2019 Clarity Touring PHEV: high rev engine when running out of EV range while driving

That's typical of the car's behavior with a depleted traction battery. The engine has to work harder to generate enough electricity to power the electric motor without taking the battery down to zero. There has to be enough in the battery to allow for whatever unknown needs may be ahead.

 

Solution: keep a few bars of charge.

 

If you search for "angry bees" on this forum, you'll find page-after-page-after-page discussing the Clarity PHEV and its high-revving engine.

 

Some of this behavior is dependant on what you are asking the vehicle to do after it reaches 0 EV miles. When reaching 0 miles, the Clarity is operating in HV mode and it attempts to maintain the SOC at somewhere around 10% which is the normal low point. If your driving is demanding (high speed, extended uphills, heavy headwinds, etc.) it will have to work very hard to maintain the SOC, and hence the "bees" will swarm. I find that with reasonable speeds and flat terrain, there are no bees, and operation is really no different than when in HV mode with a substantial number of EV miles remaining. If you stop and re-start, it is possible that you establish a new SOC 'setpoint' (a little below 10%) and thus, you stave off the bees [likely temporarily].

I generally try to not operate with zero EV miles unless it is in the final stretch before arriving at a charger (home). If I am on a trip that exceeds the EV range, then I intentionally switch to HV with ~50% of the battery capacity. Then when I reach the point where I can essentially just make it home with the remaining EV miles, I switch back to EV and proceed to deplete the battery.

I think you will find that with a little thought and experience, you can largely avoid the Bees.

 

Think about it this way. The car is equipped with a 181hp electric motor. With the exception of Engine Drive Mode, the car is propelled by the electric motor.

From the energy in the battery, the motor can produce 121hp. The engine generates electricity which is capable of producing 60hp at the motor. Once the battery is depleted, 2 bars, you’ve got a 4000lb vehicle being powered by an engine driven inverter generator that is capable of sending 60hp to the drive axle. The generator is simultaneously attempting to maintain the depleted SOC of the battery, say ~10%.

There is a disconnect between what the engine/generator is doing and feeling of acceleration one feels in the car. The engine revs and there is little or no acceleration. Similar to a slipping clutch. This is normal.

The easiest solution is to not allow the battery to become depleted. Switch to HV when there are 4-5 bars remaining. Other options are to switch to HV Charge which may maintain a steady engine RPM, or at least allow the battery to gain some charge, after which, the car could be switched to HV Mode. Others have suggested that using premium fuel reduces the noise and possibly the RPM’s.

 

My 2020 does not have that problem. Engine kicks in very nice, practically unnoticeable- unless I am climbing a big hill.

 

"Angry Bees" aren't just a symptom of the Clarity. I had a 2012 Volt that always revved high after the battery depleted. It got significantly worse as the battery degraded. Also, somewhere around 7 years and 70k miles on the odometer, the Volt started to give a "Propulsion limited" error on the dash if you ever ran out of battery and killed the engine and then restarted it (without charging the battery). When in the "Propulsion limited" mode, the Volt was no fun to drive, very sluggish and extremely slow to accelerate, and engine revving at high rpm. The fix from Chevrolet was to adjust the lower end of the battery reserve upward so that the engine would start earlier (reduce usuable battery - reducing ev range). Instead of the fix, I elected to just follow the advice here and try to never deplete the battery until I was at a recharging location. Luckily the car had "Mountain mode", somewhat like the "HV Charge" mode of the Clarity which would allow for this. The 2011-2012 Volt didn't have a "Hold" or "HV" mode. I traded the 2012 Volt for a 2019 Volt. I drive the 2019 Volt the same way as I drive the Clarity, holding a good bit of the battery until I can deplete it just as I get to a recharging location.

 

How can that possibly be?

 

If you can find the thread, you’ll be able to read all the explanations.

 

It does seem a little bit like cold fusion, but enough people have said that they notice a difference that I don't completely rule it out, even though it defies common wisdom and is also not something that occurs with other cars. Then again Clarity is not other cars, especially in regards to the software that controls the engine. After all this is the car that has been known to start the engine when you step on the brakes with a full battery. Although that also is anecdotal as not everyone experiences it. (I understand that a full battery cannot accept regen, but that still doesn't explain the engine coming on).

My personal theory about the Clarity software in general is that it overreacts at times. To be fair the software has to make decisions without knowing what is actually happening or how long it will happen. One of those situations is accelerating from a stoplight with 0 EV miles. The battery still has about 10% usable SOC in that situation (it will happily go down to 1% in some situations before starting ICE), so there should be plenty of electric power to handle the initial acceleration then gently bring on engine power as the speed increases, by which point the road and wind noise will help drown out the engine sound. But instead it's as if the moment that you step on the accelerator the car thinks you might be heading up a mountain, and oh no we don't have enough charge for that so we better go to full RPM and start building up some charge right away.

