Another theory for HV-charge vs HV

Discussion in 'Clarity' started by Walt R, Oct 26, 2019.

  1. David Towle

    David Towle Active Member

    One thing not being discussed here is why didn't Honda design the car so it would stay in gear mode more? It would simply mean that the ICE would be going strong during downhills to keep up the SOC like it does in HV Charge instead of shutting off like it does in HV. And on uphills accepting a greater drop in SOC before starting recovery on the next downhill.

    Having to regularly massage control buttons to keep the car in its highest economy mode just doesn't make any sense.
  2. MPower

    MPower Well-Known Member

    My experience suggests that you are right about high speeds being a deterrance to gear mode, but it is not true about gear mode not engaging when you are 3-4 miles into HV. On my way back from Burlington last week gear mode was happily engaged for quite a long stretch many miles from where I first engaged HV.

    I wonder if mode has any bearing. I am always in ECON. (I have had the car a year and don't think I have turned on SPORT more than once.)
    Clarity_Newbie likes this.
  3. I literally live in SPORT mode, and I see extended Gear Mode activation given the right conditions, so I don’t think the mode selected is necessarily factored in for when Gear Mode engages.
    insightman and HagerHedgie like this.
  4. HagerHedgie

    HagerHedgie Member

    I mean the battery’s state of charge. You can go 300 miles in gear mode.
    If you hit HV when the EV range is 30 miles then the car will tend to stay in gear mode (once the ice is warm) at speeds above 45mph as long as the EV range is at least 27. If, due to high energy demand, the charge level drops below that the gear will disengage and the revs will go up.

    Sent from my iPhone using Inside EVs
  5. ClarityBill

    ClarityBill Active Member

    I normally wait until the ICE rev's up a little: Are you watching EV range, and resetting before ICE rev?

    I don't find gear mode to be that mysterious, and it sounds like you don't either. This is my impression, do you agree:

    It appears the control system uses an SOC setpoint to control the gear mode operation. A different setpoint is used to control the ICE start and stop. When you enter HV mode, both setpoints take a value close to the SOC when HV started. When I do a HV reset, the gear mode setpoint is changed (reduced), but the ICE start/stop is not changed (it stays higher): This keeps the ICE from cycling on and off as much.

    A side note:
    It looks like you are using EV range to monitor SOC. I use an OBDII monitor, and watch SOC directly. I find the
    EV-range control-band changes with the full-battery range: The computer directly uses the actual SOC percentages for control range.
    Last edited: Nov 1, 2019
  6. HagerHedgie

    HagerHedgie Member

    I usually wait until the car disengages the gear to reset it. Sometimes I don’t bother.
    I have noticed the ice behaves a little differently after a quick reset. That makes sense about the start/stop point.
    I figured EV range isn’t exact but close. I thought getting a monitor. Do you think it’s worth it?

    Sent from my iPhone using Inside EVs
  7. ClarityBill

    ClarityBill Active Member

    Sounds like you operate the same way I do: Reset when it disengages, if I feel like it. I really like the quiet ride of gear mode, so I do tend to pay attention. I drove 42K miles in my first year, so it seems like I spend alot of time in the car.

    If I notice the ICE rpm's up, I tend to look at the OBDII to confirm before I reset, but it is not that helpful. I have had times when I confused road noise for RPM's, but it is not that often.

    The OBDII monitor is just a fun toy. I have two different cheap (<$100) units. I normally use the BlueDriver with phone app. The cell phone is on a mount, and it gives me a nice instrument cluster-type display of RPM, Coolant Temp, SOC, Speed, Catalytic Temp, and load. It can also record these to a text file, for analysis in Excel. I email them and do analysis on a laptop.

    My other cheap OBDII unit has a memory card for long-term recording, but I have immediate questions that don't need long-term studies. Also, that one does not display SOC, which is critical in understanding the Clarity. It also has the option of alarm when RPM's exceed a level. I set it to alarm when RPM went over 3K, and I would reset the HV. The alarm got annoying in a snow storm, when EV range went to zero, and RPM could not stay below 3K: I have not used it since then.

    My current question is when the Clarity engages Atkinson mode. I have not been able to determine when it is Atkinson mode. I have a more expensive OBDII system (~$800) that shows status of the valve timing actuator valve that puts the ICE in Atkinson. I am looking forward to recording and correlating that operation. The OBDII system requires a laptop, and I just haven't gotten around to it yet.

    There are other expensive OBII systems that show the battery health, mine does not, and battery health also interests me.
    David Bower and HagerHedgie like this.
  8. insightman

    insightman Well-Known Member

    Wow, I didn't know the Clarity wasn't always in Atkinson mode. Great info!
  9. HagerHedgie

    HagerHedgie Member

    I wasn’t aware either that there was a mode. I thought the clarity had a slightly offset crankshaft where it was always an Atkinson. I read that some engines can mimic that cycle with valve timing and I’m sure the clarity also uses adjustable valve timing.
    One of the main benefits of a hybrid drivetrain is that the engine can always be operated close to its best thermodynamic efficiency.

