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Well the Japanese hypermilers do it between 20 and 40mph! The traffic wouldn't like that very much either. Point being that the Prius can stop the ICE below 40.

I have found that on up and down back roads my Prius (I also have a Leaf) does around 75 mpg. I cruise around 45mph there but the pulse and glide effect is provided by the hills. Or is he effect just that I am going slower so there is less wind resistance? Shucks!
Also I tried pulse and glide around town but found no evidence that it works.
 

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Well the Japanese hypermilers do it between 20 and 40mph! The traffic wouldn't like that very much either. Point being that the Prius can stop the ICE below 40.

I have found that on up and down back roads my Prius (I also have a Leaf) does around 75 mpg. I cruise around 45mph there but the pulse and glide effect is provided by the hills. Or is he effect just that I am going slower so there is less wind resistance? Shucks!
Also I tried pulse and glide around town but found no evidence that it works.
Pulse and Glide is really for hypermiling ICEs because you pulse to a speed slightly more than you want then let the speed fall away in the glide. You want the deacceleration in an ICE to activate fuel injection cut-off on the overrun. Not going to work in the same way in a BEV.
 

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You want the deacceleration in an ICE to activate fuel injection cut-off on the overrun.
I don't mean to be a pain, but, no, definitely you don't want to run the engine in fuel cut off - unless you have to decelerate at that rate in which case then you do. An engine pulling vacuum is operating very inefficiently.

And if you get into a situation where engine braking is the rate of deceleration you need, then you were driving too fast already, if you were meaning to be hypermiling.

You want an ICE to run with the highest cylinder pressures at all times when generating power. Low engine speeds with high throttle openings. That's the principle of the spit-and-glide. You only run cylinder pressure high whilst generating power, then run the rest of the time at idle so the cylinder pressure is as close to ambient as possible (or just turn the engine off, if you are an extreme hypermiler).

ICE inefficiencies are inversely proportional to the difference between cylinder pressure and ambient. Never run a vacuum if you can help it, that is just all loss.
 

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This is how birds such as the Robin fly they undertake a thing called a "phugoid and short-period oscillation" Google it for more info. They have little energy but in bursts it takes them further. So yes it works and its done in nature its also undertaken by gliding aircraft. Its seen as swooping through the air.
 

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I don't mean to be a pain, but, no, definitely you don't want to run the engine in fuel cut off - unless you have to decelerate at that rate in which case then you do. An engine pulling vacuum is operating very inefficiently.

And if you get into a situation where engine braking is the rate of deceleration you need, then you were driving too fast already, if you were meaning to be hypermiling.

You want an ICE to run with the highest cylinder pressures at all times when generating power. Low engine speeds with high throttle openings. That's the principle of the spit-and-glide. You only run cylinder pressure high whilst generating power, then run the rest of the time at idle so the cylinder pressure is as close to ambient as possible (or just turn the engine off, if you are an extreme hypermiler).

ICE inefficiencies are inversely proportional to the difference between cylinder pressure and ambient. Never run a vacuum if you can help it, that is just all loss.
I had neglected to say that the ICE car needs to be in neutral for the glide, which I had thought was obvious so that the engine speed can idle whle the road speed slowly falls. I would not suggest turning the engine off because of the risk to power steering. Putting a car in neutral while rolling can potentially be viewed as a failure to be in control of the vehicle.

Using an BEV instead of an ICE will have a much flatter efficiency verses output power curve compared to an ICE and that means BEV pulse and glide will generate much smaller gains.
 

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This is how birds such as the Robin fly they undertake a thing called a "phugoid and short-period oscillation" Google it for more info. They have little energy but in bursts it takes them further. So yes it works and its done in nature its also undertaken by gliding aircraft. Its seen as swooping through the air.
The plane Solar Impuse II does it as well with a diurnal cycle. It climbs during the day to make best use of all the available solar energy and then glides back down during the night using the stored energy slowly. Ranging between about 6000 ft and 30,000 ft. Over 10000 ft and the pilot needs to be on oxygen as the cabin is unpressurised.
 

