I am on my first tank of gas with my new Prius (435 miles and I still have the last bar of fuel, very happy with that) so I am still discovering the car. Tonight I was having a look at the energy monitor but I couldn't really understand what was going on in two different moments while, in both cases, I was driving at 56 mph steady (no P&G). These "events" occurred in different moments. 1. The engine was moving the wheels and feeding the electric motor which in turn was again moving the wheels and charging the battery. What was weird is that the arrows from the electric motor kept changing direction intermittently from the motor to the battery and from the battery to the motor. Unfortunately when this weirdness stopped I was unable to replicate it. 2. The engine was moving the wheels and feeding the electric motor which in turn was charging the battery. What I found weird is that I was actually using only the gas engine to move the car as the electric motor wasn't moving the wheels (no arrow from the electric motor to the wheels) Is this possible? Later I saw the electric motor stopping recharging the battery and the only arrow displayed was the one from the gas engine to the wheels. This state lasted only 3-4 seconds. I was able to replicate this anytime I kept a sufficiently high constant speed on a flat surface with both pedal pressure control and CC. In both cases I was doing my best to keep my foot steady. Heater and AC where both off, the battery had at least 4 bars in both cases. What I would like to know is what it actually doing the HSD in those cases, for the sake of knowledge, just to know what's going on. My last question: has anybody managed to see no arrows in the EM while gliding (not in neutral)?
I've seen case #1. Most likely your battery is at its happy place (6 bars on your Energy Monitor or about 60% actual SOC) and it's trying to bleed some excess charge. Case #2. I've seen it occur only on the Gen 3. The Gen 2 never displayed this diagram but basically your battery is where the computer likes it to be and the engine is only needed to power the vehicle and the rpm is sufficient that it doesn't require extra torque or power from the elec. motors. It appears that both #1 and #2 are similar. One's feeding & discharging while the other isn't doing anything with the battery at all. I have glided but it's very difficult compared to the Gen 2. I've asked Ken and he said a very slight EV is just as good as gliding in the Gen 3.
I get 2 all the time. Remember also that the "electric motor" icon, is in fact 2 motors. The motor driving the wheels, as well as the generator. The new engine has enough torque to drive the wheels directly (direct arrow to the wheels), which I call "overdrive" mode, and at the same time provide torque to the generator to charge the battery (arrow to the motor/generator and to the battery). I think this to be the most efficient condition of the HSD. In this case, the ICE and electric motor are running at the same rpm, I assume, but I don't have data to sustain this. BTW: this mode is not described in the figures of the user's manual either (pages 190-191). On page 190 there is also a mode I cannot understand and never saw, in which the motor and the ICE have arrows to the wheels, but no arrow from the ICE or the battery is shown...??? see attachment. Another mode not shown in the user manual, is the one in which the battery is not used at all, that is there are arrows going form the ICE to the wheels, from the Motor to the wheels and from the ICE to the motor - I think this is the case in which the ICE has enough torque to create extra electricity that can be fed directly to the motor avoiding the conversion to the battery. To be honest, the manual on page 191 also states:
I see both #1 and #2 during my 60 mph commute to work. This is on fairly level ground with small inclines and valleys. Especially at these speeds, the ICE evidently is at its most efficient state and can provide all of the torque to the wheels. Even on very level ground, the arrows to and from the battery to MG2 to the wheels and from MG1 to the battery will switch back and forth as the system balances its needs. (As stated above, the electric motor symbol on the EM screen represents both MG1 and MG2) After going down a slight decline, I can see the battery arrows switching back and forth rather quickly as the battery is full and it starts "throwing off" some of the battery charge. As I go up and down gentle hills it is interesting to watch the monitor as the system does its "balancing game" to keep the ICE in its "sweet spot".
Thank you for the replies. I wonder if this "happy" states for the HSD are more fuel efficient than pulse and gliding (when you have the opportunity to keep a high constant speed, on a free long flat highway for example) as it seems this new Prius loves to be driven like a regular car in this situations, just keep the foot steady and she will do the rest. Pulse and gliding might be more suitable if you are going to stop anyway so you try to keep your momentum as long as you can. The dealer guy told me than P&G (which at these speeds is called Hyper Stealth if I am not mistaken, with the difference that the engine is off but gets dragged to avoid MG1 to overrev) was the most fuel efficient way to drive to Prius in any situation ESPECIALLY at highway speeds and that I should do my best to use this technique if want to maximize my fuel economy, even if this kind of driving is a bit tiresome sometimes. I will try experimenting a bit on this matter, in the meanwhile I would be glad to hear you experiences on this subject.
