Pulse and Glide

[surfacinglove]

OK, so there are 2 parts to the technique:

1. Pulse- accelearte up to the speed (ie 45mph) showing only the orange arrows from the engine turning the wheels and charging the battery as well on the MFD

2. Glide- let off the accelerator just enough to have no activity or energy transer (pretty much neutral) with no energy transfer shown on MFD

and repeat....


So.... using this technique 100% (I know that's not actually possible), where would you ever actually tap into the stored battery power? It seems like all you do is use fuel to move the car while charging the battery, then use nothing/charge nothing... what about the energy in the battery?! Eventually it's full, right?

Someone help me out here... seems like it's missing something...

[darelldd]

I'm sure others will chime in with relevant URL pointers and such.

I can tell you this: For best FE, you don't want to charge OR discharge the battery. EVery time you do that, you lose efficiency of the system. The battery is there to buffer *normal* driving. And in that way, it increases the FE of "normal" people. Using exclusive P&G requires that you use as little battery as possible (charge or discharge, and simply power the wheels directly with the most efficient mode of the ICE (which is a certain load, or OFF).

That said, there are many "modified P&G techniques" that work quite well in the real world.

HOpe that helps a bit.

[brick]

In a word, yes. Although the upper limit for normal P&G is really 41mph because above that speed the engine has to spin. 41mph and below the engine stops spinning entirely. And yes, used 100% over a closed course with ideal conditions the Prius will do over 100mpg. As Darell said, this takes the battery mostly out of the equation so you reduce the energy conversion losses. It also keeps the engine running in its most efficient band for short bursts rather than running less efficiently (low RPM...it's not worth trying to go into the details right here) all the time. Obviously you can't do that on your commute.

If I'm on an open, flat back road with nobody else on it I will milk it for all it's worth. Pulse up to 35mph, glide down to 20mph, rinse and repeat. That kind of thing will give you pegged 5-minute bars in short order. If I suddenly have to share the road I resume steady-state because I don't wanat to be a jerk. But there are times when you can resume P&G in traffic while you "go with the flow." Let's say you're drving along at 35mph or so and see a light changing to red down the road. You can either maintain 35mph and hit the brakes when you get there or you can feather the accelerator and glide up to it with the engine off, braking a little at the end if you need to. Either way you get to the red light and wait for it to change but the latter method is much more efficient because you take the ICE out of the equation sooner and incur smaller conversion losses through regenerative braking at the end, if you need to step on the brakes at all. That's basically P&G but using it opportunistically rather than forcing the issue.

[nerfer]

<div class='quotetop'>QUOTE(brick @ May 2 2007, 08:12 PM) [snapback]434390[/snapback]</div>

... Let's say you're drving along at 35mph or so and see a light changing to red down the road. You can either maintain 35mph and hit the brakes when you get there or you can feather the accelerator and glide up to it with the engine off, braking a little at the end if you need to. Either way you get to the red light and wait for it to change but the latter method is much more efficient ...
[/b]

And if you're lucky, or traffic is light, you can time it so that the light turns green just before you get there, and save more gasoline.

Another typical usage is in small hills - pulse up the hills to maintain traffic flow/momentum, and glide down the other side.

Hills, stoplights, same thing, both involve losing and gaining inertia. You'll find you can use this in many scenarios - off-ramps, nearly-stop-and-go traffic, wherever people slow down.

[Tideland Prius]

no because there is a slight battery drain so the battery will slowly lose charge (faster if you're using A/C).

So.. braking and regenerating will help counter the slow trickle.

(Sit with your car on and A/C, radio etc off. You'll see the bars still drop even though you're not moving or using the A/C).

[medicis]

<div class='quotetop'>QUOTE(surfacinglove @ May 2 2007, 06:50 PM) [snapback]434312[/snapback]</div>

So.... using this technique 100% (I know that's not actually possible), where would you ever actually tap into the stored battery power? It seems like all you do is use fuel to move the car while charging the battery, then use nothing/charge nothing... what about the energy in the battery?! Eventually it's full, right?

Someone help me out here... seems like it's missing something...
[/b]

Watch carefully. When you do need to accelerate during pulse, you'll notice energy coming from the battery as well as from ICE. This reduces the gas consumption. The more has been stored, the more will be available to assist. However, this battery energy is worth only 50c on the $ because of the conversion losses. Hence the benefits of true gliding vs. EV.

[JimboK]

<div class='quotetop'>QUOTE(CO2 miser @ May 4 2007, 08:07 PM) [snapback]435734[/snapback]</div>

Watch carefully. When you do need to accelerate during pulse, you'll notice energy coming from the battery as well as from ICE. [/b]

It depends on how fast you accelerate. Moderate acceleration with the ICE within its efficient RPM range (like brick describes) is probably more likely to result in flow into the battery, not out of it.

The "deadband" state (as some have called it) where, as darelldd describes, no energy flows into or out of the battery, would seem ideal. That's tough to maintain throughout a pulse. It requires constantly watching the energy display and frequent fine adjustments of the pedal. That's more attention than I want to give for something I can't maintain, so I'm content just to accelerate moderately and avoid pulling from the battery. The result usually is green arrows showing battery charging. Regardless, as long as I see no orange arrows from the battery, I'm happy. I use EV mode judiciously to extend glides, and these pulses with moderate acceleration, along with regenerative coasting and braking, are opportunities to nudge the charge back up.

[alexstarfire]

P&G may be the end all be all of hypermiling, but I don't care how good you are at it, it'll never work on hills.

[efusco]

<div class='quotetop'>QUOTE(Alexstarfire @ May 5 2007, 03:03 PM) [snapback]436122[/snapback]</div>

P&G may be the end all be all of hypermiling, but I don't care how good you are at it, it'll never work on hills. [/b]

Works ok on the hills here in the Ozarks.

Perhaps your hills need a check-up?

[brick]

Rolling hills are great for P&G. Pulse up, glide down. When things align right you can do it without changing your speed, eliminating the traffic limitation.