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Archive 1 | Archive 2 |
The whole discussion of coasting out of gear should be moved out of the accel section, into its own subsection under specialized techniques. Ccrrccrr ( talk) 12:51, 19 February 2008 (UTC)
- It's also loaded with speculative opinion: "has the added safety benefit of being able to react in any sudden change in a potential dangerous traffic situation, and being in the right gear when acceleration is required.[24]" -- the alleged 'safety benefit' is never substantiated, no imaginable scenario where such sudden acceleration would be required is described (nor can I think of one), and even if it could be, the vehicle would not be in "the right gear" for acceleration but by definition would be in a lower gear requiring a quick change to a higher gear anyway, so ultimately the point contradicts itself. — Preceding unsigned comment added by 50.55.95.219 ( talk) 16:29, 20 July 2012 (UTC)
(response) Neither of those two examples of acceleration is a legitimate safety concern; in (a) your stated course of action is not a given, and even if it is the chosen course of action, since the vehicle is in motion the same direction as the approaching one, it isn't a "sudden" enough situation to be affected by whether the car is in gear or not. Same with the stationary object in (b); traffic lights are timed and predictable. Neither of those scenaria describe "sudden". That's why it's hard to think of an example; they really don't exist in the wrong direction. A sudden change to the motion of a vehicle engaged in the act of going West lies westward, in the future, not eastward in the past. On the point about gearing: if a vehicle is coasting in gear (presumably downhill) then the gear selected is running fairly high in the range of that gear in order to engine-brake (otherwise it would be lugging); to accelerate from that point requires revving even higher, or shifting to a higher gear for proper torque, which would have to be selected pretty soon anyway -- ergo a shift to a higher gear is required regardless whether the vehicle was in gear at the start or not; ergo there's no advantage or disadvantage in being in or out of gear (IOW it wasn't in "the right gear" for acceleration; it was in the gear below the right gear). The passage is basically an extreme stretch of logic to make its preachy one-sided point and I agree the whole section is ambiguous, and full of opinionated writing. The entire page suffers from failure of NPOV (as the length of this talk page attests) and should possibly be scrapped and completely reworked.
This article was prefaced by the form statement proposing to move the article to wikibooks. I deleted this because it's now more like an encylopedic article than what is supposed to be acceptable to wikibooks. Since the wikibooks proposal was added, this article has been improved by deleting Auto-stop, finding more quality citations (including a Ph.D. thesis), and explaining why "pulse and glide" works. Much of this was done by me, David S. Lawyer. 66.81.123.41 ( talk) 17:31, 27 September 2012 (UTC)
I think the information is very outdated. All cars I've driven or friends have driven have at least a option to show the trip mileage. Most also have the option to how the current mileage. I wouldn't really call a '01 Mazda Premacy or a '99 Toyota Vitz or a '05 VW Polo a luxury vehicle. SkySilver ( talk) 19:58, 13 October 2012 (UTC)
There is at least one section here that promotes the terminology promoted by one sleb wannabe. They aren't in general use. I suggest we remove the section 2.2.3 Auto-stop, forced stop, and draft-assisted forced stop Greglocock ( talk) 10:28, 19 April 2012 (UTC)
On Oct. 2, 2012, Thumperwald changed the name of this article from "Fuel economy maximizing behaviors" to "Maximization of fuel economy". Then on Oct. 28, 2012, I (David Lawyer) changed it to "Energy-efficient driving". I claimed that the change made by Thumperwald was not right. There was no discussion of Thumperwald's change. The new "Maximization ..." title greatly broadened the scope of this article. Design of automobiles and their components such as engines, transmissions, body aerodynamics, etc. all may be used to help maximize economy, but this article was intended to cover only how driving techniques (behaviors) can improve fuel economy. If this article is to get into the details of motor vehicle design, then it would need to consider not only fuel economy, but costs, safety, etc. since there are tradeoffs. And this would amount to a big expansion of the article's scope which I don't think should be undertaken. I originally proposed (on 26 Oct., this talk) to, for the time being, revert to the old name, which does seem a little awkward. Then I suggested "Fuel efficient driving". But then after thinking about it I thought "Energy-efficient driving" would be better since it would include electric vehicles. So I've changed it. Discussion is welcome and I'll go along with any consensus reached regarding what the name of this article should be. David S. Lawyer 23:37, 28 October 2012 (UTC)
I was reading over the sources and 2004 impala's course is no source at all. there is nothing on that entire powerpoint that states this "70km/h"
the graph has nothing to do with anything.
