Don’t Hate — eCVTs Are Genius Transmissions!

[00:03] With a single planetary gear set, you can create infinite gear ratios. What? This is the genius of ECVT. One of the most brilliant transmissions ever developed without the pulleys and belts of a traditional CVT that many people,

[00:19] especially enthusiasts, tend to hate. Now, personally, I think these days that hate is misguided because modern belt driven CVTs have gotten really good and are much more reliable. But that's beside the point. This system is

[00:33] unbelievably simple. No belts, no pulleys, just a single planetary gear set. And this is far, far less complicated than a traditional automatic transmission or even a DCT or a manual transmission. The catch is that it must

[00:48] be paired with two electric motors, but it solves a very real problem in a very beautiful way. So, to start off, what is the problem with other styles of transmissions? Well, typical transmissions have fixed gear ratios.

[01:02] This forces your engine to operate across a wide RPM range while it stays in a single gear. But engines typically operate most efficiently at a specific RPM and it tends to be a lower RPM and they tend to create peak power at a

[01:16] specific RPM and that tends to be a higher RPM. But whether you want efficiency or power, typical engines sweep over an RPM range. So they're efficiency for longer than a brief

[01:30] moment and they're never sitting at peak power for longer than a brief moment. That's where a CVT comes in. Because in theory, a CVT has infinite gear ratios within a set range. This means you no longer have to link your wheel speed to

[01:44] your engine speed. You can adjust your engine RPM to whatever you want, whether for peak efficiency or for peak power, and just let the engine sit there while the transmission adjusts behind the scenes. So you can have your engine

[01:57] literally just sit at its peak efficiency RPM for the given scenario or its peak power RPM. Incredible. Well, many early CVTs used a system of pulleys along with a belt. But many of the early iterations weren't super reliable or

[02:12] they felt weird to drive, so people hated them. So what if you could eliminate the pulleys and belts and instead just use a single planetary gear set? Well, that's exactly what an electronically controlled continuously

[02:26] variable transmission or ECBT does. So, actually works. And a big thanks to that I can demonstrate this technology.

[02:38] So, we of course have our driven wheels for our transmission. We have two electric motors plus this planetary gear set. And then represented by this handle, we have our engine. So as I rotate the engine, you can see the

[02:52] driven wheels rotate. Cool. But the key to understanding this is that we have two electric motors. The green motor is our starter generator. So it can start the engine or once the engine is started, it can spin to generate

[03:06] electricity to send to the battery pack. The blue motor is our traction motor. So, it's used to power the driven wheels or if you're hitting the brake pedal, it can be used as regen to slow the vehicle down and put energy into the battery

[03:21] pack. Now, it's worth mentioning that in a real vehicle like this hybrid Ford Maverick behind me, which uses an ECBT, you're not going to have these chains. This chain connecting to the blue motor is only there so I can have a separate

[03:35] handle from the engine to independently control its motion. And this chain connected to the planetary ring gear would in reality be a direct gear drive rotating a differential that splits power between the driven wheels. The

[03:49] other key to understanding this device is that the blue traction motor is directly linked to the outer blue ring gear of the planetary gear set. The engine in red is directly linked to the planet carrier. So it forces these

[04:04] planet carrier. So it forces these planets as a collective to rotate and the center gear or sungeear in green is driven by the green motor our starter generator. All right. So now let's dive into operation starting with moving the

[04:17] vehicle forward from a stop. So first of all you don't actually need the engine to be on for this vehicle to move just like is true with the Ford Maverick behind me. So in that case the engine isn't rotating at all. So I'll hold that

[04:31] in place. But if I rotate the traction motor, you can see I drive the wheels. Awesome. Okay, but what if your battery is getting low? Well, then you need your engine on. To do this, if I hold the blue motor in place, but rotate the

[04:46] green motor counterclockwise, you can see this spins the engine. So, this is how you initially crank the engine to get it running. Okay, now that the engine is running, how do you recharge the battery? Once the engine is

[05:01] running, you can see that you can rotate the green motor without rotating the wheels by keeping the blue motor stationary. So in this scenario, the car would be idling at a stoplight, spinning the generator and charging the battery.

[05:15] Okay, so we're sitting at a stoplight, the light turns green. How do we go? So as you rotate the engine or the traction motor or both, you see that we drive the vehicle forward. And while rotating the engine, this also forces the green motor

[05:32] to rotate, which is essentially acting like our alternator in this scenario. So the engine is sending power to both the wheels and spinning the motor to charge the battery. Okay, so we'll get into gear ratios in a moment, but now that

[05:45] our vehicle is up to speed, how do we slow down? Besides brakes, of course. Clearly, while we're slowing down, we don't need the engine running. So, we shut it off and it's no longer moving. And you can prevent the engine from

[06:00] running by spinning your green starter motor in the opposite direction. Here you can see the blue motor is still spinning. And so, because the wheels are forcing the blue motor to rotate, now acting like a generator, you can use the

[06:14] electricity this motor is generating to charge your battery pack. All right. So, we come to a stop. So, now that we're at a stop, what's happening? Nothing at a stop. Nothing is rotating. So long as we have sufficient energy in the battery to

[06:29] power whatever accessories are running, radio, AC, that sort of thing. But now that we've come to a stop, let's put the car in reverse. Well, you don't actually need any special reverse gear to do this. The engine remains off, so it's

