Any difference between HV and HVCharge modes on energy screen

Atkinson, thank you for the information in your post. Could you point us to the source? I am especially interested in the "fixed throttle" aspect. I will look to see if the throttle opening data stream works on my OBDII scanner (or if the code from a Honda Accord Hybrid works)

Before the October update, I think your description of the power flow and engine coupling/decoupling is what I experienced. After the update, the behavior is different for me. If the engine is coupled, say at 70 mph, and I need to accelerate a bit or increase the power to climb even a slight grade, the engine immediately decouples and the rpm engine rpm increases (from about 2500 rpm when coupled at 70 mph) to in the range of 3400 rpm to 3800 rpm. When I settle back to an an even grade and even speed, say 70 mph, it takes a while for the engine to couple again. Also, when I release the accelerator pedal even the slightest amount to go down a grade or to slow, the engine immediately decouples. If the grade continues or if I stay slowing, the engine turns off until I speed up or stay at a slower speed for a while. Even if the speed is above 47 mph or so, it takes quite a while for the engine to couple again. Before the update, the engine usually stayed coupled at these times.

I posted earlier that I thought that the engine was louder after the update. I think this may be because the no load rpm is now 1500 rpm while it was lower previously (about 1200 rpm or lower if I recall correctly). BTW, I liked our Clarity better at highway speeds in HV mode before the update. The EV mode around town does not seem to have changed after the update.

LeoP

 

If that was true, then the Engine Drive mode would always produce the exact same road speed. I believe I've seen Engine Drive mode work at more than one road speed (with the engine sound varying proportionally with the road speed).

Then again, the chart in the Honda engineers' SAE paper shows the car's speed during Engine Drive mode as a plateau (however, it's the maximum speed depicted in the chart, perhaps varying the speed in Engine Drive mode would have made the chart too complex).

 

Engine speed will vary with road speed, but the engine will always run at full load to stay in the sweet spot.

 

My comments apply specifically to running in "engine drive" mode.

 

It makes sense that Honda wants to keep the engine running in it's most efficient "sweet spot," but I don't understand how that can work in Engine Drive mode when the speed of the engine is tied to the car's road speed. In Engine Drive mode, doesn't the accelerator have to change the throttle to send more or less gas to the engine to change the car's speed?

 

FWIW, when I got the gear icon indicating engine drive mode at speeds between 48 and 58 mph on my last HV trip, I could barely hear the engine. It was not running very fast at all; more like a gasmobile sounds at fast idle. This was with no passengers and on nothing more than rolling hills.
Definitely less than when I went up a long steep hill earlier in the year ( and even that wasn’t anywhere near the angry bees).

 

Engine speed has to be tied to road speed in engine mode, but the motor stays fully (or optimally) loaded regardless of your accelerator position.
My ballpark figures are 1500 RPM at 45 MPH, 2000 at 55, 2400 at 65, and 2700 at 75.
RPM's are lower in engine mode, but I am guessing the engaged clutch adds flywheel weight (rotating mass of the drive motor) to smooth the engine NVH.
Whatever causes it, the engine is close to silent in engine mode.
I noticed in really cold weather (maybe for coolant temps/cabin heat), the engine runs longer and varies over a much wider RPM range in HV when not in engine mode.
It purrs down to 1500 RPM or less when the load is light and doesn't trigger EV mode so much.

 

Your engine rpm notes are about what I measure using an ODBII dongle. However, I do not know how to measure the engine loading and have yet to find out how to display the throttle plate position angle. The optimal loading is unknown to me as I am not knowledgeable in the efficiency versus loading for an Atkinson cycle engine.

Could you please point us to the source of your statement on optimal loading?

LeoP

 

The source is......my observations on rolling hills in engine mode.
The throttle position sensor and % load did not change over multiple trials while in engine mode.
What changed with varying accelerator position was charge flow.
I can run with no green or blue lines (all engine power to wheels).
If I then gently increase accelerator, the only change is battery contribution (blue lines).
Similarly, gently decreasing accelerator stops battery consumption until I am running engine only (no blue or green lines).
Continuing decreased accelerator begins loading the engine by charging the battery (green lines).
In engine mode, the accelerator pedal is a virtual control for the generator/motor, adding power from the battery or sapping power to send to the battery.
The engine load (throttle) is controlled by the powertrain computer in engine mode.
Because there is no "transmission" the powertrain computer is completely free run the engine at max efficiency independent of driving speed.
That control s a factor in the Clarity's MPG.

 

I cannot get my OBDII dongle to show the throttle position sensor or the %load. Do you have a list of pid's for the Clarity that I can use to display that data?

Also, does your Clarity have the October Campaign updates (specifically 18-089 and 18-090)?

LeoP

 

I have to get the updates.
My old scangauge displays TPS and load natively.

 

Update:

At the end of the day...these updates have not negatively effected the Clarity when in HV mode.

I originally thought the gear icon was less frequent a majority of the time but after a much more methodical/analytical approach...it seems the only instance that the gear does not come on is when I climb a 5% to 7% grade (or similar steep grade) for several miles. That is the only instance I can hear the engine whine but even then it is very tolerable. I believe the gear icon would come on prior to the updates climbing these grades but not 100% certain how often or for how long. So really a moot point for me from a data standpoint to be helpful.

The gear icon comes on at ~45 mph and above and engages/disengages as I remember it before on the interstates and four lanes where I can get up some speed combined with distance. I had to purposely drive meaningful miles on the Interstate and 4 lanes to conduct my analytics which is something I don't routinely do.

Otherwise the Clarity runs great. I feel very fortunate to have avoided thus far the rev issues, angry bees, loss of power etc as all these would be disconcerting if nothing else. Hopefully Honda USA will step up and work on these issues as they may ultimately affect many more Clarity's including ours.

Any increase/decrease in mpg still TBD.

Hope this helps.

Good luck.