When does the gas engine run (other than on hard acceleration)

Fidzio

Fidzio

Member
I'm considering buying a Clarity or a new Volt. When the Volt runs in EV mode it never runs the gas engine unless the outside temperature is -10 deg C (or 0 deg C - driver selectable).
I don't know the rules for the Clarity and I'm curious.
Last week it was -10 deg C and on the Clarity test drive with a fully charged battery, the gas engine ran frequently, even if I was gentle with the gas pedal. In some blogs I read that Honda require the gas engine to run at cold temperatures (below 10 deg C)
Today it was+3 deg C and I had another test drive with a fully charged battery. The gas engine stayed off until the first time I went past the gas pedal detent (as expected) but then didn't switch off for approx 5 mins. While it was running, I stopped the car, switched it off and then back on. The gas engine stayed off. I then went on a highway and accelerated moderately to 70 mph and the gas engine came on and stayed on. When I left the highway back onto smaller roads, the gas engine stayed on for a few minutes and then went off and on for no apparent reason.
Does anyone know the logic that the Clarity uses for running the gas engine? Curious.
 
I've been looking for the engineering rules on this myself. The manual describes generally when the ICE will fire, but I don't think it gives all conditions. For example, at about 300 miles, the ICE turned on during normal EV travel. I couldn't turn it off. That is, when I powered down and then restarted, the ICE came on immediately.

I suspect this ICE start was likely triggered by a length of time. In the Prius PHEV I drove before the Clarity, the ICE would automatically turn on if it hadn't been on for a few weeks. This stirred things up, oiled the ICE, and burned off a little fuel. I suspect the Clarity has a similar condition programmed into its computer. I've never even fueled up, and I've driven the car for a little more than a month.

Since then, I attached my ScanGaugeII, and I've learned that at least in Econ mode, when I force the ICE to pop on, the ICE has to heat itself to 155º before it drops out and the car goes back into EV mode. I've observed this twice - mostly because I'm still on the top half of my original tank of gas after 600 miles. We desperately need more real time data about this vehicle and its various modes.
 
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Our conditions are:
Between 30 and 60 degrees winter temps

Typical days 30 to 50 miles, mixed freeway and city. Charging at home between drives.

Daily elevation changes about 250 feet

One half mile hill 14% grade

Seat warmers are used on most rides

Defroster may be used once a week for 20 minutes. Heat rarely used.

Odometer shows a little over 2,000 miles.

The ICE never comes on. We last filed the gas tank Dec 20 after a long trip when the ICE was in use.
 
I found some more cases where the ICE is asked to run in the following link: http://www.insightman.com/Clarity/index.htm#50-state

Extracts:
1. When you mash the accelerator pedal to the floor, you want your car to accelerate as
quickly as possible
2. When it’s cold outside, you want your car to keep you warm

As noted in the list above, there are at least two other situations when the Clarity Plug-In
Hybrid activates its ICE automatically: At certain higher speeds, the ICE is mechanically
connected to gears that turn the front wheels. The other instance is when you want to go faster
than 100 mph. At that speed, the Clarity Plug-In Hybrid cuts off all battery support, leaving
the ICE all by its lonesome to soldier on in the pursuit of triple-digit speeds. Please don’t
expect the ICE to achieve 42 mpg at 100 mph.
The Clarity may also start the engine as part of a "System Check." The Owners Manual says
this: "While the check is being conducted, the engine may periodically turn on and off. This,
however, is normal. Once the engine starts, it will continue to run until the system reaches
operating temperature."
Another engine-activation situation: The Owners Manual says "the engine starts automatically
when the engine has not started for a long time." This message appears on the instrument
panel: "Engine Started for Oil Circulation." It makes sense to keep the engine oiled up. You
wouldn't want the expensive 0W20 oil doing nothing in the oil pan while the cylinders go dry.
It will be interesting to learn how the Clarity defines "a long time."
[Question: How long is "a long time" for the engine to remain inact ive?]
So those are my speculations and some actual explanations about the priorities and that
Honda’s engineers set regarding all-electric operation. The Clarity Plug-In Hybrid won’t let
you completely eliminate time-consuming trips to the gas station, but it can make those
bothersome visits much less frequent.
 
Fidzio said:
While it was running, I stopped the car, switched it off and then back on. The gas engine stayed off. I then went on a highway and accelerated moderately to 70 mph and the gas engine came on and stayed on. When I left the highway back onto smaller roads, the gas engine stayed on for a few minutes and then went off and on for no apparent reason.
Does anyone know the logic that the Clarity uses for running the gas engine? Curious.
Click to expand...


Based on insightmans blog, the detent works for ECO mode, but not for normal or sport mode. You would have to watch the gauge. The pedal position appears to be earlier in normal and sport mode.

http://www.insightman.com/Clarity/ownerlog/index.htm
 
It would be very nice to know if one could say use one tank of gas for a year, like people in Volts do. So far I've not been able to get any answers from the local dealer, nor find any tech details about the fuel tank system.
 
While cruising above 70mph on the freeway today I noticed that the ICE came on. This was in normal (non-HV) mode, w/ A/C on and more than 1/2 charge. It appears that Honda has programmed for highest overall energy efficiency (which may not necessary mean all-electric operation) and at high speeds ICE engines are more energy efficient than electric motors.
 
As far as I'm concerned that is entirely possible. As long as the car is kept in EV/Econ mode it won't use the engine unless it is pushed hard (accelerator past detent) or runs out of battery juice.

I did go to visit my daughter last week when the battery was drained and I ended up using about a gallon of gas (about 66 miles in all). But the last time we filed the gas tank was December 20th.
 
