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Car Forum / Driving, Maintenance, Tuning / Maintenance and Repair / January 2007better mileage with higher octane?
is there any truth to the statement that using a higher octane gasoline will result in better gas mileage? I understand that it may have other beneficial properties ie. anti-knock, acceleration, etc.. how would one calculate such a statement? for reference, I usually fillup between 16-20 gallons, regular gas is 87 octane, supreme 92 octane and in our area the price difference appears to be about 20c-30c between regular and supreme. > is there any truth to the statement that using a higher octane gasoline will result in > better gas mileage? I understand that it may have other beneficial properties ie. > anti-knock, acceleration, etc.. > > how would one calculate such a statement? Dont worry about calculating anything. Octane rating has no direct relationship to gas mileage. Antiknock properties are the key. > > is there any truth to the statement that using a higher octane gasoline > will result in [quoted text clipped - 7 lines] > relationship > to gas mileage. Antiknock properties are the key. and just what do you think Octane rating a measure of? > > > is there any truth to the statement that using a higher octane gasoline > > will result in [quoted text clipped - 9 lines] > > > and just what do you think Octane rating a measure of? The octane rating is, just as I said, a number related to antiknock properties. > "stu" <nowhere@justyet.com> wrote in message > > <HLS@nospam.nix> wrote in message [quoted text clipped - 7 lines] > The octane rating is, just as I said, a number related to antiknock > properties. And good anti-knock properties ( higher octane ) allow the ignition to be advanced which *may* improve engine efficiency. It pretty much invariably improves performance. Graham Eeyore <rabbitsfriendsandrelations@hotmail.com> wrote in article <459A666F.AD243C2C@hotmail.com>... > > "stu" <nowhere@justyet.com> wrote in message > > > <HLS@nospam.nix> wrote in message [quoted text clipped - 13 lines] > > Graham In the scenario you describe, the improved performance would come from physically advancing the timing - NOT from the fuel switch alone. You could probably see a similar increase by just advancing the timing and NOT switching fuels - but the engine might suffer. The simple act of pumping $10 worth of "high test" into the tank of a car that doesn't require it, really does nothing but improve the bottom line at corporate headquarters. > > HLS@nospam.nix wrote: > > > > <HLS@nospam.nix> wrote [quoted text clipped - 23 lines] > that doesn't require it, really does nothing but improve the bottom line at > corporate headquarters. I don't understand your point. You can't just advance the timing willy nilly. In any case the ECU should control it and any advantage will be gained automatically. Graham Eeyore <rabbitsfriendsandrelations@hotmail.com> wrote in article <459AA2A1.9F1B5A35@hotmail.com>... > > > HLS@nospam.nix wrote: > > > > > <HLS@nospam.nix> wrote [quoted text clipped - 28 lines] > You can't just advance the timing willy nilly. In any case the ECU should > control it and any advantage will be gained automatically. I was thinking pre-computerized ignitions. So, the ECU has been programmed to advance the timing within safe limits of regular fuel....no more. How do YOU get it to exceed those limits? >Eeyore <rabbitsfriendsandrelations@hotmail.com> wrote in article ><459AA2A1.9F1B5A35@hotmail.com>... [quoted text clipped - 44 lines] > >How do YOU get it to exceed those limits? Depends on the ECU. Some can be "chipped" for more advance.Some OBD2 boxes can be "reflashed" Some that still have a distributor can have the timing physically advanced. On some you can adjust the cam sensor to provide more advance. On most, it's pretty well "cast in stone"  SignaturePosted via a free Usenet account from http://www.teranews.com clare at snyder.on.ca wrote in article <nlblp21g1s649pvlogdp010qi4cvrgf60q@4ax.com>... > >Eeyore <rabbitsfriendsandrelations@hotmail.com> wrote in article > ><459AA2A1.9F1B5A35@hotmail.com>... [quoted text clipped - 49 lines] > the timing physically advanced. On some you can adjust the cam sensor > to provide more advance. On most, it's pretty well "cast in stone" Which, of course, is modifying the car - NOT gaining better mileage by simply adding high octane gasoline... > Eeyore <rabbitsfriendsandrelations@hotmail.com> wrote in article > <459AA2A1.9F1B5A35@hotmail.com>... [quoted text clipped - 45 lines] > > How do YOU get it to exceed those limits? With a performance chip set.......sold at any rod shop. And while you are there pick-up your turbocharger kit....and if you want to use premium switch to bi-turbo. Arnold Walker <arnoldwalker@consolidated.net> wrote in article <1167767707_22933@sp6iad.superfeed.net>... > > Eeyore <rabbitsfriendsandrelations@hotmail.com> wrote in article > > <459AA2A1.9F1B5A35@hotmail.com>... [quoted text clipped - 49 lines] > use premium > switch to bi-turbo. Which, of course, is modifying the car - NOT gaining better mileage by simply adding high octane gasoline... > Eeyore <rabbitsfriendsandrelations@hotmail.com> wrote in article > <459AA2A1.9F1B5A35@hotmail.com>... [quoted text clipped - 45 lines] > > How do YOU get it to exceed those limits? most vehicles have a knock sensor and will try to constantly adjust the timing.If you use higher octane fuel the ecu will advance the timing further.The question is will the added mileage make up for the price difference? >> "stu" <nowhere@justyet.com> wrote in message >>> <HLS@nospam.nix> wrote in message [quoted text clipped - 11 lines] > > Graham but only if the computer calls for more timing with higher octane. If your computer calls for a max of 35 degrees and you can reach that on regular gas, 91 won't do anything. That said, I have a Trans Am that will ping if you put in anything lower than 91. Manual says so, and I accidentially put in a tank of 87 by accident. Stopped 50 miles later and bought a shot of octane boost and then filled up again at 1/2 tank to stop the pinging. Ray > >> "stu" <nowhere@justyet.com> wrote in message > >>> <HLS@nospam.nix> wrote in message [quoted text clipped - 20 lines] > accident. Stopped 50 miles later and bought a shot of octane boost and > then filled up again at 1/2 tank to stop the pinging. Saab's Trionic ECUs will deliberately advance the timing until the engine *does* pink intentionally so. And much much more besides. They even use spark plug ionisation levels to determine mixture richness ( on a per cylinder basis ) ! They're probably the most advanced around. Many cars have clueless ECUs by comparison. So it does depend hugely on the car. Graham > >> "stu" <nowhere@justyet.com> wrote in message > >>> <HLS@nospam.nix> wrote in message [quoted text clipped - 20 lines] > accident. Stopped 50 miles later and bought a shot of octane boost