— Preceding unsigned comment added by 129.97.175.37 ( talk) 22:44, 12 September 2013 (UTC)
"The optimum efficiency point is around 1750 rpm, and 90% of maximum torque at that speed, for this turbo-diesel engine."
"this turbo-diesel engine" is not referenced anywhere. This has ether been lazily copied from somewhere or someone has forgot to include the name of the engine they are referring to.
A Google search would indicate this has been copied from a website which is itself a copy from another website. attempting to track down the original was fruitless as the original article seems to have disappeared.
80.5.128.19 ( talk) 15:52, 4 June 2014 (UTC)
If you're driving for fun 35 mph might be the optimum speed (for some cars, see the article) but if you're on your way somewhere it tends to be about 50 mph. That's because saving for example 10% fuel by driving 35 mph doesn't help if you have 20% of the trip left compared to a car that's driving about 50 mph and reached already its destination. — Preceding unsigned comment added by 84.248.20.195 ( talk) 11:50, 12 August 2014 (UTC)
The label "This article contains instructions, advice, or how-to content (September' 2009)" was applied to this article. Yes, it does contain such content but this content can't be removed since the article is intended to be a scientific analysis of the results (better energy-efficiency) of experiments. Thus a description of the experiments includes a detailed description of of what was done (how the car was driven) and this is in effect certain instructions and advice (how-to). These are certain control polices (instructions) used for control of a physical system (a motorized vehicle).
One can also analyze Pulse-and-Glide by using Optimal Control theory. It's been done for railroads but not for automobiles. I've done some of this for railroads but haven't published it. The result I derived is known as a Bang-bang control policy, which is exactly what Pulse and Glide is. It's a shame that the Ph.D. thesis on pulse and glide didn't analyze it from the standpoint of Optimal Control. One impediment to applying such theory is that the Brake specific fuel consumption curves are often kept secret. David S. Lawyer 01:27, 19 November 2013 (UTC)
You go guys/gals/aliens/wikipedians, and don't be afraid to restructure the entire article, most of it is a holdover from fatuous self promotion tautologically by a self promoter. In fact, should we start a discussion of a sensible structure? Cheers Greglocock ( talk) 10:14, 19 February 2015 (UTC)
"Coasting is most efficient when the engine is not running, although some gains can be realized with the engine on (to maintain power to brakes, steering and ancillaries) and the vehicle in neutral, or even with the vehicle remaining in gear.[24] Most modern petrol vehicles cut off the fuel supply completely when coasting (over-running) in gear, although the moving engine adds considerable frictional drag and speed is lost more quickly than with the engine declutched from the drivetrain."
Not being able to see the ref that phrase in bold strikes me as borderline ludicrous at least for real conventional cars. I think we need a ref that people can see and judge for themselves. It sounds like an outcome of poor modelling or very special circumstances. Figure 3.10 in the Jeongwoo_Lee paper shows why, leaving it in gear results in a deceleration 3 to 6 times that in neutral.