My theory about the fuel is that even though the manual says "octane number of 87 or higher", which for most cars means that you are wasting money by using higher octane than the minimum, it's possible that in some situations the Clarity could really use a little bit higher. No big deal, if the sensors are indicating that ignition might be happening a little too soon then it simply richens the mixture a bit. But that also could throw the software into a different algorithm, one that has more of a tendency to overreact with higher RPM. Using higher octane fuel may help avoid those situations. That may sound crazy, but so does only charging to 95% to avoid the engine coming on when you step on the brakes, but there are people who do that and I am not going to say they are imagining things.

 

I tried premium fuel once and could not perceive any difference in performance or engine noise.

 

It's been seen in previous discussions that not everyone notices a difference. This could mean that the effect depends on driving situations, driving habits, model year, the owner's sensitivity to engine noise, etc. Either that or as some people have bluntly put it, it's all in people's minds. I just think that enough people have reported hearing a difference that it's possible that at least in some situations the RPM's that the computer selects can be affected by the type of gasoline. Keeping in mind that unlike a regular car where engine RPM is constrained by what the wheels are doing, the Clarity computer can do pretty much anything it wants to with the engine at any one moment, depending on what it perceives to be not only the current electrical demand but also predicted future electrical demand that it needs to store up for. What strategies it uses, what parameters, etc. we have no way to know, other than what we can try and infer from observation.

However the type of extensive controlled testing that would be required to prove or disprove the claim that fuel type can affect engine noise is likely far beyond what anyone is willing to do. So in the end whenever this discussion comes up there will probably continue to be people who dismiss the idea outright which is understandable, those who try it and say they notice a difference, and those who try it and don't.

 

That pretty much sums up every discussion.

 

It is trying to recharge the battery at an efficient speed so that the battery can assist the engine later. Don't try to trick the car into doing something else just because you don't like what it's doing. Revving at a constant high RPM is what the engine is designed to do and it does it efficiently. It is a generator and is not proportionally tied to speed or power like in a vehicle with a traditional transmission.

Cheers

 

I am only on week three of ownership with about 1600 miles on my ownership. Using a scangaugeII my observations for this issue.

When at zero capacity or when HV charge is selected the ICE starts up and quickly revs to about 1000RPMs more than if it was in HV hold with the clutch engaged. Zero capacity and 80mph can result in 4500-5000rpms. MPG on the scangauge shows 19-22mpg and the load display is 79-81. HV mode normally shows 30-33mpg with a load of 70. For reference zero load is ICE off and 96 load is pedal to the floor. Regardless of highway speeds from 65-85mph the mpg and load remains the near same. The higher the road speed the higher the ICE rpms. 90mph will result in 5000+rpm. A zero battery at high speeds and incline results in 1200-1500rpms more than HV mode. This could be as high as 4800-5000rpms.

As already noted- there is nothing wrong with the engine working this hard. Think about a home or camping generator. Those operate at high load and rpm all day and all night. My only concern is how quick it starts and then operates at higher RPM and high load on a cool/cold engine.

Solution as noted above by others. Don't let it drop to zero EV range. Depending on your speed and elevation: turn on HV mode 4-8miles with EV range remaining. In some cases the EV will consume a few more miles of battery before the ICE turns on. So account for your speed and elevation.

One trick is to accelerate hard enough to turn the ICE on and then back off the acceleration. This will tell the ICE to turn on and apply power, but you've then slowed down on the acceleration. The ICE will operate at 1500 rpm under a 20 load until it warms up to 160 degrees sometimes 180 degrees and then turn off. Do this trick when you know that you will soon need to use the ICE under a heavy load and heavy RPM such as HV charge or EV zero battery.

Just my brief observations using a scangaugeII to watch ICE load, ICE RPM, ICE water temp, and ICE MPG.

 

Yes. The ICE will operate at about 1000-1500rpm more than is needed for propulsion. In a parking lot it will high idle at 1200-1500rpm as it every slighty charges. As you drive away it will maintain 1000-1500 rpm above what would normally be needed until the battery levels back to a SOC that its happy with. The faster you drive the higher the rpm as more energy is needed for propulsion and charging.

 

Racers and engine tuners can hear and tell when the engines are pulling timing, retarding timing, due to knock. 87 octane will pre-ignite due to a hot spot in the combustion chamber, often this can be the hot spark plug tip. Pre-igntion can be heard by a sensitive ear or the knock sensor. The ECU will adjust timing to lower combustion temps. Older cars or non-epa tuned cars will run slightly richer A/F ratio to slightly cool the combustion chambers. Folks that alter engines for more power often use a colder spark plug tip- very common for turbo charge cars that run aftermarket software for higher psi.

I had a motorcycle built for racing with very high compression that needed race gas. If I rode on the streets and used high octane pump, still not high enough, I could hear and feel the pre-ignition.

Clarity specific- the ICE is 13:1 compression. IMO that is high compression for a normal ICE. I really don't have much knowledge on the atkins cycle engines to state if 13:1 is high or not.

I have a scangaugeII that will show ICE timing.When summer weather comes backs, I will try to see if I can observe the gauge showing any changings in ignition timing under full load with 87 octane.

Personally I use the current weather to determine which octane I buy. 87 octane if under 70 degrees.