This is a 675,101€ question (or otherwise a 1M$ question): when starting from a complete stop, in ECO mode, nobody following you, right lane - after moving the car electrically to say 20km/h-12mph to exploit the electric engine efficiency from 0mph-km/h, what is the best way to reach 30mph most efficiently (i.e. using the least fuel)? With the HSI bar shy of the right side of the middle mark, or fully to the right, shy of the PWR zone? I have noticed that in both cases the fuel consumption shoots up to 10L/100km independent of the length of the bar and I cannot really judge if there is a difference. Maybe with an MPG based display you can see the difference. In both cases the energy monitor shows arrows going from the ICE to the MG1 and the wheels, and from MG1 to MG2 and the battery. So also no difference there as well. In the first case it takes you longer, in the second case less, before you can release the gas pedal after reaching the target speed and then glide. Common sense would dictate that a shorter HSI bar (less acceleration) would yield a lower fuel consumption since you are accelerating much slower, if the rpms are in the high torque/highest efficiency region. And accelerating faster would be only a waste of fuel in comparison... But in the Prius the ICE can actually spin often independently of what the actual wheel speed and acceleration request is. Actually it seems to me that with the shorter HSI bar the ICE spins more than necessary to move the car. Is there a different contribution of current to the HV battery and to MG2 in the 2 cases? Has anybody tested, also with a Scangauge (which I don't have), what difference there would be in terms of FE and ICE rpms, in the 2 cases?
Accelerating harder and using the ICE less efficiently can be offset by being able to glide earlier and longer.
Accelerate harder right from the start. Ideally, you want to run the ICE at its most efficient power level, and you want to do this through the entire acceleration. Anything else means wasted energy in the ICE or wasted energy charging and discharging the battery. Tom
Acceleration should be brisk, but not so fast that power is drawn from the battery. Generally this is faster than what most Prius drivers think is good, but slower than a teenage driver. To get more precise than that, you have to watch the current flow in the battery. Tom
I believe Wayne Gerdes' technique is slow EV up to maybe 17mph and then low ICE (just right of the center) to speed. Others push it a bit harder, up to 3/4 of the HSI bar. The main thing stay out of the red zone and don't try to granny it all the way in EV.
Whichever method is used for the bulk of acceleration, I like to nearly plateau a little on the low side, say around 45 km/hr, and then very gradually close on 50. Sometimes I never get there.
I checked today that if you accelerate with the HSI bar right of the middle and not in the PWR area, the battery is never used and get charged by the ICE via MG1, which is also giving current to MG2, also drive by the torque of the ICE. But this is not what I was asking - I am asking what differences in FE there are by accelerating with the ICE running when the HSI is just right of the middle, and when the bar is fully to the right, just before the PWR area. Did anybody test it? does anybody have hard numbers?
The consensus is that you don't want to be just right of the midline when you are less than 46 mph. This makes the ICE run in very inefficient fashion. You also don't want to be just left of the midline, this draws many amps from the battery but you only get 27 horsepower. Much better to use the ICE to generate 27 horsepower. Of course around 55 mph and above, just to the right of the midline puts you in SHM which is not bad. You want to be around 75%-100% of the HSI bar. The same as the pulse zone. Ken (from Japan) even says he doesn't mind going to 110%. For a long time I was very hesitant to use the power band too much. I found that staying in the power band, but not exceeding it, gives good power to climb moderate hills. You don't accelerate fast, but you still do accelerate. I find it doesn't hurt MPGs much at all. Generating 70 hp with the ICE is only around 4.5% less efficient than generating 25 hp.
I have a 5 mile trip through town each morning on the way to the highway to work. I have found that if I accelerate in to the power area and "tickle the right hand side of the power bar", as Bob Wilson once described, that I can get up to speed and begin to glide quicker. I seem to get better mpg doing this than trying to accelerate below the power area and take longer to get up to speed. I am also able to keep up with traffic better. If I did not accelerate in to the power area I would not be able to keep up with the flow of traffic around here.
I'm a bit new at this, but I've watched some YouTube videos and did some reading around here (and stayed at a Holiday Inn Express last night). I've been playing with some different techniques myself in my week of Prius driving and my personal findings so far are this: I find when I roll the accelerator gently off the start through EV mode up to about 15 MPH and become a but more aggressive with pedal once I get up to ECO range (and the ICE kicks on) and accelerate with the HSI bar in the PWR range up to my desired speed and then glide, I get better MPG (66.7 in a 14.6 mile trip yesterday) than I do if I accelerate trying to keep the HSI bar in ECO while accelerating (best MPG doing this was 56.6). As I said, I'm a newb Prius driver with minimal experience going off of my intuition and experimentation so take what I say with a grain of salt. I must say, contrary to reviewer opinion, I find the Prius extremely fun to drive. Trying to maximize MPG is like a video game for me. My high score to date: 66.7 MPG
Salix, I would suggest something in between. Stay out of power mode but only slightly so if possible. You want your RPM to be around 1,800 or so which corresponds to about 3/4 of the way through the HSI display (just before the power section). In heavy traffic this may not work because of the slower acceleration. In such conditions just drive safe and courteously. Your technique works well enough and doesn't annoy people too much. If you need a little more punch off the line, try using the EV Mode button to get up to 15-20mph. It allows you to apply more throttle before the ICE kicks on then if the button was off.
I'm a bit hesitant to put any serious pressure on the accelerator until the ICE kicks on for fear of hurting the drive train. In my mind I'm equating it to something like a neutral drop or popping the clutch in a regular car. Am I wrong in this thought process?
Yup. It's totally different. The system is never disengaged like an old school ICE car. There is no true neutral either. So just drive it. You won't hurt anything. Unless you are going less than 9mph and hit the park button. Eek
Downhill. Do all or most of your acceleration while going downhill then glide the rest (and most) of the way.