Kendalf said:
While cruising above 70mph on the freeway today I noticed that the ICE came on. This was in normal (non-HV) mode, w/ A/C on and more than 1/2 charge. It appears that Honda has programmed for highest overall energy efficiency (which may not necessary mean all-electric operation) and at high speeds ICE engines are more energy efficient than electric motors.
Click to expand...
Did you have it in Econ mode? We've driven many miles at 70-75 mph without the engine ever coming on.
 
Once the clarity engine is activated it says running until it is warmed up. This is designed to prevent multiple cold engine starts in a row, which are damaging to the engine.
 
PHClarity2018 said:
Once the clarity engine is activated it says running until it is warmed up. This is designed to prevent multiple cold engine starts in a row, which are damaging to the engine.
Click to expand...

That may explain a lot of times the car does not seem go back to EV mode in a timely way.
 
PHClarity2018 said:
Once the clarity engine is activated it says running until it is warmed up. This is designed to prevent multiple cold engine starts in a row, which are damaging to the engine.
Click to expand...

Tiralc said:
That may explain a lot of times the car does not seem go back to EV mode in a timely way.
Click to expand...

Still trying to find out what that "warmed up" point is. For example, in the Prius PHEV it was exactly 130ºF. So once the ICE warmed to that temp, it would go back into EV mode (if called). So far, I've noted that once the Clarity ICE is between 150-160ºF, it will shut off. However, that temp has wiggled around between a low of 152ºF and a high of 160º, with most (8) near 155ºF. As you can see, with only 8 data points, this is very early in the data gathering stage, but that seems to be a rough range the Honda computer is set for. I'm sure a Honda engineer could give us the exact temp…
 
I am glad to find this thread.

I bought my Clarity 2.5 months back. Right now it has around 2.7K miles. I am troubled by its recent behavior. Every morning after full recharge, my car will get out of EV mode (the blue line becomes white, the EV letters disappear, only ECON and leaf icon are seen) and start to use gas, and it cannot get out of the mode until I fully shut down my car and wait for all screen display disappear. I tried pressing EV and HV buttons endless times during driving, it doesn't help. If I shut down my car too short, it will not get out of EV either. Once it's out, it can keep in EV for a whole day.

I live on a hill so I drive downhill for my first trip. My speed never exceed 40 MPH (I use cruise control to make sure of that). Every day (sometimes every other day) it's using 4-7 miles in gas. With this speed I will finish my full tank of gas in 2 months.

I brought my car to the dealer but they didn't find any issues. Have anybody seen this or have a good explanation for this? How can I use less gas and stay in EV?
 
The common theory is the car is dumping power through the engine. The battery is full from your overnight charge. You start out from home going downhill which puts you in Regen but the battery is already full.

Try charging less than 100%.
 
jwangl said:
I live on a hill so I drive downhill for my first trip. My speed never exceed 40 MPH (I use cruise control to make sure of that). Every day (sometimes every other day) it's using 4-7 miles in gas. With this speed I will finish my full tank of gas in 2 months.
Click to expand...
Check out this thread, which addresses your exact question.
 
Wow, thanks for the info of the other thread. Glad to know I am not alone and people have tried different ways to work around this issue. I would have never imagined too much electricity will be the cause of using gas.

To me the following puzzle has not been answered:

Why does it take so long for my engine to warm up properly and get out of ICE? The air temp is in 60s. The hill is only the first couple miles. But my car stuck in the ICE for at least the whole way of 12 miles, including highway. It seems I have no choice but to shut the engine cold everytime because I have arrived. So almost everyday it will burn 7 miles of gas.

I wonder how Volt solved this problem and if Honda can learn something from them. As the things are it seems it's better not to get into this mode rather than wait for it to get out by itself. Unfortunately it's almost impossible for me to figure out when the battery is 95% charged and unplug it. Everyday my usage is different, I won't be able to schedule a time to stop charging and Honda Link doesn't have a config to charge to a certain percent (it would be nice if they do!). This morning I tried to turn off Econ mode till the foot of the hill, and ICE didn't turn on. I will try a few more days to see if this continues to work.
 
jwangl said:
Why does it take so long for my engine to warm up properly and get out of ICE? The air temp is in 60s. The hill is only the first couple miles. But my car stuck in the ICE for at least the whole way of 12 miles, including highway. It seems I have no choice but to shut the engine cold everytime because I have arrived. So almost everyday it will burn 7 miles of gas.
Click to expand...

This occasionally happens to me (I don't live on a hill so it is uncommon). When the engine unexpectedly fired up at the start of my commute yesterday (probably because I had a hard braking incident), I decided to keep the engine running because I wanted to test a few hard acceleration scenarios when I got to the highway, and I wanted the engine to be warm and running. So I put the Clarity in HV mode in order to keep the engine running. Once I was done playing on the freeway (which was only a few miles), I took the Clarity out of HV mode, and it immediately dropped into EV mode (full blue bar, EV icon on dash). So, perhaps you could try shifting to HV mode, letting it run a bit, then dropping out of HV mode?
 
Here's a piece of information to go with what has been posted so far. We too have a downhill leaving home but the engine doesn't come on. The difference is we drive one mile on EV before we reach the top of the hill. the hill is a 14% grade for 1/2 mile. It seems the small drain on the battery to drive the first mile is enough to make enough room in the battery for the regen to replenish the battery before we hit the bottom of the hill. So it doesn't take much. If you don't charge to 100% overnight you might only need to charge 98% to make a difference. Just a guess of course, and I don't have the means to cut off a charge at 98% so...
 
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