    Sent from my iPhone using Inside EVs
  10. insightman

    insightman Well-Known Member

    My 2006 Insight has an offset crankshaft even though it doesn't have an Atkinson-cycle engine. The offset crankshaft provides less friction and increases combustion efficiency on the power stroke by having the connecting rod pointing straight down, rather than angled when the cylinder fires.
  11. ClarityBill

    ClarityBill Active Member

    That is a theoretic advantage. I had assumed best thermo efficiency would be tied to an RPM range: The way the Clarity jumps RPM's, either this engine is different than all others, or the Honda people did not optimize very well.

    I saw literature that suggested Atkinson is only active at 'low' RPM's, and it dumps back to conventional 4-stroke when it needs more power at higher RPM. I am looking forward to confirmation / denial on this, and what the threshold RPM would be.
  12. HagerHedgie

    HagerHedgie Member

    You are correct. That is the main reason for the offset.

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    Last edited: Nov 1, 2019
  13. HagerHedgie

    HagerHedgie Member

    1800-3500 rpms under moderate to heavy loads achieve the best efficiency.
    High rpm’s above 5000 is when timing is adjusted back to favor power over efficiency. I don’t think clarity’s ice ever goes there. It’s a dedicated aktinkin cycle. Not a cheater one with infinite valve adjustment and a perpendicular crank.. Although I believe the clarity ice does benefit from some valve adjustment.
    I read a good article on this a while ago. I’ll look for one.

    Sent from my iPhone using Inside EVs
  14. HagerHedgie

    HagerHedgie Member

  15. 60Hertz

    60Hertz New Member

    So, newbie questions: I take it from the discussion on this thread that "gear mode" means that the ICE is engaged to provide mechanical power directly to the drive train instead of providing only electrical power to the traction motor and/or charge the battery. Is that correct? I had thought this would only happen under high power demand, to achieve the car's 212 HP "combined" max power.

    Second question: How would I know when the car is in "gear mode" from the available driver displays?

    I drive ~90 percent in EV, so I don't have a lot of experience in the car's HV realm. Thanks.
  16. Yes, with speeds between roughly 45 and 65 mph and certain low/steady power requirements.

    A tiny gear icon shows up where the power flows from in the Energy displays.

    I’m looking for an image now.

    Here you go:

  17. insightman

    insightman Well-Known Member

    The Clarity has 3 underlying drive modes that provide all the user-selectable modes: EV Drive mode (battery only powering the traction motor), Hybrid Drive mode (battery + engine-driven generator powering the traction motor), and Engine Drive mode (the Engine Drive clutch connects the engine to the single-speed transmission connected to the wheels). In Engine Drive mode, the battery can contribute power, too.

    If you try to accelerate quickly while traveling in Engine Drive mode, the Clarity will drop out of Engine Drive mode and return to Hybrid Drive mode, which provides a maximum of 181 horsepower from the traction motor.

    Now we come to the question I've asked over and over on this forum: Where does Honda come up with the 212-horsepower rating for the Clarity PHEV and why is the Accord Hybrid, which also has a 181-hp motor but a more powerful engine also rated at 212 horsepower? Some have suggested that the traction motor can temporarily be driven to 212 hp. Others have suggested that Honda calculates the Clarity PHEV and the Accord Hybrid both perform like a 212-hp non-hybrid car. Honda never says, but it's almost certain that the Clarity PHEV never develops 212 horsepower in Engine Drive ("gear") mode.
    KentuckyKen likes this.
  18. True. And in Engine Drive mode the battery is sometimes charged as well, as seen in this screen shot from a video I took:

    Last edited: Nov 4, 2019
    insightman likes this.
  19. KentuckyKen

    KentuckyKen Well-Known Member

    At the risk of sounding like @insightman and I are charter members of the Clarity Mutual Admiration Society, thanks once again for keeping us straight on those 3 drive modes that are not explained very well in the manual.
  20. Dan Albrich

    Dan Albrich Active Member

    I've driven the Clarity over some really challenging terrain (say 20 hours of driving in two days each direction) to/from Eugene, OR to Tucson Az. Using the route through Eastern Oregon and following the Nevada / California state line to some degree.
    -- Effectively constantly hitting a combination of rolling (and not so rolling, mountainous hills). Under these conditions, my car could not keep SOC even in HV mode. It literally depleted SOC. The hill challenges were too frequent, and while regen is very good, it's not 100%. So a series of hills or mountains does seem to be a degenerative case. I'm glad to say that HV recharge mode works fine in such situations, and even when using it going through the repeated hills, you see the car recover-- albeit very slowly-- the SOC. With the repeated hills, it might take a couple of hours to recharge at highway speeds, where normally if on flat ground would happen much faster.

    Like others have noted, I kind of wish there was a way to make RPM's more modest and continual. It seems the car normally will permit too low SOC (if EV range=0) and it really has to rev the engine at recurring intervals to maintain hybrid operation (and hence the reason to keep SOC up, and to use HV recharge as needed to keep SOC).


    PS: I'm also a person who had six months of Clarity not operating properly, such that HV would not maintain SOC, so I used HV charge mode frequently even on flat ground. After 'rebooting' my car by temp removal of 12v battery terminal, things started working normally for me (thanks KentuckyKen). I believe this was directly related to the system power problem I experienced early in car ownership (pre service bulletin 18-097 etc.).

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