Scan Gauge Dispute: At What Speed does the ICE shut off ?

You probably did not get to S4 due to low temps. ICE will shut down below 34 MPH only if you are in S4.

 

read up on stages of operation. Here is a spreadsheet with links to extensive threads.
done prior to 2010, so it applies for the 2004-2009 models (GenII).
http://priuschat.com/forums/knowled...perating-mode-availability-reference-aid.html

 

I bet there is no single threshold, but there is a hysteresis.
I don't remember the ICE stop speed, but I'm sure the ICE continues to spin at 40 mph when decreasing the speed.
The scangauge has some limitation to display the instantaneous mpg on fuel-cut mode.

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There is a delay in ICE shutoff. If you are coasting down, that could easily account for your confusion. I've seen the ICE shut down at about 60 km/hr (scangauge goes to 0 RPM). I've also seen it go to no-fuel spin from about 65 km/hr all the way up to over 100 km/hr (scangauge indicates about 950 RPM, fuel drops to 0.02 l/hr, which is the scangauge holdover for "other technical reasons"). It does often take some time for the HSD to put the engine to sleep. At a light, for example, it usually takes around 4 sec. to shut down, yet sometimes it shuts down as I coast up to the light.

So, as ken says, it's variable. I've even seen the car -not- go to S4 when it should have (based on the above guidelines). It did it to me on Sunday. Coolant up to +70C, speed had gone up to 75 km/hr, yet I was not in S4 when I slowed to a stop (engine started for cabin heat at coolant temp of 62C while waiting at a light).

 

Many thanks for this. It has helped explain why I cannot get into glide mode in certain situations. Here in Australia, all the local city councils have now brought the speed limit down to 50kph, which I now see is below the lower limit in Note A. Whilst I do not have a ScanGauge, I have noticed that the ICE will not shut down unless I quickly accellorate upt to 60kph, and then take to foot of the pedal and let the car slow back to the speed limit, then the ICE will shut down. Once I get to an actual stop and let the idle check kick in, I then get into stage 4 and all is well. The problem I have is that I do not get that idle check opportunity until some 3 km of potential glide travel.

 

A few things I have noticed. The ice will run to 940 rpm and is dependent on the coolant temp some what. It is very unlikely to shut off under 112F. If the heater is operating it is unlikely for the ice to shut off under between unless the temp is above 155-164 range. It can be helped off be simply turning off the heat. Once it hits 164 is will tend to shut off on it's own and rather quickly until the heat is dissipated from the ICE. If a glide has been used or electric propulsion, once the ice starts up it does not want to shut off quickly again until the soc reaches a set point. I have also seen the car charge up the traction battery to all green on it's own and do a complete electric propulsion up through 50 MPH with the ice turning. It's not a long period of time but can get some great mpg average improvements. Another ICE temp factoid, 112F the fan will just start and at 128F you will have full fan on auto. 184F seems to be where the thermostat kicks in with cold outside temps can see a drop in engine temp the first time hitting this in a trip. Keep in mind I may be off a little on my values since this is from memory and observed while driving. Fun traction battery fact, there are at least 2 observed levels based on battery temperature for max current in and out. Less current is allowed to enter or leave the battery when it is cold.
In short it's moody and has a mind of it's own. Between the engine temp, the state of charge and the previous running mode it decides what is wants to do.

 

The scanguage is a great tool.

However, you must also know how the car operates. You should learn the four stages of operation S-1 thru S-4 and that will help you realize what the car is doing. The stages are both temperature and time dependant.

The ICE shut off is also dependent on other factors such as AC/heat settings and defrost settings.

If all looks good and the ICE still fails to shut off, I always check the Defrost as I usually mistakingly have that on.