Hypermilers in Clarity?

Well, I have had an original insight, a Gen 3 Prius, and now the Clarity, and all three will coast and the method is exactly the same in each one and with only very minor practice, I am able to hold the Clarity in coast easily. Cost is when the power bar is on the line between power and regen
The ability to "Glide" is the key to getting great mileage around town in both Hybrid and electric mode. When one is reading the terrain, traffic, and signals and goes into coast as soon as it is recognized that conditions will require one to slow down, a hypermiler will go into coast mode because the sooner one gets off of the power, the less power is used to begin with. Regen is not nearly as good at putting energy in the battery as the accelerator pedal is at taking it out. A very long glide then means that while you don't get as much regen, if you are doing it right, you stopped the energy drain far before another driver would have and this has saved that energy.

Clarity actually has an excellent glide, and that is probably due to advances in tires, lowering their rolling resistance. The Gen 1 Insight was a great gliding car when one over-inflated the tires, and getting 65 to 70 MPG around town was pretty easy. The Gen 3 Prius was not as good a glider as the Insight, but it was a far better hybrid than the Insight. Even running the AC destroyed the mileage in the Insight.

Why is it important to know? Well, for most people, it probably is not. Me? Well, I know that I can't be in HV mode all the time, so the question then is how much carbon emission can I prevent by driving the car as efficiently as possible? If I can reduce my gasoline consumption by 20% over what someone else might get, that means I am greatly reducing my carbon footprint.

On trips, I will likely try to travel at 65 MPH because as a hypermiler, I know from 18 years of experience that on the highway, nothing reduces mileage as much as speed, and the consumption difference between going 65 mph and 75 is quite noticeable. Would it matter to most people? No, probably not, but I like feeling like I am doing as much as do to lower my carbon footprint, and burning gasoline (which is sometimes necessary, yes, or we would likely not be driving a PHEV) makes me feel better, though I fear that we are too late in lowering the amount of global emissions.

So, a personal preference. I just wanted to hear tales from others that are actually applying hypermile techniques to driving in the Clarity.

 

Ok, here is second full segment in full HV and I am pretty happy with the result.

I would remind people that this is my third hybrid (Gen 1 Insight, Gen 3 Prius, and now Clarity) and I have been hypermileing for many years now.

The car had a full tank of gas, and battery was topped off and EV range was reported as 51 miles. Temp was about 84 average for the trip.

HV mode was engaged in the driveway before moving the car, so the entire trip out and back was made in HV mode. (I stopped for a half hour on the trip, but the car was once again put into HV mode as soon as I turned the car on, so 100% of the

The trip was mostly limited access highway with about 4 to 5 miles on regular roads, but mostly highway access type roads and I probably passed though 12 intersections with traffic lights but by careful hypermile technique, I avoided having to actually stop that much.

The biggest tip for getting a lot of mileage is to watch speed. The posted limit for much of the trip was 65, by my actual speed on the highway probably averaged 62 mph and while some of this was just the speed of the traffic, most of it was just my own desire to go a little slower when I feel that traffic conditions allow it (Hypermilers will usually do the posted limit in heavier traffic to avoid making people angry, but will often slow down a little bit when they can... That is what the sport is about).

Round trip was 35.5 mile. Mileage consumption according the car readout was 71.4mpg. Now this is really excellent. I struggled to get that kind of MPG out of my Honda Insight (mileage plummeted when the AC would come on, and while I am willing to slow down a little bit, I am unwilling to ride around without the AC on). EV Range remaining at the end of the trip was 51 miles.

This is the way the car behaved (for those interested). For the first part of the trip, the car off of the traction motor alone and the ICE did not come on until I entered the freeway on ramp about a mile from my home. As I accelerated on to the ramp the ICE came on and I could see that the mileage readout dropped from 199mpg to about 178mpg just in the time it took to come up to speed. Once at speed, the instantaneous readout showed 42 mpg, and the car display showed that the clutch that couples the ICE to the drive wheels was engaged. The car ran this way for a couple of miles, then the instantaneous readout immediately pegged back up to 199mpg, but the average of course started to lower.

As I cruised, I watched the power readout and I could see that when the ICE was on and the clutch was engaged, the instant display would drop to about 40 to 42 mpg. After a couple of miles, the instant display would jump to 199 and the clutch would disengage so the car was running only on ICE. I had thought that the ICE would mostly stay in direct drive, but it in fact cycles on and off at regular intervals, but when it comes on, it will almost always both show the clutch engaged and the generator also delivering some charge to the battery.

By the time I reached my destination, the mileage consumption had dropped to about 81mpg.

On the return, as soon as I hit the on ramp, the consumption readout fell to about 70 mpg. On the rest of the trip back, it would drop a tiny bit, then the ICE would come on and both drive and charge the wheels, though on slight hills, you could see that the current would reverse out of the battery to supplement the power of the ICE. On the way back, the instant readout would cycle between about 40/42 and 199mpg, and the consumption indicator hovered at 70 to 72 mpg. I suspect that on a very long trip, the mileage consumption would slowly creep down.

