so if one just drives in the city and always coasts under 42 mph, then there should be no problem since one can just shift into D and start driving immediately since the flick from N to D should be quick (at least in a NWH11 prius). Although it seems easier just to get into deadband mode rather than playing with the shifter all the time.

Bob have you tried deadbanding in your car? If so how hard can it be? (I found it was pretty easy when I drove a NWH20 for my first time).

 

Gen III refers to 2004-2007 model years, though it's sometimes mistakenly referred to as Gen II. The first generation was sold only in Japan beginning with the 1997 model year. See this for a great discussion on the Prius' history (along with other useful links):

http://www.cleangreencar.co.nz/page/...-model-history

(Not to hijack the thread....) I see you've posted many Prius-related questions recently. Not to detract from the substantial knowledge and helpfulness of members here, but you might consider also checking out these sites if you haven't already:

www.PriusOnline.com
www.PriusChat.com

PriusChat is the more active of the two (with both substance and fluff, I might add). But it's had a lot of downtime recently, including as we speak. It was hacked into a couple of months ago and had a major crash more recently, and I don't think it has completely recovered from either. But it's great when it's up.

Searching either site will answer most Prius-related questions, though it might take a little persistence depending on how unique your search criteria are. The archives are extensive.

 

Hi Phil,
First one caveate: most USA driving codes forbid putting the car in neutral when on a downgrade. Granted it is hard to enforce but it is in the code.

I plan to configure the mini-scanner to record the shifter position and ICE speed to see if we can map out the exact control laws that govern ICE operation in neutral. I've seen cases where in neutral, the ICE stays in the last state, either at idle or off, even after transiting 42 mph, but I really need to record the data.

I use cruise control except during the low-speed, warm-up. In the morning when the car is cold, I use "N" to coast along neighborhood streets. This minimizes the fuel burn during the warm-up but in all other cases, I use cruise control.

So far, the cruise control seems to be fairly effective but I have a design to automate the accellerator with a microcontroller. If it works as expected, it will automate all energy saving modes, 24x7, for any driver including my non-technical wife.

BTW, I'm finding that analysis of mini-scanner data has revealed other energy losses not widely reported in the past. For some of the details:

http://hiwaay.net/~bzwilson/prius/pri_power.html

Bob Wilson

 

I drive a Gen 1 HCH with a manual tranny and I coast ICE off all the time. The Prius however can get fantastic mileage without the need to coast in this manner. I'm not exactly sure how to do it since I don't have a Prius but there is a way of monkeying with the gas pedel to do a medium speed "glide" that will get you 100+ mpg. I'll see if I can find the technique.

 

Here you go:

http://www.cleanmpg.com/forums/showthread.php?t=1224

http://hybridcars.about.com/od/owner...seandglide.htm

 

Hi,
I tried to find the word "neutral" in both articles but didn't have any luck. Is it spelled some other way?

Not to worry, I've added the first link to the Prius FAQ. I've never had a problem with adding good references and thanking the source.

Bob Wilson

 

Exactly, if you have a Prius you don't do the ICE off neutral thing. My point entirely.

 

Hi,
Too bad the articles you referenced made no reference to neutral. Drivers are free to coast in neutral as long as they are not going down a hill.

In fact, neutral simply disables all power to and from the motor generators. Without power, MG1 can no longer start or stop the ICE. Without power, MG2 can no longer provide an accelleration boost or regenerative braking. The traction battery continues to supply power and the inverter continues to provide 12 VDC power. But the MGs have become so much dead weight and the ICE continues to run or not run in the state when "N" was entered.

Prius drivers quickly learn they can shift between "N", "D", "B" and even "R" while rolling down the road. The real question is whether or not there is a risk to the vehicle associated with use of "N" and the answer is yes and no. This evening I used my mini-scanner to confirm these observations:

1) Above 42 mph, it is OK to go into "N" and coast or brake down to a stop. The ICE will remain running even if at a complete stop until the car is put in "D."

2) Below 42 mph with the ICE auto-off, it is OK to go into "N" as long as the speed is kept below 42 MPH. However, if you coast down a slope with the ICE off and exceed 42 mph, MG1 will rotate faster than 6,500 rpm, the reported redline of an NHW11. This evening I had MG1 spinning at 7,000 rpm but that doesn't happen if the Prius is in "D". ("The law also forbids you to coast downhill with the transmission in neutral." Alabama Driver's Handbook, pp 74. The status of 'off ramps' is not specified.)

3) As for use of "N" when the car is cold, "N" puts the fuel injectors on the minimum, idle interval. Coasting on a flat surface in "N" will get to the end with less fuel burned than coasting in "D."

4) When travelling above 65 mph, putting the car in 'N" is safe. The ICE is already running and as the speed decays, the ICE rpm follows a simular decline. MG1 is not at risk of exceeding 6,500 rpm.

To make these factual observations, I configured my mini-scanner to monitor (1) shifter position, (2) MG1 rpm, (3) MG1 torque, (4) ICE rpm, (5) fuel injector timing, and (6) MG2 rpm. I recorded the data Wednesday morning and will share it later today.

Bob Wilson

 

I didn't know....thanks!

 

For those interested in data, I've put together a quick web page with graphs showing use of "N":

http://hiwaay.net/~bzwilson/prius/pri_neutral.html

NOTE: The NHW20, the 04-current Prius, has a thermos of hot coolant to rapidly warm-up the ICE. My testing was with an NHW11 Prius that does not have this feature.

Bob Wilson