Honda Hybrid - the best explanation I've seen!
- Thread starter Kerbe
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Groves Cooke
Active Member
Thanks for posting this. I think this answers a lot of questions that have be speculated on this forum.
JustAnotherPoorDriver
Active Member
Alex is great. I watch him often
The Gadgeteer
Active Member
Alex is the best car reviewer
So the Clarity PHEV has to go 110 mph in Engine Drive mode to produce Honda's claim of 212 horsepower? However, Honda electronically limits the Clarity's top speed to 100 mph. No soup, er, 212 hp for you!
PHEV Newbie
Well-Known Member
Alex's video explains how I got 52 mpg (actual all HV, measured by gasoline fill-ups) average on two 200 mile loops going 50-55 mph but only 44-45 mpg at 70 mph on the interstate. Also explains how braking can be all regen until the last moment under normal conditions.
ClarityBill
Active Member
I wonder about his calculation to achieve 212 HP at over 100 mph:
Looks like he is using constant torque on each engine (ICE and electric), and the same RPM on both.
212 HP = HP of ICE + HP of electric
212 HP = (99 ft-lbs x 3400 rpm /5252) + (232 ft-lbs x 3400 rpm / 5252)
212 ~ 64 + 150
232 ft-lbs on 181 HP electric motor is 4100 RPM, so we will not see 181 HP on electric motor until 4100 rpm or 121 mph.
I am wondering if there are gears to allow the electric motor to run faster than the ICE?
The gears that are present look like the electric would be running faster than the ICE.
This would negate his statements.
If the electric motor is 150% of ICE speed, 212 HP is at 74 mph
If the electric motor is 200% of ICE speed, 212 HP is at 59 mph
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How unadventurous of me to not test that limit! A voice struggling inside from my youth is telling me I should be ashamed.
Mine is limited to 100mph. Tested, for science of course. Hits 100mph and no more. I figured it was to keep electric motor in range. I figured out the electric motor rpm at some point based on the documented gear ratio and it was pretty fast.
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When you're cruising over 45 mph in HV, the Clarity can decide that it would be most fuel efficient to close the Engine Drive clutch to send engine power through a single-speed gearbox to the front wheels. Some call Engine Drive mode "gear mode" because a tiny gear appears between the wheels on the Clarity's energy-flow animation.
Engine Drive mode must be the most efficient way to use the engine or Honda would not have included all the extra mechanical elements required to implement that mode. The Chevy Volt also has a mode where it connects the engine through gears to the wheels at cruising speeds.
In Engine Drive mode, if you can hear the engine, you'll notice that its RPMs are tied to the road speed, unlike in Hybrid Drive mode, when the engine speed is whatever the Clarity thinks is best to run the starter motor/generator as a generator.
However, if you're going up a steep hill or accelerating to pass, the Clarity will drop out of Engine Drive mode by opening the clutch. Then it will return to Hybrid Drive mode, when the engine is turning the starter motor/generator to supplement the electric power coming from the battery. In Hybrid Drive mode, the Clarity's traction motor can deliver 181 hp.
Many--especially me--wonder if the Clarity can deliver 212 hp in Engine Drive mode. Honda says the Clarity can produce 212 hp, but 181 in Hybrid Drive mode, and 121 in EV Drive mode (when only the battery is powering the car). Alex on Autos says the 212 hp in Engine Drive mode is possible only at speeds in excess of 100 mph (which is supposedly the Clarity PHEV's electronically limited top speed).
Engine Drive mode must be the most efficient way to use the engine or Honda would not have included all the extra mechanical elements required to implement that mode. The Chevy Volt also has a mode where it connects the engine through gears to the wheels at cruising speeds.
In Engine Drive mode, if you can hear the engine, you'll notice that its RPMs are tied to the road speed, unlike in Hybrid Drive mode, when the engine speed is whatever the Clarity thinks is best to run the starter motor/generator as a generator.
However, if you're going up a steep hill or accelerating to pass, the Clarity will drop out of Engine Drive mode by opening the clutch. Then it will return to Hybrid Drive mode, when the engine is turning the starter motor/generator to supplement the electric power coming from the battery. In Hybrid Drive mode, the Clarity's traction motor can deliver 181 hp.
Many--especially me--wonder if the Clarity can deliver 212 hp in Engine Drive mode. Honda says the Clarity can produce 212 hp, but 181 in Hybrid Drive mode, and 121 in EV Drive mode (when only the battery is powering the car). Alex on Autos says the 212 hp in Engine Drive mode is possible only at speeds in excess of 100 mph (which is supposedly the Clarity PHEV's electronically limited top speed).
