How To Drive A Prius

I see you are from Florida. Won't work there as the first requirement is a cliff.

 

As the term is frequently used here at PriusChat, "glide" means the vehicle is moving with the Internal Combustion Engine (ICE) off, and only minimal power being drawn from or sent to the hgigh voltage (HV) battery, typically less than 7 amps.

A glide can only begin below 41 mph, and only when the ICE is sufficiently warmed up. Unless you have an EV mode modification, it may require a full stop for a few seconds after the ICE is warmed up so that the vehicle can complete an "Idle check". The following information assumes you don't have access to any aftermarket gauges (such as ScanGaugeII).

When learning to "glide", if the ICE is running and the vehicle is traveling less than 41 mph, lift your foot off the accelerator briefly (just long enough to notice that the ICE has shut off). At this point you'll see on the "Energy" screen of the Multi-Function Display (MFD) green arrows indicating power flowing from the wheels to the battery. This is typically referred to here at PriusChat as "coasting". Next gently press down on the accelerator until the energy-flow arrows disappear. You are then "gliding". The electric motors are essentially free-wheeling, and the ICE is off so the powerplant resistance to your forward momentum is at a minimum.

If you press a bit too far you'll see arrows indicating energy flowing from the battery to the wheels. You then need to let up on the accelerator slightly and slowly until the arrows disappear again.

If you see arrows indicating energy flowing from the ICE, then one of the following has happened:

1) You didn't leave your foot off the accelerator long enough for the ICE to shut off.
2) You pressed back down on the accelerator too far or too hard and the ICE has started back up.
3) The HV battery is too discharged for the vehicle to allow gliding.
4) The ICE hasn't yet reached a warm-up stage that will allow gliding.


(there may be another reason or two that I have forgotten about)

Note: While it is generally discouraged, and may not be safe, it is also possible to "glide" by switching the gear selector to "Neutral" below 41 MPH once the ICE shuts off.

 

They're steep, but not long enough that one would overheat the brakes coming down. Mt. Hamilton, now, *that* calls for "B".

 

Watch the "Energy" display on the MFD. When there are no arrows into or out of the wheels, that's gliding.

 

Unless you are traveling faster than 41 MPH. In general here at PriusChat it isn't considered "gliding" if the ICE is spinning.

Additionally, I think the question was "how to get there" not "what it is" or "how to know you are there".

That's sort of like someone asking "How does one get to Chicago" and being told, look out the window, when you see the Sears Tower, you're there.

 

Good golly, what a lot of advice from people who know how to drive a Prius. .

Let me start with the theory, then you can work out for yourself what that means in practice. For you.

All of the energy to run the Prius comes from gasoline. Gasoline engines have an efficiency peak. For the Prius, that comes (per Hobbit's posting from long ago) around 1800-2200 RPM at about 55% engine load. You'd need a scangauge or equivalent to know for sure if you're in that range. For a given amount of energy output from the ICE, the more of it that occurs in that peak, the better.

So, to get to the point up front, for optimum mpg, for given set of constraints (getting from A to B in a given amount of time), you want to run the Prius ICE as if it were a spacecraft jet engine: run it at the optimum thrust (the range per above that gives the best conversion of gas to forward motion) or shut it down.

Why? Because you lose 20(?)% in the round trip through the battery. So only if the losses from running the ICE in an inefficient range exceed the losses of running the power through the battery, only then does consciously using the traction battery make sense. Otherwise, trust the Prius software to do what's right (aka just drive it).


The native Prius software will largely do that, with two significant caveats.

Caveat 1 is hysterisis. If the ICE is on, the Prius will tend to leave it on, if its off, it'll tend to leave it off. So, I think there's room for improvement with the "forced auto stop", meaning, once you're up to speed, lift your foot off the gas for a moment and then see if the Prius will go all-electric. If so, you've just done a "forced auto stop" and I think that'll help your mileage.

Caveat 2 is anticipation of the terrain. If you just put the Prius into cruise control, it'll look no further than the current values of speed and desired speed. But you are smarter -- you can see what's up ahead. And slow down uphill and speed up downhill as required. So, in hilly terrain you can beat cruise control. Same as in a regular ICE-only car.

Otherwise, just drive it.

So, for the typical urban driving cycle: Accelerate fairly briskly using the ICE (do not use the battery to creep away from stops, that wastes gas). Once you get up to speed, see if you can shut down the ICE by briefly lifting your foot from the gas pedal.

Thththat's all, folks, in terms of practical advice. Otherwise, trust the native software to optimize for you.

There are minor issues related to delaying starup for those with an EV switch, but otherwise, that's about it. If you want to beat the native software, either you defeat the built-in hysteresis (because you understand that the ICE can be off for a long while, but the Prius cannot know that) or you allow speed to fluctuate in response to terrain in ways that the cruise control will not allow.

Otherwise, just drive it.