and > then filled up again at 1/2 tank to stop the pinging. No ECU ? What year is that ? Graham It doesn't matter if the engine is computer controlled or not if timing operates is open loop (no knock sensing). The early 90:s non-turbo EFI:s I know does not have knock sensing and will happily ping without having a clue. news <rollingviolation@domain.invalid.com> wrote in article <24zmh.543160$1T2.206797@pd7urf2no>... > That said, I have a Trans Am that will ping if you put in anything lower > than 91. Manual says so, and I accidentially put in a tank of 87 by > accident. Stopped 50 miles later and bought a shot of octane boost and > then filled up again at 1/2 tank to stop the pinging. Which "octane boost" did you buy? 104+ used to say right on the can that it "...enhances the octane effect..." by cleaning carbon out of the combustion chamber - thus lowering compression and knocking. IOW - It didn't INCREASE the actual octane of the fuel, it simply DECREASED the need for higher octane caused by higher compression pressures created by carbon deposits. > It pretty much invariably > improves performance. > > Graham Absolutely could not be more WRONG here. I race(d) in a class that limited compression to 9.5:1. We could run any fuel we wanted, and time after time, people would put race gas (Sunoco 110 or Turbo 110) then have to crank their ignition timing way up only to come close to getting the same performance that they did using 92 octane pump gas. > > It pretty much invariably improves performance. > > [quoted text clipped - 6 lines] > timing way up only to come close to getting the same performance that > they did using 92 octane pump gas. That's hardly typical though. I thought we were talking about road cars ? Also modern cars don't have manual timing adjustment., the ECU does it. Graham > > > It pretty much invariably improves performance. > > > [quoted text clipped - 9 lines] > That's hardly typical though. I thought we were talking about road cars ? Also > modern cars don't have manual timing adjustment., the ECU does it. His point was that if the engine was optimized for lower octane fuel then you have to resort to work arounds like bumping the timing way up with little if any bennefit. There are no absolutes but it has been my experience that the higher octane fuel has a slower flame speed for a given temperture/pressure. Increasing the compression ratio will increase the temp/pressure. Without the compression increase you resort to advancing the timing to get the temp/pressure back up where you need it. But that works against you because the engine has to overcome the rise in cylinder pressure before the piston gets to TDC. So even if the ECU advances the timing to take advantage of higher octane you get little if anything extra for your money. If you have a turbo you can crank the boost up and make more power, but that's not the same thing as mileage, which is what this thread is about. Bruce if it help anyone at all my camaro on regular gets 24-25 mpg and pings and what not and on higher octane gas it gets 30-32 and never pings and seems to run better but thats just my car my dads built 350 in his s10 gets 14 mpg on regular and 15 on higher octane but it doesnt seem to run better so i guess it just depends on your vehicle. Signaturerscamaroboy89 http://www.automotiveforums.com > if it help anyone at all my camaro on regular gets 24-25 mpg and pings > and what not and on higher octane gas it gets 30-32 and never pings and > seems to run better but thats just my car my dads built 350 in his s10 > gets 14 mpg on regular and 15 on higher octane but it doesnt seem to > run better so i guess it just depends on your vehicle. Makes perfect sense. If you have a Camaro that gets that kind of mileage, its obviously an LS-1 or LT-1 with full digital engine management and knock sensors, plus a pretty high static compression. The engine managment system is having to pull back the timing to let the engine survive on regular octane gas, but can use its optimal settings on premium. An old carbureted HEI ignition 350 can't tell the difference in fuels because it doesn't have knock sensors and digital engine management. You could *manually* set the timing up to use premium, but then you couldn't run regular at all without risking damage. | The octane rating is, just as I said, a number related to antiknock | properties. Wikipedia says lower octane petrol usually produces less heat , this I find true in BP's RON92 compared with RON97 : both my mitsubishi 4G15P & honda F20A ( original cr 9.2 & 9.6, both have improved cooling via copper wires ) can use RON92 , esp in humid air here & on flat land ( no towing / climbing ), but RON92 produces less heat ( & so torque ), so its 1.56% lower price cannot justify 2-4 % less torque. My brother's mitsubishi 6G72 ( cr is just 9 ) needs just RON92 per owner's manual, but he buys RON97, & I agree as wise. >>is there any truth to the statement that using a higher octane gasoline > [quoted text clipped - 11 lines] > relationship > to gas mileage. Antiknock properties are the key. Precisely. Just think about it -- at one time, octane was increased by adding lead compounds. Why would lead increase a fuel's energy? SignatureThe e-mail address in our reply-to line is reversed in an attempt to minimize spam. Our true address is of the form che...@prodigy.net. > > "dido" <dido@north.za> wrote in message > > [quoted text clipped - 11 lines] > Precisely. Just think about it -- at one time, octane was increased > by adding lead compounds. Why would lead increase a fuel's energy? It doesn't. Energy has nothing to do with it. High octane fuel has less energy than low octane in any case. Graham >> > "dido" <dido@north.za> wrote in message >> > [quoted text clipped - 17 lines] > >Graham Not necessarily (and usually not) true. This is a MYTH that has been going around for years. If octane is increased by adding ethanol, it is true. If it is inproved by catylitic cracking og the feed stock, it is not true. SignaturePosted via a free Usenet account from http://www.teranews.com >>>is there any truth to the statement that using a higher octane gasoline >> [quoted text clipped - 14 lines] >Precisely. Just think about it -- at one time, octane was increased >by adding lead compounds. Why would lead increase a fuel's energy? It didn't - but it allowed the engine to extract more of the energy that the fuel contained by running at a more efficient setting. SignaturePosted via a free Usenet account from http://www.teranews.com Octane slows down the burn and allows more power to be extracted from the fuel, stops the pinging but the engine timing must be adjusted to suit. Lead had more cooling effect for lower temperature valves and other parts. >>>is there any truth to the statement that using a higher octane >>>gasoline [quoted text clipped - 15 lines] > Precisely. Just think about it -- at one time, octane was increased > by