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I just bought a new, 2019 Touring. I've put maybe 60 miles on it, and just noticed that the engine came on during around town driving, with fully charged battery. About how often does this occur, and for how long?I understand why, but I'm just curious.
 

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Every six to eight weeks. Honda's paternalistic attitude keeps them from telling Clarity owners things like how often the ICE will run when it hasn't been used, how old will the car allow the fuel to get, if the car will engage the ICE below a certain external temperature, and other maintenance items. Their maintenance minder system is designed to keep dealerships happy, not ensure owners are actually doing the required maintenance as needed.
 

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Are you sure you didn't momentarily accelerate and cause the engine to come on? It's very easy to do without realizing it. You may have noticed the power needle on the display that moves around a semicircle as you press the accelerator, indicating how much power is going to the wheels. The first 3/4 of the circle is blue and represents EV. The last 1/4 of the circle is gray which indicates the point where the engine will come on to provide additional power. Sometimes when you press the accelerator a little harder than normal to do some quick acceleration you can momentarily go just barely into the gray area. Even if this happens for only a fraction of a second it will turn on the engine. However you probably won't hear the engine come on unless you are putting the pedal to floor, if you have just barely gone into the gray area then the engine will come on but it will just basically idle quietly, and it will remain on for several minutes until warmed up. So what can happen is a few minutes later you hear the engine and you think it just came on at that random moment, when that happens think back over the last few minutes and try and remember if you did some higher than average acceleration for a moment.

Also on the semicircle you will notice that when slowing down the power needle goes "negative" indicating that regenerative braking is occurring and generating electricity. If you leave the house with a full battery and within a few miles stop at a stop sign or something it will not have a place to store the electricity that is being generated and so it will use the excess electricity to spin the engine, which unfortunately causes the engine to start up and like in the other situation it will run for several minutes until warm. And again you may not realize this has happened until a few minutes later and not associate it with coming to a stop.

I have gone up to a month without the engine coming on by avoiding the above two situations. When the engine did finally come on it was always because I accelerated a bit too much, or I did too much regen on a full battery. If I didn't do either of those for more than a month and avoided starting the engine I don't know how long before it will just start on its own randomly. Some people say a month and half or so.
 

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I just bought a new, 2019 Touring. I've put maybe 60 miles on it, and just noticed that the engine came on during around town driving, with fully charged battery. About how often does this occur, and for how long?I understand why, but I'm just curious.
The worst thing for a engine is to sit idle...I think Honda will cycle the engine on at certain intervals. I run on 90% battery and will switch to HV for awhile on the highway to run the engine once or twice a week..
 

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The worst thing for a engine is to sit idle...I think Honda will cycle the engine on at certain intervals. I run on 90% battery and will switch to HV for awhile on the highway to run the engine once or twice a week..
My observations: If you accelerate hard-ish enough while running on the battery, the gas engine will come on, anticipating a high energy requirement drive.

I've found it to be challenging when I need to accelerate somewhat quickly (as to not cause another driver to need to slow when I enter traffic) without starting the engine.
 

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Where the thick arc starts is dependent on the driving mode (ECO, Sport, Normal, HV or HV+), so how hard you can accelerate from just the battery depends on driving mode.
Same amount of electric motor power is available in all modes. In EV mode the thicker gray line where engine start occurs is in the same 2 o'clock position for ECO, Normal, and Sport. The difference in these modes is the accelerator pedal mapping. In Normal mode you will reach the grey line with less pedal movement than you do in ECO mode, and in Sport mode you reach the grey line with less pedal movement than you do in Normal mode.

Just before the accelerator pedal reaches the floor you can feel a detent, some people call it a click although it's not audible while driving when you press past the detent, but you can feel it. In ECO mode the accelerator pedal is mapped so that you reach the detent at the same point where you hit the gray line and the engine comes on. So in ECO mode it's a lot easier to avoid starting the engine, because first of all you have to press the pedal almost all the way to the floor, and also with some practice you can stop when you feel the detent, thus getting maximum power without activating ICE. In the other modes you hit the gray line and start the engine prior to reaching the detent, especially Sport mode which reaches the gray line with much less pedal movement. So the easiest way to avoid accidentally starting ICE is to drive in ECO mode. However then you lose some of the benefits of the other two modes, such as one-pedal driving which only works in Sport Mode.

In HV things work a little different, when ICE is running the power bar is all gray. But there are brief periods in HV mode when ICE shuts off, you can tell this because the EV indicator appears at the top of the instrument panel, and also the power bar is again a combination of blue and gray. Although the location of the gray line is more like around the 12 o'clock position, or even the 10 o'clock position, and as it uses up battery power the gray line keeps moving to the left. In theory you could keep ICE from coming on by steadily reducing power to keep the needle in the blue area, but at some point the gray line will catch up with you and ICE will come on.
 