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Cash Traylor
Well-Known Member
I can say that in EV mode (no ICE) the car ceases acceleration rather dramatically approaching 100 MPH, however, that is not the case in HV mode with the ICE on. I have to go back down to Austin on the SH 130 Loop to gather more data. Passing someone requires testing this "upper limit" at times... or someone has told me! The speed limit on that "loop" is 85 MPH. Of course that is also the average speed on the North Dallas Tollway after about 7pm or before 7am....
Cheers,
Cash
Cheers,
Cash
The Honda document on the Clarity Powertrain development states that it is possible to reach a maximum speed of 100mph in EV Mode.
Green Car Reports was reviewing the new CR-V Hybrid and spoke with Naritomo Higuchi, the chief engineer for hybrid powertrain systems for Honda in Japan. First, Higuchi discussed various options for providing four-wheel drive with Honda's 2-motor hybrid system. Here's what he said about the i-MMD system after that (Higuchi didn't say if the CR-V's engine is "deadened" or running with spark plugs and fuel injectors when regen braking occurs with a fully charged battery, I wish I could ask him how this works when the Clarity runs its engine with spark plugs and fuel injectors to handle excess regen electricity):
One thing we admired on our drive of the CR-V Hybrid was the predictability and consistency of the accelerator’s response and of the three modes of engine braking. And Higuchi revealed an interesting detail: For safety, even if the hybrid battery becomes full on a long downhill grade, Honda has found a way to preserve the same level of regenerative braking—by sending electricity from the traction motor over to the starter/generator, which spins the engine a little higher just to use that energy.
[Insightman's never-ending confusion: It sounds like Higuchi is saying the engine is fully running and the starter motor/generator is working hard to spin the engine faster than the rotation caused by the combustion of the injected fuel. The Accord Hybrid supposedly turns off the spark plugs and the fuel injectors--why would the CR-V be different? Why would a system designed specifically to improve fuel efficiency waste that fuel?]
One of the key distinctions of Honda’s system, Higuchi said, is that “as much as possible we don’t send the electricity through the battery to the motor.” As much as possible it’s sent directly to the traction motor, eliminating that efficiency loss. In various cases the battery acts as a buffer, to help provide enough power when more is needed suddenly. But overall the strategy helps keep the battery smaller, keeping both cost and weight down. The whole hybrid powertrain is just 198 pounds heavier than a comparable gasoline vehicle.
Maximum performance does depend on the battery, Higuchi confirmed—so if you have a low state of charge the CR-V Hybrid won’t dash to 60 mph quite as quickly as the nine seconds we observed. The system works to keep the battery state of charge around 50 percent, to be ready for sudden performance needs or extra energy. And 50 percent would definitely access the max performance, he confirmed. It’s again part of keeping weight at a minimum.
[That's interesting to learn that the CR-V maintains its 1.4 kWh battery's State-of-Charge at just 50%. That means there's 0.7 kWh of headroom for regen braking to send power to the battery before the system starts using up excess power to spin the engine faster. That is not much headroom so the fuel-expending abatement of excess regen power might occur frequently.]
Higuchi was quick to say that the next step toward developing a more efficient hybrid system isn’t the battery; it’s the engine. With Honda’s last round of improvements to the two-motor system, it increased the most efficient range of the engine—the width of the engine’s efficiency “sweet spot”—and it’s now operating about 90 percent of the time in its most efficient range. Future development is focused on raising that absolute value, he said, and pushing the whole efficiency curve up with a higher max efficiency.
[Naritomo, why not just shut off the engine like the Accord Hybrid does? I'm sure I'm missing something--something that others on this forum have already explained.]
One thing we admired on our drive of the CR-V Hybrid was the predictability and consistency of the accelerator’s response and of the three modes of engine braking. And Higuchi revealed an interesting detail: For safety, even if the hybrid battery becomes full on a long downhill grade, Honda has found a way to preserve the same level of regenerative braking—by sending electricity from the traction motor over to the starter/generator, which spins the engine a little higher just to use that energy.
[Insightman's never-ending confusion: It sounds like Higuchi is saying the engine is fully running and the starter motor/generator is working hard to spin the engine faster than the rotation caused by the combustion of the injected fuel. The Accord Hybrid supposedly turns off the spark plugs and the fuel injectors--why would the CR-V be different? Why would a system designed specifically to improve fuel efficiency waste that fuel?]
