Don’t Hate — eCVTs Are Genius Transmissions!

0:00 With a single planetary gear set, you can create infinite gear ratios.

0:08 What?

0:08 This is the genius of ECVT.

0:11 One of the most brilliant transmissions ever developed without

0:15 the pulleys and belts of a traditional CVT that many people,

0:19 especially enthusiasts, tend to hate.

0:21 Now, personally, I think these days that hate is misguided because modern

0:26 belt driven CVTs have gotten really good and are much more reliable.

0:30 But that's beside the point.

0:32 This system is unbelievably simple.

0:35 No belts, no pulleys, just a single planetary gear set.

0:39 And this is far, far less complicated than a traditional

0:43 automatic transmission or even a DCT or a manual transmission.

0:47 The catch is that it must be paired with two electric motors,

0:51 but it solves a very real problem in a very beautiful way.

0:55 So, to start off, what is the problem with other styles of transmissions?

0:59 Well, typical transmissions have fixed gear ratios.

1:02 This forces your engine to operate across a wide

1:05 RPM range while it stays in a single gear.

1:08 But engines typically operate most efficiently at a specific

1:12 RPM and it tends to be a lower RPM

1:14 and they tend to create peak power at a specific

1:17 RPM and that tends to be a higher RPM.

1:19 But whether you want efficiency or power,

1:22 typical engines sweep over an RPM range.

1:25 So they're typically never sitting at a peak efficiency for longer than a brief

1:30 moment and they're never sitting at peak power for longer than a brief moment.

1:34 That's where a CVT comes in.

1:35 Because in theory, a CVT has infinite gear ratios within a set range.

1:41 This means you no longer have to link your wheel speed to your engine speed.

1:45 You can adjust your engine RPM to whatever you want,

1:48 whether for peak efficiency or for peak power, and just let the engine sit there

1:53 while the transmission adjusts behind the scenes.

1:56 So you can have your engine literally just sit at its

1:59 peak efficiency RPM for the given scenario or its peak power RPM.

2:03 Incredible.

2:04 Well, many early CVTs used a system of pulleys along with a belt.

2:09 But many of the early iterations weren't

2:11 super reliable or they felt weird to drive, so people hated them.

2:15 So what if you could eliminate the pulleys and belts

2:18 and instead just use a single planetary gear set?

2:22 Well, that's exactly what an electronically

2:25 controlled continuously variable transmission or ECBT does.

2:29 So, let's get into how this transmission actually works.

2:32 And a big thanks to Console Lab who sent

2:35 this trainer so that I can demonstrate this technology.

2:38 So, we of course have our driven wheels for our transmission.

2:41 We have two electric motors plus this planetary gear set.

2:45 And then represented by this handle, we have our engine.

2:49 So as I rotate the engine, you can see the driven wheels rotate.

2:53 Cool.

2:54 But the key to understanding this is that we have two electric motors.

2:58 The green motor is our starter generator.

3:01 So it can start the engine or once the engine is started,

3:05 it can spin to generate electricity to send to the battery pack.

3:09 The blue motor is our traction motor.

3:11 So, it's used to power the driven wheels or if you're hitting the brake pedal,

3:16 it can be used as regen to slow

3:18 the vehicle down and put energy into the battery pack.

3:22 Now, it's worth mentioning that in a real

3:24 vehicle like this hybrid Ford Maverick behind me,

3:26 which uses an ECBT, you're not going to have these chains.

3:30 This chain connecting to the blue motor is only there so I

3:34 can have a separate handle from the engine to independently control its motion.

3:39 And this chain connected to the planetary ring gear would in reality be

3:43 a direct gear drive rotating a differential

3:45 that splits power between the driven wheels.

3:48 The other key to understanding this device is that the blue traction motor

3:53 is directly linked to the outer blue ring gear of the planetary gear set.

3:58 The engine in red is directly linked to the planet carrier.

4:03 So it forces these planets as a collective to rotate and the center

4:08 gear or sungeear in green is driven by the green motor our starter generator.

4:14 All right.

4:14 So now let's dive into operation starting

4:17 with moving the vehicle forward from a stop.

4:19 So first of all you don't actually need the engine to be

4:22 on for this vehicle to move just like is true with the Ford Maverick behind me.

4:27 So in that case the engine isn't rotating at all.

4:30 So I'll hold that in place.