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This is how birds such as the Robin fly they undertake a thing called a "phugoid and short-period oscillation" Google it for more info. They have little energy but in bursts it takes them further. So yes it works and its done in nature its also undertaken by gliding aircraft. Its seen as swooping through the air.
Not sure about the birds, but gliders use this for a different reason - when flying cross country you fly at the optimum lift/drag ratio speed or faster and when you hit a thermal you pull up violently to take maximum benefit of the rising air, you then push over just before you leave the thermal to continue on at high speed. The reason for flying faster is that thermals are strongest in the middle of the day and fall of in strength either side, so if going a long distance you fly faster than than optimum to get best advantage of the fact the thermal weaken towards the end of a long distance flight.

Not relevant here but performance gliders also carry ballast - usually in the form of water - to increase the rate and push the optimum gliding speed to a higher point. When the conditions start to weaken the ballast can then be dropped to best use the weaker thermals.
 

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Discussion Starter #28 (Edited)
My objection to pulse & coast is the aerodynamic fact that windage losses go up with the square of your speed. So if you do x miles at 50 (coasting) and x at 70 (applying power) your windage energy loss is proportional to (5*5)+(7*7) =74. If instead you did it all at 60 it's proportional to (6*6)+(6*6)=72. Not a huge difference and I doubt you would vary your speed so much, but the principal remains. My dad tried this to the limit on fosse way circa 1960 having read a newspaper article saying this was best, so he accelerated to 70 overtaking lorries & cars, then coasted to 30 as they overtook him, then he accelerated to 70 again, overtaking, etc. Before long the others were flashing & tooting him furiously!!! After about 50 miles of this he pulled into a cafe for a sticky bun ! he declared himself satisfied with the experiment, to the immense relief of his passenger, the North Leicestershire coroner!!! He never repeated this tactic.. :)
50 to 70 is a wide spread. I believe, the best pulse and glide maintains the car's best speed with very little variance plus or minus. If the throttle is pulsed for short intervals with only a 1 second glide in-between, the change in speed is not perceivable at cruise. I can say this because, I have set my timing for 3.5 second pulse and 1 second glide and the car does not lurch. I can only tell that it is working by the amp meter which clearly shows a sharp drop in current each glide. Anything that is taken to the extreme will have a negative outcome or at least it will become annoying to anyone who experiences the extreme changes in speed. Also, if the speed is very nearly a constant, so is the aerodynamic drag. The glide duration is 22.2% of the pulse + glide time. The pulse time is 77.8% of the total time. How does this effect the range? I have yet to find out for certain.
 

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Birds do that too - but they don't drop water (n)
But they do drop ballast. One left a statement on my car smack bang in the middle of the bonnet which also appeared to set the alarm off - by the size of the deposit it was either a Vulture or felt really strongly about the Model S!
 

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Reading this thread has taken me back to my gliding days. Being a tall chap I had difficulty fitting in many gliders so the loss of shoe thickness was a benefit. Eventually I went and bought some dancing pumps which were just material on the sole. Never did progress as far as having to fill with ballast.
 

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50 to 70 is a wide spread. I believe, the best pulse and glide maintains the car's best speed with very little variance plus or minus. If the throttle is pulsed for short intervals with only a 1 second glide in-between, the change in speed is not perceivable at cruise. I can say this because, I have set my timing for 3.5 second pulse and 1 second glide and the car does not lurch. I can only tell that it is working by the amp meter which clearly shows a sharp drop in current each glide. Anything that is taken to the extreme will have a negative outcome or at least it will become annoying to anyone who experiences the extreme changes in speed. Also, if the speed is very nearly a constant, so is the aerodynamic drag. The glide duration is 22.2% of the pulse + glide time. The pulse time is 77.8% of the total time. How does this effect the range? I have yet to find out for certain.
50 to 70 is too high for hypermiling because of the higher wind resistance. More typical is 20 to 40. The aim is to accelerate at a rate which needs the engine power output where the engine is operating at its best efficiency. It highlights how anti-social and impractical determined 'pulse and glide' on UK roads could be. :(
 

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Discussion Starter #34 (Edited)
I had neglected to say that the ICE car needs to be in neutral for the glide, which I had thought was obvious so that the engine speed can idle whle the road speed slowly falls. I would not suggest turning the engine off because of the risk to power steering. Putting a car in neutral while rolling can potentially be viewed as a failure to be in control of the vehicle.

