Car drops into HV mode randomly & engine racing

10595 Views 20 Replies 14 Participants Last post by 2002, Jan 20, 2022

[email protected]

Discussion Starter · Sep 8, 2018

I drive around town daily and rarely go enough miles to drop into HV mode, as the ~47 mile EV range is 95% sufficient for me. I keep the car in EV Econ mode and I find that the car will occasionally shift into HV mode at low speeds at a near-full charge on flat residential streets. After a few minutes, it will usually move back into EV mode, but this is frustrating as I really don't want to be in HV mode while I have a charge.

A secondary issue is that while in HV mode, the engine speed doesn't necessarily have anything to do with your current speed, acceleration or grade. I've had multiple instance where I'm at a steady slow speed (e.g. 20-25 MPG), or coasting on the freeway (65-70 MPH), or decelerating using regenerative braking, where the engine is revving at a very high speed. In a couple of those cases, the revving was high-enough to vibrate the interior panels and make the car sound like a 1976 Honda Civic 1600cc. Not good.

I'm wondering if anyone else has run into this issue. From a software standpoint, this vehicle has been updated with the patches in SB 18-069 and SB 18-079.

Please advise if you have experienced this and/or if you know of a solution.

Thanks,

Kevin

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firsthonda

· #2 · Sep 8, 2018

The same thing happens to me. The first time I noticed it I was sitting in my car with the window down talking to a neighbor and I heard the ICE start (it probably happened before and I never noticed it because I usually drive with the windows up and can't hear it but this time I had the window down and was stopped so there was no road noise to cover up the sound of the ICE running). I realized that it was probably normal and surmised that that was done intentionally by Honda to keep the ICE lubricated. All ICE cars need to be started occasionally to keep the ICE in good condition. Do not be worried the amount of gas used is insignificant I recently topped off the gas tank with slightly less than 2,000 on the odometer. I had a hard time squeezing 0.04 gallons in the tank.When I owned a Volt I talked with Volt owners that went for a year without using any gas. Can you imagine what would happen to the ICE if the ICE did not run for a year? I suggest that you top off the gas tank and drive for about 1,000 and then try too add gas to the tank. I am guessing that you will only be able to add about 0.02 gallons of gas which is a small price to pay to insure the ICE remains lubricated and in good condition.
I am interested to see how much gas you use. If you use much more than 0.02 gallons of gas take it to the dealer. Please get in touch with us in 1,000 and lets us know how much gas you used.

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[email protected]

Discussion Starter · #3 · Sep 8, 2018

I appreciated your reply. It makes sense that the ICE would run occasionally (mine did again this morning). I haven't filled the tank in about 500 miles, so I'll get to the 1,000 mark soon and try the top-off.

Have you experienced the racing engine in HV mode?

firsthonda

· #4 · Sep 9, 2018

I honestly do not know what you consider or define a racing engine. When my engine runs it mimics the speed and sound of an old fashioned engine way back when the ICE was using carburetor that used an automatic choke and you if it ran on a cold morning to warn the cabin.

I Wrote this a few hours ago and forgot to hit the send button, because I have been falling in and out of sleep due to the fact that I have been suffering from a migraine for the past 18 hours. Although there was a delay in sending the additional info. I hope the additional information has helpful

Also please ignore any typos because the migraine makes it difficult to focus

pqdad

· #5 · Sep 10, 2018

when you experience the ICE racing what is the % charge in the battery. I have noticed it but not completely odd times. Say if i am climbing a tough hill/mountain in HV or even with low charge the ICE will rev probably to get the power at low speeds esp to get up the hill/mountain. Hasn't happened much and then other times i realize the ICE is running and realize I never even heard it.

firsthonda

· #6 · Sep 10, 2018

We are talking about two separate issues. The first issue was brought up by the OP that the ICE running a minute or two. This is done through computer being programed to run every week or two. This is to make sure the engine stays lubricated

Now to answer your issue

First of all remember that The Clarity ICE is approximately the same size as Honda Gold Wing or Harley motorcycle engine but the Clarity weighs about five times more than those motorcycles. The reason that Honda was designed to hold two bars of battery in reserve is the small engine. it has enough power to drive a car on a flat level surface but a small ICE is going to need help to climb a steep high mountain. and that is why the car's computer is programed to hold two bars in reserve. If you are driving up a long steep grade and you anticipate that you will need greater assist you car charge the battery using the ICE or you can hold more than two bars in reserve

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firsthonda

· #7 · Sep 10, 2018 (Edited)

just for the heck of it I checked the net and found out the largest Harley Davidson engine is 110 cubic inches which makes the Clarity engine slightly less 400 CCs Smaller. It's somewhat amazing that a Clarity is able to propel the car with an ICE smaller than a Harley.