adding lead compounds. Why would lead increase a fuel's energy? > Octane slows down the burn and allows more power to be extracted from > the fuel, stops the pinging but the engine timing must be adjusted to > suit. A decent ECU will do that instantaneously 'on the fly'. Graham > > Octane slows down the burn and allows more power to be extracted from > > the fuel, stops the pinging but the engine timing must be adjusted to [quoted text clipped - 3 lines] > > Graham In any case and slight increase in mpg will be more than offset by the additional cost. Just my opinion but I am on the side of 'no increase'. I have seen this thing discussed and written about many times. The "experts" all say it is just a waste of money. Harry K > > > Octane slows down the burn and allows more power to be extracted from > > > the fuel, stops the pinging but the engine timing must be adjusted to [quoted text clipped - 8 lines] > increase'. I have seen this thing discussed and written about many > times. The "experts" all say it is just a waste of money. You may not get any increase in mpg but decent cars will see an improvement in performance. I had one car in fact that allowed to me select the 'ideal' octane as either 95 or 98 ( RON ). Graham Say, whatever happened to the water injection systems that they used in the world war II fighter planes? They could advance the timing, reduce the ping, get better performance and economy. So, how come these brilliant automotive engineers aren't using this technology? > Say, whatever happened to the water injection systems that they used in > the world war II fighter planes? They could advance the timing, reduce > the ping, get better performance and economy. So, how come these > brilliant automotive engineers aren't using this technology? What water injection systems ? There were ethanol and methanol injection sytems ( improve the octane rating ) but water ? Graham Well, let me see what Mr. Wikipedia has to say about the subject... http://en.wikipedia.org/wiki/Water_injection_(engines) --------------------- > What water injection systems ? > > There were ethanol and methanol injection sytems ( improve the octane rating ) > but water ? > > Graham > Well, let me see what Mr. Wikipedia has to say about the subject... > http://en.wikipedia.org/wiki/Water_injection_%28engines%29 [quoted text clipped - 6 lines] > > > > Graham > Well, let me see what Mr. Wikipedia has to say about the subject... > http://en.wikipedia.org/wiki/Water_injection_(engines) It says very little. So ? Maybe it was found not to be terribly useful ? I can see there would be logistical issues. Your turn. Graham > Well, let me see what Mr. Wikipedia has to say about the subject... > http://en.wikipedia.org/wiki/Water_injection_(engines) Ok. 2nd take. I notice the comment that water injection has fallen out of interest since the advent of intercooled turbo engines. One problem with turbo'ing is the that the intake air becomes very hot due to compression and the air-fuel mixture can prematurely detonate in the cylinder. My own Saab ( lpt ) without an intercooler is limited to about 0.3 bar boost for example to avoid such a problem.. Water injection into the hot intake air would actually cool the mixture thus resolving the problem. However since intercoolers perform the same function without the added complexity of water or water-alcohol injection there's simply no longer any need for it. http://en.wikipedia.org/wiki/Intercooler Graham > > Say, whatever happened to the water injection systems that they used in > > the world war II fighter planes? They could advance the timing, reduce [quoted text clipped - 7 lines] > > Graham Used to be add-ons sold through places like J.C. Whitney. Running the old 30s and 40s cars, there was a very noticeable improvesment in performance (don't know about economy) when the humidity was high or it was raining. Never noticed it after the advent of modern engine control systems. Harry K >> > Say, whatever happened to the water injection systems that they used in >> > the world war II fighter planes? They could advance the timing, reduce [quoted text clipped - 11 lines] >was raining. Never noticed it after the advent of modern engine >control systems. Water injection was a big deal in the 1940s and was used in a lot of WWII aircraft engines. The notion here is that you get the phase change of the water during combustion, which produces additional effective power (ie. more energy into the piston stroke, less energy wasted as exhaust heat) as it turns to steam. I don't think I have seen it on anything modern.... but it was one of the big secret features on the B-29. Normally it's not just water either, but a water/surfactant mixture so that the fuel-air-water mixture would be more even. --scott Signature"C'est un Nagra. C'est suisse, et tres, tres precis." >>>>Say, whatever happened to the water injection systems that they used in >>>>the world war II fighter planes? They are used (beyond their designers' wildest dreams, in fact) every year at the Reno National Championship Air Races ;-) > They could advance the timing, reduce >>>>the ping, get better performance and economy. So, how come these >>>>brilliant automotive engineers aren't using this technology? Advancing the timing wasn't the goal, raising the BOOST PRESSURE from supercharger or turbochargers was the goal. Advancing timing is counter-productive beyond a certain point because combustion is just pushing "the wrong way" on the piston. But raising boost pressure is advantageous in many ways. The problem is that thanks to good ol PV=nRT, compressing the intake charger with a super- or turbo-charger raises the temperature of the intake charge. Too high an intake temperature results in detonation regardless of the ignition timing, and can also result in manifold explosions. Aftercoolers (air-to-air or air-to water) help, but are limited in how much heat they can reject and also add weight to the aircraft. Water injection in WWII aircraft engines primarily reduced the temperature of the intake charge to a manageable level because the evaporating water absorbs a LOT of heat (latent heat of vaporization.) Running the engine excessively rich also does the same thing using the fuel itself to absorb heat, but the drawback is that over-rich combustion produces less power than stoichiometric combustion. In addition, the water adds inert gas to the combustion cycle, and that slows down the flame front and reduces the peak temperature in the cylinder and further suppresses harmful detonation of the type where a pocket of charge in a remote corner of the cylinder self-ignites after the primary flame-front starts increasing cylinder pressure. Modern automobile engines (since the late 70s) actually use a metered dose of their own exhaust gas (exhaust gas recirculation or EGR) to do this (slow combustion, reduce peak combustion temperature) as well as to reduce nitrogen oxide