What part of HSD is vulnerable to loss of traction requiring Traction Control

I think that's my impression. Next to nothing happening. Might as well be nothing.

 

I too would say that the gears have to be the weak link. But I've suspected for a long time that the polar moment of inertia of the motors is a significant factor. Prius does have a mechanical slip clutch with circumferential springs at the end of the engine's crankshaft that would dampen torque spikes, but this may not be as effective as a conventional torque converter. All said, the difference between a Prius transaxle and a manual transmission is the motors and the use of planetary gears rather than a countershaft gear arrangement.

 

But in general? Isn't it better to agree that TC for electric engine in Prius is just required? It will not accelerate faster than 10s to 100 kmh (64 mph) because it already losts traction when floored. When you change tires to those with better traction it will go faster (as long as power/torque permits) and thats all.

TRC system will protect PSD from overreving (assuming that MG1 has to counteract to MG2 electronics may not be fast enough to detect stall condition on MG2 and stop MG1 at the same time which would result in revving ICE for no reason (when off) or stalling it (when on) - both conditions would be very dangerous for all engines and for valve control system in ICE).

As far as I observed TRC system in modulating power/torque without applying brakes, so as mentioned above, if one wheel slips the other stalls as in any car without traction control.
VSC is selectivly using brakes to stablize driving car to regain control.

I've been driving a FWD car with TRC that featured applying brakes to limit slip (simulating limited slip differential) - it was great on snow or partial ice but front brake pads disappeared very fast.

In my opinion Prius does a great job driving on the snow/slippery conditions, except some extremes but in range for compact class cars. I still preffer active TRC protecting the car from accidental slip (some times you can stop on black ice without noticing it) than ability to burn tires on every stop-lights which is not the nature of this car.

And yes - it is possible to deliver hybrid with VSC off option - I've seen pics of Lexus cars with VSC off button so it must be possible but with higher price point / better materials.

 

Had Toyota chosen to put torque limiting clutches (like the one between the ICE and the HSD) in each front axle half shaft, The so-called "TC" would not be as critical and could be made less obtrusive when a drive wheel slips.

JeffD