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#11
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$ 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 |
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$ per mile: high compression/high test vs. low compression/regular
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 |
#13
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$ per mile: high compression/high test vs. low compression/regular
"Jim Wilkins" > wrote in news:ke4bln$5ml$1@dont-
email.me: > "Existential Angst" > wrote in message > ... >> Awl -- >> >> As all usenet thermodynamicists know, engine efficiency increases >> with higher compression. >> But high test can cost 10% more than regular. Does high compression >> increase engine efficiency by at least 10% to account for the higher >> cost of high test gas? >> >> My crude PV=nRT calcs + Carnot's law indicate that it does not, not >> by a long shot. >> Opinions? >> >> Somewhat related: WTF decided to make diesel more so much more >> expensive than gas, when it's much cheaper to produce (comes off >> much earlier in the fractionating column)?? >> -- >> EA > > If your engine has a knock sensor it will slowly advance the spark > until it senses knock, then back off and try again. This gives the > maximum advance that the fuel, temperature, humidity and load > conditions allow, and does improve the performance when you put in > hi-test. You'd have to make measurements to see if the gain is worth > the added cost Sorry but your not quite right. the comp will only adv the timing up to the ign map in the comp.not untill ping unless it is within the map range already. high test in an eng not rated for it will just waste the hi test because the fuel map is not optimized for the higher octaine gas. some of the newer eng with a higher comp ratio will do it but the run of the mill car will not. KB > > Buick introduced the sensor on the 1978 Turbo V-6. The company I > worked for built the test station for the sensors. > > http://en.wikipedia.org/wiki/Ultra-low-sulfur_diesel > "ULSD has a lower energy content due to the heavy processing required > to remove large amounts of sulfur from oil, leading to lower fuel > economy. Using it requires more costly oil." > jsw > > |
#14
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$ per mile: high compression/high test vs. low compression/regular
On 01/29/2013 02:31 PM, Kevin Bottorff wrote:
> "Jim Wilkins" > wrote in news:ke4bln$5ml$1@dont- > email.me: > >> "Existential Angst" > wrote in message >> ... >>> Awl -- >>> >>> As all usenet thermodynamicists know, engine efficiency increases >>> with higher compression. >>> But high test can cost 10% more than regular. Does high compression >>> increase engine efficiency by at least 10% to account for the higher >>> cost of high test gas? >>> >>> My crude PV=nRT calcs + Carnot's law indicate that it does not, not >>> by a long shot. >>> Opinions? >>> >>> Somewhat related: WTF decided to make diesel more so much more >>> expensive than gas, when it's much cheaper to produce (comes off >>> much earlier in the fractionating column)?? >>> -- >>> EA >> >> If your engine has a knock sensor it will slowly advance the spark >> until it senses knock, then back off and try again. This gives the >> maximum advance that the fuel, temperature, humidity and load >> conditions allow, and does improve the performance when you put in >> hi-test. You'd have to make measurements to see if the gain is worth >> the added cost > > Sorry but your not quite right. the comp will only adv the timing up to > the ign map in the comp.not untill ping unless it is within the map range > already. high test in an eng not rated for it will just waste the hi > test because the fuel map is not optimized for the higher octaine gas. > some of the newer eng with a higher comp ratio will do it but the run of > the mill car will not. KB > This is quite true. But one factor you are all forgetting is how much better the exhaust sounds on a high-compression engine vs. a similar engine with less compression nate -- replace "roosters" with "cox" to reply. http://members.cox.net/njnagel |
#15
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$ per mile: high compression/high test vs. low compression/regular
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$1@dont- >> email.me: >> >>> "Existential Angst" > wrote in message >>> ... >>>> Awl -- >>>> >>>> As all usenet thermodynamicists know, engine efficiency >>>> increases >>>> with higher compression. >>>> But high test can cost 10% more than regular. Does high >>>> compression >>>> increase engine efficiency by at least 10% to account >>>> for the higher >>>> cost of high test gas? >>>> >>>> My crude PV=nRT calcs + Carnot's law indicate that it >>>> does not, not >>>> by a long shot. >>>> Opinions? >>>> >>>> Somewhat related: WTF decided to make diesel more so >>>> much more >>>> expensive than gas, when it's much cheaper to produce >>>> (comes off >>>> much earlier in the fractionating column)?? >>>> -- >>>> EA >>> >>> If your engine has a knock sensor it will slowly advance >>> the spark >>> until it senses knock, then back off and try again. This >>> gives the >>> maximum advance that the fuel, temperature, humidity and >>> load >>> conditions allow, and does improve the performance when >>> you put in >>> hi-test. You'd have to make measurements to see if the >>> gain is worth >>> the added cost >> >> Sorry but your not quite right. the comp will only adv >> the timing up to >> the ign map in the comp.not untill ping unless it is >> within the map range >> already. high test in an eng not rated for it will just >> waste the hi >> test because the fuel map is not optimized for the higher >> octaine gas. >> some of the newer eng with a higher comp ratio will do it >> but the run of >> the mill car will not. KB >> > > This is quite true. > > But one factor you are all forgetting is how much better the > exhaust sounds on a high-compression engine vs. a similar > engine with less compression To you, maybe. All your modern cars can't run dual glass packs -- Andrew Muzi <www.yellowjersey.org/> Open every day since 1 April, 1971 |
#16
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$ per mile: high compression/high test vs. low compression/regular
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 |
#17
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$ per mile: high compression/high test vs. low compression/regular
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 |
#18
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$ per mile: high compression/high test vs. low compression/regular
"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 |
#19
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$ per mile: high compression/high test vs. low compression/regular
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 |
#20
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$ per mile: high compression/high test vs. low compression/regular
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 |
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