Adding second MG2 for increased EV performance?

Ok, I realize this is probably far from practical or economical, but looking at the various transaxle tear downs it seems like it could almost be possible. The idea would be to basically bolt a second MG2 on the end of the existing MG2 to provide more electric drive torque during acceleration and high speed drive. Assuming this would require a second inverter to avoid a current bottleneck driving the motors. Might need a second HVECU as well to run the second inverter, unless you could run both inverters on the CAN bus at the same time without it freaking out. A second battery and/or PHEV battery would also likely be required to meet the current demands of the second inverter, but not sure it would make sense to do this without a PHEV battery. As if it would really make sense anyway

Anybody ever thought about it? Sounds crazy, but could address some of the challenges to getting max EV usage out of a PHEV Prius, not to mention provide a performance enhancement.

Been debating for years whether to do a full BEV conversion on a small car (insight maybe?) for commuting and autocrossing, or just do a PHEV conversion on a Prius. Things are tilted heavily toward the PHEV since we bought two Priuses a few years back when we had kids and needed back seats, but can't quite shake the EV autocross bug Don't want to do anything to the Prius that would degrade gas mileage, but enhancing electric performance would be pretty cool

Rob

 

Thanks all for the comments. A few more thoughts:

- Should have clarified, my interest is mostly in the Gen 2, but I imagine much is similar Gen2/3.

- The idea of adding electric drive on the rear wheels has been around for decades, not sure its ever been demonstrated to work well. In theory it does create AWD, but without a sophisticated controller to allocate power between the four wheels its unlikely to provide any of the traction benefits of actual AWD. Hub motors have been teased for a long time, but practically it seems like you'd have to add another transaxle in the the back. This would be much more feasible in a vehicle like a RAV4 that you can get as FWD but source parts from the rear end of an AWD model. Spent some time thinking about doing exactly that to RAV4 back before we bought the first Prius.

- Transmission failure is always an option when increasing power, but I'm not sure its a big concern in this case. MG2 is I believe on the output shaft after the PSD. That should be the beefiest part of the transaxle. It should be able to handle the full output of the ICE and MG2 with plenty of margin. While the output of MG2 is touted as "295 ft-lb" in practice I believe its much lower. ORNL verified the motor can put out 400NM at 0 rpm as advertised, but it takes ~250A to get there. I don't believe the battery/inverter ever puts out nearly that much, most I've ever seen mentioned is about 100A. If the goal is more electric drive capability, you'd potentially be substituting 2xMG2 for MG2+ICE on acceleration. If not in an ICE lockout mode, really stomping on it could introduce 2xMG2 plus ICE which would certainly exceed normal output torque.

- This does bring up another interesting area of possible performance enhancement, increasing the current drive available to MG2. With a PHEV kit the battery portion is likely taken care of, but I believe the inverter becomes the bottle neck. It could be possible to up the output devices, or run more devices in parallel but this gets very tricky very fast when dealing with these sorts of current. A slight mismatch in devices causes the weakest device to smoke, which can then lead to each output device blowing in sequence. The filter network is also likely designed for a particular device characteristic and power, and changing that could wreck the output waveform quality. Another solution could be to add a second inverter to run in parallel, doubling the output current at any given time, but you'd have to find a way to "slave" the controller off the primary inverter to keep the outputs perfectly in phase sync. If you could do all that, you could still find there is a very good reason Toyota is running the motor at de-rated output, in terms of reliability or longevity for example. Still, could be fun

- While more complicated, in some ways adding a second MG2 and inverter might actually be safer. Then each MG2 is only running at its Toyota designed power levels, and you don't have to worry about synchronizing the inverter outputs. Of course slapping an extra MG2 on the end is not exactly trivial from a mechanical perspective