emissions. The big drawback to water injection is maintenance. Corrosion in the plumbing, pumps, valving, etc. is a big problem. Also, the water/ethanol mixture has to be replenished along with fuel and oil and it has to be PURE water which requires reverse-osmosis, distillation, or at least deionization. Otherwise deposits build up in the system and in the engine. Water injection really isn't practical for cars, especially since most drivers can't even be persuaded to check their own oil these days. > Water injection was a big deal in the 1940s and was used in a lot of WWII > aircraft engines. The notion here is that you get the phase change of > the water during combustion, which produces additional effective power > (ie. more energy into the piston stroke, less energy wasted as exhaust heat) > as it turns to steam. My understanding is that the water/alcohol is fully vaporized well before it passes through the intake valve(s). > Water injection really isn't practical for cars, especially > since most drivers can't even be persuaded to check their own oil these > days. Did they ever? Ah, for the good old days when the guy at the pumps always asked if I wanted the oil checked... Signaturederek >>Water injection really isn't practical for cars, especially >>since most drivers can't even be persuaded to check their own oil these >>days. > > Did they ever? Yeah. The summer of 1975... > Ah, for the good old days when the guy at the pumps always > asked if I wanted the oil checked... I miss that. I'm sure some folks DON'T miss the occasional crook at the pumps who made sure to put the stick in "short" so it read a quart low, the guys who dropped antacid tablets in the battery and said that the foam was due to the alternator overcharging the battery, etc. etc. etc. Gladly those guys were a small minority, but they were out there! >>>Water injection really isn't practical for cars, especially >>>since most drivers can't even be persuaded to check their own oil these [quoted text clipped - 3 lines] > > Yeah. The summer of 1975... Ah, yes. Those were the days when I didn't ever have to check my oil - every 100 miles it needed another quart. >> Ah, for the good old days when the guy at the pumps always >> asked if I wanted the oil checked... > > I miss that. I'm sure some folks DON'T miss the occasional crook at the > pumps Well, me neither, but it does come as a huge surprise these days when someone asks... Signaturederek Two could play at that game. I remember when you could reset the counter on the gas pump ever $5.00 just by flipping it off and on. That way a fillup only ever costed $5.00 Oh wait a minute, it only cost $5.00 to fill up then anyway. Sorry... ------------------ > >>Water injection really isn't practical for cars, especially > >>since most drivers can't even be persuaded to check their own oil these [quoted text clipped - 12 lines] > foam was due to the alternator overcharging the battery, etc. etc. etc. > Gladly those guys were a small minority, but they were out there! > > Water injection was a big deal in the 1940s and was used in a lot of WWII > > aircraft engines. The notion here is that you get the phase change of [quoted text clipped - 4 lines] > My understanding is that the water/alcohol is fully vaporized well > before it passes through the intake valve(s). My understanding (not very good I admit) is that you get nothing for free. Seems to me any power produced by flashing to steam has been from heat stolen from the fuel combustion. I doubt that there is any additional power produced by steam. The basic theory seems to have been to cool the intake mixture thus getting a denser (and more fuel) charge into the cyslinder. Harry K >> > Water injection was a big deal in the 1940s and was used in a lot of >> > WWII [quoted text clipped - 15 lines] > > Harry K Steam expanses more for a given temperature than air. And with the improved heat expansion and anti-ping control offered by water injection. You did indeed got more power and the exhaust would be half as hot at the same time. In piston engine a 1/3 more and on turbines double the horsepower.You got to remember the piston engines were running 50psi boost(22+:1 effective compression ratio or in otherwords the compression stroke would heat the air to 900F before you burned any fuel ) in the air,not automotive turbo pressures. With the exception of Stubaker ,whose car engines did with a blower on their sports model. They did water injection and avgas.....to contol the ping.and like the aircraft had a switch in the water tank/pump to kill the ignition advance and blowoff the boost psi, if the tank ran low. In both the Stubaker and the plane,if the water switch failed the engine was trash in seconds from preignition detonation.But when it worked a Stubaker Commander could hang with 427 high performance engines running half the engine displacement.The engine was dropped because of complex construction ....little did they know that modern engines now make they look simple ,50years later. >> > Water injection was a big deal in the 1940s and was used in a lot of WWII >> > aircraft engines. The notion here is that you get the phase change of [quoted text clipped - 13 lines] > >Harry K Almost. Getting higher density of the air charge is no problem on a turbo engine. It is the cooling of the COMBUSTION CHAMBER that was the challenge - and water injection helped significantly. It DID have the side effect of acting a bit like an intercooler - but any heat absorbed in the intake reduced it's primary effect in the cyl. A higher density intake charge actually INCREASED the tendancy to detonate by increasing the effective cyl compression - which was part of the problem in the first place (wouldn't ping without boost) SignaturePosted via a free Usenet account from http://www.teranews.com >>>Water injection was a big deal in the 1940s and was used in a lot of WWII >>>aircraft engines. The notion here is that you get the phase change of [quoted text clipped - 13 lines] > > Harry K You're right in that the main gain is getting a denser cooler mixture into the cylinder, but I think there is a *small* additional gain when water vapor is present in the combustion chamber because we're not dealing with ideal gasses. If all the gasses involved were truly ideal, then you would be correct. In addition, most WWII aircraft engines made some small use of the jet thrust from the exhaust stacks, and water certainly adds mass-flow to the engine and would add some jet thrust. IIRC, I've seen an estimate that a P-51's Merlin engine produces a few hundred pounds of jet thrust from its exhaust at full power. Not enough to even move the aircraft on the ground by itself, but certainly enough to offset the drag of the exhaust system itself sticking out into the slipstream, and therefore a net benefit. >Say, whatever happened to the water injection systems that they used in >the world war II fighter planes? They