Stealth at higher speed

ScottY · 06-21-2006, 01:03 PM

I've noticed this for a while now. When the speed is between ~35 to 41mph, lift my feet off the gas pedal, the car will go into stealth mode almost all the time. But when my speed is lower than 30mph, this won't happen. If my speed starts out below 30mph, ICE running. ICE won’t stop till couple of seconds after the car completely stop. From CAN-View, I know the ICE is warmed up already at that time (around 190 degrees F).

Anybody know why it is easier to get in stealth mode at higher speeds?

**TonyPSchaefer** · 06-21-2006, 01:09 PM

I always assumed that it's due to inertia. At slower speeds, you have to work to move the weight. At higher speeds, however, since the weight is already moving, it's easier to just keep it moving. I always figured that around 35mph was the tipping-point.

**efusco** · 06-21-2006, 01:57 PM

The algorythm clearly prefers to allow immediate ICE off stealth b/w 35-41, it can be very difficult b/w 30&35, but will under some conditions. The next cut-off seems to be speeds below 20mph where it usually will go into stealth, but again, not always.

I intentionally keep my speed at 35mph or even intentionally accelerate to 35 when normally i'd have only gone to 33 or so just to make the transition to stealth easier. The advantage of doing that over using the EV button is that it will stay in stealth at speeds over 34mph whereas with EV the ICE will spin up briefly until you exceed 35 again.

ScottY · 06-21-2006, 02:14 PM

<div class='quotetop'>QUOTE(efusco @ Jun 21 2006, 01:57 PM) [snapback]274747[/snapback]</div>

Quote:

...
I intentionally keep my speed at 35mph or even intentionally accelerate to 35 when normally i'd have only gone to 33 or so just to make the transition to stealth easier. The advantage of doing that over using the EV button is that it will stay in stealth at speeds over 34mph whereas with EV the ICE will spin up briefly until you exceed 35 again.
[/b]

yeah, that's what I do sometimes. Accelerate over 35mph then stealth~

sub3marathonman · 06-21-2006, 03:14 PM

<div class='quotetop'>QUOTE(efusco @ Jun 21 2006, 01:57 PM) [snapback]274747[/snapback]</div>

Quote:

The algorythm clearly prefers to allow immediate ICE off stealth b/w 35-41, it can be very difficult b/w 30&35, but will under some conditions. The next cut-off seems to be speeds below 20mph where it usually will go into stealth, but again, not always.
[/b]

I guess it could be too that the people programming figured if you wanted electric mode under 35 mph you would be using the EV switch.

**efusco** · 06-21-2006, 03:27 PM

<div class='quotetop'>QUOTE(sub3marathonman @ Jun 21 2006, 02:14 PM) [snapback]274788[/snapback]</div>

Quote:

I guess it could be too that the people programming figured if you wanted electric mode under 35 mph you would be using the EV switch.

[/b]

Maybe, my thought was that that was considered more of an 'in between' speed where they expect you'll be accelerating to a higher speed and by keeping the ICE spinning it's 'ready to go' when you touch the accelerator.

But that's purely a guess....it may have something to do with the physics of the system or ideal MG1 RPM rate or something like that...I just can't say with certainty.

ScottY · 06-21-2006, 04:14 PM

Seems like everything is guessing at this point. Anybody has something solid on this topic?

Where are the Prius gurus?

**efusco** · 06-21-2006, 04:17 PM

<div class='quotetop'>QUOTE(ScottY @ Jun 21 2006, 03:14 PM) [snapback]274819[/snapback]</div>

Quote:

Seems like everything is guessing at this point. Anybody has something solid on this topic?

Where are the Prius gurus? [/b]

the Prius "gurus" (which I'm typically considered one of) have nothing but guesses. There's no way to know/test without asking a programmer...this is the kind of information that is secret and can only be infered by observation.

**TonyPSchaefer** · 06-21-2006, 05:30 PM

Quote:

Where are the Prius gurus?[/b]

MMMmmmm Prius gyros

donee · 06-21-2006, 07:42 PM

Hi All,

Yes, the 35 to 41 mph stealth ease was also observed here. I learned to do it in 25 F weather, and at that temp, at the end of my commute, this was the only time I could get the car to drop into stealth! With warmer weather the ease and range has expanded.

I think it might have something to do with tire friction. I have yet to find any reference on this. I remember from casual reading in the 70's that rolling resistance fell linearly with speed, as aerodynamic drag increased with the square of speed. If this is so, depending on the max rolling resistance and min rolling resistance over the speed range of the vehicle, and the aerodynamic force curve, there would be a speed where there is a propulsion force minima.

