FROM: Artist SUBJECT: Re: diesel question DATE: Mon, 11 Sep 2000 22:53:45 -0700 ORGANIZATION: Ye 'Ol Disorganized NNTPCache groupie NEWSGROUPS: rec.autos.4x4 Centipede wrote: > I'm looking into buying a SUV and was wondering if any have been made with a > diesel engine in the past 15 years. Gas is getting way too expensive. > > Thanks > Mark If you are going to get a diesel make sure it is one that was designed from the ground up to be a diesel engine, and avoid ones made from engine blocks originally designed for gas. There will be a big difference in engine noise and reliability. ( My ears are still ringing from the Rabbit Diesel I owned in the '80's.) Also consider the ineveitability of breathing its fumes due to the mere fact of being in its vicinity. As currently made diesel fumes are far more harmful than gas. Diesel engines have been exempt from most emissions standards because the politically powerfull trucking industry does not want the expense of meeting them. But there are signs that this is ending in California in spite of them. -- If sj. appears in my email address remove it to respond. It is a spam jammer. Fight the mark of the beast: http://www.house.gov/paul/privacy Support antispam legislation: http://www.cauce.org Hulk Hogan for President! FROM: cj SUBJECT: Re: diesel question DATE: Tue, 12 Sep 2000 09:42:59 -0600 ORGANIZATION: Hewlett-Packard Co., MNS Boise NEWSGROUPS: rec.autos.4x4 Artist wrote: > > If you are going to get a diesel make sure it is one that was designed from the > ground up to be a diesel engine, and avoid ones made from engine blocks > originally designed for gas. There will be a big difference in engine noise and > reliability. ( My ears are still ringing from the Rabbit Diesel I owned in the > '80's.) > > Also consider the ineveitability of breathing its fumes due to the mere fact of > being in its vicinity. As currently made diesel fumes are far more harmful than > gas. Now, here's a guy who has no idea what he's talking about! Diesel engines are used in enclosed places like mines because the exhaust is far safer than that from gasoline engines. Carbon monoxide is practically non-existent in diesel exhaust, gasoline exhaust will kill you quickly. You go sit in your garage with your gas engine running, I'll sit in mine with my diesel. I'll come over in a couple of hours to see if you're still alive... Diesel exhaust looks bad because it has high particluate content. The black smoke is essentially just carbon. Diesel exhaust does have relatively high levels of nitrous oxide (so do gas engines, but catalytic converters remove a lot), but new catalysts are being developed to remove this from diesel exhaust. Gasoline engines run with a air/fuel ratio of 14:1, diesels run about 100:1 at idle, up to around 20:1 full out. In heavy traffic, engines spend a lot of time idling, so diesels are hardly using any fuel (and consequently producing small amounts of emmissions). Diesels are far more efficient than gasoline engines, so they produce far fewer emmissions per mile than gas engines. FROM: "Mike Locke" SUBJECT: Re: diesel question DATE: Tue, 12 Sep 2000 21:52:41 -0700 ORGANIZATION: http://extra.newsguy.com NEWSGROUPS: rec.autos.4x4 Actually, this fuel-air-diesel Idle myth is just that and it needs to be stopped right now. Each of your statements alone are correct except the final conclusion. That's because you left out the all important fact: at Idle a gas engine has nearly no air at all going through it, while diesels have no throttle and have essentially full air volume cycling through the engine at any fuel input setting. It's not the fuel-air mixture, but the absolute amount of fuel that makes the difference. Also, in health related SMOG studies (not toxicology studies) the only SMOG component that has been positively proven to cause harm to the public at large is fine particulates, such as that found in diesel exhaust. These particulates will trigger asthma attacks in suceptable folks, sometimes with fatal results. All 50 states now regulate tail pipe emissions from diesel vehicles. The regulations are more generous than for gas engines, but tough enough to scare away almost all of the foreign manufacturers. Most critically, non-tail pipe emissions are not regulated and significant blow-by emissions are common on diesel engines. In fact, most of the "diesel smell" coming from my truck has been traced to breather pipe emissions. -- S'later, Mike Locke lockem@scrserv.com 2000 Dodge/Cummins 2500 QC 4x4 6spd long bed FROM: Bob Bartch SUBJECT: Re: diesel question