Jgillmer

· #8 · Jan 31, 2019

I've had the 2nd issue happen, too - revving...but it is random, not just when low on charge or climbing a hill. It can feel like the car is suddenly thrown into neutral. One day, I had a hard time getting the car out of the parking lot at work and went straight to the dealer...of course I got the "I can't recreate." The revving feeling isn't always there...there are times when on the ICE, it drives fine (not tearing up any roadways, but does the job). But when it does it's revving thing, I want to scream...feels like a transmission issue, like it's forgotten how to shift gears.

lefty

· #9 · Feb 5, 2019

See my 'Scary Problem' thread

for my description of the same problem recurring repeatedly.

Groves Cooke

· #10 · Feb 13, 2019

From the owner's manual:

"Auto Engine Stop/Start
The car will select the appropriate source of power depending on the drive mode you select.
As a result, the engine will automatically start or stop as needed to either charge the battery or provide supplemental power.
Under certain circumstances, the engine may turn on or, if it is already on, it may not turn off.
● You are going uphill or accelerating aggressively.
● The climate control system is in heavy use.
● The Ambient temperature is too hot or too cold.
● The High Voltage Battery state of charge is very low.
● The vehicle is running a system check.
System Check
When the engine initially starts (between the time the POWER button is turned on and turned off), the vehicle conducts a system check.
● While the check is being conducted, the engine may periodically turn on and off. This, however, is normal.
● The curved blue line in the POWER/CHARGE Gauge will not appear during the system check (EV indicator may still turn on).
● Once the engine starts, it will continue to run until the system reaches operating temperature.
The curved blue line in the POWER/CHARGE Gauge will reappear once the system check is completed."

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Datadad

· #11 · Feb 18, 2019

What do the various colors on the power charge gauge signify? and what do the green "Fleur de Lis" that appear when I turn off the ICE signify. "Can't think of a better description of these symbols and there are more each time they PPEAR)

MPG+

· #12 · Jan 30, 2020

I have experienced the engine racing also, at least twice since I bought the car in October. Today I was driving on a secondary road when it started (while in HV mode); didn't last as long as before, only about 30 seconds, but the engine was absolutely screaming, as if I had pushed down on the gas without releasing the clutch in a manual shift car. This can't be good for any engine. I don't buy the explanation that the engine is only lubricating itself; it should not have to rev so much to accomplish that. I wonder if the continuously variable transmission belt is slipping? Plus, I've always wondered why the engine must rev to a smaller extent whenever the engine turns on. What is the purpose of that? My old C-Max hybrid never exhibited any engine racing. I wonder if there are any Honda engineers watching this forum who could provide technical explanations for the Clarity's behavior.

Kerbe

· #13 · Feb 1, 2020

MPG+ said:
I wonder if the continuously variable transmission belt is slipping?

The Clarity doesn't have a "traditional" CVT - the secondary electric motor (the starter/generator) serves as a computer-controlled "e-cvt", serving the same purpose. So there's no belt to slip. The e-cvt decides how much torque the car needs and how to produce it: From the traction battery, from the generator and traction battery, from the generator and ICE or from the generator, traction battery and ICE. It also sets the speed at which the ICE needs to run.

quiet-cheese

· #14 · May 19, 2021

the mismatch between engine RPM and speed is very typical for Honda i-MMD hybrid system. As in most case, (below ~ 60 mph) the engine never directly drive the wheel. It spins the generator unit, instead. When it spins the generator to generate electricity, the electricity generation rate does not need to match the current power needs of the vehicle. The computer will determine what's the most efficient RPM to run the engine in a longer time scale (long than the instant moment of power request) If engine's current power generation output is smaller than demand, then the battery is used to supplement the needs. If the power generation is greater than the needs, then it stores the extra energy into battery for later use. This way, it avoids constantly spinning up and down the engine, keep it running more efficiently. That's the beauty of this system.

miserly

· #15 · Jan 3, 2022

I'm here because of issue #1, where the engine runs even though there is plenty of charge in the batteries; sometimes it is from the start at leaving the house. i'm guessing it is because it's been very cold (high 30's and low 40's).

