Pulse and Glide

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.

 

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.

 

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

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.

 

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

 

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

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.

 

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.

 

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.

 

P&G and slower speeds works great. I bought my Prius last Monday in Atlanta. I got 45.9 per the MFD for both my first and second tanks. This included city driving, but mostly hwy at 80MPH. At the very end of my second tank, this morning, I attended the first ever Richmond, VA Prius rally at Haley Toyota, organized by JimBok and Skwyre7. Both these guys taught the other attendees how to P&G. I learned from JimBok and filled up and drove to Charlottesville, VA this afternoon (where I needed to be and is why I was in the area). Using the P&G method, I averaged 72.3 MPG!!!!! This was highway driving, but at 45 to 55 MPH.

 

Way to go, EarthCare!

It was great to meet you, BTW. Glad you made it to C'ville safely -- and fuel efficiently!

 

<div class='quotetop'>QUOTE(JimboK @ May 5 2007, 09:08 PM) [snapback]436199[/snapback]</div>

It was a lot of fun meeting all of you. Thank you so much for your help. I really can't believe how much of a difference it makes. You DA MAN!

 

<div class='quotetop'>QUOTE(brick @ May 5 2007, 06:50 PM) [snapback]436188[/snapback]</div>

Bingo. You store energy as potential energy (height) instead of kinetic (speed). It's no different from pulse-and-glide on the flat, just without the annoying changes in speed.

 

I think I figured out pulse and glide...or at least a version of it.

Driving along on the highway, I noticed I get the best economy if the little arrow between the motor and the battery seems to be oscillating back and forth. First one way, and then the other way, but quite fast. Sometimes it would disappear for bout half a second, but never more. It's very hard to control.

I used to just watch the consumption gauge in my BMW, so now I just watch the consumption gauge on the MFD and try to follow that instead. With a single glance you can get an idea of "Hey, back off the gas" or "I can push a little harder"

I'm 320Km into my first tank. Sitting on 5.3l/100km. Is that respectable?