Yes, so far it seems the funny lesson here is the Prius has this great new feature on it that can get you to around 52-55mpg without too much effort. To do better, you need to stop using this great new feature.

 

No, it's not funny. It is very reasonable if you understand the technology correctly.
You still don't understand the Prius.
It is not a good idea to use too much batery power, period.
The Japanese and European Prius comes with the EV button, and the UK owners manual says...
"As your vehicle is designed to have the best fuel economy during normal driving (driving in the combination of gasoline engine and electric motor power), frequent use of the "EV" drive mode may worsen fuel economy."

Maybe, people think a lot of regen icon is good, but it is not true.
A lot of regen icon means you used the battery power before, then the system needs to regen.
I rarely see the regen icons everytime when I see hyper-miler's screens.

Ken@Japan

 

Right... I understand that. So a normal driver will get better MPG without much thought in the Prius, partly because of good Regen. A hypermiler will get better MPG by avoiding scenarios that involve Regen - or at least, ones that make use of that battery power. I find that ironic, and so, funny.

 

It helps to separate regen vs ICE power. Regen is better than heating the brakes but not a good way to charge the battery. To generate the momentum that is being converted to electrical energy, ICE generated power had to be expended first and regeneration is not 100% efficient.

In contrast, ICE generated power is necessary to maintain the SOC and power the batteries for EV mode. While generating power, the ICE also powers the car. This relatively higher power mode means the ICE tends to run in a more efficient power generation range. An ordinary Otto cycle vehicle would suffer throttle pumping losses and inefficiencies.

Bob Wilson

 

My 0.02. I think it is better to accelerate gradually with an arrow to the battery and with an arrow from the engine to the wheels. So two of the three possible arrows during a pulse. This allows for extended electric only modes during a glide (not my preferred glide, but used at times).

Yes, I know there are conversion losses associated with repeatedly charging and discharging the battery. I have experimented with trying to accelerate without arrows to or from the battery and have found that traffic and traffic lights really make it difficult to glide for any respectable distances. It really hurts the tank mileage to accelerate at an impg of 12 mpg to only have to apply the brakes becuase you have to stop for a light. Now on open lane no traffic conditions, I could see where no arrows to or from the battery would work (I will have to test that later when there is no traffic).

I pulse as described in the first paragraph and the slower acceleration allows me to see what the traffic and the traffic lights are doing in front of me so that I can anticipate my next move ahead of time. This typically yields a 24-30 impg value (higher in warmer temps) which over a .1 to .2 pulse distance means that I don't have to glide very far. I use a little electric only mode (no EV button, pedal controlled) for appropriate situations to either get me through a light or keep me going so I don't get run over. I would rather glide with no arrows at all and then pulse again as a high SOC when pulsing (pulse as described in the first paragraph) yields a higher impg value during the pulse, which in turn means I don't have to glide as far to get a higher overall mpg.

I also try to not regen at all. I don't want to see any green cars on my consumption screen. If I regen then I have not anticipated well enough. Ideally, I would like to glide all the way down to 7 mph if I have to come to a stop sign or stoplight. Obviously, traffic will not let me do this, but I try as much as possible to do this.

My overall mpg is only in the low 60's, but I have been getting 70-75 mpg per trip lately with outside air temperatures in the 40's. On a warm day last month I was able to get 84ish mpg for 42 miles driving as I have described.

Bob Wilson has proved that steady state driving at low speeds in a prius yields very high mileage. However, my commute with 34 stoplights does not allow for this; therefore I P&G.

 

I frequently get this situation when sustaining a Glide - accelling from 32mph to 41mph - but getting it below 20mph seems impossible. Have you been able to consistently get this situation to arise when starting from a stop? Any tips if so?

I agree the anticipating stop lights can do a lot more for you than any accelleration strategy, although it's an interesting point that perhaps accellerating a little aggressively - especially when you risk holding up traffic behind you - offers a longer Glide opportunity in a typical series of intersections. I guess I need to play with this possibility some more.

 

SoopahMan,

From your last post:

VaBeachPrius: I think it is better to accelerate gradually with an arrow to the battery and with an arrow from the engine to the wheels.