Greglocock (
talk)
22:40, 6 December 2015 (UTC)
http://scholar.lib.vt.edu/theses/available/etd-09172009-234744/unrestricted/ETD_PhD_Dissertation_Jeongwoo_Lee.pdf figure 4.5 assumes a fuel flow rate of zero when the vehicle is coasting. that implies the engine is off, which means we are no longer in Kansas. I can imagine smug little gits driving along the freeway switching their engine on and off every 40 seconds. I can also imagine them being wiped off the face of the earth when one of several things happens. Incidentally that PhD is a fail in my book, a bit of stuffing around with a simple computer mode and no actual complex maths means the guy doesn't understand anything particularly new, the level of maths is high school. Greglocock ( talk) 22:40, 6 December 2015 (UTC)
"The National Renewable Energy Laboratory in a 2000 report suggest that a 400 W load on a conventional engine can decrease the fuel efficiency by up to 20%.[4]"
Well i'm sure it does, especially if the engine is producing about 2000W or less, ie idling. So what? The given reference does not support that statement. Greglocock ( talk) 10:43, 7 December 2015 (UTC)
These sections were deleted on 1 May 2015 and manually restored by me today (24 Nov. 2015). There's a newer thesis on this topic by Jansen that need to be better incorporated into these sections P&G needs to be integrated into the rest of the article and at present, it seems to be just a note tacked onto the article as an afterthought. I hope to find time to work on this. It turns out that it is not optimal to just travel at steady speed and P&G (Pulse and Glide) illustrates this. Thus the implication that steady speed is most efficient needs correcting. On a road with long up and downgrades, one can use the equivalent of P&G by driving uphill (efficient since the torque is high) and then coast down the following downgrade. The pulse is the uphill part (a long pulse) and the glide is coasting downhill. A few years ago I wrote an article on P&G and placed it on my website: | Case for coasting. This article is more like a How_to and I use a lot of "you's" so it doesn't fit in with Wikipedia style, except it does contain more technical information that needs to be put into Wikipedia (with more reference). David S. Lawyer 05:52, 22 November 2015 (UTC)David S. Lawyer 08:10, 24 November 2015 (UTC)David S. Lawyer 08:14, 14 December 2015 (UTC)
The fellow who modified his Honda civic and is reportedly getting 100-120mpg seems to be notable (
http://www.aerocivic.com).
The people who are helping honda insight owners take full control over their electric assist (MIMA) are interesting. ( http://99mpg.com/mima/mimaintroduction/) They are selling a joystick that allows you to drive your hybrid and control when it charges and assists. Chickpecking ( talk) 03:14, 6 December 2015 (UTC)
There once was a mention in this article of a claim that a motorcyclist drafted behind a truck for hours and most of the time just "coasted". This coasting must have meant that the aerodynamic drag on the motorcycle was negative, and that the wake of the truck provides enough forward thrust to overcome the rolling resistance of the motorcycle. Is this feasible? In [1] it shows the drag coefficients of two cylinders of equal diameter, the first cylinder shielding the second from the wind. It turns out that for close spacing (the second cylinder being approximately less than one cylinder diameter behind the first (leading) cylinder, the drag coefficient is negative (the aerodynamic drag is reduced by about 130%). That is, the wake of the first cylinder creates a forward aerodynamic thrust on the second cylinder, pushing it in a direction opposite to the wind. This experiment is like the second cylinder was "drafting" behind the leading cylinder. Somewhat similar results are shown for two circular disks, one behind the other (but the induced thrust isn't as pronounced).
The above result tends to support the feasibility (in some cases) of drafting without applying any motor-driven thrust to the drafting motor vehicle. Another question is that of stability. If the induced thrust (due to the negative drag coefficient) increases the closer the drafting vehicle gets to the "truck" (leading vehicle) then the vehicle behind the truck might accidentally crash into it. But it turns out that for the cylinders, there is a stable zone about 1.7 diameters behind the leading cylinder. If motor vehicles behaved similar to cylinders then for drafting behind a truck: move closed to the truck and the drag goes positive, tending to push the drafter back away from the truck. And conversely, should the drafter move back further away from the truck the drag coefficient goes negative, providing forward thrust. But perhaps not strong enough negative to overcome rolling resistance. When the trailing cylinder is close to the leading cylinder (within 1/2 of the cylinder diameter) the negative drag (per the curve in ref. 1) stays nearly constant. However, there are not enough data points in this region to accurately determine the shape of this curve so the negative drag may not actually be constant in this region and a stable situation might exist.