2002

· #16 · Jan 3, 2022

miserly said:
I'm here because of issue #1, where the engine runs even though there is plenty of charge in the batteries; sometimes it is from the start at leaving the house. i'm guessing it is because it's been very cold (high 30's and low 40's).

Do you have a stop sign or a downhill within a few blocks of your house? Some people have experienced that if they leave home with a full battery, and shortly afterwards use the brakes to slow down on a hill, or stop at a stop sign, the engine comes on. This is apparently because with a full battery there is no room to store regen. Now other PHEV's and EV's seem to handle this by simply using only the friction brakes in those situations. But Clarity apparently handles it in a bizarre way by starting the engine. Now spinning a cold engine makes sense to dissipate unwanted kinetic energy (and I think it would circulate oil so should be okay). But starting the engine makes no sense. And unfortunately once the engine starts it will go through the entire warmup cycle before shutting off.

However not everyone seems to experience this even in similar situations, adding somewhat to the mystery. People who do experience it on a regular basis find that sometimes they can avoid it by running maximum heat when they leave the house, which uses up battery charge. If that doesn't work some people charge a little less than 100%. Although that requires using scheduled charging and some estimating since you can't set a maximum charge percentage.

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Teri W

· #17 · Jan 20, 2022

Jgillmer said:
I've had the 2nd issue happen, too - revving...but it is random, not just when low on charge or climbing a hill. It can feel like the car is suddenly thrown into neutral. One day, I had a hard time getting the car out of the parking lot at work and went straight to the dealer...of course I got the "I can't recreate." The revving feeling isn't always there...there are times when on the ICE, it drives fine (not tearing up any roadways, but does the job). But when it does it's revving thing, I want to scream...feels like a transmission issue, like it's forgotten how to shift gears.

Same with me…sounds like it needs to shift. Helps to not let the battery get too low.

ClarityDave

· #18 · Jan 20, 2022

Teri W said:
Same with me…sounds like it needs to shift. Helps to not let the battery get too low.

But since there are no gears in the transmission to “shift”, we know it’s not that.

ClarityDave

· #19 · Jan 20, 2022

2002 said:
Do you have a stop sign or a downhill within a few blocks of your house? Some people have experienced that if they leave home with a full battery, and shortly afterwards use the brakes to slow down on a hill, or stop at a stop sign, the engine comes on. This is apparently because with a full battery there is no room to store regen. Now other PHEV's and EV's seem to handle this by simply using only the friction brakes in those situations. But Clarity apparently handles it in a bizarre way by starting the engine. Now spinning a cold engine makes sense to dissipate unwanted kinetic energy (and I think it would circulate oil so should be okay). But starting the engine makes no sense. And unfortunately once the engine starts it will go through the entire warmup cycle before shutting off.

I don’t understand the specifics of why it’s done, but I can tell you that the Clarity is not the only PHEV that does this. In addition to a 2020 Clarity, we have a 2018 Chrysler Pacifica PHEV and it does the same thing. If you have a full or almost full charge and then you go down a hill and apply the brakes, the engine will start up.

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2002

· #20 · Jan 20, 2022

ClarityDave said:
I don’t understand the specifics of why it’s done, but I can tell you that the Clarity is not the only PHEV that does this. In addition to a 2020 Clarity, we have a 2018 Chrysler Pacifica PHEV and it does the same thing. If you have a full or almost full charge and then you go down a hill and apply the brakes, the engine will start up.

The only thing I can think of is that to avoid wear on the friction brakes or possible brake overheating on an extended downhill, they spin the engine. But maybe they are worried that spinning the engine could throw some leftover fuel into the catalytic converter, so they fire up the engine to warm up the converter and burn off the fuel.

Or maybe they are worried that spinning a cold engine for long periods of time is bad for it since the moving parts will not be expanded to their operating shape. Whatever the reason, it's most likely worrying about something that is unlikely to actually happen, but they decided to take the safe route, which is always the result when anything is designed by a committee.

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