You may already be doing this, but another way to accelerate with minimal assist is to gradually press the gas pedal. The amount of assist seems to be more related to how fast the pedal is moving rather than just how far in it is. So, while you have to press very softly to accelerate off the line with no assist, you can gradually keep pressing the pedal in farther and farther, steadilly increasing the RPM's without assist.

Starting from zero without assist is pretty hard, so I usually give in and let it do 2-3 bars, but once I get up to 10-15 mph, those bars go away and I can accelerate up to 60 without any assist, and in less time than it would take if I just held my foot locked in the same position. It did take some practice.

 

I'll try to take that into consideration, NASA.

 

I just ran a route both using S and using D. Temperature was 50 degrees, thus both values were low, and the battery was nearly full at the beginning of each test. Using S to accelerate onto the highway, and to go up a big hill while accelerating to 80, I got a round-trip of 37.6 MPG. Staying in D and using assist to get on the highway or go up that hill, I got 37.5 MPG. 0.1 MPG is well within the margin of error so basically they resulted in the same mileage on this trip. Since S mode definitely lowered FE more than D when accelerating, the fact that it was able to make up the difference, in 11 miles of highway driving each way, means in my mind that going a longer distance would show S mode being a real improvement over D.

After going up the hill, starting with a full battery, D mode got the battery down to 4 bars and then it used 3 bars of regeneration while I was driving. It eventually got the battery to 5 bars but I don't think it got to 6 (not sure).

 

I agree with this. I don't view the "light recharging" that is done while riding as a detrement to MPG, I look at it as increasing my MPG during my next time through the gears. I have noticed that the MPG is significantly lower on acceleration from 0-30, no matter how EASY you are on the pedal, if the battery charge is low or nothing. A low battery makes the car sluggish, too.

I do everything in my power to KEEP the battery at 75-90 percent of the allowable charge.

 

Interesting test, CGameProgrammer. How many bars of assist were you using in D?

 

All. It wouldn't have been possible to get up the big hill otherwise, not at 80 mph at least. I tried to accelerate at similar rates with both methods to ensure a fair test.

 

I've been playing around with S mode, and from what I'm seeing, it actually uses more assist than D off the line, but drops to no assist once you hit around 15 MPH. I believe that's what you were describing too, CGame?

 

That may be a clue that S is behaving like a true second gear - i.e. starting out with a lower gear ratio than "first gear".

 

Yes,

that is also my observation with 'S' mode while driving home tonight. The issue with 'S' mode is that at 50km/h (30MPH), then engine is around 3500RPM and therefore very close to HI-VT mode which wouldn't be what we are looking for.

Going from 'S' to 'D' once at 15MPH does lower the RPM substantially. However, I personally wouldn't 'shift' like this on a regular basis.

Thanks,
Stephane.

 

A thought about this;

It takes about 2-3 seconds to get up to 15MPH. Those are the three worst seconds in terms of FE in your whole trip. I think the more assist you can get during that time the better off you are, and it hardly lasts long enough to impact your batteries much.

The reason the Prius gets better MPG in city driving than the HCH may be attributable solely to the fact that it can get to 15MPH on battery power alone.