I have a Prius 2, and recently was driving a Civic Hybrid.

In the Civic you use the accelerator to decide on Coast mode - you press it very lightly and the engine turns off and nothing happens - you just roll.

So, in the Prius I attempted this same thing below 40mph and to my delight this exact same feature existed - once you're cruising, you can get everything to turn off if you lightly press the accelerator.

However, in high-speed California the times I could most use this are above 70mph on flat land or downhill. I can't tell why but no matter what I do, I can't get the engine to do nothing above 40 (or perhaps that magical 42mph number). I press it lightly and I see the ICE pushing; I let up just a little bit and I see the ICE off with the battery doing regen; I can't seem to get it to just coast.

So, what's the best strategy here? Should I just shift into Neutral? I'd like the engine available to speed up, especially battery-only, going downhill in these scenarios, but for the most part I'd like to just coast.

 

At speeds above 42 the ICE will always be spinning. However, you can get something that some people have called "warp stealth", which uses the battery to keep the ICE spinning. I've successfully used this technique in my daily commute when I have fairly lengthy downhills. Just be aware that if the downhill is steep enough you will accelerate. So keep an eye on anyone in front of you. And you'll lose speed once on level road. But if you transition from the warp stealth to an iMPG of about 75, you'll be able to hold your speed longer.

Some great resources:

• This article from CleanMPG discusses pulse & gilde plus warp stealth.<

• An old article on PriusChat describes the 5 stages of Prius operation.<

• You can also check out Hobbit's Prius pages for a lot great information, including a very in-depth discussion on warp stealth.<

 

How much have you been improving fuel economy using the "warp stealth" technique?
I was asking Hobbit about that many times, but he could never show the data.

My recommendation above 42 mph is just drive using the CC and relax.
You'll be tired and doing scatterbrained driving to watch the MFD for keeping "warp stealth" mode.

Ken@Japan

 

So I just coasted through a LOT of info in all that.

It says in a couple places that the ICE burns gas in Neutral..? Why is that? That's really unfortunate, it would sure make Glide a lot easier, and it would sure make that shifter's location and style make more sense.

It does make me feel better about attempting to get the engine to shut down above 70mph though - it sounds like it just can't be done. Either the battery is absorbing, the battery is firing, or both are firing, but it's never truly just off. I guess it might endanger MG1?

 

I recently learned the European Prius has a bias built into the speedometer that makes it read higher than the actual speed. Without going nuts about it, it is possible the speedometer may be misreading the speed. If you get a chance, how about 'benchmarking' the speedometer versus a stopwatch and mile markers next time you are out?

You are running into serveral problems not the least of which is the lag of the display and what is actually going on. Some of us have installed instrumentation that is 'real time.' The MFD is really more 'eye candy' than engineering data.

You have options:

1) 'Fo Gat A-buoot it' (Gangster accent) - just set the cruise control and enjoy the ride. You can get reproducable results letting cc handle the speed and enjoy the ride.

2) master driving with a time-delayed display - think about it as if you had a steering wheel that had an huge amount of 'play' in the linkage. You start to turn, nothing happens . . . you turn some more and nothing happens . . . you start to turn again and you're HEADED FOR THE DITCH!! To drive by that display, you'll have to develop a feel for the delay. Then put in an input and wait for the effect. After the delay, try again. . . . It won't be fun.

3) put in your own instrumentation - a little more challenging but you'd basicly put your own instrumention in the engine compartment and other places and build up your own display. For 'gear heads' like me, this is fun:

http://home.hiwaay.net/~bzwilson/prius/magnetic.html
http://home.hiwaay.net/~bzwilson/prius/motor.html
http://home.hiwaay.net/~bzwilson/prius/pri_tt.html

4) put in a computer - but this is a little more involved:

http://home.hiwaay.net/~bzwilson/auto_glide/Auto_glider.htm

5) neutral downhill - most states have a traffic law against coasting down a grade 'out of gear.' It dates for the 1920-30s when brakes and engine braking were not as advanced as today. IMHO, neutral is easy but like speeding, illegal. Just remember that "B" is your friend and will help slow you down without risking overheating your brakes.

Bob Wilson

 

Hi Bob, that Auto Glider link seems to be dead; did it move? I'm not necessarily installing one but I have brief fleets of imagination where I'm capable of working on a car without causing disaster. Then reality returns.

 

Hi,
I was running out of space and needed to free some space.

What I'd like to do is post the 'as built' in a couple of months.

Bob Wilson

 

Way to go, looking forward to it.