Is "Gliding" a Programmed-in Prius Illusion?

The short answer is, yes, it is an illusion.

The "no arrows glide" isn't a true zero energy glide. The closest to that you
can get is to be in Neutral. Go here for the whole story:

http://priuschat.com/forums/prius-t...parison-methods-pedal-control-vs-neutral.html

It is important to recall that the Energy Monitor its a rough approximation of
what's going on in the HSD -- the Elec. Motor is really two motor/generators.
Somewhere I have seen the Energy Monitor called a "mimic." OK, and a
simplistic one at that.

 

Hi ekpolk,

The true glide in a Prius is very temperature sensitive. To be sure to drop be able to drop into a engine off glide, one needs to have the coolant up to 90 C. Below that , there are various temperature ranges it will do a true glide, but sometimes not, for some reason. The Prius display will often display no arrows while the engine idling along. If you get a tachometer and coolant/engine temp gauges, you can see this action.

So, the thing is, are you getting that big engine and its catalytic converters up to temp ? Maybe you need some grill blocking, even down there in FL?

 

This is a guess, not knowledge:

Perhaps the folks programming the display put in a smaller deadband range in the TCH than the Prius.

I think, but am not sure, that with the Scangauge II hooked up in a Prius to display traction battery current you can find out a small range of positive and negative current over which the arrows are off--not a zero range, even though the SGII display of CAN-bus data is itself both quantized and time-sampled instead of "real truth".

If a traction battery current code is known for the TCH, perhaps someone with an SGII could take a look?

Surely the right goal is to get the pedal close to the position that is the cross-over between current in and out. Seeing arrows off actually blinds you, so the TCH display choice may help you get a bit closer to the ideal.

 

I agree.
I can't comment about the TCH because we don't have the TCH in Japan.
However, the 2001-2003 NHW11 Prius owners are saying it is very hard to do no arrows gliding.
I believe the 2004-2009 NHW20 Prius has a wider display deadband range.

Ken@Japan

 

It is very difficult to get into glide mode in my TCH. It only happens when going down hill and it last about 5 seconds., no long glide.

 

After using a ScanGauge for many months, I've come to realize that gliding is really two things: the engine is off and the current into/out of the battery is minimal. Not zero, minimal. It is nearly impossible to get zero battery amps. On the MFD, with the arrows gone, it may appear that there is no energy flow, but it's there, just very slight. I've seen it as high as 5 amps in/out and show no arrows. In fact, with the engine completely warmed up and the car in park, and no accessories running, there will still be about 1.5 amps being discharged from the HV traction battery. I think this trickle current is the minimum "self sustaining" energy necessary to charge the 12 volt battery and power all the car's electronics.

So the whole point of "gliding" is to minimize the battery current. If you can feather the accelerator to maintain +/- 5 amps, that is good enough to call it a "glide". I'm using 5 amps as an arbitrary number. The goal is to minimize it during a glide, but not obsess over the exact magnitude or the lack of arrows. The arrows are a useful tool for those without a ScanGauge.

The reason to minimize the battery current is that usage of the battery is actually an inefficient use of energy transfer. You can minimize this inefficient energy transfer by minimizing battery current during a glide.

 

Aha--an SG-II in place to answer the question: what is the deadband between in arrow and out arrow? If you have the required XGauge definition and thus can answer that for the car in question, and you or someone else for current generation Prius, we'll have an idea whether this difference is real or Memorex.

If no one else volunteers on the Prius side, I'll pull my SGII out of my A4, wheedle use of the Prius from my wife, and submit a deadband estimate based on observations of our 2006 Prius.

 

What I have found from my SG, there is about a 1.0 amp draw on the HV pack when in a "N" no-arrows glide when the headlights are off. When it's dark and the lights are on, the draw goes up to around 1.6 amps. I have seen as high as ~16 amps going into the HV pack when the speed reaches 37 mph. Once you get above 37, the SG reading goes back to the 1.0 or 1.6 amp level. This charge going into the pack begins to show up at around 32 mph. I should note that when gliding(no arrows) and still in "D", the current draw on the pack is around the 2-2.5 amp level. When the SG is showing the charge going into the pack there is a very noticeable feeling of drag. In light of this, I try to keep my Pulse speed at or below 31 mph since the majority of my driving is on rural county/country roads.

 

You're talking Prius, not TCH, right? If you have some X-Gauge commands to get this info for the TCH I'm all ears. I've had my TCH for about a year and a half, and the X-Gauge same time, but cannot anywhere find any X-gauge commands (or the related CAN codes) to give battery SOC or current for the TCH. They're not the same as for Prius. I've tried. Any ideas?

 

Just a thought. Perhaps the percieved glide is merely that "sweet spot" or visual representation where you get the best fuel economy in Prius 04-09.

 

Hi Spitnuri,

The glide is where the car rolls along without the engine rotating. It actaully does happen. The display screen in the Prius will be all blank, but there are times when the Prius display screen is all blank, and the car is idling the engine. In both cases above about 20 mph, the display will read 99.9 mpg. But, with the engine off, the instantaneous fuel economy is infinite. As one slows below 20 mph, if the engine is idling, the instantaneous fuel economy will drop down below 99.9 mpg, but not if the engine is truely not turning.