DATE: Wed, 13 Sep 2000 15:32:09 -0700 NEWSGROUPS: rec.autos.4x4 Mike Locke wrote: > Actually, this fuel-air-diesel Idle myth is just that and it needs to be > stopped right now. > > Each of your statements alone are correct except the final conclusion. > That's because you left out the all important fact: at Idle a gas engine has > nearly no air at all going through it, while diesels have no throttle and > have essentially full air volume cycling through the engine at any fuel > input setting. It's not the fuel-air mixture, but the absolute amount of > fuel that makes the difference. You wish. The absolute amount of fuel is MUCH smaller for diesels at idle than for gas engines on a liter per liter displacement basis. Hence the extreme sfc gain of diesels over gas. Less fuel is burned because pumping losses are eliminated in the diesel. The vast excess of oxygen in the chamber results in no CO production, plus extreme dilution by all the O2 present. > > > Also, in health related SMOG studies (not toxicology studies) the only SMOG > component that has been positively proven to cause harm to the public at > large is fine particulates, such as that found in diesel exhaust. These > particulates will trigger asthma attacks in suceptable folks, sometimes with > fatal results. I believe the subject was engine exhaust, however. If you believe that, have I got a bridge for you! You seriously believe that particulate carbon is more toxic than carbon monoxide?? People still succeed at committing suicide by closing their garages, thanks to the CO, but you could spend all day in a diesel garage. The heart & lung folks also cite CO in inducing heart attacks & strokes. One of the big problems facing EPA now is their push for NG powered diesels. They bash diesels for producing PM10 (which EPA regulates) and then advocate NG engines that produce ultra fine particulates way below PM2.5 Now if you believe their crap about particulates being carcinogenic by virtue of their small size, you really have to wonder where they're going with pushing ULTRA fine particles on us lung breathers. It's all a control scam for political power. BB FROM: "Mike Locke" SUBJECT: Re: diesel question DATE: Wed, 13 Sep 2000 21:42:41 -0700 ORGANIZATION: http://extra.newsguy.com NEWSGROUPS: rec.autos.4x4 Bob Bartch wrote in message news:39C00069.EE0E911C@jps.net... > > > Mike Locke wrote: > > > Actually, this fuel-air-diesel Idle myth is just that and it needs to be > > stopped right now. > > > > Each of your statements alone are correct except the final conclusion. > > That's because you left out the all important fact: at Idle a gas engine has > > nearly no air at all going through it, while diesels have no throttle and > > have essentially full air volume cycling through the engine at any fuel > > input setting. It's not the fuel-air mixture, but the absolute amount of > > fuel that makes the difference. > > You wish. The absolute amount of fuel is MUCH smaller for diesels at idle than > for gas engines on a liter per liter displacement basis. Hence the extreme sfc > gain of diesels over gas. Less fuel is burned because pumping losses are > eliminated in the diesel. The vast excess of oxygen in the chamber results in no > CO production, plus extreme dilution by all the O2 present. Diesel engines are more efficient than gas engines due to the high compression ratio of the diesel. The high compression ratio is possible due to the type of fuel injection system on the diesel engine. It's possible that this results in the diesel using somewhat less fuel to idle than a gas engine, but the fuel air mixture ratio IS NOT THE REASON. BTW: NO DIESEL MANUFACTURER RECOMMENDS EXTENDED IDLING OF A DIESEL ENGINE. Because of the lack of a throttle, the engine cools very rapidly at idle and a cool engine is not a happy engine. > > Also, in health related SMOG studies (not toxicology studies) the only SMOG > > component that has been positively proven to cause harm to the public at > > large is fine particulates, such as that found in diesel exhaust. These > > particulates will trigger asthma attacks in suceptable folks, sometimes with > > fatal results. > > I believe the subject was engine exhaust, however. If you believe that, have I > got a bridge for you! You seriously believe that particulate carbon is more > toxic than carbon monoxide?? People still succeed at committing suicide by > closing their garages, thanks to the CO, but you could spend all day in a diesel > garage. The heart & lung folks also cite CO in inducing heart attacks & > strokes. CO