Is it possible to turbocharged a gen2?

M/G1 uses engine power to make electricity, so more engine power can mean more electrical power. M/G2 uses electricity to make power so more electrical power can mean more power at the wheels. Both M/G1and M/G2 have a maximum power they can never exceed, so peak power may not change.

 

OK, let's throw some numbers down. Some base assumptions here, some of which are oversimplifications - namely, I'm ignoring MG2's power curve (only looking at peak power handling capability - and I'll note that MG2's peak is at lower speeds), and I'm ignoring losses.

Starting with the stock Gen 2:

1. 57 kW @ 5000 RPM stock ICE power output, or 108.9 Nm @ 5000 RPM torque output
2. MG1 can handle 33 kW, and can spin up to 10,000 RPM
3. This occurs at a ring gear (and therefore MG2) RPM of 3077, corresponding to 87.6 km/h assuming 185/65R15 tires
4. Due to the 78T ring/23T planet/30T sun gear configuration of the Power Split Device, MG1 must be able to absorb 28% of torque generated (if it can't, engine output will be reduced to meet MG1's needs), and the ring gear gets the remaining 72% of torque.
5. If you get power back out from that divided torque (the MG1 and ring gear RPMs are all you need, you get 25.3 kW going from the ICE to the wheels mechanically, and 31.7 kW going from the ICE to MG1. That works!
6. Worth noting that MG2 can only handle 50 kW. This means that 18.3 kW is coming from the battery, when it can supply up to 21 kW per Toyota specifications - we have a total system power of 75.3 kW.
7. To maximize power, we can speed up to 96.9 km/h, with a MG1 RPM of 9158, resulting in 28 kW going from the engine to the wheels mechanically, 29 kW going from the engine through MG1 to MG2, and 21 kW coming from the battery to MG2 - going any faster will still be limited to 78 kW total due to the battery being the limiting factor.

Now, let's go to the 1NZ-FE - the Otto-cycle version of the engine. I'll do the numbers based on 5000 RPM and 6000 RPM, as I've got them. First the 5000 RPM numbers, they're more directly comparable.

1. Looks like it's about 73 kW @ 5000 RPM, or 139.4 Nm @ 5000 RPM torque output.
2. Same MG1, same 33 kW, same 10,000 RPM.
3. Same 3077 RPM ring gear/MG2, same 87.6 km/h.
4. Same torque split.
5. And here's where we have a problem. 32.4 kW goes to the ring gear, 40.6 kW goes to MG1. So, we need to throttle back, all the way down to 59.4 kW - barely more than stock. (Note that in reality, the control laws would likely reduce RPM instead of throttling back - more efficient that way. The math is a hell of a lot easier to assume it's throttling back though.) At that point, 26.4 kW is going to the ring gear, 33 kW to MG1.
6. Once this is done, we do get slightly more power at the wheels, though, at 76.4 kW - 17 kW is coming from our battery.
7. As before, though, we can always just... speed up. At 108.0 km/h, MG1 RPM of 8137, we can finally open our throttle all the way. 40 kW to the wheels mechanically, 33 kW through MG1, and still 17 kW from the battery (you'll see that number a lot). We've actually made a significant power gain, we're now to 90 kW. Note, however, that the battery is still not being taxed fully - but if we speed up further, we can feed in more ICE power, so let's re-run the numbers assuming the 1NZ-FE's actual power peak.

Full power and engine RPM this time.

1. 81 kW @ 6000 RPM now, 128.9 Nm @ 6000 RPM torque output.
2. Same as before.
3. As the engine's now going faster, the car has to be going faster - we're now doing 4462 RPM ring gear/MG2, for 127.1 kmh.
4. Same as before.
5. We still need to throttle back, though - at these parameters, 43.5 kW is going to the ring gear, 37.5 kW is going to MG1. Throttling back to 71.3 kW works, with 38.3 kW going to the ring gear, 33 kW to MG1.
6. This means we have 88.3 kW to the wheels (again, 17 kW from the battery - this number comes up a lot when you're MG1-limited). (Note that reducing engine RPM can paradoxically help power output here - we were getting 90 kW at the wheels at 5000 RPM at a lower vehicle speed before.)
7. We definitely need to speed up - at 140.2 km/h, MG1 RPM of 8800, we're producing full engine power, 48 kW to the ring gear, 33 kW to MG1, 17 kW from the battery, for 98 kW to the wheels.
8. Let's go ahead and tax that battery. At 151.9 km/h, MG1 RPM of 5333, 52 kW is going to the ring gear, 29 kW to MG1, 21 kW from the battery, for 102 kW to the wheels.

So, what did we learn?

What we learned is that we've gotta be going fast to take advantage of power increases at the high end, without overloading MG1. (However, power increases at lower RPM may be another story, as hinted by running the Otto engine at 5000 RPM - slower engine means slower MG1, and slower MG1 means more of the power can go to the ring gear.)

You may notice that this is also part of why the Lexus LC 500h and LS 500h have a 4-speed automatic on the end of their power split devices - this is done to maximize power at low vehicle speed (short gearing lets the ring gear RPM get high, which allows it to take more power so MG1 doesn't have to), while maintaining the ability to actually do high speed.

 

For those of you who are interested, here is the Gen M/G2 power 'curve'.