
> compression
>
> nate
>
>

you're an unspeakable retard. what you're in fact hearing is the
difference in the manifolds and engines that are built for higher and
lower outputs. if you had two otherwise identical engines, same
manifolds and exhausts, with only compression ratios different, you'd
have a real hard time telling the difference. especially if you were a
cloth-eared idiot with no analytic skills and even less sense about
opening their mouth on a topic on which they've go no experience and
even less knowledge.


--
fact check required

"AMuzi" wrote in message ...

On 1/30/2013 7:08 PM, Nate Nagel wrote:
> On 01/29/2013 02:31 PM, Kevin Bottorff wrote:
>> "Jim Wilkins" > wrote in
>> news:ke4bln$5ml$1@dont-
>> email.me:
>>
>>> "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
>>
>> Sorry but your not quite right. the comp will only adv
>> the timing up to
>> the ign map in the comp.not untill ping unless it is
>> within the map range
>> already. high test in an eng not rated for it will just
>> waste the hi
>> test because the fuel map is not optimized for the higher
>> octaine gas.
>> some of the newer eng with a higher comp ratio will do it
>> but the run of
>> the mill car will not. KB
>>
>
> This is quite true.
>
> But one factor you are all forgetting is how much better the
> exhaust sounds on a high-compression engine vs. a similar
> engine with less compression


To you, maybe.
All your modern cars can't run dual glass packs

--
Andrew Muzi
<www.yellowjersey.org/>
Open every day since 1 April, 1971

================================================== ======

I can't access the original post, but EA, I think your premise is wrong. You
thinking is good, though. <g>

Octane ratings originally were done in the lab with mixtures of octane,
pentane, and heptane. The ratings were based on *percentages* of octane in
the mix. I don't think there was a straight-line ratio between octane rating
and potential compression ratio.

I could be wrong about that, since it's based on reading some book from MIT
Sloan Automotive Labs many years ago. But I think that's right. Of course,
to get ratings over 100 required projecting what it *would* be, based on
whatever formula they worked out at the time.

In fact, IIRC, the compression ratios were slightly *higher* than the octane
percentages would indicate. So, if I'm guessing right about how you ran the
relationship to the Carnot cycle, you may have started with an incorrect
assumption that octane rating should translate directly to relative
compression ratios.

--
Ed Huntress

On 01/30/2013 09:38 PM, AMuzi wrote:
> On 1/30/2013 7:08 PM, Nate Nagel wrote:
>> On 01/29/2013 02:31 PM, Kevin Bottorff wrote:
>>> "Jim Wilkins" > wrote in
>>> news:ke4bln$5ml$1@dont-
>>> email.me:
>>>
>>>> "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
>>>
>>> Sorry but your not quite right. the comp will only adv
>>> the timing up to
>>> the ign map in the comp.not untill ping unless it is
>>> within the map range
>>> already. high test in an eng not rated for it will just
>>> waste the hi
>>> test because the fuel map is not optimized for the higher
>>> octaine gas.
>>> some of the newer eng with a higher comp ratio will do it
>>> but the run of
>>> the mill car will not. KB
>>>
>>
>> This is quite true.
>>
>> But one factor you are all forgetting is how much better the
>> exhaust sounds on a high-compression engine vs. a similar
>> engine with less compression
>
>
> To you, maybe.
> All your modern cars can't run dual glass packs
>

My only modern car can, and probably would sound good with them (likely
similar to an old "Jimmy Six") as long as I don't get pulled over

Sadly, I'm pretty sure that glasspacks are illegal in VA. I'm sure that
they are in MD; I checked.

(fires up the google machine)

§ 46.2-1049. (Effective October 1, 2012) Exhaust system in good working
order.