Of course the above results don't prove that no-fuel drafting is feasible, but indicate that it might be. Additional wind tunnel testing would be of interest to resolve (if only partially) this question. Has anyone done this? David S. Lawyer 07:52, 14 December 2015. David S. Lawyer 18:58, 14 December 2015 (UTC)
References
![]() | This is an archive of past discussions. Do not edit the contents of this page. If you wish to start a new discussion or revive an old one, please do so on the current talk page. |
Archive 1 | Archive 2 |
The whole discussion of coasting out of gear should be moved out of the accel section, into its own subsection under specialized techniques. Ccrrccrr ( talk) 12:51, 19 February 2008 (UTC)
- It's also loaded with speculative opinion: "has the added safety benefit of being able to react in any sudden change in a potential dangerous traffic situation, and being in the right gear when acceleration is required.[24]" -- the alleged 'safety benefit' is never substantiated, no imaginable scenario where such sudden acceleration would be required is described (nor can I think of one), and even if it could be, the vehicle would not be in "the right gear" for acceleration but by definition would be in a lower gear requiring a quick change to a higher gear anyway, so ultimately the point contradicts itself. — Preceding unsigned comment added by 50.55.95.219 ( talk) 16:29, 20 July 2012 (UTC)
(response) Neither of those two examples of acceleration is a legitimate safety concern; in (a) your stated course of action is not a given, and even if it is the chosen course of action, since the vehicle is in motion the same direction as the approaching one, it isn't a "sudden" enough situation to be affected by whether the car is in gear or not. Same with the stationary object in (b); traffic lights are timed and predictable. Neither of those scenaria describe "sudden". That's why it's hard to think of an example; they really don't exist in the wrong direction. A sudden change to the motion of a vehicle engaged in the act of going West lies westward, in the future, not eastward in the past. On the point about gearing: if a vehicle is coasting in gear (presumably downhill) then the gear selected is running fairly high in the range of that gear in order to engine-brake (otherwise it would be lugging); to accelerate from that point requires revving even higher, or shifting to a higher gear for proper torque, which would have to be selected pretty soon anyway -- ergo a shift to a higher gear is required regardless whether the vehicle was in gear at the start or not; ergo there's no advantage or disadvantage in being in or out of gear (IOW it wasn't in "the right gear" for acceleration; it was in the gear below the right gear). The passage is basically an extreme stretch of logic to make its preachy one-sided point and I agree the whole section is ambiguous, and full of opinionated writing. The entire page suffers from failure of NPOV (as the length of this talk page attests) and should possibly be scrapped and completely reworked.
This article was prefaced by the form statement proposing to move the article to wikibooks. I deleted this because it's now more like an encylopedic article than what is supposed to be acceptable to wikibooks. Since the wikibooks proposal was added, this article has been improved by deleting Auto-stop, finding more quality citations (including a Ph.D. thesis), and explaining why "pulse and glide" works. Much of this was done by me, David S. Lawyer. 66.81.123.41 ( talk) 17:31, 27 September 2012 (UTC)
I think the information is very outdated. All cars I've driven or friends have driven have at least a option to show the trip mileage. Most also have the option to how the current mileage. I wouldn't really call a '01 Mazda Premacy or a '99 Toyota Vitz or a '05 VW Polo a luxury vehicle. SkySilver ( talk) 19:58, 13 October 2012 (UTC)
There is at least one section here that promotes the terminology promoted by one sleb wannabe. They aren't in general use. I suggest we remove the section 2.2.3 Auto-stop, forced stop, and draft-assisted forced stop Greglocock ( talk) 10:28, 19 April 2012 (UTC)
On Oct. 2, 2012, Thumperwald changed the name of this article from "Fuel economy maximizing behaviors" to "Maximization of fuel economy". Then on Oct. 28, 2012, I (David Lawyer) changed it to "Energy-efficient driving". I claimed that the change made by Thumperwald was not right. There was no discussion of Thumperwald's change. The new "Maximization ..." title greatly broadened the scope of this article. Design of automobiles and their components such as engines, transmissions, body aerodynamics, etc. all may be used to help maximize economy, but this article was intended to cover only how driving techniques (behaviors) can improve fuel economy. If this article is to get into the details of motor vehicle design, then it would need to consider not only fuel economy, but costs, safety, etc. since there are tradeoffs. And this would amount to a big expansion of the article's scope which I don't think should be undertaken. I originally proposed (on 26 Oct., this talk) to, for the time being, revert to the old name, which does seem a little awkward. Then I suggested "Fuel efficient driving". But then after thinking about it I thought "Energy-efficient driving" would be better since it would include electric vehicles. So I've changed it. Discussion is welcome and I'll go along with any consensus reached regarding what the name of this article should be. David S. Lawyer 23:37, 28 October 2012 (UTC)
I was reading over the sources and 2004 impala's course is no source at all. there is nothing on that entire powerpoint that states this "70km/h"
the graph has nothing to do with anything.
