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Discussion in 'Clarity' started by MNSteve, Dec 18, 2018.
In case anybody's wondering. It was months before I finally discovered the "gear" icon.
The gear icon is also available on the dash version of the energy screen, although its smaller and even harder to see.
I've given up trying to figure out the logic of the gear as well as when the engine stops in HV mode. I drive the same 200 mile journey once a week and sometimes the engine just won't turn off, even if descending down a mountain pass -- unless I stop. Other times it will shut the engine off even if I'm a little bit in the blue....
I do have fun when the engine turns off and I try to keep my acceleration in the blue for as long as possible to keep the engine from going back on (as long as no one is stuck behind me, since it tends to make my speed vary ~10-15 mph).
A few things I've observed about the direct drive (aka the "gear icon"):
It seems like it never engages during the initial engine warm-up period.
It won't engage in HV Charge mode.
Beyond a certain speed (around 76-78 mph) it won't engage.
I haven't established a minimum speed, but I've never seen it below 50 mph or so.
I found this Aeroforce Technology Interceptor gauge that will display two OBD-II values, such as engine RPM and engine temperature, both of which would be interesting to Clarity PHEV drivers. It's likely that any OBD-II scanner could do that, and more, but this Aeroforce unit has an interesting and possibly unique optional relay module:
> New optional relay output module allows you to control a
> 12v relay based on values of OBD2 or analog input data.
If an OBD-II code is found for the Clarity PHEV's Engine Drive clutch activation, the Aeroforce Interceptor's optional relay module could be used to implement an audible alert that signals when the clutch engages and disengages. This audible alert could help solve the problem of the Clarity PHEV being too quiet inside, right?
I think it should be called the Clutch icon instead of the Gear icon. No gears change in the process, just a clutch engaging.
Sorry to be dense, but what info does the gear icon give you? Does it appear and disappear?
It just tells you when you are in Engine Mode when the ICE is on (also will see engine icon above it lit) and therefore it’s mechanically coupled to the drive train going to the wheels. At times you will also notice that electrical power may be going to the traction motor (wheels icons) or to the battery when in Engine Mode.
This chart shows the Clarity's various modes. Note that the Engine Drive clutch (or "lock-up" clutch) closes to activate Engine Drive mode.
When HV mode is in effect the Clarity's brain selects from its 3 underlying (not user-selectable) modes: EV Drive mode (battery-power only), Hybrid Drive mode (battery- and engine-power), and Engine Drive mode (battery- and engine-power with the engine connected by the clutch through the differential to the wheels), whichever it deems most efficient. However, because the single-speed transmission is like a 6th gear in a a regular car, Engine Drive mode only happens at speeds greater than 41 mph in my experience (45 mph is the nominal minimum speed).
OMG! I looked at the chart and it made my mind ache. Breathe deeply and repeat after me, "Just press the On button, the Drive buttom, and press your foot on the gas."
If you know what you are looking for, it’s pretty easy to see on the dash. I’m always using Waze in the main display (traffic in NYC can often send you on a big detour), so always have to watch for it on the dash.
The Gear icon is really kind of useless because if you want to use your map, you can't really see the tiny gear on the display in the driver gauge area.
I recommend just using the instantaneous fuel consumption display when in HV mode. When you are in HV mode, you know the ICE goes off when you see the Instantaneous display go to 199.9 MPG. If the ICE is in direct drive, the mileage will generally be above 44 mpg on the display. For example if you are going about 60 mph, when the ICE is in direct drive, the instantaneous display will be maybe 55 to 60 mpg. If you see this, the ICE is actually powering the car.
When the Instantaneous display drops to 44mpg to 38mpg, the ICE is running the generator and the electric motor is providing power. The ICE only provides enough power to move the car when the load is light (below about 65 mph maybe, on reasonably flat roads, with no head wind.). If the load increases a little bit, the electric motor will assist, but if the load gets more than just a little bit the ICE just disconnects and starts revving enough to provide current to the electric motor.
Again, the gear icon is (in my own opinion) just a novelty. You can generally tell what you want to know by looking at the instantaneous readout.
