WEBVTT Kind: captions Language: en 00:00:00.066 --> 00:00:03.636 This is a 2021 Toyota Sienna. 00:00:03.670 --> 00:00:04.971 It's a minivan. 00:00:05.038 --> 00:00:07.540 The best kind of three row vehicle out there, 00:00:07.540 --> 00:00:11.244 according to everyone who can get over themselves. 00:00:11.244 --> 00:00:12.345 For this model year, 00:00:12.345 --> 00:00:14.748 Toyota did something very daring. 00:00:14.814 --> 00:00:18.785 They dropped the V6 engine and made every single one of these 00:00:18.818 --> 00:00:20.754 a hybrid electric vehicle. 00:00:21.121 --> 00:00:22.389 In doing so, 00:00:22.422 --> 00:00:26.626 Toyota ruffled more than a few feathers, but they also released a minivan 00:00:26.626 --> 00:00:29.229 which could go more than 50% farther 00:00:29.229 --> 00:00:32.899 on every gallon of gasoline it burns than its competition. 00:00:33.299 --> 00:00:36.302 This thing has gotten a shockingly consistent 00:00:36.302 --> 00:00:39.939 34 miles per gallon over its life, city or highway. 00:00:40.473 --> 00:00:42.442 And it's a minivan. 00:00:42.475 --> 00:00:45.879 My first car, a Honda Civic, could barely squeeze 00:00:45.879 --> 00:00:49.549 that out on the highway and got far worse fuel economy in the city. 00:00:49.549 --> 00:00:52.052 And that thing was a small two door coupe. 00:00:52.352 --> 00:00:54.721 This is a three row minivan. 00:00:54.821 --> 00:00:56.322 It's even all wheel drive. 00:00:56.356 --> 00:00:57.924 The thing’s quite impressive. 00:00:58.324 --> 00:01:04.697 By now, most people know that hybrid cars get better fuel economy than their non-electrified counterparts 00:01:04.697 --> 00:01:09.035 through the use of a battery pack which stores electrical energy and electric motors 00:01:09.035 --> 00:01:11.805 which use that energy to assist the engine. 00:01:12.105 --> 00:01:15.241 But to explain this video's title, 00:01:15.475 --> 00:01:20.547 something which I think is less well understood, is that those batteries and motors 00:01:20.580 --> 00:01:27.787 actually have relatively little to do with how hybrid cars attain their amazing fuel economy numbers. 00:01:28.455 --> 00:01:33.860 See, this vehicle is not one of those newfangled plug-in hybrids. 00:01:33.960 --> 00:01:37.397 It's a conventional hybrid like the original Toyota Prius. 00:01:37.430 --> 00:01:41.835 And that means all of the energy available to its drivetrain 00:01:41.835 --> 00:01:44.404 comes from the gasoline in its fuel tank. 00:01:44.704 --> 00:01:48.174 There is no way to charge its batteries except driving it. 00:01:48.208 --> 00:01:53.179 And that means all of the energy the hybrid system uses to make the car go? 00:01:53.713 --> 00:01:56.683 It ultimately came from the gasoline and the engine. 00:01:57.217 --> 00:02:01.721 So why does it even have those electric motors and batteries? 00:02:02.322 --> 00:02:05.158 Well, because without them, driving this thing would suuuuccccck. 00:02:05.158 --> 00:02:09.529 To explain, we need to back up a bit. 00:02:09.596 --> 00:02:12.732 I wasn't intending on making this video yet. 00:02:12.732 --> 00:02:16.669 I'm in the middle of a series on engine management technology, and so far 00:02:16.669 --> 00:02:18.705 I've only covered the catalytic converter 00:02:18.705 --> 00:02:22.275 and a mechanical overview of the internal combustion engine. 00:02:22.342 --> 00:02:27.080 So skipping ahead to hybrid drivetrains sure is skipping a lot. 00:02:27.113 --> 00:02:33.520 But you see, my spidey senses keep picking up on frankly wild misunderstandings 00:02:33.520 --> 00:02:39.192 about hybrid cars and how they work, and also why they work the way they do. 00:02:39.792 --> 00:02:42.896 Now that suddenly people care about fuel economy again, 00:02:42.929 --> 00:02:46.232 I figured it would be worth providing some actual information 00:02:46.232 --> 00:02:49.035 and not just a collection of hot takes. 