I just installed a Scan-Gauge and noticed something interesting that I didn't expect. At speeds under 35MPH, during no-load conditions (glide, coasting down hill, etc.) the ICE turns off and the Scan-Gauge shows 0RPM (This part I expected...) Above 35MPH, though, under similar no-load conditions it appears as if the ICE is on. The indicated RPMs are in the neighborhood of 940-960 (idle?). This is with a warmed up engine. Coolant temp is between 160-180 degrees F in either case. Not having any information to the contrary, I would assume that this is the intended behavior but at the same time, it's not the behavior that, in my infinite ignorance, I would have expected. Can anyone confirm that this is what should happen and perhaps educate me on why the car behaves this way? Thanks!
at 35mph.. or 36.. whatever it is... you've reached the max rpm for the electronic motors. everything is based off these ratios... so the engine has to start spinning or they will burn up. looks up more info on "prius psd" this, for example... {Link}
For the 2010, the 0 RPM threshold is 46 MPH. That 35 was just an anecdotal observation. With the scangauge, you'll easily be able to confirm this. There are many factors which influence Stealth mode (automatic electric-only), like coolant temp. Draw from the battery is a big influence. Pay attention to the Eco-Meter. The green zone is for Stealth. Once you hit that color change to white, the engine will start back up. That doesn't mean it will run for long. But it won't necessarily stop afterward. It will sometimes just spin without using any gas. .
I will specifically tool around town at 34 mph pissing people off behind me so that I'll run on the electric motor instead of the ICE in my '05. Hey, that link is pretty cool to play with, its kinda neat what happens when you set the MPH at 34 and have all the sliders in a horizontal line.
As John pointed out the actual threshold, assuming the battery is up and the engine is warm, is 46 MPH. If the engine is off I can creep up to 46 on a down hill slope before it starts if I keep the HSI to the left of center. If the engine is on I can't get it to go off until the speed drops below 41 MPH.
Quite right. Since I had more important things to do (like avoiding hitting other cars, street furniture, and pedestrians) no attempt was made to measure the threshold accurately. I figured a rough guesstimate would be sufficient to get the answer regarding the observed behavior...
