Purpose of Buttons (EV/ECO/PWR)?

No there is actually 4 operating states..or modes but only 3 buttons. No button pressed is "Normal" mode, which is suppose to be a compromise between ECO and POWER that simulates a "normal" driving feel the best.

There are actually differences. Most notably in the mapping of the distance to depress for reaction from the accelerator.

I use ECO the most, efficiency is a priority to me. Since it's a big reason I bought a Prius, I keep it in ECO mode the most.

I hardly ever use EV, and only use Power when merging onto a busy highway. "Normal"? Well I've experimented between ECO and NORMAL, and the functional difference seems minute. Evidently the operation of the air conditioning is adapted with ECO mode, so that's another reason I use it.

 

not to mention the owners manual...

 

The service tech told me that the throttle plate position is what changes between PWR and ECO along with the AC output. EV (battery only) is good for about a mile depending on the state of charge when you begin.

 

Sigh.

Hokay. Put up your Cartesian coordinates. Bottom axis is "gas pedal depression". Left axis is "power demanded of engine complex". Draw a 45-degree line starting at the origin and going up and to the right a ways. All the way to the right end of this line is the terminal point, which is maximum engine complex power.

1. Normal mode. No lights on the dash. The further one presses the gas pedal, the more power one gets out of the engine complex. Push the pedal all the way down: Max power. If you're not in Normal, then pressing the mode you're in (Power, Eco, or EV) again puts you there.
2. Eco mode. Modify the curve so it's concave down (i.e., it sags in the middle). In this mode, if you're in the beginning part of the range, it takes more movement on the gas pedal to get different power levels: That is, the engine can be "feathered" easier. Press the pedal all the way down: Same max power as in Normal mode. If you're not in Eco, pressing the ECO button puts you there.
3. Power mode. Modify the curve so it's concave up (i.e., it pushes up in the middle). In this mode, if you're in the beginning part of the range, a little movement on the gas pedal results in a big change in engine complex power level. Max power is still max power when the pedal is all the way down but, in the beginning part of the range, it kinda feels like somebody stuffed a Corvette engine in there. If you're not in Power, pressing the PWR button puts you there.
4. EV Mode. Weird. Only works if the engine is warm and/or the outside temperature is above 68. You can do electric drive only for a mile or so, but:
   1. If the engine is cold and/or it's below 68 F outside, the car won't allow it.
   2. If you try to go too fast (above 25 mph?) it'll pop you out.
   3. If you discharge the battery too far it'll pop you out.
   4. If you push down the gas pedal too far it'll pop you out.

Nobody knows exactly why EV mode is in there; there are people around here who have claimed that they used it in a traffic jam, but, if you've driven into a traffic jam, you probably had the car running in electric below 35-40 mph anyway. It's handy for running around a parking lot, I guess, with a "cold" engine on a warm day. I use it when backing out of the garage, so long as it's not winter, in which case it wouldn't work anyway. Probably the least used mode on the Prius. I think Toyota stuck it in there for the cache.

If you haven't figured it out already, the Prius is fly-by-wire. That is, there's no cable going from the gas pedal to the throttle. There's a couple of Hall-effect sensors at the root of the gas pedal that feed into the engine control computer, so all these changes in engine response vs. pedal angle is strictly under software control.

Minor but interesting things: If you're in ECO mode, the AC/Heat and fans are put into a lower power mode, the better to save gas with. If you're in Power mode the "ECO" light in the display goes out and stays out, whereas when you're in ECO or Normal it goes on or off depending upon how much throttle you're asking for.

$RANDOM posters have claimed that they got better gas economy in ECO/POWER/NORMAL mode, thus gaining local fame. The truth.. Who knows? I guess that ECO might get better, but if it does, it's probably because of (a) better control at low speeds and (b) the air conditioning fan running slower. Neither of these is much. Me, I find Eco useful for tooling around town (better feathering in turning the engine on and off and not jerking the car), Normal for the freeway at speed, and Power when going up steep hills. The last of this list is actually endorsed by Toyota in the manual.

Basic rule with the Prius: Just drive the blame car.

KBeck

 

... which contradicts what Toyota and its individual Prius engineers have told the world and the PC honored guests at special introduction events.

 

Silly me, and I believed him. I now stand corrected.

 

It is technically correct. It changes the throttle plate position in relation to the accelerator pedal position. The button remaps it.

 

I like to use the B as well.. it charges my battery faster when I come to a stop. its like down shifting but with MG2.

 

? really?

 

It is much easier to maximize mileage using ECO mode. Even at freeway speeds, the accelerator position is easier to control, resulting in better mileage opportunities. There is nothing available in normal or PWR modes that is not available in ECO. other than the fan control as noted above. I do not understand the need to go to PWR when accelerating....the same power is there in ECO, you just need to push the pedal down a little further. Over-accelerating unnecessarily is a major mileage-loss factor. The difference in segment mileage between 1/4 power bar (above midway) and 3/4 is substantial.

 

In the trivial sense, yes, it is technically correct. Just about all changes in power in regular cars are performed by moving the throttle plate. By moving the throttle pedal.

Of course, I responded based on the Toyota's indications that the available throttle range and power levels for each of these modes is identical, it is just the mapping curve between the endpoints that changes. The endpoints themselves are fixed.

When it comes to charging the battery, B mode cannot beat optimal use of the brake pedal. And when engaged at high enough speed to spin the ICE (about 25 mph), B mode cannot even equal optimum braking.