00:02:49.235 --> 00:02:52.105 For example, if you've been under the impression 00:02:52.105 --> 00:02:54.908 that a car like this has two separate drivetrains, 00:02:54.941 --> 00:03:01.414 an electric one and a gasoline one that have been Frankensteined together into a wildly complex contraption, 00:03:01.447 --> 00:03:03.583 that's simply not true. 00:03:04.150 --> 00:03:07.320 What Toyota's hybrid system does is replace 00:03:07.320 --> 00:03:11.758 the traditional transmission with a new device, which is in fact much, 00:03:11.858 --> 00:03:18.298 much simpler than even the six speed manual gearbox you'll find in this Nissan cube. 00:03:19.232 --> 00:03:20.466 Let me say that again. 00:03:20.500 --> 00:03:26.973 This thing's drivetrain is simpler than a conventional manual transmission, and in fact, 00:03:26.973 --> 00:03:29.375 it isn't even really a transmission at all. 00:03:30.176 --> 00:03:31.711 But I'll get back to that. 00:03:31.744 --> 00:03:36.149 The reason hybrid drivetrains were developed is that, frankly, 00:03:36.249 --> 00:03:42.555 the internal combustion engine is just not very good at what it's supposed to do. 00:03:42.889 --> 00:03:48.995 Yes, these are very interesting devices which tickle the ‘tisms and make lots of very satisfying noises. 00:03:48.995 --> 00:03:52.432 But when you boil them down to their core job, 00:03:52.465 --> 00:03:57.503 turning the chemical energy in a fuel into mechanical energy to move a car, 00:03:58.137 --> 00:03:59.806 they're quite terrible. 00:04:00.039 --> 00:04:06.779 You are lucky to capture just one quarter of the energy contained in gasoline using an engine, 00:04:06.779 --> 00:04:09.349 and the rest will just be wasted as heat. 00:04:09.582 --> 00:04:12.352 That's why your car's got such a big radiator, 00:04:12.352 --> 00:04:16.022 and why cooling system problems can quickly destroy an engine. 00:04:16.422 --> 00:04:18.558 But what I'd like to explain today 00:04:18.558 --> 00:04:23.463 is that part of the reason engines are like that is due to a compromise. 00:04:24.230 --> 00:04:27.900 You see, engines produce wildly different amounts of power 00:04:27.900 --> 00:04:30.536 depending on how fast they're going. 00:04:30.536 --> 00:04:35.341 Each combustion event which occurs in the cylinders can only produce so much power. 00:04:35.341 --> 00:04:38.111 So when you need to produce more engine power, 00:04:38.244 --> 00:04:40.913 you need those events to happen more frequently 00:04:40.913 --> 00:04:43.449 which means you need the engine to speed up. 00:04:43.683 --> 00:04:51.124 For example, this MR-18DE found in the Nissan Cube can only produce its rated 122 horsepower 00:04:51.124 --> 00:04:55.295 when the crankshaft is spinning at about 5,200 RPM: 00:04:55.495 --> 00:04:58.031 not that far from engine redline. 00:04:58.164 --> 00:05:00.867 At any slower engine speed, 00:05:00.867 --> 00:05:03.870 it cannot produce full power, and in fact, 00:05:03.870 --> 00:05:06.105 when running at normal cruising speeds, 00:05:06.139 --> 00:05:08.775 this thing can barely put out 50 horsepower. 00:05:09.309 --> 00:05:12.011 That is why your car has a transmission. 00:05:12.145 --> 00:05:17.183 We need to be able to vary the ratio between how quickly the engine crankshaft is spinning 00:05:17.183 --> 00:05:23.389 and how quickly the wheels are spinning in order to make practical use of an engine given its operating characteristics. 00:05:23.856 --> 00:05:27.994 When accelerating, we want to allow the engine to rev up fast 00:05:27.994 --> 00:05:30.830 so it can produce more power to get the car moving, 00:05:30.897 --> 00:05:33.333 which is why we have low gear ratios. 00:05:33.533 --> 00:05:42.141 But as the car speeds up, the wheels will start spinning too fast for the engine to keep up and that would limit how fast the car can go. 00:05:42.308 --> 00:05:47.480 But with a transmission, we can change the gear ratio as we accelerate 00:05:47.480 --> 00:05:52.819 which will slow the engine back down while keeping the wheels moving as quickly as they were before. 00:05:53.019 --> 00:05:56.622 It's the exact same principle as the different gears on a bicycle. 