And by the way, this is the trick to getting really good fuel economy out of the ICE. The best mileage will be when the ICE is actually in direct drive. I can get 55mpg to 60mpg by watching the instant readout. If it is in the 38 to 44 range, the ICE is busy spinning the generator and this is not as efficient as when it is directly driving the car. If you slow down to the point where the ICE is driving the car most of the time, this will give the best trip mileage. Of course it means that the trip will take a bit longer though. For a trip of 50 miles where the difference in arrival time might be 5 minutes difference by going 65 rather than 70, the fuel saving can be considerable, making the small 7 gallons go a lot further (less frequent fuel stops) At 70 mph, you get maybe 40 MPG. It 65, you get far better fuel economy (over 15%, with mileage over 50mpg vs a max of 44 mpg if the electric motor is providing propulsion, and maybe 40 mpg if going over 70mph and the ICE spinning at 2500 to 3000 RPM to keep the battery charge up). Again, I routinely get between 50mpg and 60mpg, but I rarely drive over about 65 mph on shorter trips. Actually, this is not much different than what I used to get in the GEn 3 Prius running about the same speed, and the Clarity is far more refined and quiet than the Prius was. I expected to take a big hit on fuel economy because of the EPA rating, but in practice, I get about the same if I drive the same speed, and around town in HV mode, I can get between 65 mpg and 70mpg which was actually hard to do in the Prius especially in summer, when getting more than 47mpg around town was very hard.)
To recap from my last post. If the instant readout is showing 38 mpg to 44 mpg the ICE is running in generator mode. If it is higher than 44 mpg but less than 199, the ICE is driving the wheels (though the electric motor may provide some small assist..). When the instant display goes to 199, the ICE is off and the electric motor is providing all propulsion. In HV mode, this will happen from time to time because if the battery goes slightly above the state of charge that was present when you entered into HV mode, it will turn off the ICE and run that little bit of surplus charge off, then turn on again and resume propulsion.
When you learn to read the instant display, using it makes the gear icon pretty irrelevant, and if you care about getting the best fuel economy, it is far more important to see the instant readout than it is admiring the silly little gear icon coming on and going off. Again, best possible fuel economy in HV mode is keeping the ICE in direct drive as much as possible but this generally means going slower than about 65 mph. This is about as much torque as the ICE can provide efficiently. About 44 mpg or less on the instant mpg display means electric motor is providing propulsion and the ICE is running as a generator.
I run almost all the time in gear mode and my mileage varies from the low 30s to 40 tops, so I'm not sure how your method works. I keep it in gear mode by keeping the power gauge between about 5 and 50 except on long downhills it goes to zero. Speed average usually 72-74.
If the radio isn't on too loud, you can tell your Clarity is operating in Engine Drive mode (when the gear icon appears) because that's the only time the engine speed changes proportionally with the road speed. If the engine all of a sudden starts revving, you know the car is not in Engine Drive mode.
I think that these two quotes illustrate my point that the algorithm that determines direct-drive mode is not straightforward. My experience is that it must depend on parameters that I can't measure, perhaps the SOC when HV was selected or how many milliseconds it has been since the last engagement of direct drive. The other behavior that is unpredictable to me is dropping into EV mode, usually but not always on downhills, when HV is selected.
Normally this is not a big deal. The only time it annoys me is when the ICE revs up when I wouldn't expect it. The other day I was on the highway and someone passed me and I thought "Gee, that car is really loud" only to realize that what I was hearing was the reflection of my own engine noise from the car as it passed.
If you look at the following diagram, you can see there is a very narrow range of vehicle speed and torque where engine driving mode is used. It wouldn't take much change in required torque at any given speed to take you out of this mode.
Good point. A difference in wind speed might be enough to tilt it out of that tiny sliver.
I think that the thing to bear in mind is that it is not a specific speed, but the amount of energy needed to propel the car. I have seen the little gear icon in the 40s and also in the 70s. As long as everything in easy peasy, the little ICE is enough to do the job without the help of the big motor.
It makes sense, a "normal" car is probably running at a similar rpm on the highway, but its engine is relatively much larger so it can pull that high gear under a much wider range of conditions.