[06:44] not moving. The traction motor spins in the opposite direction, and ta, the wheels rotate backwards. So, the only thing left to understand are the gear ratios. All right. When you're talking about gears, what you're

[06:59] really talking about is how many times does the engine rotate versus how many times do the wheels rotate. If the engine is spinning fast, but the wheels are spinning slowly, that's a high gear ratio. So, for example, in a traditional

[07:13] automatic or manual transmission, first and second gear, your lower gears are using a high gear ratio. This means the engine spins many times for the wheels to rotate just once. If the engine is spinning slowly and the wheels are

[07:28] spinning fast, that'd be a low gear ratio. This is similar in principle to your car being in the highest gear, like sixth or seventh or eighth while you drive down the highway. You have a low engine RPM, but the wheels are spinning

[07:41] fast. Okay, so how does this ECVT account for these scenarios? Let's start off at a low vehicle speed and assume we want a high gear ratio like a traditional first gear. Well, if the green motor spins faster than our

[07:56] engine, you can see the wheels basically stop. So, in this case, the engine is spinning a lot relative to the wheels. In other words, a high gear ratio, like being in a lower gear or first gear in an automatic transmission. Okay, but

[08:12] what about the traditional equivalent of say third or fourth gear? If the green motor doesn't move while the engine continues to rotate, the wheels move at a decent speed. This is a middle gear, like third or fourth gear. And finally,

[08:26] what about a top gear like a traditional sixth or seventh for cruising on the highway? If the green motor spins in the opposite direction while the engine continues to rotate normally, the wheels spin very fast. This is like being in a

[08:41] higher gear like sixth or seventh where the engine doesn't spin much for how the engine doesn't spin much for how fast the wheels are spinning. fast the wheels are spinning. Let's crank it.

[08:57] Well, you can choose any rotational speed for this green motor from fast clockwise to fast counterclockwise. And that gives you your entire range of gear ratios. So, we've got, for example, like a first gear. Then we've got maybe like

[09:12] a fourth gear. And then we've got our top gear, like sixth or seventh gear. So, because you can set the motor speeds to whatever you want within their range of operation, you essentially have infinite gears. All of this means you

[09:28] can change the speed of the motors relative to the engine through the planetary gear set, which means you can set the engine speed to whatever RPM you want. Ideally, a lower RPM if you're seeking peak efficiency and trying to

[09:43] maximize fuel economy, or a higher RPM if you're seeking peak power and trying to maximize acceleration. You might still wonder what makes this possible, and it comes down to the planetary gear set. Typically in an automatic

[09:57] transmission, which also uses planetary gears, between the sun, planet carrier, and ring, you have one input. You hold one static, and the other is your output, giving you a fixed gear ratio. With this ECBT, you have two inputs,

[10:13] With this ECBT, you have two inputs, both this engine and this motor. So in the scenario where you're commanding a certain engine RPM, if you change the motor speed, manipulating the sungeears speed, this ultimately changes the

[10:28] output speed, giving you effectively a continuously variable gear ratio. Now, it's worth mentioning I demonstrated this using the green motor, but you can also do this using the drive motor. So, for example, if I rotate both the engine

[10:43] and the drive motor at the same speed, I have the wheels rotating at a set speed. But if I keep the engine rotating at the exact same speed, but rotate the drive exact same speed, but rotate the drive motor faster, the wheels spin faster

[10:57] without changing the engine RPM. And it's easier to show that just using this one. And you can see that the blue traction motor is driving faster than the planet carrier in red, which is causing you to accelerate the wheel

[11:10] speed. The wheel speed is now faster with a low engine speed. But really, you're doing that with this blue motor. So, if I increase the drive motor speed relative to the engine, I'm decreasing the engine's gear ratio relative to the

[11:25] putting it into a high gear, like sixth or seventh. The engine speed doesn't change, but the wheels spin faster. How cool. Now, this technology is super

[11:37] cool, but it's not a new idea. In fact, it's not even new for Ford, who was using this same style of transmission 20 years ago in the 2005 Ford Escape Hybrid. And Toyota has been using a similar design to this since the 1990s

[11:54] with the release of the first Prius. But there is a downside I haven't yet mentioned, and that is what many call the rubber band feel, which has nothing to do with belts and can just as easily be felt in something like this, an ECBT.

[12:08] The reason is because in traditional transmissions, there is a direct link between the engine RPM and the wheel speed. But here, that's not true. So, for example, if you were to floor it, the smart logic would be to use the

[12:22] transmission to bring the engine speed all the way up to peak power and then provide peak power. But because there's a delay between when you ask for power and when you get it, this feels weird. So, realistically, what you might do in

[12:35] this scenario is slowly bring up torque and the engine RPM so that it feels more natural. And even worse, the reality is for maximum acceleration, you'd want to hold the engine at peak power, a specific RPM. But people think this both

[12:51] sounds and feels weird. So manufacturers force the engine RPM to slowly increase and then drop down, mimicking a traditional automatic while sacrificing performance. In other words, because people hate change, we intentionally

[13:06] strip away performance in these kinds of vehicles. Good job everyone. you ruined a nice thing. Regardless, the tech is super cool and you can get away with holding a fixed low RPM if you're at low throttle since most people don't care if

[13:21] they're not pressing the accelerator pedal hard. And this leads to some remarkable efficiency from vehicles with these transmissions. A big thanks to help demonstrate this. And thank you all so much for watching. If you have any

[13:35] questions or comments, feel free to leave them below.