Power Mode anecdote

I'm sure the vast majority of owners do exactly as you suggest and get great mileage compared to what they drove before.

Then there are a bunch of us, many of which it seems you can find around here, that are curious just how to best to use the computer to optimize their mileage. Much of that does focus on watching the road, not the dash.

Since I spent a long time learning to coax the city mileage on my Yukon up from 12 to 16 mpg before I got the Prius, I'm one of those that ended up curious.

I have no doubt, given the driving habits I'd already established before getting the car, that no tank would be under 50 mpg for me without paying much attention at all. For others, including members of my family, that number drops into the mid-40's.

A 20% improvement (45 mpg to 55 mpg) translates to a savings of 60 cents/gallon at the pump, which I think a lot of people, Prius owners or not, would be interested in. There would be lines around the block at a station selling gas for $2.15/gallon today.





For some of us, it's just fun to try for more. That the computers already do such a great job is what makes it so challenging.

 

45% better than my Civic driving in town. This works for me with normal driving habits.

--Mickey

 

If find ECO fine for driving in the City with minimal acceleration requirements. If I have hills(which I don't normally), I find normal and sometimes the power mode to come in nicely. I do most of driving on the freeways highways and you have to drive in the power section or you take way too long to accelerate for highway/freeway driving. So I would say just get there and level out....and enjoy.

--Mickey

 

I now use PWR mode exclusively because there is no observed hit to the MPG and the car is noticeably more responsive.

Anybody know how to make PWR the default mode at startup?

 

I believe if you turn the car off in pwr mode, at next restart it will remain in pwr mode. I have only had to use pwr mode on a few occasions, one was to catch up to someone who almost hit me and another vehicle. To me, pwr mode allows you to accelerate at a faster rate than eco. Try this; have the car in eco mode and from a stop, smash the accelerator pedal while timing your 0-60mph run, then from a stop do the same thing in the pwr mode. You will find that in eco the speedo increases in approx 1 mph increments per second (not accross the entire hp band), while in the pwr mode it will increase at a faster rate. Similar to using your accel button while on cruse control.

 

The car will not stay in power mode after a restart. It defaults to ECO.

 

Goes to show how often I use pwr mode. Again, if you need to blaze out of your garage then you will be switching to pwr mode often.

 

Further Power Mode speculations:

Because there is little direct mechanical throttle linkage to the ICE and, presumably, throttle control and direction is all software based, wouldn't the throttle programs be optimized differently for performance with the ICE, MGs, and CVT?

That is to say, in Power Mode, The MG's instant, 100% torque will be directed to the CVT, so as to maximize acceleration, until the ICE gets to optimum RPMs. Now, maybe the software programming will presume the Power Mode to only be used sporadically and infrequently, and will make more use of the MGs. Punching the accelerator to the floor in other modes would produce the same effect, as the software would recognize this as an "emergency", and give priority to acceleration.

So, would it be reasonable to assume, since Toyota engineers went out of their way to configure separate throttle buttons, that the software was tweeked differently in each mode, and that by using a heavy foot in other non-Power Modes would not access the same performance algorithms i.e. power distribution between the ICE, MGs, through the CVT?

 

Unless Toyota is lieing, there are two differences in the modes, greater sensitivity of the pedal in power mode and reduced AC output in ECO. Floorboarding it in any mode will result in the same amount of acceleration, unless Toyota is lieing. Disapponinting, I know. Be nice to think there were different fuel injection and timing maps based on the modes etc., but there isn't.
So no, if the acceleration is the same, there should be very little or no difference in mileage, just don't have to push your foot as far in power mode, and your AC is a little more powerful is all.
There really isn't much to the "modes" is there?

 

The total time elapsed going up the hill has an effect, the valve train parasitic losses will be lower if the time is lower. If you poke along quasi-statically, the engine will be on so long that you will get near zero mpg. If you move along briskly, the engine will be on for a shorter time and you will get better mileage - - - to a point- - -and then various other inefficiencies will come into play and lower mileage will again happen. So, the thing is to determine the optimum time / speed / power efficiency that Ken alluded to for your particular hill. It is not an ECO/POWER thing, it is a speed thing.

This sort of speeding up to get better mileage happens all the time when the car is warming up going downhill in the morning. The faster you go the better the mileage because the engine is burning lots of gas to warm up, so you might as well go fast while it is doing it so that you increase the distance traveled while that fuel burns anyway. Whenever the engine is running, it takes a certain amount of fuel to overcome the friction and other losses, balancing that against extra fuel to generate speed and minimize time while managing resistence to motion is the whole business of hypermiling.

