EV Position Confusion?

EV mode offers power in the WHITE zone...



...which is why the top speed for it is limited 24 mph. But you can take advantage of that (once the system is warmed up) in a variety of situations which would otherwise cause the engine to start.

STEALTH mode is limited to the GREEN zone, but with it you can drive in electric-only up to 46 mph. That's automatic too, no need for a button.

 

EV mode will also allow "driveway" maneuvers even if the car has cooled down for a while. It will cancel out of this if you get much above a walking pace, but it saves starting up the ICE just for getting the car in and out of the garage.

 

In order to lower emissions the car will run the engine soon after you turn it on in order to help it get up to normal operating temperature. If you are just turning the car on to move it a short distance, such as on a driveway or a parking lot, it's more efficient to use the existing charge and avoid the unnecessary, inefficient warm-up cycle.

You're right that at the end of a journey the car is usually warmed up enough that it doesn't have to run the engine anyway, but after the car sits for a while it'll cool down enough that the car would again run the engine to complete the warm-up, so you can use EV to tell it that it shouldn't bother.

As you note, the same acceleration is always available. Driving in ECO, you simply adjust to pressing the pedal harder if you need it. I accelerate at the top of the eco zone and can hit it easily without going into the power zone.

PWR makes it much harder to control throttle at low demand which leads to inefficiency through lost glides and excess throttle in most driving.

As I noted above and John noted in his post, while EV mode is limited, it does have its uses.

 

Just to add to the confusion...

Unless you're driving a PIP (avail. '12 and up only, so not you) or add-on PHEV kit, you should NOT use EV mode except in very LIMITED circumstances. This is because for a non-PIP Prius, ALL electricity in the battery comes from running the ICE. This is true whether it comes from regen braking or direct recharge from the ICE.

Conversion loss from going from gas to electricity, to battery, from battery to electricity, to electric motor...to wheels, is much greater than going direct from ICE to wheels.

A hybrid gains its efficiency by NOT wasting momentum as heat (regen braking) and shutting off at stoplights, etc. when not needed.

Guidelines for EV mode:
o use for moving short distances (driveway/parking lot) where starting ICE is inefficient
o use to kill ICE (FAS) at stoplights, etc. before warmup complete (turn off as soon as you start moving again).
o use if HV battery is full/over-full.

Most anything more than above results in decreased mpg.

 

Add to that "neighborhood hill climbing", for lack of a better term.

Both directions for entering my neighborhood require a quick & steep climb, then slow driving following. EV was great for that. I could get from the main road all the way to my house with the engine off using EV mode.

Interesting, that's something I cannot do with the PHV... since it doesn't have that particular button. Once you use up the plug-supplied electricity, the HV capacity isn't accesslible like it is for the 2010-2012.

 

What they said above.

 

I use stealth to sneek up behind the guys I work with when they're standing in the parking lot smoking. You should see them jump.

I use EV on the way home. There's a short, steep hill I go up where EV keeps the ICE from starting up. On the other side, there's a long slope that allows me to glide home.

 

That was the term coined back in August 2000 to identify when the Prius is propeled with the electric motor while the engine is stopped.

Then many years later, when the EV button was introduced, it turned out that there where 2 distinct sets of electric-only power & speed tolerances. So, it made sense to continue using STEALTH since it was so different from EV.