SoopahMan: I frequently get this situation when sustaining a Glide - accelling from 32mph to 41mph - but getting it below 20mph seems impossible. Have you been able to consistently get this situation to arise when starting from a stop? Any tips if so?

Do you glide with green arrows. If so, push the pedal slightly until the green arrows disappear. This will work when the car is warmed up. You will glide much further.

With light accelerations and below 20ish mph there are generally always three sets of arrows, engine to wheels, electric motor to wheels, and to battery. As the speed rises, the electric motor to wheels arrows usuallly disappears. However, I do sometimes see no arrows to or from battery at these lower speeds (10-15 mph; for a second or two).

Since I use the battery to assist my glides depending upon the conditions, I like the charging of battery during my pulses. It may not be the most efficient, but it works for me. I will however try the no arrows (to or from battery) acceleration method on a remote stretch of road and see what happens.

 

I Glide with no arrows. I would refer to the green arrow situation differently - I'd probably call it Regen. There ought to be a "Vocab" section to this forum since Coast actually means idling the ICE while drawing no motive power from it and letting the wheels spin freely, and Glide is the same except the ICE is off. Regen is either of those with wheel energy going to the battery.

Having recently seen the torque map of the Prius ICE I may have to accept the yellow arrow from the battery in traffic during low speed accelleration - at least I now understand why it happens - between 1000 and 2000rpm the ICE torque is quite low so Assist is the only way you're getting the kind of accelleration typical on US roads.

I don't want to suggest that accellerating with a green arrow going to the battery is inefficient - I've seen no data to support that. The yellow arrow coming from the battery is the bad one, according to both Ken here on this forum (who knows a LOT about the Prius) and data he and Bob have provided. I estimated the fuel efficiency of battery power used to drive the wheels (battery power generated previously by the ICE) is just barely over 50%, while the ICE driving the wheels directly can get close to 80%. Regen energy (ICE to wheels to road back to wheels to battery, then finally back out to wheels) used in this way must be even lower. So, for the absolute best efficiency, when the ICE is running, avoiding a yellow arrow from the battery is the way to go - but again, this may be just unreasonable in typical US traffic.

 

SoopahMan,

I had to run an errand today (Monday) after work and it took me down a 7-ish mile road with a 35 mph speed limit. By the time the car had warmed up there were six bars on the SOC (what I would call a high SOC; not full, but in the upper third of what is shown).

I had noticed a month ago or so that when I pulsed with a higher SOC that my impg values were much higher and my mileage was better overall after my pulse and glide events. Remember, that I usually pulse with an arrow from the engine to the wheels and from the electric motor to the battery.

However, today for whatever reason, I pushed the pedal a little harder during my pulses with a higher SOC (after thinking more about the efficiencies of not involving the battery and trying to get the arrow to the battery to disappear) and the arrow that usually is to the battery disappeared and I was still getting 23-25 impg during my pulse. There was an arrow from the engine to the wheels and from the electric motor to the wheels, but not arrow from the electric motor to the wheels.

The limited amount of traffic allowed me to glide without having to use stealth mode at all to stretch my glides. Therefore, I was able to pulse and glide while keeping the battery at a "high" SOC. Results:

87.1 mpg over 41 miles (using starting and ending mileage and mpg data from the MFD to get an idea of what is going on for my segment). .

Granted it was in the low 60's F instead of the mid 50's. This also played a role as I didn't have to fight the car to get it to glide with no arrows at all. It will be interesting to see what I get for mpg values with my commute in the morning and see if I can apply this type of pulse and glide without getting run over. I raised my tank avg mpg by 1.0 mpg over 41.0 miles. That was awesome, as it had been dropping continously for about 4 days. I really think the OAT had a bit to do with this too as it allowed my impg values to remain high enough to make my glide distances feasible.

Note that there are no regen cars showing. The segment between 10 and 15 minutes would have been at 100 mpg if I didn't have to stop at a light just after pulsing from a stop. Oh, well.

 

Very cool. What did you typically accellerate to, and at what speed (barring hitting a stop light) did you typically break your Glide and begin re-accellerating?

My graphs lately usually look more like one short bar, one tall one, short, tall, etc, the tall ones being 99.9 for Glide and the short ones being a Pulse, so I'm wondering how you managed to get several tall bars with Pulsing having to happen in there somewhere.