On the surface streets, anything over about one and a half major hashes on the power indicator would start the ICE. Very gentle acceleration would allow me to get to 40 or 50 mph before the ICE would kick in, and while I have read that the clutch engages at 47, I found that it does not engage until almost 60 in light acceleration with the ICE running at mid speed (you can hear it but not annoying) to provide extra current. At very low speeds, the ICE is audible when it comes on, but no more so than my Gen 3 Prius was when accelerating at low speed. Of course it is not super placid quite of full EV mode, but it was subdued enough that it was not at all bothersome.

I had expected that at highway speed, the ICE clutch would always stay on, but the car did alternate back and forth between ICE direct drive, ICE Motor generator, and full electric. Perhaps if the car had a couple of passengers and baggage, the ICE clutch would stay engaged more more of the time because gasoline engines are more efficient when the engine is under load at mid range throttle (less pumping loss) but clearly the 1.5L engine is not able to keep the car going up even slight inclines without electric assistance (or at least this is perhaps the more efficient way to do it, which is to keep the ICE running in its most efficient throttle plate opening for the load and using the traction motor to supply the delta power needed for slight acceleration or climbing).

I would assume that the engine does revolution matching when it engages the clutch (good because clutch wear would be a serious concern if it did not) because engagement is so seamless at highway speed that the only thing that gives it away is the very sharp drop in the instant readout.



At the completion of the trip, the EV battery still showed full charge and I used so little fuel that the fuel gauge still read full. Of course this means that I used a half gallon of gas on this trip, but that makes it so that this trip was actually cheaper for me running in HV mode than it would have been in full electric.

This is only my second segment where I ran fully in HV mode, but the first one (about 23 miles) I pulled in 68mpg, and that was mostly around town with almost no highway driving. This was hard to get, but no harder than it was to get that same mileage in the city driving the Prius.

For others that have hypermile experience, I would expect you to be able to get the same result without too much effort. It is a pretty easy car to exceed EPA rating in (the Prius was harder for short trips because of the need to heat the cats, which meant many shorter in town trips I would never get over about 38mpg).

 

I also considered this... Since I started with a 100% full battery, it is possible that I saw more cycling back and forth between ICE and traction motor because the generator has to keep putting current into the battery to offset the drain of the environmental and electrical systems in the car. I may do a segment with the battery staring at maybe have of a charge state to see what happens but clearly the program tries to always ensure that the battery is maintained at the charge state that it was at when the car was put into HV mode.

It is a very different kind of hybrid than the Prius (which I greatly admire as having the most advanced power spit in the industry. No clutches, and I was and actually am quite concerned about the Clarity clutch longevity after replacing the clutch in the CVT on the Insight after 60,000 and the traction battery twice, once in warranty and once not in warranty. I swore I would never buy another Honda Hybrid again, and I hope that I do not come to regret the decision to do so. It is a very complex car).

 

Update. Had to run an errand this afternoon, and with the heat of the day, the mileage in HV mode really plummeted I am sure due to the AC. I was going south and had to cross the lake, so I lost 200 feet of elevation on the way to the lake, but almost 400 ft in the climb out of the valley, and this dropped my 71.4mpg starting average down to 66 MPG and in the remaining 15 miles on the highway, it fell another 4 mpg, so with the AC chugging, drop was pretty substantial.

I re-set the trip meter when I got off the highway for the drive across town. I got 52 mpg going across town and this included a hang up at the commuter train crossing that lasted through two cycles of the traffic light. I was just sitting there sucking battery (that the ICE of course tried to recharge when the ICE did finally come one after I was moving). Within two blocks, the mpg average had gone from 199mpg to about 28mpg, and in the next 3 miles I was able to bring it up to 54 mpg, but it was true effort. I had to do a lot of coasting, and I did not have enough time for the battery to fully recharge back to 51 estimated range. That segment was fairly flat, and if I had not been stopped by the train, I probably could have gotten a bit more, or if I had a bit longer to roll, I could perhaps have also brought it up a bit.

This is where the Clarity will struggle. In HV mode, the program seems to try to put the battery to where it was when you when into HV. On the climb up from the river, I dropped a bar, and of course when I got back to flatter highway, the engine was both driving the car and charging the battery at the same time, so instant mileage was 38 for about 3 miles. That really took down the earlier numbers and when I exited the highway, I was at 64 mpg, but it was falling very slowly during the trip, and I suspect it was just the AC. Darned hot in Austin these days.

Also, in spite of the EV range staying at 51mpg on the first trip today, I do believe that it did use some small amount from the battery so the first report of 71.4 was probably a couple of MPG to high. When I finished the running around today I took 2.4KW. I know that I lost some of that to the hill and the HV probably never had time to fully recharge the battery and sitting at the railroad crossing for four minutes consumed a lot too, so in both cases, mileage was clearly not quite as high as I reported, though I am pretty comfortable that with good weather, I can stay ahead of the EPA rating for HV mode.

Around 60 mph steady state is probably going to yield the highest HV mileage. At this speed, the ICE does quite a bit to propel the car by itself, but even a slight touch of the throttle will bring in the battery and that is what kills the HV mileage. (It was the same with the Prius and Insight. Oddly, the best mileage was usually obtained by using the battery as little as possible because the ICE recharging the battery to move the car is not nearly as efficient as the ICE directly driving the wheels).