— Preceding unsigned comment added by 129.97.175.37 ( talk) 22:44, 12 September 2013 (UTC)
"The optimum efficiency point is around 1750 rpm, and 90% of maximum torque at that speed, for this turbo-diesel engine."
"this turbo-diesel engine" is not referenced anywhere. This has ether been lazily copied from somewhere or someone has forgot to include the name of the engine they are referring to.
A Google search would indicate this has been copied from a website which is itself a copy from another website. attempting to track down the original was fruitless as the original article seems to have disappeared.
80.5.128.19 ( talk) 15:52, 4 June 2014 (UTC)
If you're driving for fun 35 mph might be the optimum speed (for some cars, see the article) but if you're on your way somewhere it tends to be about 50 mph. That's because saving for example 10% fuel by driving 35 mph doesn't help if you have 20% of the trip left compared to a car that's driving about 50 mph and reached already its destination. — Preceding unsigned comment added by 84.248.20.195 ( talk) 11:50, 12 August 2014 (UTC)
The label "This article contains instructions, advice, or how-to content (September' 2009)" was applied to this article. Yes, it does contain such content but this content can't be removed since the article is intended to be a scientific analysis of the results (better energy-efficiency) of experiments. Thus a description of the experiments includes a detailed description of of what was done (how the car was driven) and this is in effect certain instructions and advice (how-to). These are certain control polices (instructions) used for control of a physical system (a motorized vehicle).
One can also analyze Pulse-and-Glide by using Optimal Control theory. It's been done for railroads but not for automobiles. I've done some of this for railroads but haven't published it. The result I derived is known as a Bang-bang control policy, which is exactly what Pulse and Glide is. It's a shame that the Ph.D. thesis on pulse and glide didn't analyze it from the standpoint of Optimal Control. One impediment to applying such theory is that the Brake specific fuel consumption curves are often kept secret. David S. Lawyer 01:27, 19 November 2013 (UTC)
You go guys/gals/aliens/wikipedians, and don't be afraid to restructure the entire article, most of it is a holdover from fatuous self promotion tautologically by a self promoter. In fact, should we start a discussion of a sensible structure? Cheers Greglocock ( talk) 10:14, 19 February 2015 (UTC)
"Coasting is most efficient when the engine is not running, although some gains can be realized with the engine on (to maintain power to brakes, steering and ancillaries) and the vehicle in neutral, or even with the vehicle remaining in gear.[24] Most modern petrol vehicles cut off the fuel supply completely when coasting (over-running) in gear, although the moving engine adds considerable frictional drag and speed is lost more quickly than with the engine declutched from the drivetrain."
Not being able to see the ref that phrase in bold strikes me as borderline ludicrous at least for real conventional cars. I think we need a ref that people can see and judge for themselves. It sounds like an outcome of poor modelling or very special circumstances. Figure 3.10 in the Jeongwoo_Lee paper shows why, leaving it in gear results in a deceleration 3 to 6 times that in neutral.