4:32 But if I rotate the traction motor, you can see I drive the wheels.

4:37 Awesome.

4:37 Okay, but what if your battery is getting low?

4:40 Well, then you need your engine on.

4:41 To do this, if I hold the blue motor in place,

4:45 but rotate the green motor counterclockwise, you can see this spins the engine.

4:51 So, this is how you initially crank the engine to get it running.

4:56 Okay, now that the engine is running, how do you recharge the battery?

5:00 Once the engine is running, you can see that you can rotate the green motor

5:04 without rotating the wheels by keeping the blue motor stationary.

5:09 So in this scenario, the car would be idling at a stoplight,

5:12 spinning the generator and charging the battery.

5:15 Okay, so we're sitting at a stoplight, the light turns green.

5:18 How do we go?

5:20 So as you rotate the engine or the traction motor or both,

5:25 you see that we drive the vehicle forward.

5:27 And while rotating the engine, this also forces the green motor to rotate,

5:33 which is essentially acting like our alternator in this scenario.

5:36 So the engine is sending power to both

5:38 the wheels and spinning the motor to charge the battery.

5:42 Okay, so we'll get into gear ratios in a moment,

5:45 but now that our vehicle is up to speed, how do we slow down?

5:49 Besides brakes, of course.

5:51 Clearly, while we're slowing down, we don't need the engine running.

5:55 So, we shut it off and it's no longer moving.

5:58 And you can prevent the engine from running

6:00 by spinning your green starter motor in the opposite direction.

6:04 Here you can see the blue motor is still spinning.

6:08 And so, because the wheels are forcing the blue motor to rotate,

6:11 now acting like a generator, you can use the electricity this motor

6:15 is generating to charge your battery pack.

6:18 All right.

6:18 So, we come to a stop.

6:20 So, now that we're at a stop, what's happening?

6:24 Nothing at a stop.

6:26 Nothing is rotating.

6:27 So long as we have sufficient energy

6:28 in the battery to power whatever accessories are running,

6:32 radio, AC, that sort of thing.

6:34 But now that we've come to a stop, let's put the car in reverse.

6:38 Well, you don't actually need any special reverse gear to do this.

6:42 The engine remains off, so it's not moving.

6:45 The traction motor spins in the opposite direction,

6:48 and ta, the wheels rotate backwards.

6:52 So, the only thing left to understand are the gear ratios.

6:56 All right.

6:56 When you're talking about gears,

6:58 what you're really talking about is how many times does

7:01 the engine rotate versus how many times do the wheels rotate.

7:05 If the engine is spinning fast,

7:07 but the wheels are spinning slowly, that's a high gear ratio.

7:12 So, for example, in a traditional automatic or manual transmission,

7:15 first and second gear, your lower gears are using a high gear ratio.

7:21 This means the engine spins many times for the wheels to rotate just once.

7:25 If the engine is spinning slowly and the wheels are spinning fast,

7:29 that'd be a low gear ratio.

7:31 This is similar in principle to your car being in the highest gear,

7:35 like sixth or seventh or eighth while you drive down the highway.

7:38 You have a low engine RPM, but the wheels are spinning fast.

7:42 Okay, so how does this ECVT account for these scenarios?

7:46 Let's start off at a low vehicle speed and assume

7:49 we want a high gear ratio like a traditional first gear.

7:53 Well, if the green motor spins faster than our engine,

7:56 you can see the wheels basically stop.

7:59 So, in this case, the engine is spinning a lot relative to the wheels.

8:04 In other words, a high gear ratio,

8:07 like being in a lower gear or first gear in an automatic transmission.

8:11 Okay, but what about the traditional equivalent of say third or fourth gear?

8:15 If the green motor doesn't move while the engine continues to rotate,

8:20 the wheels move at a decent speed.

8:22 This is a middle gear, like third or fourth gear.

8:26 And finally, what about a top gear like

8:28 a traditional sixth or seventh for cruising on the highway?

8:31 If the green motor spins in the opposite

8:33 direction while the engine continues to rotate normally,

8:37 the wheels spin very fast.

8:40 This is like being in a higher gear like sixth or seventh

8:43 where the engine doesn't spin much for how fast the wheels are spinning.

8:50 Let's crank it.

8:54 So, where do infinite gears come in?

8:57 Well, you can choose any rotational speed

9:00 for this green motor from fast clockwise to fast counterclockwise.

