Gliding above 55 mph & other observations

[Green Hokie]

I drove up to & back from Roanoke, VA to visit my mother-in-law yesterday. All interstate driving (I-64 & I-81). About 380 miles round-trip with lots of rolling hills. I decided to use cruise control (set at 58 mph) to see how much of hit I would take on mpg versus a manual warp stealth technique. Two interesting observations.

1. On several occasions, my Prius put itself into a pure glide for 4-5 seconds, followed by regen, then back to pure glide for another 4-5 seconds, & so on. That's right, folks. Pure glide. No energy flow at all. How can this be possible? Had I seen no energy flow for just 2 seconds or so, I would have simply concluded that I was observing just a normal transition between regen & warp stealth or another mode. However, this was definitely not just a short transition. I realize the ICE must spin to prevent damage to MG1 (or is it MG2?) at speeds above 42 mph. Again, my cruise control was set to 58 mph. Therefore, did my eyes deceive me? What did I actually observe?

2. The cruise control did a much better job at maximizing fuel economy than I ever could with manual warp stealth (on hilly roads). While I'm certainly not a "master" when it comes to employing warp stealth, I do consider my technique pretty darn good. To my surprise, the cruise control was able to get the MFD to show 99+ mpg on several occasions where the grade was actually on a slight incline (uphill grade). I could never accomplish this manually, without a slight reduction in speed. This has me thinking that cruise control is actually better at these higher interstate speeds. On this particular 377 mile trip, I averaged 60.3 mpg using cruise control set at 58 mph. I always thought cruise control could not outperform the driver in terms of fuel economy. Did Toyota do something different to the program logic for cruise control in the 2007 Prius?

Please offer your comments/explanations.

[ken1784]

<div class='quotetop'>QUOTE(Green Hokie @ May 13 2007, 02:23 PM) [snapback]440916[/snapback]</div>

1. On several occasions, my Prius put itself into a pure glide for 4-5 seconds, followed by regen, then back to pure glide for another 4-5 seconds, & so on. That's right, folks. Pure glide. No energy flow at all. How can this be possible? Had I seen no energy flow for just 2 seconds or so, I would have simply concluded that I was observing just a normal transition between regen & warp stealth or another mode. However, this was definitely not just a short transition. I realize the ICE must spin to prevent damage to MG1 (or is it MG2?) at speeds above 42 mph. Again, my cruise control was set to 58 mph. Therefore, did my eyes deceive me? What did I actually observe?
[/b]

You're viewing the energy flow screen. It is not an engine status screen.
The screen does not show the ICE spinning on highway downhill above 42 mph in fuel-cut mode and some warming up stages. I installed tachometer and it shows the ICE spinning at about 1000 rpm without using any fuel. The ICE is spun by MG1, so it does use some energy.

2. The cruise control did a much better job at maximizing fuel economy than I ever could with manual warp stealth (on hilly roads). While I'm certainly not a "master" when it comes to employing warp stealth, I do consider my technique pretty darn good. To my surprise, the cruise control was able to get the MFD to show 99+ mpg on several occasions where the grade was actually on a slight incline (uphill grade). I could never accomplish this manually, without a slight reduction in speed. This has me thinking that cruise control is actually better at these higher interstate speeds. On this particular 377 mile trip, I averaged 60.3 mpg using cruise control set at 58 mph. I always thought cruise control could not outperform the driver in terms of fuel economy. Did Toyota do something different to the program logic for cruise control in the 2007 Prius?
[/b]

I think your observation is correct.
The pedal band for warp stealth is very narrow, and you'll exhaust your nerves on a long trip.
So, my recommendation is just use cruise control and be relax for a long trip.

Ken@Japan

[bestmapman]

<div class='quotetop'>QUOTE(Green Hokie @ May 13 2007, 01:23 AM) [snapback]440916[/snapback]</div>

I averaged 60.3 mpg using cruise control set at 58 mph. I always thought cruise control could not outperform the driver in terms of fuel economy. [/b]

What else are you doing? I can only get about 50 MPG on the interstate in cruise.

[JimboK]

Good morning, Peter!

Knowing your route, yesterday's weather, and the Prius' capabilities, I'm pretty sure I can push mileage well into the 60s on a drive like that, keeping average speed the same as yours. I've done I-95 between Richmond and Washington in weather similar to yesterday's. Using warp stealth and glide, but keeping my minumum speed at about 63 for safety's sake, I've gotten in the low 60s. Not as hilly as your route, but some pretty good hills nonetheless.

Having said that, it's hard to argue with Ken's logic. Most folks probably won't want to work the pedal on a long trip in the way that method requires, and I can't fault them for letting CC do their work.

[daniel]

I would attribute it to your patience: You were driving at a sensible speed. If your speedo is like mine, yuou were actually going a little slower than the speedo says. And, yes, at the "double nickel" you get very high mpg. People who drive faster are burning gas to heat the air.

[Green Hokie]

<div class='quotetop'>QUOTE(ken1784 @ May 13 2007, 03:38 AM) [snapback]440962[/snapback]</div>

You're viewing the energy flow screen. It is not an engine status screen.
The screen does not show the ICE spinning on highway downhill above 42 mph in fuel-cut mode and some warming up stages. I installed tachometer and it shows the ICE spinning at about 1000 rpm without using any fuel. The ICE is spun by MG1, so it does use some energy.[/b]

I understand now. Thanks, Ken. I just always thought that no energy flow on the MFD indicated that the ICE is completely off and not spinning at all. Guess I need to install something like Scangauge II, if I really want to see what the ICE is doing.