is at very low levels in the atmosphere in smoggy areas, particulates are not. Because particulates are not obviously toxic and only have severe effects on a minority of the population, they tend to get ignored and/or tolerated too much. Read my post again, I did not state anywhere that particulates are more toxic than CO. I said that more health problems for people at large are caused by particulates than CO. Nasty old or badly tuned diesel engines produce extremely large volumes of particulates. CO emmissions are measured in parts per million. > > One of the big problems facing EPA now is their push for NG powered diesels. > They bash diesels for producing PM10 (which EPA regulates) and then advocate NG > engines that produce ultra fine particulates way below PM2.5 Now if you believe > their crap about particulates being carcinogenic by virtue of their small size, > you really have to wonder where they're going with pushing ULTRA fine particles > on us lung breathers. > It's all a control scam for political power. Since I don't know squat about NG engines, I have no basis for comment. -- S'later, Mike Locke lockem@scrserv.com FROM: Stephan Rothstein SUBJECT: Re: diesel question DATE: Wed, 13 Sep 2000 18:32:49 -0500 ORGANIZATION: SBC Internet Services NEWSGROUPS: rec.autos.4x4 Mike Locke wrote: > > Actually, this fuel-air-diesel Idle myth is just that and it needs to be > stopped right now. > > Each of your statements alone are correct except the final conclusion. > That's because you left out the all important fact: at Idle a gas engine has > nearly no air at all going through it, while diesels have no throttle and > have essentially full air volume cycling through the engine at any fuel > input setting. It's not the fuel-air mixture, but the absolute amount of > fuel that makes the difference. This makes no sense. If a diesel has no throttle, how do I get it to accelerate? Quite obviously all engines used in cars/trucks have a throttle. If this throttle lowers the amount of air sucked in at idle for a gas engine, it will also do so for a diesel. As a matter of fact, either engine can be thought of as an air pump. To get the amount of air passed through the system, multiply the number of cylinders times the displacement of each cylinder times the revolutions per minute. Seems like any engine has air going through it at idle and at higher speeds. > > Also, in health related SMOG studies (not toxicology studies) the only SMOG > component that has been positively proven to cause harm to the public at > large is fine particulates, such as that found in diesel exhaust. These > particulates will trigger asthma attacks in suceptable folks, sometimes with > fatal results. If it is health related, how can it not be toxicology? Toxicology is the study of the effects of a substance on the health. If particulate matter is what is so important, how come I have to put up with Ozone Alert Days every time we get a temperature inversion or hot weather? According to the EPA, Ozone is the most dangerous part of smog, and this is primarily produced by gasoline engines over diesels. > > All 50 states now regulate tail pipe emissions from diesel vehicles. The > regulations are more generous than for gas engines, but tough enough to > scare away almost all of the foreign manufacturers. Most critically, > non-tail pipe emissions are not regulated and significant blow-by emissions > are common on diesel engines. In fact, most of the "diesel smell" coming > from my truck has been traced to breather pipe emissions. > I don't think any car manufacturer has been scared away by emissions standards. After all, since they are all affected alike, and all have profit as a base motive, how can GM say we will produce diesels for a profit and a foreign manufacturer not say it? Also, I see quite a few foreign manufacturers selling diesels, as a primary example use Mercedes. What has kept most manufacturers from selling diesels in the US is the MARKET. People won't buy diesels because of a public perception that they are slower, noisier, more expensive, and harder (read costlier) to maintain. Note that in small trucks where the pulling power of the motor (as in torque) is more important to most people than the speed, diesels sell well. Of course, this is just my opinion, and you may feel free to disagree since I could well be wrong. Steve Rothstein FROM: sbest@TAKEOUTglinx.com (sbest) SUBJECT: Re: diesel question DATE: Thu, 07 Sep 2000 22:50:10 GMT ORGANIZATION: Newsfeeds.com http://www.newsfeeds.com 80,000+ UNCENSORED