Using an BEV instead of an ICE will have a much flatter efficiency verses output power curve compared to an ICE and that means BEV pulse and glide will generate much smaller gains.
Coasting in neutral is certainly one way to do it and many automakers are doing that with aid of a computer. However, it is possible to adjust the throttle such that the electric motor is not operating under load or operating as a load (brake) for a short time. The motor will consume very little energy in this state. Advancing the throttle for short intervals (pulse) will maintain the speed. Everything that happens takes time and delicate control and timing can produce the desired result. The BEV is already extremely efficient and because it is impossible to exceed 100%, there is a narrow margin for improvement. See the picture for my solution to the problem. Red wire 12v. Blue wires parallel connect to pot box. 3.5 second pulse and 1 second glide. Throttle is reduced as much as 25% at full throttle or as little as 5% on the low end, assuming that the motor will idle when the pot box is at 500 ohm. Green led is power light. Yellow led is activity light. As you can see it is quite simple. A common 555 timer controls a high speed switching transistor which turns a load resistor on and off thru a diode bridge rectifier. It sure beats working the throttle up and down with your bare feet to get the timing right.

perform1.jpg
 

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This thread reminds me a bit of those 1940's housekeeping tips, invariably aimed at attractive looking housewives, and designed to maximise thrift during rationing. Must admit, I am thrifty myself when it comes to food waste, and always scrape the jam or butter jar with a rubber scraper to extract the last drop, but having driven a 24 kWh Leaf for three years, making the change to the 30 kWh Leaf is a bit like having a lot bigger jar to play with, so I tend to just drive it the same as I would any kind of car unless venturing into the Highlands, where chargers are few and far between, and reliability very dodgy due to the lack of a mobile signal.
 

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Discussion Starter #36
This thread reminds me a bit of those 1940's housekeeping tips, invariably aimed at attractive looking housewives, and designed to maximise thrift during rationing. Must admit, I am thrifty myself when it comes to food waste, and always scrape the jam or butter jar with a rubber scraper to extract the last drop, but having driven a 24 kWh Leaf for three years, making the change to the 30 kWh Leaf is a bit like having a lot bigger jar to play with, so I tend to just drive it the same as I would any kind of car unless venturing into the Highlands, where chargers are few and far between, and reliability very dodgy due to the lack of a mobile signal.
Just as a larger gas tank has been a long favored solution, a larger battery might have great appeal so long as fuel economy, the cost of electricity and the supply of energy in general are not concerns. But, I wonder if the power grid will stay up when everyone demands twice as much energy from it. Just as miles per gallon became of interest, miles per Kwh might enter the consciousness of drivers who will pay dearly to fill the bigger jar (battery). It is difficult for people to grasp at the moment because charging is often free at many locations. I don't think that free or cheap will last.
 

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Just as a larger gas tank has been a long favored solution, a larger battery might have great appeal so long as fuel economy, the cost of electricity and the supply of energy in general are not concerns. But, I wonder if the power grid will stay up when everyone demands twice as much energy from it. Just as miles per gallon became of interest, miles per Kwh might enter the consciousness of drivers who will pay dearly to fill the bigger jar (battery). It is difficult for people to grasp at the moment because charging is often free at many locations. I don't think that free or cheap will last.
+1

I have made a similar points before. Eventually people will cotton on to the efficiencies of EVs too, but the thing is that because it turns the cost into 'virtually nothing' you can halve or double 'virtually nothing' and it'd still be 'virtually nothing'.

The thing that would change this is if somehow road duty was applied to electricity and the p/mile shot up.
 

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Most of us charge at night using cheap rate leccy, so otherwise the electricity would be wasted. The wind does blow at night too, apparently, even if we are tucked up in our duvets. But everything else apart from the fridge is switched off.
 

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Most of us charge at night using cheap rate leccy, so otherwise the electricity would be wasted.
Every time I look at night rate electricity and do some back of fag packet calcs it is never worth it as much higher day rate charges take away any advantage. The break even point is well beyond me considering jumping through the hoops.
 

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Maybe you should shop around? Nearly half my leccy is at cheap rate. That said I probably pay over the odds to Ecotricity because I happen to believe in their mission to reinvest back into renewables, because I get an EV discount, and because they give me loads of free leccy on the road - every good turn deserves a favour in return..
 
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