could advance the timing, reduce >the ping, get better performance and economy. So, how come these >brilliant automotive engineers aren't using this technology? GM did, back in '60 to '63 with the turbo Olds Jetfire and IIRC, the Turbo Monza Corvair. Don't think it was standard on the Monza, but I know some did use it (possibly a "dealer add-on" using Olds parts) SignaturePosted via a free Usenet account from http://www.teranews.com Eeyore <rabbitsfriendsandrelations@hotmail.com> wrote in article <459B3611.D785D2B9@hotmail.com>... > You may not get any increase in mpg but decent cars will see an improvement in > performance. Talk about hi-jacking a thread..... The OP's question concerned using hogh octane for better fuel mileage, and you've morphed it into discussing better performance. I think that the message that I was trying to get across was that water injection effectively raises the octane level and performance of an engine. The wikipedia link was talking about the same thing. http://en.wikipedia.org/wiki/Water_injection_%28engines%29 ---------------- > Talk about hi-jacking a thread..... > > The OP's question concerned using hogh octane for better fuel mileage, and > you've morphed it into discussing better performance. Water cannot increase the octane level but it can make the engine perform like a higher octane fuel is present by slowing the explosion down so more thrust can be harnessed with less cylinder head damage. >I think that the message that I was trying to get across was that >water [quoted text clipped - 8 lines] >> mileage, and >> you've morphed it into discussing better performance. >Water cannot increase the octane level but it can make the engine >perform like a higher octane fuel is present by slowing the explosion >down so more thrust can be harnessed with less cylinder head damage. Water injection reduces the octane requirement of the engine by cooling the combustion chamber. This is partly due to the latent heat of vaporization of water. The water "sucks up" some of the heat that would otherwize work on the end-gasses. >>I think that the message that I was trying to get across was that >>water [quoted text clipped - 8 lines] >>> mileage, and >>> you've morphed it into discussing better performance. SignaturePosted via a free Usenet account from http://www.teranews.com >Eeyore <rabbitsfriendsandrelations@hotmail.com> wrote in article ><459B3611.D785D2B9@hotmail.com>... [quoted text clipped - 7 lines] >The OP's question concerned using hogh octane for better fuel mileage, and >you've morphed it into discussing better performance. So? Better performance GENERALLY also translates to better fuel mileage if you do not use the extra power available. SignaturePosted via a free Usenet account from http://www.teranews.com clare, at, snyder.on.ca wrote: > >Talk about hi-jacking a thread..... > > [quoted text clipped - 4 lines] > Better performance GENERALLY also translates to better fuel mileage if > you do not use the extra power available. LOL. And sometimes it's *so* tempting to do just that. Graham >> Eeyore <rabbitsfriendsandrelations@hotmail.com> wrote in article >> <459B3611.D785D2B9@hotmail.com>... [quoted text clipped - 11 lines] > Better performance GENERALLY also translates to better fuel mileage if > you do not use the extra power available. Everything you have post up to this last statement have been on the money. But..... One has to distinguish between fuel economy and performance as the engine is operating in different regimes. For performance one is invariably at high-load and moderate to high speeds. In this region of the engine speed/load map octane requirements are highest. And "if" the engine is unable to run at optimal ignition timing on low octane fuel, then going to a higher grade of fuel can increase performance if the ignition timing is adjusted. For fuel economy though, most of the time the engine is at lighter loads/lower speeds. At light-load the engine just doesn't need high octane fuel. Most modern engines are calibrated to run very close to optimal ignition timing at part-load. Here, increasing the octane rating of the fuel is wasted as there is no need to change ignition timing. The only iffy part is if the driver spends a lot of time at high-load during accels. >Octane slows down the burn and allows more power to be extracted from >the fuel, stops the pinging but the engine timing must be adjusted to >suit. Lead had more cooling effect for lower temperature valves and >other parts. Not true. Higher octane fuel, generally, does NOT burn slower. In many cases it can actually burn FASTER. High octane fuel simply resists dis-associating the hydrogen radicals(H1, not H2) from the hydrocarbon fuel under heat and pressure. It is the presence of these "free radicals" which causes the fuel to detonate in the cyl. To reduce detonation you either increase the Octane rating of the fuel or reduce the amount of heat acting on the end gas. This is done by reducing compression, retarding spark, increasing RPM, or engineering the combustion chamber for a FASTER burn. Lead did not have a "cooling effect". The lead COATING acted as both an insulator and a lubricant on the valve seats, preventing the valve from being "hammer welded" to the seat, pulling metal from the seat and causing "seat errosion". This was a side benefit - TEL was added to act as a "negative catalyst" to prevent the breakdown of the end-gasses, reducing the production of the highly unstable hydrogen radicals. >>>>is there any truth to the statement that using a higher octane >>>>gasoline [quoted text clipped - 15 lines] >> Precisely. Just think about it -- at one time, octane was increased >> by adding lead compounds. Why would lead increase a fuel's energy? SignaturePosted via a free Usenet account from http://www.teranews.com In order to use unleaded fuels car engines has to increase the temperature handling of the valves and seats. Lead acted like a coolant. >>Octane slows down the burn and allows more power to be extracted >>from [quoted text clipped - 51 lines] >>> by adding lead compounds. Why would lead increase a fuel's >>> energy? >In order to use unleaded fuels car engines has to increase the >temperature handling of the valves and seats. Lead acted like a >coolant. No it did not. It was a lubricant and prevented the valve face from "welding" to the seats. Seat recession was caused by pits being torn out of the valve seats. Stelite or induction hardened seats resist this action. It also took VERY LITTLE lead to have this effect. One gallon of leaded fuel per 100 gallons is enough to protect the valves of a "lead era" car. The result is also quite long lasting. A car that has run leaded fuel can and will survive for many many hours without valve damage on unleaded fuel. >>>Octane slows down the burn and allows more power to be extracted >>>from [quoted text clipped - 51 lines] >>>> by adding lead compounds. Why would lead