"Normal" PU (my current understanding of the layout)
<-front) [ICE]=||=[MGU-K]=[Gearbox]=[Differential] (rear->
<-front) [ICE]=||=[Gearbox=||=[MGU-K]]=[Differential] (rear->
On the Honda PU, the MGU-K is built into the transmission casing and separated from the transmission with a clutch which has several benefits but also a few drawbacks.
The transmission only needs to be built to transmit the torque the ICE can generate, which means it can be lighter
The MGU-K is connected to the differential and can be decoupled from the ICE, which means that the torque to the wheels can be mapped very precisely (if you ask for 200Nm of torque from an electric motor, you get precisely 200Nm. If you ask for 200Nm of torque from an ICE, you can get 200+/-15Nm -- paraphrasing the example Kiesa used)
The power from the MGU-K is not subjected to the losses in the gearbox, which means that the Honda PU can potentially utilize both ERS-K and ERS-H with higher efficiency due to less energy wasted as friction (and heat) in the transmission
The MGU-K gets up to 300 degrees Celsius when recovering and deploying energy. As it runs inside the gearbox, it needs to be sealed against the gearbox to avoid gearbox oil entering the MGU-K and to ensure that whatever cools the MGU-K doesn't leak out into the gearbox (not sure what the latter part is supposed to mean -- maybe there's some liquid cooling inside the MGU-K?)
The seal between the MGU-K and the gearbox is apparently not durable enough to withstand the temperatures seen in real driving conditions, which means that the MGU-K needs to be run in a lower setting to avoid it failing and becoming leaky.
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