<div class='quotetop'>QUOTE(ken1784 @ May 13 2007, 03:38 AM) [snapback]440962[/snapback]</div>

I think your observation is correct.
The pedal band for warp stealth is very narrow, and you'll exhaust your nerves on a long trip.
So, my recommendation is just use cruise control and be relax for a long trip.[/b]

Yes. It can be quite exhausting to manually employ/optimize warp stealth on long trips. I will definitely use cruise control from now on... at least on long trips. However, I am going to experiment with cruise control on shorter trips as well (less than 30 miles) and on various roads (level, hilly, etc...) to see if I experience similar increases in mpg with cruise. This will all be at interstate speeds, of course (between 55-65 mph). At speeds below 42 mph, I am certain cruise cannot come close to matching my FE with manually induced pulse & glide.

Thanks again for the feedback. I was starting to wonder if my MFD was just playing games to me with some of the results I was seeing. :P

Regards,
Pete

[Green Hokie]

<div class='quotetop'>QUOTE(bestmapman @ May 13 2007, 04:39 AM) [snapback]440969[/snapback]</div>

What else are you doing? I can only get about 50 MPG on the interstate in cruise.
[/b]

Bestmapman. Nothing else special, really. My tires are set at 42/40 psi. It was warm yesterday (lower 80's I think) with very light winds. My 07 Prius has about 3700 miles on it. So, perhaps the engine is now broken-in and I'm seeing a slight boost in FE as a result. I can't take the credit for this trip. The cruise control did all the work! I just sat back and smiled whenever I saw the MFD showing an instantaneous reading of 90+ mpg.

<div class='quotetop'>QUOTE(JimboK @ May 13 2007, 09:50 AM) [snapback]441023[/snapback]</div>

Good morning, Peter!

Knowing your route, yesterday's weather, and the Prius' capabilities, I'm pretty sure I can push mileage well into the 60s on a drive like that, keeping average speed the same as yours. I've done I-95 between Richmond and Washington in weather similar to yesterday's. Using warp stealth and glide, but keeping my minumum speed at about 63 for safety's sake, I've gotten in the low 60s. Not as hilly as your route, but some pretty good hills nonetheless.

Havind said that, it's hard to argue with Ken's logic. Most folks probably won't want to work the pedal on a long trip in the way that method requires, and I can't fault them for letting CC do their work.
[/b]

Good morning, Jim!

Yes, that drive to Roanoke can definitely wear you out if you try to manually warp stealth & glide. As you know, there are some killer hills, especially the one on Afton mountain. If you ever find yourself driving up to Roanoke, please let me know what type of FE you get without CC. As mentioned in my reply to Ken, I probably need to invest in a Scangauge if I hope to do better than CC (at interstate speeds).

[Green Hokie]

<div class='quotetop'>QUOTE(daniel @ May 13 2007, 10:03 AM) [snapback]441030[/snapback]</div>

I would attribute it to your patience: You were driving at a sensible speed. If your speedo is like mine, yuou were actually going a little slower than the speedo says. And, yes, at the "double nickel" you get very high mpg. People who drive faster are burning gas to heat the air.
[/b]

Thanks, Daniel. The posted speed limit along this particular route is 65 mph, mostly. Must have been lucky yesterday, cause I didn't get any middle fingers or blown horns.

Come to think of it, no one has ever made any of these gestures to me... and I consistently drive beween 5-10 mph below the posted speed limits. I'm sure it's just a matter of time! :P

[dmckinstry]

<div class='quotetop'>QUOTE(bestmapman @ May 13 2007, 01:39 AM) [snapback]440969[/snapback]</div>

What else are you doing? I can only get about 50 MPG on the interstate in cruise.
[/b]

Even at 58 mph on level road? Maybe you can't hold down to 58 mph on the interstate.

Dave M.

[pola]

<div class='quotetop'>QUOTE(Green Hokie @ May 12 2007, 11:23 PM) [snapback]440916[/snapback]</div>

I drove up to & back from Roanoke, VA to visit my mother-in-law yesterday. All interstate driving (I-64 & I-81). About 380 miles round-trip with lots of rolling hills. I decided to use cruise control (set at 58 mph) to see how much of hit I would take on mpg versus a manual warp stealth technique. Two interesting observations.

1. On several occasions, my Prius put itself into a pure glide for 4-5 seconds, followed by regen, then back to pure glide for another 4-5 seconds, & so on. That's right, folks. Pure glide. No energy flow at all. How can this be possible? Had I seen no energy flow for just 2 seconds or so, I would have simply concluded that I was observing just a normal transition between regen & warp stealth or another mode. However, this was definitely not just a short transition. I realize the ICE must spin to prevent damage to MG1 (or is it MG2?) at speeds above 42 mph. Again, my cruise control was set to 58 mph. Therefore, did my eyes deceive me? What did I actually observe?

2. The cruise control did a much better job at maximizing fuel economy than I ever could with manual warp stealth (on hilly roads). While I'm certainly not a "master" when it comes to employing warp stealth, I do consider my technique pretty darn good. To my surprise, the cruise control was able to get the MFD to show 99+ mpg on several occasions where the grade was actually on a slight incline (uphill grade). I could never accomplish this manually, without a slight reduction in speed. This has me thinking that cruise control is actually better at these higher interstate speeds. On this particular 377 mile trip, I averaged 60.3 mpg using cruise control set at 58 mph. I always thought cruise control could not outperform the driver in terms of fuel economy. Did Toyota do something different to the program logic for cruise control in the 2007 Prius?

Please offer your comments/explanations.
[/b]

very interesting !! Does cruise control come on every package # ?
thanks, pola