I have started coasting in Neutral (hold lever for 2secs in N). The ICE turns off and the car coast beautifully. This is inherently more efficient (to achieve speed and then coast to a stop) than accelerating and braking as the regeneration process produces heat (both tyre friction and heat from generator). My only question is - is it detrimental to the car in any way ( I assume not as why would Toyoya allow that option) but would like a techies answer if possible. THanks from far away New Zealand

Hi,
I can't answer for the NHW20 models but I've seen some interesting characteristics with the NHW11 Prius:

1) coasting down a hill in neutral after engine has stopped - the ICE does NOT come on at 42 miles per hour to prevent MG1 over-reving. Potentially dangerous since MG1 is rated at 6.5k rpm.

(NOTE: I need to repeat this test with the mini-scanner to confirm the observation.)

2) coasting up a hill in neutral with engine running - the ICE continues to run even as speed drops below 42 miles per hour. This is not a problem beyond the minor fuel consumption.

Otherwise, I see no problem with coasting in neutral. As a general rule, you'll go from a higher to lower speed and if the ICE is running, there is no problem. Since the NHW20 has a higher MG2 redline, 10k rpm, it is probably OK.

Bob Wilson

Operation Iraqi Oil Freedom:

Automatic, stock, project car.

My other 1500 cc car:

Automatic, stock, backup car.
Free speech, dialog and knowledge thrives without the poison of SPAM.

It's never okay to coast any automatic transmissioned car in neutral for extended distances. For manual transmissions it is fine but not automatics. I think it is even worse if you coast in neutral with the engine off.

Hi,
For an ordinary hydromechanical transmission that is true. However, the Prius transaxle is substantially different and not subject to the same limitations. For example, the transaxle oil pump is driven by the ICE. Often, when running in 'stealth mode', the transaxle has not oil pumping.

Our Prius transaxles use the oil pump to 'sling' cool the motors as well as lubricate the gears. There is no high-pressure lubrication involved. One of the better places to study the transaxle starts here:

http://eahart.com/prius/psd/

Understanding the HSD is not easy.

Bob Wilson

Operation Iraqi Oil Freedom:

Automatic, stock, project car.

My other 1500 cc car:

Automatic, stock, backup car.
Free speech, dialog and knowledge thrives without the poison of SPAM.

Thanks, I have a gen III 2004 model. When you put it in neutral the ICE always switches off, charging and discharging go blank. There is no sense that you are dragging any transmission, it feels like complete disengagement from both engines and freewheeling. The input regarding neutral in automatics is good as this is no automatic!! What I am surprised at is why noone uses this option - never seen it in any fora.

The Gen III is out already?

As an experiment, open the hood tomorrow before starting the car; put the parking brake on; start car; and shift it into neutral. I suspect you'll find the engine continues to run.

The accepted definition of neutral is bascly all power to and from the MGs is turned off. If you go by the MFD, it will look like the ICE is off. If you go by a ICE monitors, it is less predicatable.

Bob Wilson

Operation Iraqi Oil Freedom:

Automatic, stock, project car.

My other 1500 cc car:

Automatic, stock, backup car.
Free speech, dialog and knowledge thrives without the poison of SPAM.

I think I commented that four days ago.
http://www.greenhybrid.com/discuss/s...92&postcount=5

Ken@Japan

Hi,

I don't know about NHW-11 Prius, but the transaxle oil pump is driven by the ICE on NHW-20 Prius.
So, there is no oil pressure on the engine-off coasting.

Ken@Japan

The same is true with the NHW-11.

Bob Wilson

Operation Iraqi Oil Freedom:

Automatic, stock, project car.

My other 1500 cc car:

Automatic, stock, backup car.
Free speech, dialog and knowledge thrives without the poison of SPAM.