KBB on Clarity transmission

bwilson4web

bwilson4web

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Hi,

I was reading this Kelly Blue Book article: https://www.kbb.com/car-news/all-the-latest/2019-honda-clarity-phev-ownership-review/2100006471/

And this is where things get more complex. Honda doesn’t use a continuously variable transmission (CVT) to link the engine to the wheels, like most other automakers. Instead, the 1.5-liter engine is connected to the driving wheels through a simple single-speed gearbox that is lighter and much more efficient than a CVT. Based on speed and load, the engine will drive the wheels alone or ask for assistance by sending electricity to the traction motor for additional propulsion.​

At first, I thought it was a Toyota style, eCVT, but here they claim it is "single-speed gearbox." Is this accurate?

Is there a good technical source showing something like a cut-away or illustrated parts breakdown?

Thanks,
Bob Wilson
 
Yep. Clarity is a single speed "transmission". The electric motor simply spins faster and faster as the car speed increases. Super simple and super reliable. When the speed of the car reaches a certain level to be synchronized with the gas engine a clutch can connect the gas engine directly to the drive wheels.

You can observe this behavior by seeing the "gear" icon which shows when the gas engine is connected to the wheels.

DSC04137-X4.jpg
 
Honda calls it an e-CVT as in electronic. Somewhat confusing since it does not have the belts and inverted cones arrangement of the usual CVT. It is largely as you described it. Perhaps they went with that moniker since the motor (ICE) speed is decoupled from the mph travel speed when not in gear lockup. And this sounds like the rpm/mph disconnect of a gasmobile CVT. So the when in use, motor turns the starter/generator at different rpms to augment the power from the battery and it’s rpm and associated electrical power output adjusts up and down like a real CVT independently of mph. It just does it without the belts and cones of a conventional infinitely “geared” CVT that every one is used to. Good news is that it works, is simple and reliable, and has long fluid change intervals (3 years under severe service and longer under regular service).
It only uses 2.23 qts of Honda ATF DW-1 or equivalent.
 
Thanks!

I found this review very useful:


So it is like our BMW i3-REx but with a parallel, mechanical drive above 45 mph. In contrast, our BMW is only a serial hybrid.

Bob Wilson
 
"Is there a good technical source showing something like a cut-away or illustrated parts breakdown?"

Check out this youtube video.

 
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Richard Kelly said:
the "transmission" must have a reverse gearing though. So it is shifting gearing at some point, right?
Click to expand...

The electric motor can be reversed without any gearing change (I presume). The engine could be generating the electricity to do so, but it can't directly drive the wheels in reverse (but it also can't directly drive the wheels forward at slow speeds either).

This is really interesting to see the different technologies of "transmissions" in these cars. The Toyota system as in the Prius and our Highlander Hybrid is a set of 3 fixed planetary gears where the engine to wheel "gear ratio" can come from varying the motor speed (so the engine can drive the wheels directly at low speed but even there the motor is still the primary low speed torque). And both of these are different from a mechanical "CVT" where there is an actual cone, belt, or other physical mechanism that changes the ratios (which personally I feel is more likely to break than either of these hybrid systems). Neat!
 
KentuckyKen said:
So the when in use, motor turns the starter/generator at different rpms to augment the power from the battery and it’s rpm and associated electrical power output adjusts up and down like a real CVT independently of mph.
Click to expand...

In theory, the Clarity in HV mode should not adjust the RPMs very much. The RPMs are adjusted for peak efficiency and the gasoline fed in is varied to create the amount of electric power needed. The idea is to optimize the BSFC (engine efficiency) for whatever amount of power is asked for. Usually the RPMs at peak efficiency vary only a small amount from minimum to maximum power output. On this map, it varies between 1500 and 2200 RPM. Angry Bees.
Brake-Specific-Fuel-Consumption-BSFC.webp
 
Last edited:
Agreed. It does seem to adjust it in steps and not a continuous curve as it tries to make the most efficient use of the Atkinson cycle engine.
 
bwilson4web said:
Hi,

I was reading this Kelly Blue Book article: https://www.kbb.com/car-news/all-the-latest/2019-honda-clarity-phev-ownership-review/2100006471/

And this is where things get more complex. Honda doesn’t use a continuously variable transmission (CVT) to link the engine to the wheels, like most other automakers. Instead, the 1.5-liter engine is connected to the driving wheels through a simple single-speed gearbox that is lighter and much more efficient than a CVT. Based on speed and load, the engine will drive the wheels alone or ask for assistance by sending electricity to the traction motor for additional propulsion.​

At first, I thought it was a Toyota style, eCVT, but here they claim it is "single-speed gearbox." Is this accurate?

Is there a good technical source showing something like a cut-away or illustrated parts breakdown?

Thanks,
Bob Wilson
Click to expand...
For those not following the Kelly Blue Book 2019 Honda Clarity One Year Ownership Review, Michael Harley has posted a May update about the lumber hauling capabilities of the Clarity.
 
bwilson4web said:
Hi,

I was reading this Kelly Blue Book article: https://www.kbb.com/car-news/all-the-latest/2019-honda-clarity-phev-ownership-review/2100006471/

And this is where things get more complex. Honda doesn’t use a continuously variable transmission (CVT) to link the engine to the wheels, like most other automakers. Instead, the 1.5-liter engine is connected to the driving wheels through a simple single-speed gearbox that is lighter and much more efficient than a CVT. Based on speed and load, the engine will drive the wheels alone or ask for assistance by sending electricity to the traction motor for additional propulsion.​

At first, I thought it was a Toyota style, eCVT, but here they claim it is "single-speed gearbox." Is this accurate?

Is there a good technical source showing something like a cut-away or illustrated parts breakdown?

Thanks,
Bob Wilson
Click to expand...
Wow great "long term" article on our PHEV Clarity!
I am still learning a lot more tidbits from all of you and the Internet!

1. Windows double laminated and wheel wells acoustically dampened = quieter ride.
2. ICE engine disconnects to prevent friction loss during EV.
3. Honda's computer maximizes distance than humans trying to "outsmart" it...
 
bwilson4web said:
Hi,

I was reading this Kelly Blue Book article: https://www.kbb.com/car-news/all-the-latest/2019-honda-clarity-phev-ownership-review/2100006471/

​
Click to expand...
​
This seems like one of the dumber articles about the Clarity I have seen. Statements like "it did an amazing 156 mpg" never seem to make any mention of the fact that they were using electricity for most of those miles. You could get a million miles per gallon if you always plug it in, but it means nothing. You gotta separate out the gas from the electric miles. Especially since its an automotive publication and not some general interest blog. He also seems to be trusting the dash readout of mpg! Not good journalism at all. It falls fully into the category of fake news.
 
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