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The worst thing for a engine is to sit idle...I think Honda will cycle the engine on at certain intervals. I run on 90% battery and will switch to HV for awhile on the highway to run the engine once or twice a week..
Engine Maintenance Mode occurs every four to eight weeks in the Clarity PHEV. I think it depends on how much you drive.
 

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I run on 90% battery and will switch to HV for awhile on the highway to run the engine once or twice a week..
That's probably best, for those who drive almost exclusively EV, the few minutes of warmup that occurs every few weeks is brief and also low RPM. Seems like it's better to get some higher compression in every once in a while to avoid carbon build up. I tend to think that they designed the car with the assumption that people will be using ICE on a regular basis in addition to EV. Although I doubt if it would harm the engine to drive only on battery for months at a time, with the only ICE usage being those few minutes of warmup every few weeks. Modern engines can last a long time even if not perfectly maintained. It's more about what happens after say 100,000 miles or 200,000 miles when things like this might make a difference. Although obviously most people are not going to be worried about what happens that far out as they will likely have sold the car by then. That's why I try to avoid discussions about oil change frequency, brand of oil, etc., because people say things like, "I've been using this type of oil for 75,000 miles and my car is running fine". Well sure, you would expect it to. There's almost nothing you can do wrong in that number of miles that would cause a noticeable difference, short of letting it run low on oil, or literally never changing it.
Engine Maintenance Mode occurs every four to eight weeks in the Clarity PHEV. I think it depends on how much you drive.
Don't see why how much you drive would make any difference if you are driving solely EV. If you drive 50 miles during the month or 1,000 miles, the gas engine is just sitting there going along for the ride and is unaffected by how many miles are driven. But it makes sense that after a several weeks it will start up ICE to keep things lubricated.
 

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Don't see why how much you drive would make any difference if you are driving solely EV. If you drive 50 miles during the month or 1,000 miles, the gas engine is just sitting there going along for the ride and is unaffected by how many miles are driven. But it makes sense that after a several weeks it will start up ICE to keep things lubricated.
I have no idea what's going on here, but I've noticed that if I drive my wife's car more frequently it goes into EMM more frequently. I almost wonder if there's something in the transmission itself that needs lubricating and that this only occurs when the ICE is running. Yesterday the car went into this mode twice - once in the morning and once in the afternoon. Neither time was I pushing the power past about 40% on the power dial and the car was in EV/ECO mode both times. When the car sits more it seems to not trigger the gas as often relative to the miles driven.
 

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Same amount of electric motor power is available in all modes. In EV mode the thicker gray line where engine start occurs is in the same 2 o'clock position for ECO, Normal, and Sport. The difference in these modes is the accelerator pedal mapping. In Normal mode you will reach the grey line with less pedal movement than you do in ECO mode, and in Sport mode you reach the grey line with less pedal movement than you do in Normal mode.

Just before the accelerator pedal reaches the floor you can feel a detent, some people call it a click although it's not audible while driving when you press past the detent, but you can feel it. In ECO mode the accelerator pedal is mapped so that you reach the detent at the same point where you hit the gray line and the engine comes on. So in ECO mode it's a lot easier to avoid starting the engine, because first of all you have to press the pedal almost all the way to the floor, and also with some practice you can stop when you feel the detent, thus getting maximum power without activating ICE. In the other modes you hit the gray line and start the engine prior to reaching the detent, especially Sport mode which reaches the gray line with much less pedal movement. So the easiest way to avoid accidentally starting ICE is to drive in ECO mode. However then you lose some of the benefits of the other two modes, such as one-pedal driving which only works in Sport Mode.

In HV things work a little different, when ICE is running the power bar is all gray. But there are brief periods in HV mode when ICE shuts off, you can tell this because the EV indicator appears at the top of the instrument panel, and also the power bar is again a combination of blue and gray. Although the location of the gray line is more like around the 12 o'clock position, or even the 10 o'clock position, and as it uses up battery power the gray line keeps moving to the left. In theory you could keep ICE from coming on by steadily reducing power to keep the needle in the blue area, but at some point the gray line will catch up with you and ICE will come on.
Thanks! I'll delete what I now know to be a bad "observation".
 

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Thanks! I'll delete what I now know to be a bad "observation".
It's understandable, I didn't pay any attention to the blue and gray lines until I had driven the car for at least a couple of months, then I started noticing it and I realized oh, it's actually showing useful information.
 
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