One of the key distinctions of Honda’s system, Higuchi said, is that “as much as possible we don’t send the electricity through the battery to the motor.” As much as possible it’s sent directly to the traction motor, eliminating that efficiency loss. In various cases the battery acts as a buffer, to help provide enough power when more is needed suddenly. But overall the strategy helps keep the battery smaller, keeping both cost and weight down. The whole hybrid powertrain is just 198 pounds heavier than a comparable gasoline vehicle.
Maximum performance does depend on the battery, Higuchi confirmed—so if you have a low state of charge the CR-V Hybrid won’t dash to 60 mph quite as quickly as the nine seconds we observed. The system works to keep the battery state of charge around 50 percent, to be ready for sudden performance needs or extra energy. And 50 percent would definitely access the max performance, he confirmed. It’s again part of keeping weight at a minimum.
[That's interesting to learn that the CR-V maintains its 1.4 kWh battery's State-of-Charge at just 50%. That means there's 0.7 kWh of headroom for regen braking to send power to the battery before the system starts using up excess power to spin the engine faster. That is not much headroom so the fuel-expending abatement of excess regen power might occur frequently.]
Higuchi was quick to say that the next step toward developing a more efficient hybrid system isn’t the battery; it’s the engine. With Honda’s last round of improvements to the two-motor system, it increased the most efficient range of the engine—the width of the engine’s efficiency “sweet spot”—and it’s now operating about 90 percent of the time in its most efficient range. Future development is focused on raising that absolute value, he said, and pushing the whole efficiency curve up with a higher max efficiency.
[Naritomo, why not just shut off the engine like the Accord Hybrid does? I'm sure I'm missing something--something that others on this forum have already explained.]
Mr. Smith
New Member
Yes, when in HV mode, and the engine drive clutch pack is engaged, the engine runs at 0.805 times the 181 hp electric motor rpm (engine is turning slower than the 181 hp electric motor). Below is my understanding of how the Clarity PHEV gas engine and two electric motors operate.
There is a larger 181 hp electric motor (aka traction motor coupled to front wheels), and a smaller ~100 hp electric motor (direct coupled to the gas engine). Both function as an electric motor or generator. The 181 hp electric motor is always mechanically geared to the front wheels, and rotates 3.42 times tire rpm.
The gas engine and its smaller ~100 hp electric motor are always mechanically coupled together, whether operating or stopped. Some Clarity owners go days or weeks driving their cars with the gas engine never running. When the gas engine is needed, it's ~100 hp electric motor first starts the gas engine, and then is turned by the gas engine to generate electric power. During HV mode at highway cruising speeds of 45 mph and up, the engine drive clutch pack can engage to mechanically connect the engine to the wheels through a 0.805 overdrive gear ratio, which combines with the 3.42 final drive ratio (gear ratio of differential to wheels), resulting in an overall ratio of 2.75 (engine rpm is 2.75 times faster than wheels rpm).
Example motor and gas engine rpm relative to speed.
EV mode 181 hp electric motor driving the wheels (tires 790 rev/mile), 3.42 final drive ratio:
1,351 motor rpm at 30 mph
1,801 motor rpm at 40 mph
HV mode, and with the 1.5 liter gas engine direct driving the wheels through the 0.805 overdrive, 3.42 final drive ratio:
1,812 engine rpm at 50 mph (e-motor 2,252 rpm, 232 ft-lb max torque available 0 to 2,000 rpm)
2,175 engine rpm at 65 mph (e-motor 2,927 rpm)
2,900 engine rpm at 80 mph (e-motor 3,602 rpm)
3,625 engine rpm at 100 mph (e-motor 4,503 rpm)
I obtained the 3.42 final drive ratio and 0.805 engine overdrive ratio from a 2019 Honda Clarity Specs document (online).
ClarityBill
Active Member
That means the calculation would give 212 HP about 85 mph. (Constant torque on ICE and electric.)
I have been in gear mode at 85 mph, so both sources are providing horsepower. I do much of my driving in gear mode at 78 mph, and it stays locked in pretty well: 78 mph calculates to about 200 HP.
Cash Traylor
Well-Known Member
Darn, was really wanting the math to prove out the sweet spot was "88 MPH" (for obvious reasons...)
Cheers and I love this thread - Cash
Cheers and I love this thread - Cash