Greglocock (
talk)
22:40, 6 December 2015 (UTC)
http://scholar.lib.vt.edu/theses/available/etd-09172009-234744/unrestricted/ETD_PhD_Dissertation_Jeongwoo_Lee.pdf figure 4.5 assumes a fuel flow rate of zero when the vehicle is coasting. that implies the engine is off, which means we are no longer in Kansas. I can imagine smug little gits driving along the freeway switching their engine on and off every 40 seconds. I can also imagine them being wiped off the face of the earth when one of several things happens. Incidentally that PhD is a fail in my book, a bit of stuffing around with a simple computer mode and no actual complex maths means the guy doesn't understand anything particularly new, the level of maths is high school. Greglocock ( talk) 22:40, 6 December 2015 (UTC)
"The National Renewable Energy Laboratory in a 2000 report suggest that a 400 W load on a conventional engine can decrease the fuel efficiency by up to 20%.[4]"
Well i'm sure it does, especially if the engine is producing about 2000W or less, ie idling. So what? The given reference does not support that statement. Greglocock ( talk) 10:43, 7 December 2015 (UTC)
These sections were deleted on 1 May 2015 and manually restored by me today (24 Nov. 2015). There's a newer thesis on this topic by Jansen that need to be better incorporated into these sections P&G needs to be integrated into the rest of the article and at present, it seems to be just a note tacked onto the article as an afterthought. I hope to find time to work on this. It turns out that it is not optimal to just travel at steady speed and P&G (Pulse and Glide) illustrates this. Thus the implication that steady speed is most efficient needs correcting. On a road with long up and downgrades, one can use the equivalent of P&G by driving uphill (efficient since the torque is high) and then coast down the following downgrade. The pulse is the uphill part (a long pulse) and the glide is coasting downhill. A few years ago I wrote an article on P&G and placed it on my website: | Case for coasting. This article is more like a How_to and I use a lot of "you's" so it doesn't fit in with Wikipedia style, except it does contain more technical information that needs to be put into Wikipedia (with more reference). David S. Lawyer 05:52, 22 November 2015 (UTC)David S. Lawyer 08:10, 24 November 2015 (UTC)David S. Lawyer 08:14, 14 December 2015 (UTC)
The fellow who modified his Honda civic and is reportedly getting 100-120mpg seems to be notable (
http://www.aerocivic.com).
The people who are helping honda insight owners take full control over their electric assist (MIMA) are interesting. ( http://99mpg.com/mima/mimaintroduction/) They are selling a joystick that allows you to drive your hybrid and control when it charges and assists. Chickpecking ( talk) 03:14, 6 December 2015 (UTC)
There once was a mention in this article of a claim that a motorcyclist drafted behind a truck for hours and most of the time just "coasted". This coasting must have meant that the aerodynamic drag on the motorcycle was negative, and that the wake of the truck provides enough forward thrust to overcome the rolling resistance of the motorcycle. Is this feasible? In [1] it shows the drag coefficients of two cylinders of equal diameter, the first cylinder shielding the second from the wind. It turns out that for close spacing (the second cylinder being approximately less than one cylinder diameter behind the first (leading) cylinder, the drag coefficient is negative (the aerodynamic drag is reduced by about 130%). That is, the wake of the first cylinder creates a forward aerodynamic thrust on the second cylinder, pushing it in a direction opposite to the wind. This experiment is like the second cylinder was "drafting" behind the leading cylinder. Somewhat similar results are shown for two circular disks, one behind the other (but the induced thrust isn't as pronounced).
The above result tends to support the feasibility (in some cases) of drafting without applying any motor-driven thrust to the drafting motor vehicle. Another question is that of stability. If the induced thrust (due to the negative drag coefficient) increases the closer the drafting vehicle gets to the "truck" (leading vehicle) then the vehicle behind the truck might accidentally crash into it. But it turns out that for the cylinders, there is a stable zone about 1.7 diameters behind the leading cylinder. If motor vehicles behaved similar to cylinders then for drafting behind a truck: move closed to the truck and the drag goes positive, tending to push the drafter back away from the truck. And conversely, should the drafter move back further away from the truck the drag coefficient goes negative, providing forward thrust. But perhaps not strong enough negative to overcome rolling resistance. When the trailing cylinder is close to the leading cylinder (within 1/2 of the cylinder diameter) the negative drag (per the curve in ref. 1) stays nearly constant. However, there are not enough data points in this region to accurately determine the shape of this curve so the negative drag may not actually be constant in this region and a stable situation might exist.
Of course the above results don't prove that no-fuel drafting is feasible, but indicate that it might be. Additional wind tunnel testing would be of interest to resolve (if only partially) this question. Has anyone done this? David S. Lawyer 07:52, 14 December 2015. David S. Lawyer 18:58, 14 December 2015 (UTC)
References