The rolling resistance of tires might be related to the centrifugal lift that the heavy tire circumference would exert. Ever see drag racers go full throttle? The large diameter wheels lift the car. I think the same thing might be happening with road cars. The more round the tire (at the higher speed) is the higher the car will be, and the less side-wall flex occurs in the tire. And this results in less rolling resistance.

Does anybody have any real references on tire rolling resistance?

06-21-2006, 01:03 PM	#1
ScottY Senior Member Join Date: May 2005 Location: Long Island, NY Posts: 1,249 My Car: 2005 Prius Model: Package: #3 Thanks: 0 Thanked 2 Times in 2 Posts Friends: 1	I've noticed this for a while now. When the speed is between ~35 to 41mph, lift my feet off the gas pedal, the car will go into stealth mode almost all the time. But when my speed is lower than 30mph, this won't happen. If my speed starts out below 30mph, ICE running. ICE won’t stop till couple of seconds after the car completely stop. From CAN-View, I know the ICE is warmed up already at that time (around 190 degrees F). Anybody know why it is easier to get in stealth mode at higher speeds? __________________ 05 Millennium Silver Metallic, Package #3 (package with SKS and all airbags) mud flaps MFD hood bumper protector CAN-View with OBD-II function Coastal EV mod mesh grill DICE iPod integration + ground loop isolated audio in "Prius" license plate frame Thule roof rack and snowboard carriers (winter only)

06-21-2006, 01:57 PM	#3
efusco Troll Slayer Join Date: Nov 2003 Location: Nixa, MO Posts: 17,231 My Car: 2004 Prius Model: Package: #9 Thanks: 49 Thanked 249 Times in 148 Posts Friends: 37	The algorythm clearly prefers to allow immediate ICE off stealth b/w 35-41, it can be very difficult b/w 30&35, but will under some conditions. The next cut-off seems to be speeds below 20mph where it usually will go into stealth, but again, not always. I intentionally keep my speed at 35mph or even intentionally accelerate to 35 when normally i'd have only gone to 33 or so just to make the transition to stealth easier. The advantage of doing that over using the EV button is that it will stay in stealth at speeds over 34mph whereas with EV the ICE will spin up briefly until you exceed 35 again. __________________ Evan E. Fusco, MD "It's a damn poor mind that can only think of one way to spell a word." -Andrew Jackson

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06-21-2006, 01:09 PM	#2
TonyPSchaefer Your Friendly Moderator Join Date: May 2004 Location: Far-North Chicagoland Posts: 10,498 My Car: 2004 Prius Model: Package: #9 Thanks: 39 Thanked 165 Times in 106 Posts Friends: 23	I always assumed that it's due to inertia. At slower speeds, you have to work to move the weight. At higher speeds, however, since the weight is already moving, it's easier to just keep it moving. I always figured that around 35mph was the tipping-point.

06-21-2006, 04:14 PM	#7
ScottY Senior Member Join Date: May 2005 Location: Long Island, NY Posts: 1,249 My Car: 2005 Prius Model: Package: #3 Thanks: 0 Thanked 2 Times in 2 Posts Friends: 1	Seems like everything is guessing at this point. Anybody has something solid on this topic? Where are the Prius gurus?

06-21-2006, 07:42 PM	#10
donee Senior Member Join Date: Aug 2005 Location: Chicagoland Posts: 2,244 My Car: 2006 Prius Model: Package: #2 Thanks: 2 Thanked 54 Times in 47 Posts Friends: 0	Hi All, Yes, the 35 to 41 mph stealth ease was also observed here. I learned to do it in 25 F weather, and at that temp, at the end of my commute, this was the only time I could get the car to drop into stealth! With warmer weather the ease and range has expanded. I think it might have something to do with tire friction. I have yet to find any reference on this. I remember from casual reading in the 70's that rolling resistance fell linearly with speed, as aerodynamic drag increased with the square of speed. If this is so, depending on the max rolling resistance and min rolling resistance over the speed range of the vehicle, and the aerodynamic force curve, there would be a speed where there is a propulsion force minima. The rolling resistance of tires might be related to the centrifugal lift that the heavy tire circumference would exert. Ever see drag racers go full throttle? The large diameter wheels lift the car. I think the same thing might be happening with road cars. The more round the tire (at the higher speed) is the higher the car will be, and the less side-wall flex occurs in the tire. And this results in less rolling resistance. Does anybody have any real references on tire rolling resistance?