increase a fuel's >>>> energy? SignaturePosted via a free Usenet account from http://www.teranews.com OK the valves and seats had to be hardened to stop the "sticking" action of the valve due to less lubrication from the lead but not the higher temperature. My bad. However you stated that higher octane fuels do not burn slower and then proceded to say they do again. Most articles will agree that octane stops pinging by slowing down the detonation of the fuel under heat and presure. This is not faster and the chemical reason doesn't really matter, as it appears to support my statement and disagree with yours. When you disagree and then set out to re-enforce the other posters statement it appears as an obsession. >>Octane slows down the burn and allows more power to be extracted >>from [quoted text clipped - 27 lines] > end-gasses, reducing the production of the highly unstable hydrogen > radicals. > OK the valves and seats had to be hardened to stop the "sticking" > action of the valve due to less lubrication from the lead but not the [quoted text clipped - 6 lines] > really matter, as it appears to support my statement and disagree with > yours. Mustn't confuse detonation with normal combustion. The fuel/air mixture should burn across the chamber at about 100 feet per second. Detonation is a different process and flame fronts can reach 5000 fps or more. The enormous pressure spikes and abrupt release of heat does plenty of damage. Detonation happens when the complex fuel molecules, under the rising pressure ahead of the flame front of normal combustion, begin to break down into simpler structures that can autoignite; they don't wait for the flame front to set them off in a normal chain reaction. The whole works might go off at once just becuse they're being squeezed and their temp is rising. Detonation requires time for those molecules to break down, so low RPM is a problem, large combustion chambers (which require more flame-travel time) are a problem, lean mixtures (which burn more slowly due to the distance between molcules) are a problem. Normal combustion is not an explosion; it's a controlled burn. Detonation is an explosion, totally uncontrolled, and higher octane fuels were designed to increase the capability of handling the higher pressures and temps without breaking down into autoignitable components. In aircraft we're still using leaded fuels because the engine technology is stuck in the 1950s. Some avgas grades have large amounts of lead in them, and sparkplug fouling is a big problem, even in the heat of an aircooled engine. Those amounts of TEL are necessary for the big cylinders found on aircraft engines, their low operating RPM, and the higher operating temps (cylinder head temps to 550?F, depending on the engine). We've been promised unleaded avgas for some time now but haven't seen it yet. Dan > Mustn't confuse detonation with normal combustion. The fuel/air >mixture should burn across the chamber at about 100 feet per second. [quoted text clipped - 24 lines] >the engine). > We've been promised unleaded avgas for some time now but Right on Dan, So much misinformation flying around about Octane - good to see there are a few others who understand it. (Are you a Canuk? Member of RAA? Perhaps read my artical the other month?) SignaturePosted via a free Usenet account from http://www.teranews.com clare wrote: > Right on Dan, > So much misinformation flying around about Octane - good to see there > are a few others who understand it. (Are you a Canuk? Member of RAA? > Perhaps read my artical the other month?) Canuck. Flight Instructor. Aircraft Maintenance Engineer. Aircraft Systems instructor. Former member of EAA (1972-1992). Member of COPA. Fly my Jodel D-11 when I have the time. Building a Hummelbird. Should join RAA, but spend so much time working in aviation that by the time I get home I don't want to read any more about it. Barely have time for the H-Bird. Dan >clare wrote: > [quoted text clipped - 11 lines] > > Dan Wherere you located? SignaturePosted via a free Usenet account from http://www.teranews.com clare wrote: > >clare wrote: > > [quoted text clipped - 12 lines] > > Dan > Wherere you located? Three Hills, Alberta. Dan, You seemed to know what you're talking about. Me too I have seen what you described, however there is a way to control the Detonation into a controllable burn. And the trick is, I can't share until I get paid for my research. The saving is huge. Venus Solar Flare wrote: > OK the valves and seats had to be hardened to stop the "sticking" > action of the valve due to less lubrication from the lead but not the [quoted text clipped - 6 lines] > really matter, as it appears to support my statement and disagree with > yours. Mustn't confuse detonation with normal combustion. The fuel/air mixture should burn across the chamber at about 100 feet per second. Detonation is a different process and flame fronts can reach 5000 fps or more. The enormous pressure spikes and abrupt release of heat does plenty of damage. Detonation happens when the complex fuel molecules, under the rising pressure ahead of the flame front of normal combustion, begin to break down into simpler structures that can autoignite; they don't wait for the flame front to set them off in a normal chain reaction. The whole works might go off at once just becuse they're being squeezed and their temp is rising. Detonation requires time for those molecules to break down, so low RPM is a problem, large combustion chambers (which require more flame-travel time) are a problem, lean mixtures (which burn more slowly due to the distance between molcules) are a problem. Normal combustion is not an explosion; it's a controlled burn. Detonation is an explosion, totally uncontrolled, and higher octane fuels were designed to increase the capability of handling the higher pressures and temps without breaking down into autoignitable components. In aircraft we're still using leaded fuels because the engine technology is stuck in the 1950s. Some avgas grades have large amounts of lead in them, and sparkplug fouling is a big problem, even in the heat of an aircooled engine. Those amounts of TEL are necessary for the big cylinders found on aircraft engines, their low operating RPM, and the higher operating temps (cylinder head temps to 550°F, depending on the engine). We've been promised unleaded avgas for some time now but haven't seen it yet. Dan Gee Mr. Venus, where should I send my money? Do you have a paypal account or should I send cash? I'll bet you have that perpetual motion thing figured out too. > Dan, > You seemed to know what you're talking about. Me too I have seen what you [quoted text clipped - 47 lines] > > Dan Cheese Bob makes you think I am lying? You see, you guys have enormous egos and you think no one else could come up with the right answer except yourselves. When the Chinese launched their Space program you thought they bragged, and