Emulate ICE with Automatic Transmission

Yeah I absolutely am wondering why on Earth anyone would want to do this. I'm genuinely curious, and if we knew more we may be able to help more.

You're basically asking if the Prius can be turned into a traditional ICE-only vehicle with an Automatic gearbox. It can't. You want a different car if you want that. The whole point of a Prius is its hybrid synergy drive. If you only want the ICE part then there seems little point in paying a considerable sum of money for the other half that you don't want to use.

To answer your questions though...

It doesn't have a gearbox at all, so you can't in any way choose the gearing or gear ratios. This is all done automatically by the eCVT. There just isn't any way to shift up or down gears, as there physically isn't a gearbox to do this with. The closest you can get to this is pressing the accelerator hard which will cause the eCVT to do something akin to changing down gears in a normal gearbox, or letting your foot off the accelerator which will do the opposite. You cannot dictate or choose what ratio the eCVT will choose though.

You can also shift from D mode into B (Engine Braking) mode. This will keep the ICE running all the time, and instead of energy lost through deceleration/braking being used to charge the batteries, some of it is instead sent to the engine where it's lost as heat, just like in a traditional car. However, the energy for forward motion will still be provided by a combination of the electric motor and ICE. Again, you cannot choose to just use the ICE. The Prius will use battery power whenever it can.

 

sorry, no.

 

It's simply not mechanically capable of doing that. Here's a brief description in lay terms of how the synergy drive system works.
How does Toyota Hybrid Synergy Drive work? - Toyota

This video of the Gen 2 transaxle gives more detail.

 

Yes. Remove Prius drivetrain and install Yaris/Echo engine+4spd transmission. Voila`.

 

I believe there are maintenance modes that keep the ICE running so diagnostics can be run. (Obviously, they are not intended for normal operation)

No amount of jiggery-pokery is going to get you the rev, shift, rev, shift of either a manual* or a normal Automatic transmission. There is only one gear and no clutch, in the non-Prime Prius.

What you seem to want could be done on a lift, but if the tires touch the ground, you will have insufficient torque to move. (just like a Manual in top gear)

*Technically it is a one speed manual with no clutch, all the CVT magic is in software. Nothing ever shifts, there are only one set of gears.

Since it will never move from a stop without torque from the motors, do you mind explaining why you would ever want this? (if you push the Prius to 60 MPH, your idea could work at higher speeds. With no clutch, this will be very jerky)

There is a reason that Atkinson Engines are invariably used in Hybrids, the Electric motors hide the weaknesses of the A.tkinson Cycle

 

I kind of disagree with the "not physically capable" response. It sounds like what you want is for (a) the engine to run all the time, and (b) the transmission to transmit power in some small number of fixed ratios and shift with jerks between them, instead of smoothly adjusting ratio to demand.

The transmission covers a wide range of possible input-to-output ratios as built, completely under control of the timing and width of gate pulses to the H-bridges in the inverter. If you get hold of a first generation, the bridges themselves are 'naked' in the inverter assembly, the gate signals are brought out on wires, and the HV ECU directly supplies the pulses. Starting with Gen 2, the bridges are built into "intelligent power modules" inside the inverter, and the HV ECU just sends them commands for the pulse timing they should generate (I assume they may also have direct access to the motor resolver signals) and they generate the pulse trains themselves, eliminating the need for all that high-frequency gate signal wiring between the inverter and the ECU.

You should probably be able to work with either variety. You'd end up building your own replacement for the HV ECU and programming it. For a later generation, you'd need to get reverse-engineered information about the "commands" you can send to the intelligent power modules. For a first gen, you'd just have to generate the pulse trains yourself, but then you're looking at (probably) a more challenging hard-real-time programming task and more exacting high-frequency circuit design.

I imagine you'll probably let the magic smoke out of the first several transaxles/inverters you prototype with, but it might be kind of fun once it works. The number of 'gears' in the transmission you emulate, and how smooth or jerky the 'shifts' between them, is all up to you as the programmer.

-Chap

Edit: one thing I imagine you won't feasibly reverse-engineer is the cryptographic handshake between the HV ECU and the immobilizer ECU. For your project, I'm guessing you don't care much about keeping the immobilizer functionality, and could just build an ECU that ignores it and starts and runs the car anyway. There might be some other miscellaneous hackage needed to complete that picture (maybe to keep the horns from honking and lights from flashing).

 

Chap, I do not think you can get by this requirement:

If you emulate step gearing, there ought to be MORE load on the Motor/Generators, not less.

And yes, by far the simplest solution would be a Yaris Engine/Transaxle.

 

The ICE provides all of the forward motion anyway (except for those moments when the battery supplements), though some of the power flows through wires and some through shafts.

Program the ECU never to use power from the battery (except, of course, to start the engine), and the condition is met. Of course acceleration won't be great. And there won't be any opportunity to send power to the battery beyond maintaining it at a more or less fixed state of charge, so the benefits of regen are left on the table.

-Chap

 

that oughta do it.