MFD and power flow

[lenjack]

My Prius is almost 2 months old and I'm fascinated by it and have been devouring this site. I've been through the manual 3 times and will do so again. I need some clarification on the power flow as shown on the mfd. I've noted there are times when I'm driving at a steady speed and the display shows no flow to the drive wheels, either form the ice or the electric motor. How can this be? Somethiing is powering the front wheels.

[Bill Merchant]

First, the Power screen is just almost real time, it frequently lags reality for a second or two. What you may be seeing is the very desired, no-arrows, glide mode. You are rolling for free.

When you are accellerating, power flows from the ICE or battery to power the wheels (sometimes called the pulse phase). When you take your foot off the accellerator pedal, the simulated auto-tranny drag applies light regenerative braking. But if you apply just the right pressure, not enough to accelerate, hard enough to avoid the fake drag, you are just rolling with 0.28 coefficient of drag (sometimes called the glide phase). A slight down hill or a good wind behind you, you may be able to have infinite MPG for quite a while when gliding.

Switch over to the Consumption screen, do you have a lot of 100 MPG bars?

Oh, and congratulations on driving the smartest car on the road and welcome to PriusChat!

[hdrygas]

I would suspect you are in no arrows glide. There is some energy and I have suspected that MG2 is spinning the wheels so that it will not go into regen "engine breaking" mode. Typically I will be using 2-7 amps in that mode slightly more than when I am at a stop light. The feel of the car in glide mode is very similar to the feel of the old SAAB 850 2 cycle 3 cylinder that freweeled when you took your foot off the gas. There was an automatic clutch that separated the engine from the wheels when the engine was not powering the wheels. Very strange feel compared to other cars.

[lenjack]

Thanks, but there has to be SOME power to the drive wheels. Are you saying it is coming from somewhere besides the ice and the electric motor?

[jasonko]

<div class='quotetop'>QUOTE(lenjack @ Feb 3 2007, 01:32 PM) [snapback]384938[/snapback]</div>

Thanks, but there has to be SOME power to the drive wheels. Are you saying it is coming from somewhere besides the ice and the electric motor?
[/b]

The power is not coming from the ICE or the electric motor--it's coming from momentum.

[lenjack]

I understand momentum, but how is it sustained. It doesn't appear to be momentary. Twilight Zone?

An incredible vehicle...absolutely dazzling.

[hdrygas]

<div class='quotetop'>QUOTE(J Dogg @ Feb 3 2007, 02:01 PM) [snapback]384943[/snapback]</div>

The power is not coming from the ICE or the electric motor--it's coming from momentum.
[/b]

If that were the case why do I see higher - Amps than when the car is at rest on CAN View during glide on the MFD. With the V4 Can View I have both the Energy Screen and the CAN View on the Lillput touch screen at the same time to compare them. Some electrical energy is going to MG2 to move the PSD at the speed necessary to keep it neutral with respect to wheel speed. If your foot is completely off the gas regeneration starts to simulate engine breaking. The MFD does not show all of the energy flows.

[donee]

Hi Lenjack,

There can be a variety of reasons the car may move along at the same speed without any power from the drive system.

You could be going downhill, and if the steepness of the hill is enough to overcome the friction of the tires the car will maintain, and even speed up. The brakes on the Prius seem to have very little parasitic drag. And of course, there is no fluid torque converter drag. So it will coast along, or even speed up if you let it down hill.

Another reason is suction from trucks. If the wind is in the right direction, and the truck upwind, and moving fast, the truck can tow you along by aerodynamics. This takes allot of wind, but we are moving toward the time of year when that commonly happens in the midwest here. And on the west coast they have the the Santa Anna winds.

At slower speeds with strong winds, the wind can even push the car. Say a 40 mph wind at 30 mpg vehicle speed.

[TonyPSchaefer]

<div class='quotetop'>QUOTE(lenjack @ Feb 3 2007, 04:34 PM) [snapback]384949[/snapback]</div>

I understand momentum, but how is it sustained. It doesn't appear to be momentary. Twilight Zone?

An incredible vehicle...absolutely dazzling. [/b]

I had to laugh when I read this. I just thought it was funny.

If you were able to maintain the "no arrows" glide, you would eventually come to a standstill. Trust me (us), the Prius rolls very easily and you can glide with no arrows on flat terrain for a relatively long distance.

Enjoy the ride.

And it would seem that you are making up for all those people who refuse to read the manual. Good for you!

[ukr2]

Glide Mode -

Trying to Pulse, then release the accelerator, then slightly pressing the pedel to turn off the regen arrows to get to Glide Mode can be tricky.

I wish we could get a Glide button on the Cruise stick.

I also wish the computer would use more EV Mode, instead of using the ICE and getting under 20 mpg driving under 40 mph without having to install an EV button.

Does anyone have info of the logic tables used by the computer when Cruise Control is used to increase and decrease speed? Does calculated mpg have any affect on the logic?


ukr2