they did go into space, and many countries in Europe can do what you did. Insulting people won't get you any where. > Gee Mr. Venus, where should I send my money? Do you have a paypal account > or [quoted text clipped - 53 lines] >> >> Dan Venus is posting as a fake Komin in other discussion groups . > Cheese Bob makes you think I am lying? You see, you guys have enormous egos > and you think no one else could come up with the right answer except [quoted text clipped - 59 lines] > >> > >> Dan I didn't insult you and cheese didn't make me think you were lying. Good luck with everything else..... wow > Cheese Bob makes you think I am lying? You see, you guys have enormous > egos [quoted text clipped - 61 lines] >>> >>> Dan >OK the valves and seats had to be hardened to stop the "sticking" >action of the valve due to less lubrication from the lead but not the [quoted text clipped - 6 lines] >really matter, as it appears to support my statement and disagree with >yours. You are being nitpicky and don't know what you are talking about. It is NOT the speed of the burning of the gasoline that is slowed down. It is the virtual explosion of the dis-associated end gasses that is ELIMINATED. Slower fuel burn INCREASES the tendancy of an engine to detonate. >When you disagree and then set out to re-enforce the other posters >statement it appears as an obsession. [quoted text clipped - 30 lines] >> end-gasses, reducing the production of the highly unstable hydrogen >> radicals. SignaturePosted via a free Usenet account from http://www.teranews.com > OK the valves and seats had to be hardened to stop the "sticking" > action of the valve due to less lubrication from the lead but not the [quoted text clipped - 4 lines] > octane stops pinging by slowing down the detonation of the fuel under > heat and presure. I assume you mean "slowing down combustion," whch can be re-stated as "slowing down the speed of the flame front away from the spark plug in the cylinder. Higher octane fuel doesn't do that. Most "articles" are wrong ;-) Water/alcohol injection, OTOH, DOES slow down the flame front as well as pre-cooling the intake charge. Exhaust-gas recirculation slows down the flame front, but actually heats the intake charge a little bit. > Octane slows down the burn and allows more power to be extracted from > the fuel, stops the pinging but the engine timing must be adjusted to > suit. Lead had more cooling effect for lower temperature valves and > other parts. High octane unleaded racing fuel supposedly burns faster once ignited. However - it has a higher resistance to detonation or preignition. A spark is usually hot enough to ignite the mixture. High compression needed it to reduce dieseling. >> Octane slows down the burn and allows more power to be extracted >> from [quoted text clipped - 8 lines] > A > spark is usually hot enough to ignite the mixture. >High compression needed it to reduce dieseling. Dieseling is part of it - but you can totally eliminate dieselling by totally closing the throttle on shut-down.Dieseling is more pre-ignition (or auto ignition) than detonation. It is still a "normal" slow burn. No air and/or no fuel means no dieseling. It is DETONATION that is prevented by higher octane fuel. Detonation, if unchecked, will almost invariably also cause pre-ignition. The combination of the two ia almost always deadly. Detonation scrubs the barrier layer off the pistons - the pistons absorb excessive heat and start to melt down. The hot piston lights the fuel before the prescribed ignition point and the pressure peaks while the piston is still coming up. This blows the weakened overheatred piston. Funny thing - chicken and egg type - pre-ignition can cause detonation. Detonation can cause pre-ignition. Knowing which came first is essential to prevent the problem repeating itself. >>> Octane slows down the burn and allows more power to be extracted >>> from [quoted text clipped - 8 lines] >> A >> spark is usually hot enough to ignite the mixture. SignaturePosted via a free Usenet account from http://www.teranews.com > High compression needed it [higher octane] to reduce dieseling. Or forced induction. Pretty much anything that increases the fuel/air pressure in the cylinders would require higher octane fuel. My 2004 WRX with a 2.0L turbo four engine has a compression ratio of 8.0:1. It sounds low, but then you add the boost. >>High compression needed it [higher octane] to reduce dieseling. > [quoted text clipped - 3 lines] > My 2004 WRX with a 2.0L turbo four engine has a compression > ratio of 8.0:1. It sounds low, but then you add the boost. 7:1 isn't uncommon when boost is anticipated. And the other cool thing about boosted engines is that they have cam profiles with very minimal valve overlap so they generally idle as smooth as a Packard v12. Whereas a normally aspirated engine with similar performance would have 10:1 compression and a wild cam that would lope at idle like a '67 426 Hemi. > >>High compression needed it [higher octane] to reduce dieseling. > > [quoted text clipped - 9 lines] > a normally aspirated engine with similar performance would have 10:1 > compression and a wild cam that would lope at idle like a '67 426 Hemi. Well - mine is a horizontally opposed four, so I do feel a bit of shake at idle. :-( My '69 Cutlass 350 Olds engine ran a 13.8:1 compression ratio and yup...it needed high octane. >>>High compression needed it [higher octane] to reduce dieseling. >> [quoted text clipped - 11 lines] > would have 10:1 compression and a wild cam that would lope at idle > like a '67 426 Hemi. >My '69 Cutlass 350 Olds engine ran a 13.8:1 compression ratio and >yup...it needed high octane. Factory CR on '69 Olds 350 rocket is 9.0 Up to 10.0:1 on the high output version. 13.8 is VERY high. The 429 Cobra Jet Super Cobra Jet, or Boss 429 ran 11.3:1 That's the highest stock north american CR I've seen in the sixties. The Olds Diesel was 22.1:1 Diesels can run from 15:1 up. >>>>High compression needed it [higher octane] to reduce dieseling. >>> [quoted text clipped - 11 lines] >> would have 10:1 compression and a wild cam that would lope at idle >> like a '67 426 Hemi. SignaturePosted via a free Usenet account from http://www.teranews.com Just as another data point, I have a '63 Studebaker Avanti engine that is spec'd at 10.25:1 CR but it's currently got composition head gaskets so it's likely more like 9.75ish. I think the "R4" version (304ci, hand-assembled by Paxton Products, dual quads) was 12:1. Yes, I would very much like to try one of those, but I'm not sure how I would feed it :) nate >>My '69 Cutlass 350 Olds engine ran a 13.8:1 compression ratio and >>yup...it needed high octane. [quoted text clipped - 22 lines] >>>would have 10:1 compression and a wild cam that would lope at idle >>>like a '67 426 Hemi. Signaturereplace "fly" with "com" to reply. http://home.comcast.net/~njnagel clare, at, snyder.on.ca wrote: > >My '69 