No person shall drive and no owner of a vehicle shall permit or allow
the operation of any such vehicle on a highway unless it is equipped
with an exhaust system in good working order and in constant operation
to prevent excessive or unusual levels of noise; provided however, that
for motor vehicles, such exhaust system shall be of a type installed as
standard factory equipment, or comparable to that designed for use on
the particular vehicle as standard factory equipment. An exhaust system
shall not be deemed to prevent excessive or unusual noise if it permits
the escape of noise in excess of that permitted by the standard factory
equipment exhaust system of private passenger motor vehicles or trucks
of standard make.

The term "exhaust system," as used in this section, means all the parts
of a vehicle through which the exhaust passes after leaving the engine
block, including mufflers and other sound dissipative devices.

Chambered pipes are not an effective muffling device to prevent
excessive or unusual noise, and any vehicle equipped with chambered
pipes shall be deemed in violation of this section.

The provisions of this section shall not apply to converted electric
vehicles.

(end quote)

So, chambered exhausts are explicitly prohibited, however, glasspacks
are not - but the wording of the law is such that it is entirely likely
that it's essentially at a police officer's discretion as to whether
your exhaust system is too loud or not, or if he considers a glasspack
to be similar enough to a factory muffler to let you go or not.

Personally, I think glasspacks would be fine on a turbo engine, but I'm
obviously not the guy with the ticket book.

nate

--
replace "roosters" with "cox" to reply.
http://members.cox.net/njnagel

On 01/31/2013 03:46 AM, jim beam wrote:
> On 01/30/2013 05:08 PM, Nate Nagel wrote:
>> On 01/29/2013 02:31 PM, Kevin Bottorff wrote:
>>> "Jim Wilkins" > wrote in news:ke4bln$5ml$1@dont-
>>> email.me:
>>>
>>>> "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
>>>
>>> Sorry but your not quite right. the comp will only adv the timing
>>> up to
>>> the ign map in the comp.not untill ping unless it is within the map
>>> range
>>> already. high test in an eng not rated for it will just waste the hi
>>> test because the fuel map is not optimized for the higher octaine gas.
>>> some of the newer eng with a higher comp ratio will do it but the run of
>>> the mill car will not. KB
>>>
>>
>> This is quite true.
>>
>> But one factor you are all forgetting is how much better the exhaust
>> sounds on a high-compression engine vs. a similar engine with less
>> compression
>>
>> nate
>>
>>
>
> you're an unspeakable retard. what you're in fact hearing is the
> difference in the manifolds and engines that are built for higher and
> lower outputs. if you had two otherwise identical engines, same
> manifolds and exhausts, with only compression ratios different, you'd
> have a real hard time telling the difference. especially if you were a
> cloth-eared idiot with no analytic skills and even less sense about
> opening their mouth on a topic on which they've go no experience and
> even less knowledge.
>
>

Bull****. I actually have experience with of what I speak. When I
swapped engines in my '55 Stude - WITHOUT CHANGING MANIFOLDS, PIPES, OR
MUFFLERS - I noticed a distinct difference in the "sharpness" of the
exhaust note.

I swapped from a '63 or '64 model (I forget now) standard 289 which was
in the car when I bought it to an engine built from a service block (but
also a 63-64 casting.) The replacement engine was built to Avanti R1
spec, the main differences between the two engines being the compression
ratio (8.something to 1 to 10.25:1) and slightly more aggressive cam
timing. Displacement, combustion chamber shape and head port
configuration, manifolds, etc. all remained either very similar or
exactly identical.

Again, I did not change anything past the heads, because I'd already
replaced the exhaust as part of the initial process of getting the car
on the road, and the original '55 C-K body exhaust system actually used
good sized pipes capable of supporting more horsepower than the original
'55 engine choices put out. Studebaker actually downsized the diameter
of the tailpipes for 56-64, even for the Golden Hawks and supercharged
GT Hawks, so my system was actually less restrictive than the factory
system on a "Super" package GT Hawk.

nate

--
replace "roosters" with "cox" to reply.
http://members.cox.net/njnagel