9:05 And that gives you your entire range of gear ratios.

9:08 So, we've got, for example, like a first gear.

9:11 Then we've got maybe like a fourth gear.

9:14 And then we've got our top gear, like sixth or seventh gear.

9:18 So, because you can set the motor speeds

9:21 to whatever you want within their range of operation,

9:24 you essentially have infinite gears.

9:27 All of this means you can change the speed

9:29 of the motors relative to the engine through the planetary gear set,

9:34 which means you can set the engine speed to whatever RPM you want.

9:39 Ideally, a lower RPM if you're seeking

9:41 peak efficiency and trying to maximize fuel economy,

9:44 or a higher RPM if you're seeking

9:47 peak power and trying to maximize acceleration.

9:50 You might still wonder what makes this possible,

9:52 and it comes down to the planetary gear set.

9:55 Typically in an automatic transmission, which also uses planetary gears,

10:00 between the sun, planet carrier, and ring, you have one input.

10:05 You hold one static, and the other is your output,

10:08 giving you a fixed gear ratio.

10:10 With this ECBT, you have two inputs, both this engine and this motor.

10:16 So in the scenario where you're commanding a certain engine RPM,

10:21 if you change the motor speed,

10:23 manipulating the sungeears speed, this ultimately changes the output speed,

10:29 giving you effectively a continuously variable gear ratio.

10:33 Now, it's worth mentioning I demonstrated this using the green motor,

10:37 but you can also do this using the drive motor.

10:40 So, for example, if I rotate both the engine

10:43 and the drive motor at the same speed,

10:45 I have the wheels rotating at a set speed.

10:48 But if I keep the engine rotating at the exact same speed,

10:52 but rotate the drive motor faster,

10:55 the wheels spin faster without changing the engine RPM.

10:59 And it's easier to show that just using this one.

11:02 And you can see that the blue traction motor

11:04 is driving faster than the planet carrier in red,

11:07 which is causing you to accelerate the wheel speed.

11:10 The wheel speed is now faster with a low engine speed.

11:14 But really, you're doing that with this blue motor.

11:16 So, if I increase the drive motor speed relative to the engine,

11:21 I'm decreasing the engine's gear ratio relative to the wheels.

11:25 This is the equivalent of putting it into a high gear, like sixth or seventh.

11:29 The engine speed doesn't change, but the wheels spin faster.

11:34 How cool.

11:35 Now, this technology is super cool, but it's not a new idea.

11:39 In fact, it's not even new for Ford,

11:42 who was using this same style of transmission

11:44 20 years ago in the 2005 Ford Escape Hybrid.

11:49 And Toyota has been using a similar design to this since

11:52 the 1990s with the release of the first Prius.

11:56 But there is a downside I haven't yet mentioned,

11:59 and that is what many call the rubber band feel,

12:02 which has nothing to do with belts and can just

12:04 as easily be felt in something like this, an ECBT.

12:08 The reason is because in traditional transmissions,

12:11 there is a direct link between the engine RPM and the wheel speed.

12:16 But here, that's not true.

12:18 So, for example, if you were to floor it,

12:20 the smart logic would be to use the transmission to bring the engine

12:23 speed all the way up to peak power and then provide peak power.

12:28 But because there's a delay between when you ask

12:30 for power and when you get it, this feels weird.

12:34 So, realistically, what you might do in this scenario is slowly bring

12:37 up torque and the engine RPM so that it feels more natural.

12:41 And even worse, the reality is for maximum acceleration,

12:45 you'd want to hold the engine at peak power, a specific RPM.

12:50 But people think this both sounds and feels weird.

12:53 So manufacturers force the engine RPM to slowly increase and then drop down,

12:58 mimicking a traditional automatic while sacrificing performance.

13:03 In other words, because people hate change,

13:05 we intentionally strip away performance in these kinds of vehicles.

13:09 Good job everyone.

13:10 you ruined a nice thing.

13:12 Regardless, the tech is super cool and you

13:15 can get away with holding a fixed low RPM

13:18 if you're at low throttle since most people don't

13:21 care if they're not pressing the accelerator pedal hard.

13:24 And this leads to some remarkable

13:26 efficiency from vehicles with these transmissions.

13:29 A big thanks to Console Lab for sending their unit to help demonstrate this.

13:33 And thank you all so much for watching.

13:34 If you have any questions or comments, feel free to leave them below.