Cutlass 350 Olds engine ran a 13.8:1 compression ratio and > >yup...it needed high octane. [quoted text clipped - 6 lines] > The Olds Diesel was 22.1:1 > Diesels can run from 15:1 up. My 1970 Rover 2000TC was about 10:1 IIRC and had a prominent label under the bonnet / hood insisting that *5 star* petrol be used - 99 or 100 RON IIRC. To my amazement you can still even get something similar for classic cars. http://www.jec.org.uk/thrust.htm Graham >clare, at, snyder.on.ca wrote: > [quoted text clipped - 11 lines] >My 1970 Rover 2000TC was about 10:1 IIRC and had a prominent label under the >bonnet / hood insisting that *5 star* petrol be used - 99 or 100 RON IIRC. Yes, the TC really liked Sunoco 260 back in the day. Responded well to an extra 2 degrees of timing if you NEVER ran it on anything less. >To my amazement you can still even get something similar for classic cars. >http://www.jec.org.uk/thrust.htm > >Graham SignaturePosted via a free Usenet account from http://www.teranews.com clare, at, snyder.on.ca wrote: > >clare, at, snyder.on.ca wrote: > >> [quoted text clipped - 14 lines] > Yes, the TC really liked Sunoco 260 back in the day. Responded well to > an extra 2 degrees of timing if you NEVER ran it on anything less. Rover called the vernier adjustment on the distributor the 'octane selector'. When I had it of course it had to be retarded to run on 4 star which was the best you could get then. It was a very nice car for its day. Probably the 'best' in some respects I've had until the Saab I drive now. Graham > Rover called the vernier adjustment on the distributor the 'octane selector'. > When I had it of course it had to be retarded to run on 4 star which was the best > you could get then. Can you see that sort of thing successful these days, in an era where most car owners wouldn't even know where to find the oil dipstick? Some might not even be able to open the hood. Electronics have allowed us to abrogate our responsibility to know at least something about the automobile, so much so that the slightest malfunction means a tow truck for most folks, and leaves them at the mercy of the mechanic. I dread the day when the manufacturer welds the hood onto the car after everything's installed. It's bad enough now trying to get at some stuff. Dan > I dread the day when the manufacturer welds the hood onto the >car after everything's installed. It's bad enough now trying to get at >some stuff. UPDATED MAINTENANCE SCHEDULE: 1. Replace vehicle at 50,000 mile intervals. --scott Signature"C'est un Nagra. C'est suisse, et tres, tres precis." >> Rover called the vernier adjustment on the distributor the 'octane selector'. >> When I had it of course it had to be retarded to run on 4 star which was the best [quoted text clipped - 12 lines] > > Dan May as well weld it shut on a 24 valve Mondeo/contour/mystique for all you can reach without dissassembly - SignaturePosted via a free Usenet account from http://www.teranews.com clare, at, snyder.on.ca wrote: > >> Rover called the vernier adjustment on the distributor the 'octane selector'. > >> When I had it of course it had to be retarded to run on 4 star which was the best [quoted text clipped - 15 lines] > May as well weld it shut on a 24 valve Mondeo/contour/mystique for all > you can reach without dissassembly - A friend of mine had a V6 Vauxhall/Opel Vectra. For the life of me I couldn't see how you could get to anything under there. Graham >>Rover called the vernier adjustment on the distributor the 'octane selector'. >>When I had it of course it had to be retarded to run on 4 star which was the best >>you could get then. > > Can you see that sort of thing successful these days, Its called a knock sensor with feedback electronic engine management, and virtually every car now has a system like that... ;-) in an > era where most car owners wouldn't even know where to find the oil > dipstick? Some might not even be able to open the hood. Electronics > have allowed us to abrogate our responsibility to know at least > something about the automobile, so much so that the slightest > malfunction means a tow truck for most folks, and leaves them at the > mercy of the mechanic. Very true. And sad. I find it ironic that the enviro crowd wails and moans about exhaust emissions, but doesn't do anything to prevent the huge waste of good automobiles (and all the energy and pollution required to produce each one) that are destroyed by owner negligence every year. At least nothing more than a token "tune your car and inflate your tires to save the planet!" type ad now and then. > I dread the day when the manufacturer welds the hood onto the > car after everything's installed. It's bad enough now trying to get at > some stuff. Some car company- I think it was T*yota, I'd expect it from them- had an ad based on welding the hood of one of their cars shut. Of course it was tongue-in-cheek, but its amazing how many fools think that way about cars. It has worked for computers. And for those that persist they changed the box so nothing fits too. >> Rover called the vernier adjustment on the distributor the 'octane >> selector'. [quoted text clipped - 16 lines] > > Dan clare wrote: > >My '69 Cutlass 350 Olds engine ran a 13.8:1 compression ratio and > >yup...it needed high octane. [quoted text clipped - 3 lines] > The 429 Cobra Jet Super Cobra Jet, or Boss 429 ran 11.3:1 > That's the highest stock north american CR I've seen in the sixties. Seem to recall Dodge had a 413 wedge with 13:1 around 1963. It may have been a special order from the factory thing. The 1964 hemi had about 12:1. My '68 340 Barracuda has 10.5:1 stock. When I put a turbo kit on my Kawasaki 1000 I put in a set of 7:1 blower pistons so that I could crank the boost up to 18 psi. Makes a lot more power that way than running higher compression with less boost. Bruce > The Olds Diesel was 22.1:1 > Diesels can run from 15:1 up. [quoted text clipped - 14 lines] > >> would have 10:1 compression and a wild cam that would lope at idle > >> like a '67 426 Hemi. >clare wrote: >> [quoted text clipped - 14 lines] > >Bruce OK, did some more research in my fairly extensive library. 1961-65 413 was only 10:1 on the high compression version - 9:1 on the RC1 and VC1. The early 426 was 10.25:1 (1966-67) The NASCAR version was 12.5:1 in 1964, down to 12.0:1 in '65. The "Street Hemi" was an 11:1 engine Dodge only got the 413in 1965 in Canada - was a Chrysler only engine from '61 up. In the US the D500 got the 413 in '61 with 10.0:1, even on the 375 horse version. In the US for 1962/63 there WAS a very limited edition "RamCharger Max Wedge"413 at 13.5:1, but this was a COMPETITION engine. The "Street" max wedge was 11:1 >> The Olds Diesel was 22.1:1 >> Diesels can run from 15:1 up. [quoted text clipped - 14 lines] >> >> would have 10:1 compression and a wild cam that would lope at idle >> >> like a '67 426 Hemi. 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