I know this is a three-year-old thread - I just found it. I just can't leave all of this misinformation uncorrected, even though I have explained it elsewhere (and I'm not sure I was believed). Also, I'm not trying to talk down to anyone, which I think may have been the impression there.
Most of what non-automotive engineers think they know about an ICEV's drivetrain is pretty superficial. And that's not a bad thing, because they don't need to know more. The problems come up when they try to translate that superficial knowledge to Hybrid Electric Vehicles and Battery Electric Vehicles. Those drivetrains simply do not work the same way, and the knowledge does not apply, even superficially.
POINT #1: Electric Motor Generators (MGs) do not perform the same task as Internal Combustion Engines (ICEs). Or more accurately, an ICE performs two tasks, and an MG performs only one of them - arguably the less significant one. The ICE (1) converts stored energy into usable power and (2) converts that usable power into mechanical power in the form POWER=TORQUE*RPM. An MG needs some other device to turn stored energy into usable power in the form POWER=VOLTAGE*CURRENT, and the MG changes that into POWER=TORQUE*RPM.
POINT #2: The power rating of an ICEV is the maximum power that the ICE can put out. It applies at only one rpm, so it is almost never possible to achieve. I suppose a perfect CVT could do it, but I'm not sure that any will choose that rpm. And it is measured at the crankshaft, with the ICE taken out of the car and put on a test bed. The point here is that this power rating is meant for comparison only, not to suggest it can be applied to propulsion.
POINT #3: Other devices in the car need power, and in an ICEV they take it from the crankshaft. Then there are losses in transmission. So even if the ICE runs full throttle at the right rpm, not all of that power can reach the wheels. An
estimate that I have heard in several places (
one is here) is that at most 85% of the ICE's maximum power can reach the wheels. I don't know how good that is, or how commonly it is used, but I do know Honda uses it.
POINT #4: The power rating of an MG in an HEV or BEV is completely different. It is the power that the MG can convert to mechanical power, and it is applied after all other power draws and most other losses. Essentially, it
can be considered to be propulsion power. While I'm not suggesting that the power curves work the same way in ICEVs and EVs, the simplest comparison is that an ICEV "has the same power" as an EV whose MG is rated at 85% of the ICE rating.
POINT #5: These Honda iMMD hybrids achieve maximum power in Hybrid Drive, not Engine Drive. That is, clutch open, not closed. That is the 181 HP MG in the Clarity, Accord, and CR-V. In order to fully power this MG, using the same 85% rule, the electrical system would need to provide 181/0.85=212 HP of electrical power. This is where the 212 HP rating comes from. It is a value for comparison, not a rating of any part of the system. It can probably make more, but (according to the estimation rule) never needs to. Before 2023, every Honda iMMD hybrid used this same method - the HP rating of the HEV was the HP rating of the drive motor, divided by 0.85.
POINT #6. Only a serial hybrid can use this simple method; other types mix ICE power and MG power. I don't know when it happened, or how it works, but there now is an ISO standard for the HP rating of an HEV. It makes some measurement of performance, and gives the HEV the rating of an ICEV with the same measure. Like I said earlier, since the power curves are very different, this really isn't meaningful. But the pre-2023 Accords and CR-Vs were "downgraded"
to 202 HP. I don't know about the Clarity.