Newsgroups. NEWSGROUPS: rec.autos.4x4 On Wed, 13 Sep 2000 18:32:49 -0500, Stephan Rothstein wrote: >This makes no sense. If a diesel has no throttle, how do I get it to >accelerate? Quite obviously all engines used in cars/trucks have a >throttle. If this throttle lowers the amount of air sucked in at idle >for a gas engine, it will also do so for a diesel. Nope, Mike is right. There is no throttle in a diesel. I have had them apart and can assure you there is no throttle plate choking the air intake of a diesel, engine speed is solely regulated by the amount of fuel injected into the cylinder. This is a big reason for some of a diesel's benefits. Good economy and more complete combustion at mid-range because of excess oxygen and higher effective compression. It is also the reason a diesel has little vacuum and tends to vent blow-by fumes as Mike mentioned. Diesels do have almost no CO output for the reasons Mike mentions. The particulate problem is readily addressed by a catalytic convertor and/or better combustion through injection changes. >What has kept most manufacturers from selling diesels in the US is the >MARKET. People won't buy diesels because of a public perception that >they are slower, noisier, more expensive, and harder (read costlier) to >maintain. Note that in small trucks where the pulling power of the motor >(as in torque) is more important to most people than the speed, diesels >sell well. > >Of course, this is just my opinion, and you may feel free to disagree >since I could well be wrong. I hold the same opinion Steve. GM's adventure with the 5.7 diesel and the resultant bad publicity about diesels didn't help. I hold the opinion that it really wasn't that bad an engine for what it was, a light duty diesel, but that the dealer's and public's lack of knowledge about what it was and what it would do and how to look after it killed it. This 5.7 ledgend still lives in the minds on many anti-diesel fans. In Europe diesels sell well, as they do in Quebec which has the highest fuel prices in North America. Given a choice, most people would pick the smooth power of a lightweight gas engine. It takes the need for economy to drive them to a diesel. Steve Best, Nova Scotia, Canada 4x4 van website: http://www.glinx.com/users/sbest Sign up for the 4x4van newslist: http://www.onelist.com/community/4x4van -----= Posted via Newsfeeds.Com, Uncensored Usenet News =----- http://www.newsfeeds.com - The #1 Newsgroup Service in the World! -----== Over 80,000 Newsgroups - 16 Different Servers! =----- FROM: "Mike Locke" SUBJECT: Re: diesel question DATE: Wed, 13 Sep 2000 22:14:31 -0700 ORGANIZATION: http://extra.newsguy.com NEWSGROUPS: rec.autos.4x4 Stephan Rothstein wrote in message news:39C00EA1.C89DA0FB@swbell.net... > Mike Locke wrote: > > > > Actually, this fuel-air-diesel Idle myth is just that and it needs to be > > stopped right now. > > > > Each of your statements alone are correct except the final conclusion. > > That's because you left out the all important fact: at Idle a gas engine has > > nearly no air at all going through it, while diesels have no throttle and > > have essentially full air volume cycling through the engine at any fuel > > input setting. It's not the fuel-air mixture, but the absolute amount of > > fuel that makes the difference. > > This makes no sense. If a diesel has no throttle, how do I get it to > accelerate? Quite obviously all engines used in cars/trucks have a > throttle. If this throttle lowers the amount of air sucked in at idle > for a gas engine, it will also do so for a diesel. NOPE. My Cummins diesel has a big filter connected to a big hose connected to a big turbo charger connected to another big hose connected to an intercooler connected to another big hose connected to the side of the engine. On the other side of the engine various wide open metal pipes route the exhaust out the back. No throttle in sight anywhere. Diesels vary power production by varying the amount of fuel injected into the engine. The turbo charger of a turbo diesel will cause more air to pass through the engine when more fuel is going through the engine, but there still is no throttle. > As a matter of fact, either engine can be thought of as an air pump. To > get the amount of air passed through the system, multiply the number of > cylinders times the displacement of each cylinder times the revolutions > per minute. Seems like any engine has air going through it at idle and > at higher speeds. Yes, but the amount of air going through the engine depends on the intake and exhaust