The myth of pulse and glide

[WPWoodJr]

Originally Posted by msirach

You must be a rookie of Pulse and Glide if you can't realize a true benefit. It is a proven technique.

Guilty of being a rookie! Didn't mean to imply that P&G wasn't beneficial.

[a priori]

Originally Posted by WPWoodJr

Guilty of being a rookie!

That part is understood, Bill!

Originally Posted by WPWoodJr

Didn't mean to imply that P&G wasn't beneficial.

There's the rub, because the title of the thread, regardless of your intention, allows most every reader of PriusChat to infer you have "found out" P&G and that it isn't anything more than a myth.

You'll likely suffer a few slings and arrows for that one!

[justlurkin]

Originally Posted by WPWoodJr

In the FFH, there are three types of regen - regen from braking, regen from the ICE when it is providing more power than the car needs, and regen from taking your foot off the pedal. Regen from braking is displayed on the battery SOC display on the dash as 3 arrows in a circle; regen from the ICE or lifting your foot from the pedal is displayed as an upwards-pointing arrow. If the FFH has nav there is also a large power-flow diagram similar to the Prius but it is harder to read - no color-coding and the arrows that indicate power flow direction are small and hard to see while driving; so I don't use this much.

On the FFH its hard to keep the balance between regen and acceleration during a glide. Its much easier to put it in neutral for the glide, but then you lose all regen capability so I don't use neutral often. I find where I drive that I usually either need to slow down, so I let it regen, or I need to keep the glide going longer, so I apply a little EV power.

Thanks for the description-- I think it's informative to see how it's implemented the FFH, considering the Prius and the FFH uses very similar drive systems.

For a casual pulse-and-glider like me, I find the Prius energy flow display to be very helpful in maximizing glide distance. I don't know if it's the pedal setup in the Prius, but on highways I find it pretty easy to keep the gas pedal in the right position to prevent regen. It's only on really hilly or bumpy roads when I find it more challenging.

I'll have to rent a Ford Fusion Hybrid one of these days and do a comparison to see if it's any harder to do than in the Prius.

[WPWoodJr]

Originally Posted by a priori

There's the rub, because the title of the thread, regardless of your intention, allows most every reader of PriusChat to infer you have "found out" P&G and that it isn't anything more than a myth.

You'll likely suffer a few slings and arrows for that one!

Maybe I should have called it "Mathematics behind natural inclination to overestimate mileage attained during pulse and glide" - that would have gotten huge interest

[ken1784]

Originally Posted by WPWoodJr

The interesting thing is the easy misconception that the average MPG during P&G is higher than it really is. To get 60 mpg in my example of a 20 mpg pulse and 100 mpg glide, your glide needs to be 5 times the length of the pulse - I believe that is counter-intuitive to most people.

Are you saying the FFH consumes some fuel during the 100mpg gliding?
Prius does not consume any fuel during gliding, therefore we see an infinity mpg then.

Ken@Japan

[WPWoodJr]

Originally Posted by ken1784

Are you saying the FFH consumes some fuel during the 100mpg gliding?
Prius does not consume any fuel during gliding, therefore we see an infinity mpg then.

Ken@Japan

FFH consumes no fuel during glide unless going more than 47 mph, like Prius Gen III above 45. However, unless there is no A/C, no lights, no radio - basically no battery losses at all - you are consuming mpg because the battery is discharging and will need to be recharged at some point. So equivalent mpg even when gliding is not actually infinite.

[ken1784]

Originally Posted by WPWoodJr

FFH consumes no fuel during glide unless going more than 47 mph, like Prius Gen III above 45. However, unless there is no A/C, no lights, no radio - basically no battery losses at all - you are consuming mpg because the battery is discharging and will need to be recharged at some point.

OK, I understand what you're saying.
But, you're saying between 20 and 150 glide MPG's which consume no fuel and consume some battery power.
it's very hard to imagine how we consume battery power on such wide range of MPG numbers.
Would you please explain how do you assume the battery power?
Such as...
20 MPG glide: (it must be a huge battery power:heavy A/C use???)
80 MPG glide: (it may be moderate?)
150 MPG glide: (It's very little battery consumption?)

Anyway, I believe following chart is better to understand how the Pulse & Glide work.
I assume the Glide part does not consume any fuel, therefore an infinity MPG.
The "Glide %" means gliding distance percentage of total driving.

Ken@Japan

[Shawn Clark]

Originally Posted by WPWoodJr

Here's an article on the myth of pulse and glide. You may not be getting as great an MPG boost from P&G as you thought.

What myth? That's not pulse and glide. In P&G you extend the glide as long as possible with no gasoline consumption until the pulse. That's why in low speed situations where light timing and such are possible it's not too difficult to get 80-100 mpg.

At any rate, I remember watching some PBS or other documentary about P&G without a hybrid drivetrain ~15 years or so ago. The engine was only operating briefly and efficiently which is what P&G does. (I don't recall what terminology they used, and it might have been a motorized bicycle or something like that but I still remember the central theme.)

[CharlesJ]

Originally Posted by WPWoodJr

You're correct that a good glide will be longer in distance than the pulse, and I wasn't disputing that. I'm also not disputing P&G as a technique.

The interesting thing is the easy misconception that the average MPG during P&G is higher than it really is. To get 60 mpg in my example of a 20 mpg pulse and 100 mpg glide, your glide needs to be 5 times the length of the pulse - I believe that is counter-intuitive to most people.

How would the numbers stack up if that glide mph in reality is 9999mpg instead of that 100mpg? Or any number between 9999 and 100? Maybe that makes a huge difference? the dash readout only goes to 99.9 but, a scan gage will read 9999mpg, or can.

[hobbit]

Most folks are treating P&G as some sort of cookbook procedure,
without understanding that it's a simplified version of the real
purpose -- to run the engine as efficiently as possible when
it's running, and let it shut down in between. The run times
and off times and speed ranges don't have to be some exact
regime; all you have to do is realize when conditions are most
optimal for one or the other and adapt the right scenario to
the traffic and terrain around you. It's madness to hit a rise
and think "but it's time to glide!" and slow way down because of
some rote notion that it wasn't time to light the engine yet.
It's all about anticipation and understanding how to work the
car best for what's coming up.
.
Don't think of it as "P&G" per se, think of it as efficient
running conditions and judicious use of the one form of energy
storage that requires no conversion to be used for the desired
purpose -- momentum.
.
_H*