My experience is that P&G not only is tiresome and not applicable in cities (at traffic lights you P&G do that in any case... ) but it is not going to increase the fuel consumption and it does end you having the battery often not much charged. My experience is either to: 1) drive the Prius like a normal car and trying to avoid useless breaking and strong acceleration (this would increase the fuel consumption on *any* car, BTW) 2) drive the Prius using the cruise control so that the desired speed is kept constant and the speed control makes sure that only the right amount of gas pedal is applied, thus having the engine run on its most efficient point for that speed. Even in town for "short" stretches I tend to use the cruise control at speeds of 60-65km/h. My feeling is that there is no reason not to keep the HSI bar away from the middle. My perception is that the HSD works in such a way that the engine is always at max efficiency and the MG1 and MG2 work buffering the extra energy or the lack of it at a certain rpm of the ICE, depending on the amount of acceleration required, speed, load on the wheels, battery charge level, temperature, etc. I am a firm believer that most Gen 2 driving techniques, do not apply on the Gen 3. For me the most efficient and lowest fuel consumption is achieved when the ICE drives directly the wheels and manages to recharge the battery at the same time. Typically the fuel consumption is anything between 4 and 5L/100km (now, still!, in winter) from what I see, at the speeds I drive the most in town (high speed roads are available in Munich), that is at 55-65km/h. Plus, I didn't buy a car like this, to worry all the time how to drive it to get a good fuel consumption - if I wanted to do that, I could have saved money, bought a 1990 technology car, and worry then how to drive it... My current average is 5.5L/100km in very cold winter, in town (90% of the time) - I am pretty happy with that. The only thing I am doing different than in my previous car, is keeping the A/C down to 16C (I always have a jacket on and when it is -7C outside, 16C feel *very* hot ) and keep ECO all the time, at least until temps are not in the range of 5-10C. All this to avoid the ICE running idle at traffic lights or when crawling in traffic, and to reduce overall consumption (the heat needs to be generated also when driving at speed, the rpms might be the same, but likely more fuel is necessary to keep the thermal cycle at the right point).
Nice reply Pakitt, well I wasn't too sure but I was under the same impression. Being used to a high performance vehicle one morning I woke up in frustration and decided to switch off all those fuel economy gizmos and to drive it like a normal car, taking over, maintaining the speed, and so on. I wasn't racing, just driving normally. Not only I enjoyed the ride, since the Prius handles quite well, but I didn't ruin my average fuel consumption at all. However when looking at the 5 min graph when pulse and gliding I cannot ignore the minimal consumption I can obtain while gliding, well below 5 l/100 km (which is my current average, exactly 4,8 l/100 km). So I have yet to draw a definitive conclusion about the effectiveness and proper usage of P&G. In short, even if I agree on the fact that I don't want to be obsessed by fuel consumption optimization, if the usage of P&G under certain circumstances can lead to a significant decrease in fuel consumption, I might consider using this technique daily.
I have to apologise. By gliding I meant really "coasting". (checked on Merriam Webster English dictionary just now...). "coasting" is when you take off completely the gas and you let the car roll (maybe by pressing the gas a tad so to avoid regen braking completely) below as certain speed, say x-10km/h - then you pulse again to speed x+10km/h so that you get on average speed x. I this find annoying and it is what I seen to be a way to hypermile on some threads here and on other Gen 2 websites. Maybe I am wrong and they meant really "gliding" - in any case "P&C", pulse and coasting, is impracticable in town and personally I find it a bit dangerous and disturbing for the passengers. Depending on the road you might have to do it often and I hate people that do not give gas continuously but in bursts - I hate that. "gliding" instead is when you keep constant speed after reaching it, right? That is what you mean? In that sense we were talking about the same thing. I deprecate the use of "coasting" but not gliding instead (and on the Prius it *so* smooth! ). I usually speed up to speed x, and then set the cruise control to keep it there. The car does what is necessary to keep it. I find it very difficult to keep a certain speed by adjusting gas continuously with my foot, way more than a computer would do - and me trying to keep speed, that might well be not efficient at all. Actually the cruise control of the Prius does a very good job in keeping the speed - in downhills it does brake, in uphills it accelerates smoothly and not like a rocket (it happened to me on many american cars, with what I believe cheap implementations). Only a few rare times I need to turn it off because it is accelerating too much compared to traffic - in which case I use the lever, and not the brakes. What I also mean, is that driving the Gen 3 like a granny, will not help improve fuel consumption, quite on the contrary. Somehow I have noticed that when I drive too slow (very slow accelerations, slow speeds, etc), the battery tends to discharge more often, and when you really need it because you hit a traffic jam, you don't have enough charge. And that is when fuel consumption shoots up. If you instead drive normally, as you also described, you end up with a more charged battery that does come really handy when you are in a traffic jam, or when you want to glide a bit more. But to me gliding is more efficient and overall provides the best fuel consumption when you get the ICE in "overdrive" and it can drive the wheels directly. In that case I find this 1.8L engine to consume really not much (and still charging a huge battery!).
The gliding part in P&G is actually coasting, since your speed slowly decreases and you'll have to give another burst as soon as your speed decreases too much. That's the tiresome part, in fact. Both for the driver and for the guy behind you! I don't know if the word "gliding" is most appropriate in this context, but whenever I used that term in my previous post I meant gliding as it is meant in P&G, which is "coasting". The idea is to keep your momentum as long as possible without adding any extra energy, which at low speed is feasible since the ICE shuts off completely, whereas at high speeds it is not, as the ICE stops burning gas but still rotates (a complete stop would cause MG1 to overrev), so you will still be consuming some energy to drag the engine. I am sorry about the misunderstanding. The dilemma is in fact about which technique is the most fuel efficient: coasting and then giving a burst as soon as your speed gets too low, or just maintaining the speed (controlling the throttle manually or using cruise control) as you would do in a regular car. As you say the latter seems to be the best way (and the easiest!) as the CC does it job properly and at constant speed the engine reaches that "happy" state in which it can push the car without any extra help from the electric motor which in turn keeps charging the battery.