manifold pressure. A gas engine at idle has a large vacuum in the intake manifold. A diesel engine at idle has atmospheric pressure in the intake manifold. > > Also, in health related SMOG studies (not toxicology studies) the only SMOG > > component that has been positively proven to cause harm to the public at > > large is fine particulates, such as that found in diesel exhaust. These > > particulates will trigger asthma attacks in suceptable folks, sometimes with > > fatal results. > > If it is health related, how can it not be toxicology? Toxicology is the > study of the effects of a substance on the health. If particulate > matter is what is so important, how come I have to put up with Ozone > Alert Days every time we get a temperature inversion or hot weather? > > According to the EPA, Ozone is the most dangerous part of smog, and this > is primarily produced by gasoline engines over diesels. Ozone is produced by ultra violet light and electrical discharges. Your office photocopier probably produces copious quantities of Ozone (ever notice a sickly sweet smell next to it while it is running?). Ozone is destroyed by contact with almost anything solid almost instantiously. Liquid Ozone would be a good explosive if it weren't so unstable (worse than nitroglycerin). I worked in a air pollution laboratory where we had to artificially produce ozone, and contact with practically anything would make it break down into O2. It was a real pain to get from the generators to the exposure chambers, a distance of about 15 feet. As soon as the sun sets ground level ozone disappears. Particulates stay put until they are blown away or rained down and in some areas these monodirectional winds and rain are very uncommon events (but very common in Europe-who cares about smog, it all gets blown to eastern europe anyway!). Ground level Ozone is produced by a chemical soup combined with the relatively low levels of UV that reach the ground. The HC produced by vehicles is a significant component in this chemistry, so cars get associated with this problem. However, diesel engine manufacturers are having plenty of trouble meeting the HC limits set by the EPA and these limits for diesels are about double what they are for gas engines. It is unclear to me that diesels do not contribute to any ozone problems. > > All 50 states now regulate tail pipe emissions from diesel vehicles. The > > regulations are more generous than for gas engines, but tough enough to > > scare away almost all of the foreign manufacturers. Most critically, > > non-tail pipe emissions are not regulated and significant blow-by emissions > > are common on diesel engines. In fact, most of the "diesel smell" coming > > from my truck has been traced to breather pipe emissions. > > > > I don't think any car manufacturer has been scared away by emissions > standards. After all, since they are all affected alike, and all have > profit as a base motive, how can GM say we will produce diesels for a > profit and a foreign manufacturer not say it? Also, I see quite a few > foreign manufacturers selling diesels, as a primary example use > Mercedes. I haven't seen a new Mercedes diesel auto in a very long time. I've not seen a Euro-diesel that doesn't smoke, and yes I have been to Europe recently. You can pick out the diesel autos in a parking lot very easily: they are the ones with soot all over the back. All the diesels I see are light (or heavier) trucks or older cars. Note that the EPA regs are weight based, so that it is much easier to get an light truck engine to pass than to get a car engine to pass. I see a lot of medium duty foreign made trucks, most of which are cleaner than they were 10 years ago but still emit significant and visible smoke. I don't know of any foreign manufacturer trying to sell a real light truck (Toyota's lame attempt aside) in the USA, so finding a diesel in such a non-existant machine is not likely to happen. > What has kept most manufacturers from selling diesels in the US is the > MARKET. People won't buy diesels because of a public perception that > they are slower, noisier, more expensive, and harder (read costlier) to > maintain. Note that in small trucks where the pulling power of the motor > (as in torque) is more important to most people than the speed, diesels > sell well. Torque is useless, you have to have power to pull anything at a useful speed. Diesels are favored in light trucks (not the same as "small trucks") because they get good fuel economy and last a long time even if heavily loaded most of the time. Some