My concerns with both CVTs and direct injection is of long term reliability. Neither has yet developed a strong enough history to make me feel comfortable. I’m not a risk taker by nature.
Twenty years ago I would have avoided turbochargers too, but I think they’ve become more reliable… and I don’t think there’ll be a new car offered in the very near future that doesn’t have a turbocharger. Regulatory standards “creep” is forcing the industry to try every trick in the book regardless of its reliability or lack thereof.
...there would be one differential gear and two electric motor/generators.
Toyota uses one planetary gear set. The IC engine powers the planet carrier, MG1 powers the sun gear, and MG2 powers the ring gear and the differential/wheels. Without the hybrid batteries, MG2 has no useful purpose. MG1 is all that’s needed to vary the ratio, but I don’t know if the car’s 12V system and a 12V MG1 is feasible for that application.
“MG2 has no useful purpose”
Actually it does.
Without battery storage where would the energy flow of MG1 go to/from?
Power will flow from MG1 to MG2 or vice versa, depending on conditions.
12V operation would result in high currents and “copper losses” in the MG windings.
^^ So, if coasting, energy would flow from MG2 to MG1, right? What would be the point of that?
Edit: However, I do see that, at startup and cruising, energy from MG1 would go to MG2…point taken.
In “low” gears power would flow MG1 to MG2, increasing torque to the drive axles.
At high speeds and “tall” gearing power would flow MG2 to MG1, eventually reversing the direction of MG1.
http://eahart.com/prius/psd/
?? Where’s the power for the electric motors coming from with no battery?
^^ Start IC engine (ICE) at idle. Planet carrier spins at ICE rpm. Ring gear is stationary so sun gear and MG1 freewheel, spinning much faster in the same direction as ICE. Now, start braking the sun gear by turning it into a generator and send the power to MG2. Both ICE and MG2 are now sharing in the propulsive effort. When MG1 is slowed to match the ICE rpm, the transmission is at a 1:1 ratio. As MG1 is further slowed, overdrive is achieved. I have yet to convince myself that stopping MG1 and reversing it for more overdrive is desirable.
Added: Think about how a Prius works at steady cruising. The battery isn’t being used.
Why bother?
It would be far simpler mechanically than a 5+ speed auto or CVT. See my earlier post.
The synergy drive has proven to be very reliable.
I’ve seen no reports of transmission or mo-gen failure in the Prius.
But without battery power/charging, the electric motors do nothing beneficial.
Well, it does make it simpler, as pointed out. But, you also need most of the electronics so why not add a 1kWh battery and make it a hybrid? Obviously, the industry believes it doesn’t make economic sense without the hybrid angle. Generators and electric motors do use more energy than gears.