00:05:57.290 --> 00:06:01.260 But we don't just want those gears to unlock the engine's power. 00:06:01.294 --> 00:06:04.931 In general, internal combustion engines are more fuel efficient 00:06:04.931 --> 00:06:07.166 when they are running at lower speeds. 00:06:07.533 --> 00:06:11.137 There are many reasons for this which aren't worth picking apart too much, 00:06:11.137 --> 00:06:17.009 but remember that an engine is full of metal parts sliding against each other very quickly. 00:06:17.243 --> 00:06:20.880 While the lubrication system will do its best to reduce friction, 00:06:20.913 --> 00:06:26.419 there's still lots of it working to slow the engine down and generate heat as it runs. 00:06:26.419 --> 00:06:30.656 And the faster the engine spins, the more friction there is. 00:06:30.957 --> 00:06:35.695 There are also plenty of pumping losses which get worse as engine speed increases. 00:06:35.695 --> 00:06:38.331 But again, it's not worth dwelling on this. 00:06:38.498 --> 00:06:40.933 What's important is that ideally, 00:06:40.933 --> 00:06:46.873 we want an engine which can spin quickly when we need it to produce lots of power to accelerate, 00:06:46.873 --> 00:06:52.445 but which operates very efficiently at lower speeds for fuel efficient cruising. 00:06:53.212 --> 00:06:54.814 But here's the problem: 00:06:55.415 --> 00:06:58.251 Life is cruel, and we can't have that. 00:06:58.618 --> 00:07:03.055 The best we can manage is a pretty major compromise named Otto. 00:07:03.656 --> 00:07:06.159 When discussing the four stroke engine cycle, 00:07:06.192 --> 00:07:09.996 we are in fact almost universally discussing the Otto cycle. 00:07:10.029 --> 00:07:13.966 That's O - T - T - O, named for my man Nick over here. 00:07:14.233 --> 00:07:15.234 Quick recap: 00:07:15.234 --> 00:07:19.071 The reciprocating pistons work in conjunction with intake and exhaust valves. 00:07:19.105 --> 00:07:22.809 During the intake stroke, the piston is descending and the intake valve is open, 00:07:22.809 --> 00:07:25.812 resulting in an air fuel mixture being drawn into the cylinder. 00:07:25.812 --> 00:07:27.180 When the piston is at the bottom, 00:07:27.180 --> 00:07:30.049 the intake valve closes and the cylinder is then sealed. 00:07:30.116 --> 00:07:34.253 The air fuel mixture will then be compressed as the piston travels up back towards the top, 00:07:34.253 --> 00:07:37.256 and when it's near the top, the spark plug fires, 00:07:37.256 --> 00:07:43.396 and the conflagration of hot expanding gases forces the piston back down into the engine block producing engine power, 00:07:43.429 --> 00:07:50.036 after which the exhaust valve will open to allow the piston to push those spent gases out of the chamber as it comes back up, 00:07:50.036 --> 00:07:51.771 so the process can repeat. 00:07:52.071 --> 00:07:53.039 Cool. 00:07:53.039 --> 00:07:58.911 And the Otto cycle does a decent job of making an engine powerful when it needs to be, 00:07:58.911 --> 00:08:02.615 and also reasonably efficient when under moderate load. 00:08:02.915 --> 00:08:06.719 This is why the Otto cycle engine is what gets put in cars. 00:08:06.752 --> 00:08:10.156 It's a decent compromise between power and efficiency, 00:08:10.156 --> 00:08:14.093 and meets the varying needs of an automobile reasonably well. 00:08:14.894 --> 00:08:19.632 But then this guy named James Atkinson realized that since the power 00:08:19.665 --> 00:08:23.636 the engine produces comes from the expansion of hot gases, 00:08:23.736 --> 00:08:29.542 the Otto cycle wastes a bit of energy by constraining how much those gases can expand. 00:08:30.309 --> 00:08:32.111 See, in the Otto cycle, 00:08:32.144 --> 00:08:37.617 the length of the intake and compression strokes are identical to the power stroke. 00:08:37.950 --> 00:08:43.222 Since the volume of gas after combustion is much greater than before ignition, 00:08:43.356 --> 00:08:45.558 Atkinson saw this as a problem. 