Dodge/Cummins folks will beat their chests and claim that their engine can do anything, but the MOPAR V10 gas engine will outrun that Cummins every time, at least at sea level and if the V10 driver is willing to run the engine up to the RPM required for it to make some power (and watch the fuel gauge fall in real time!). > Of course, this is just my opinion, and you may feel free to disagree > since I could well be wrong. > > Steve Rothstein The point of a discussion group is to have a discussion. That's what we have here isn't it? :-) -- S'later, Mike Locke lockem@scrserv.com 2000 Dodge/Cummins 2500 QC 4x4 6spd long bed 245 70R19.5(G) wheels FROM: arcaeh@aol.com (Andrew) SUBJECT: Re: diesel question DATE: 15 Sep 2000 01:04:03 GMT ORGANIZATION: AOL http://www.aol.com NEWSGROUPS: rec.autos.4x4 > NO DIESEL ENGINE MANUFACTURER recommends idling its > engines for extended periods of time. Directly from the Cummins FAQ: << Q: Can I Leave the engine idling for long periods? A. Do not idle the engine for excessively long periods. Long periods of idling (more than 10 minutes) can damage an engine because combustion chamber temperatures drop so low the fuel will not burn completely. This will cause carbon to clog the injector spray holes and piston rings, and can cause the valves to stick. If the engine coolant temperature becomes too low (60 degrees C [140 degrees F]), raw fuel will wash the lubricating oil off the cylinder walls and dilute the crankcase oil; therefore, all moving parts of the engine will not receive the correct amount of lubrication. (For more information, refer to Cummins Operation and Maintenas. nce Manual section 1-5, Bulletin 3810205-12.) >>> From Josh Berman to the Cummins mail list: << The only time when extended idling becomes a problem is when it is cool-to-cold outside. At that point, the engine may not be able to generate enough heat to stay warm inside. When that happens, fuel can condense on the inner walls of the cylinders, washing away the oil film and causing accelerated wear. Carbon from the incompletely burned fuel can also clog injector tips and stick the piston ring >>> Andrew FROM: "Mike Locke" SUBJECT: Re: diesel question DATE: Thu, 14 Sep 2000 22:02:38 -0700 ORGANIZATION: http://extra.newsguy.com NEWSGROUPS: rec.autos.4x4 Douglas A. Shrader wrote in message news:ss2e6rpuct6105@corp.supernews.com... > > > -- > Douglas A. Shrader & Jake (RIP) > "Mike Locke" wrote in message > news:8ppnb701lgm@enews1.newsguy.com... > > > > Douglas A. Shrader wrote in message > > news:ss0c9o1gct618@corp.supernews.com... > > > > > > > > > -- > > > Douglas A. Shrader & Jake (RIP) > > > "Mike Locke" wrote in message > > > news:8pn0kd014vq@enews3.newsguy.com... > > > > > > > > Actually, this fuel-air-diesel Idle myth is just that and it needs to > be > > > > stopped right now. > > > > > > > > Each of your statements alone are correct except the final conclusion. > > > > That's because you left out the all important fact: at Idle a gas > engine > > > has > > > > nearly no air at all going through it, > > > > > > A gas engine always has 14.7 parts air for every one part fuel. Engine > > speed > > > has no bearing on this. Diesels vary from 100 parts air at idle to > around > > > 20-25 parts at full throttle. Less fuel per air equals less fuel total. > > > Simple math really. You can find all this in any competent diesel > manual, > > > you really should try reading a few. > > > > Don't be so presumptious about what I have or have not read. > > Comparing idling gas and diesel engines of equal displacement, the diesel > > engine will have *MORE AIR* going through it. *A LOT* more air. > > 4 times more air in fact, they still burn less fuel, hence the proven > increase in fuel economy. Just using your numbers, 14.7:1 with 1/4 the air vs 100:1 with the full air The gas engine to diesel engine ratio of idle fuel consumption is 59:100. OK the diesel gets better idle fuel economy, just like it gets better on road fuel economy no surprise there. This ratio is pretty close to the difference in compression ratios. This is not enough to make the really huge difference you claim in idle times. It is also not even close to the 1:7 that just discussing the fuel-air mixture ratios implies. > > The gas > > engine has a butterfly throttle (or similar) that restricts the air intake > > so that the correct amount of fuel energy required to turn the engine over > > at idle can be reasonably efficiently burned. > > > > Your statement is equivalent to something like > > > > A gold coin is 100% gold. > > A gold