 

I would like to see a test. Eliminating the acceleration portion, one can get on highway, place cruise control, reset trip meter and test mpg for desired distance in eco mode. Then repeat the test in power mode, over the same test course. Any substantial difference in FE (excluding minor differences for wind direction and speed) would signify something more than just pedal feel.

 

Sorry, double post

 

What's stopping you?

I don't think there is a difference, or it would impact the EPA mileage numbers, and as far as I know, there is only one set of numbers.

 

There could be a difference if the A/C is on, because ECO optimizes A/C use for better FE.

If comparing the 2 modes with the A/C off and same or very similar weather pattern, cruising steady in a FLAT road, the MPG would be very similar in both because PWR does not change the way the car works, just the accelerator sensitivity.

 

Theory:
I think Power mode may be advantageous in certain situations like stop lights in 35mph+ zones with light traffic because the engine uses less battery and gets into the "sweet spot" for rpm's sooner, providing more efficient accelleration.
In hilly terrain, I think Power mode may also help (esp. with cruise control) since it doesn't "fall behind" as much at the start of a hill and have to play catch-up later (which pushes the engine beyond the sweet spot).

Practice:
I got a reading of 50mpg doing a 100-mile round-trip to a ski slope (temps in the teens/20's), using Power mode the whole time. Speeds were under 65 and cruise was used a little also. Several dead stops in 35mph zones, little traffic. Hilly.

Doing similar terrain/speeds/temps using Normal mode and babying the throttle a lot (and driving slower), I haven't done as well - more like 48mpg readings. On the highway with cruise @74mph, mileage is closer to 46mpg in Normal mode.

One last thing to test would be using Normal mode but being heavier on the throttle to see if that produces similar results to Power mode - unfortunately this won't change anything on the highway with cruise control, so I think I'm going to get used to putting it into Power mode every time and try not to become corrupted. I have a long ride coming up this weekend and will post results.

(those mpg numbers above are all taken from the display - actual is about 2mpg less. Overall real mileage has been about 45mpg, despite the cold weather and new engine - interested to see what I might get in the Spring.)

 

Interesting results. Keep us updated.

--Mickey

 

I'm not thoroughly convinced that the power response is exactly the same on the 2nd half of the pedal in all modes (pedal response may be the same, but I think the power feels different), however, using Normal mode seems to provide plenty of power if the pedal is pushed hard/far enough (I just have to get past my own reluctance), although I think PWR fires up the ICE more quickly... If I were in really steep terrain (like driving to that ski slope), Power mode would make more sense, but for relatively normal rolling hills and such, I think I'm getting similar results with Normal mode and a heavier foot. I would like to make this work so that I don't have to "remember" to put it into Power mode every time I start.

Gliding is really tough in power mode - too touchy... (yet another reason to use Normal mode for flatter terrain and simply push harder when needed)

Will be doing some highway tonight and will try Power mode with cruise control @ 70ish mph (assuming the roads aren't snowy). Will have to rely on the tripmeter for results and it's not a long trip (35mi each way), but if I switch between PWR and Normal on each leg, I should at least get a thumbs-up/thumbs-down/inconclusive from the results. (wind forecast is basically calm, so that should keep some noise out of the data)

I may also be doing some 35mph stop&go driving this afternoon which might be another opportunity to compare.

Another thought: maybe PWR mode is also better in cold weather since the ICE is running anyway? I know the engine is less efficient at colder temps (therefore pushing it harder wastes more gas), but more revs would also warm it up get it into the sweet spot sooner...

Prius: fun for the mad scientist inside all of us!

 

Perhaps not, but that's what we were told by the chief engineer when we were in Detroit. Maybe he doesn't know how it works.

Tom

 

You're the one suggesting that he's incompetent, not I. But I think it might be more useful to know exactly what he said and what his wording was - engineers are almost as bad as lawyers in that respect.

Did he say that the actual output to the wheels is exactly the same in all modes when the pedal is beyond halfway, or did he simply say that fuel flow to the ICE is identical? It may seem like a subtle distinction, but they are not the same.

I read elsewhere that each mode feeds through different processor, so if the amount of flow to the battery vs the electric motor is less aggressive / more aggressive in different modes, then the output to the wheels would also be different even with identical power output from the ICE.

The only real way to prove this (either way) would be with the wheels on a dynometer and a gauge measuring the exact pedal position - I don't have that and haven't seen any test results using that scenario, which is why I said that based on my own experience I wasn't thoroughly convinced (either way). Possibly what feels like 2/3rds to me is still below what they consider halfway.

Looks like I'm snowed in today (don't want to put my new baby in harm's way), so I won't be able to run the other tests just yet.