mine is 0.1% to 0.01% gold (that would be a really good mine :-) > > > > Therefore (you conclude) if I own a gold coin I have more gold than if I > own > > a gold mine. > > > > You wanna sell me that mine for a coin? > > There is more energy in a gallon of diesel than a gallon of gas, thus again > less fuel used, gold has nothing to do with it. You obviously have never heard of an analogy. Remember 8th grade English? > > Because that diesel truck of yours has an enormous fuel tank > > Oh it does not. It has a twenty gallon tank, same as our gas chevy with a > 350. The gas uses far more fuel to idle than the diesel, proven fact. But you said your truck "drinks fuel" on the highway, implying that it uses a lot of fuel. OK, maybe your Chevy diesel does. Have you actually measured the idle rate of fuel consumption for these two engines? > > NO DIESEL ENGINE MANUFACTURER recommends idling its > > engines for extended periods of time. > > They don't recommend it for gas engines either, in fact they warn against > idle gas engines for more than I beleive ten minutes due to exhuast > overheating. Diesels are the ooposite. Because they burn so little fuel at > an idle they cool off to the point where the fuel maybe able to slip past > the rings and dilute the oil. I've seen no evidence of this happening on > mine but the amount of fuel would be so small I doubt it could be noticed. On gas engines it is the catalytic converter that overheats, due to excessive unburnt fuel making it to the converter. If a diesel engine had a catalytic converter it might have this problem too. Adding an exhaust brake to a diesel engine (a throttle butterfly in the exhaust pipe) will stop the diesel engine cool off problem and reduce the idle engine air. I don't know if it reduces idle engine fuel usage. > > If you try driving your truck as fast as it will go at idle you will most > > likely get horrible fuel economy. At idle, the only thing your engine is > > doing is turning itself, and that is getting you 0 MPG. > > Not if it is in gear and moving. It can idle in gear. Sheesh, read it again > and pay attention this time. I stand by my statement. At idle your engine is only making enough power to turn itself, it cannot move your vehicle. The fuel injection system increases the fuel rate when the engine is loaded so that the RPM starts to fall below idle, thus explaining how you can let the clutch out at idle RPM. The engine is not really idling in this condition (in gear at idle RPM), it is just running at the idle RPM. The engine is grossly inefficient at this RPM, though and you will get terrible fuel economy. > > Max fuel economy in my truck is at 1400 RPM in 6th gear at ~45MPH. I get > > around 30MPG. > > > That's great. Those economy figures also apply when you are idling as well. > An idleing diesel uses less fuel than an equiavilent gas engine. Maybe, but not 1/7 the fuel use as implied by the numbers that you quoted. -- S'later, Mike Locke FROM: James Clark SUBJECT: Re: diesel question DATE: Fri, 15 Sep 2000 18:56:29 -0700 ORGANIZATION: Global Network Services - Remote Access Mail & News Services NEWSGROUPS: rec.autos.4x4 Mike Locke wrote: > > The gas engine to diesel engine ratio of idle fuel consumption is 59:100. > OK the diesel gets better idle fuel economy, just like it gets better on > road fuel economy no surprise there. This ratio is pretty close to the > difference in compression ratios. > > This is not enough to make the really huge difference you claim in idle > times. It is also not even close to the 1:7 that just discussing the > fuel-air mixture ratios implies. > Think of a diesel as a big air spring. Most of the energy is used to compress the spring is returned on the power stroke, even with no fuel present. Adding fuel just increases the "bounce" of the spring. You just have to add enough fuel to overcome the friction of the bearings and rings as well as the pumping losses from filling and purging the cylinders. Not being throttled, these pumping losses are negligible. A gas engine has to pull air through the throttle, incurring pumping losses. Then there must be enough gas in the mix to sustain combustion. > Adding an exhaust brake to a diesel engine (a throttle butterfly in the > exhaust pipe) will stop the diesel engine cool off problem and reduce the > idle engine air. I don't know if it reduces idle engine fuel usage. Only by increasing the load on the engine. So, yes, it does increase fuel consumption. I understand that the T444E EMC uses an exhaust brake to reduce warm up time of the engine.