00:08:45.825 --> 00:08:50.196 He figured at the end of the power stroke, when the piston is back at the bottom, 00:08:50.196 --> 00:08:55.268 the newly expanded hot gases are still exerting pressure on the piston. 00:08:55.701 --> 00:08:58.871 That could be captured, but in the Otto cycle, 00:08:58.905 --> 00:09:03.309 the exhaust valve will open at that point, relieving the pressure inside the cylinder 00:09:03.309 --> 00:09:05.945 and preventing us from harnessing that energy. 00:09:06.612 --> 00:09:08.948 Atkinson got pretty hot and bothered by this, 00:09:08.948 --> 00:09:11.951 so he designed... this contraption. 00:09:12.385 --> 00:09:17.089 If this looks familiar, you've probably spent some time taking the green stairs. 00:09:17.089 --> 00:09:21.827 Engines of the 19th century were all sorts of different from how we imagine them today. 00:09:21.827 --> 00:09:26.766 And Atkinson used two opposing pistons in the same combustion cylinder, 00:09:26.766 --> 00:09:29.435 which were being driven by an external crankshaft 00:09:29.435 --> 00:09:34.774 and some totally normal linkages to make them move like that. 00:09:35.508 --> 00:09:38.811 Yeah, this thing is quite strange and perhaps a little difficult to follow, 00:09:38.811 --> 00:09:41.614 even with this lovely animation by Michael Frey. 00:09:42.014 --> 00:09:45.918 But the key thing to notice is that the distance between the two pistons 00:09:45.952 --> 00:09:48.921 varies dramatically throughout a full cycle. 00:09:49.488 --> 00:09:53.526 This effectively enlarges the combustion chamber during the power stroke, 00:09:53.526 --> 00:09:59.031 which in turn allows the expanding gases to do more work before they're tossed out of the cylinder. 00:09:59.532 --> 00:10:04.003 Atkinson would later redesign his engine to be slightly less steampunk, 00:10:04.003 --> 00:10:06.272 but still extremely weird. 00:10:06.839 --> 00:10:09.108 We sure did love linkages back in the day, huh? 00:10:09.542 --> 00:10:13.312 But in this design, you can see the point a little more clearly. 00:10:13.579 --> 00:10:18.150 The piston hardly moves at all in the intake and compression strokes, 00:10:18.150 --> 00:10:21.253 but it moves much farther during the power stroke, 00:10:21.320 --> 00:10:25.057 allowing those hot gases to perform more work on the piston. 00:10:25.858 --> 00:10:27.860 Now, back in 1887, 00:10:27.860 --> 00:10:30.896 we didn't have the same valve technology we do now, 00:10:30.896 --> 00:10:33.799 so this contraption made more sense in the past. 00:10:33.799 --> 00:10:37.236 But today we can accomplish more or less the same thing 00:10:37.236 --> 00:10:40.106 with a conventional Otto cycle engine design 00:10:40.139 --> 00:10:43.309 simply through messing with the intake valve timing. 00:10:43.709 --> 00:10:48.948 If we allow the intake valve to remain open through part of the compression stroke, 00:10:48.981 --> 00:10:52.718 the ascending piston will force some of the air fuel mixture 00:10:52.752 --> 00:10:59.225 out of the cylinder and back into the intake manifold before the cylinder is sealed for compression. 00:10:59.659 --> 00:11:04.063 When done this way, it's known as a modified Atkinson cycle engine, 00:11:04.063 --> 00:11:09.669 and that's what you'll find in any decent hybrid vehicle going back to the original Toyota Prius. 00:11:10.269 --> 00:11:14.240 Leaving the intake valves open as the piston begins to ascend 00:11:14.373 --> 00:11:19.945 means we can effectively shrink the size of the combustion chamber during the compression stroke 00:11:19.945 --> 00:11:25.384 and enlarge it during the power stroke, attaining the same effect that Atkinson did 00:11:25.418 --> 00:11:27.453 with all those wild linkages. 00:11:27.887 --> 00:11:29.021 The result? 00:11:29.255 --> 00:11:37.129 A modified Atkinson cycle engine can get over 40% of the chemical energy in gasoline converted to mechanical energy. 00:11:37.563 --> 00:11:43.869 Toyota claims the 2.5l engine in this Toyota Sienna can hit 41% thermal efficiency. 00:11:44.370 --> 00:11:49.108 I've also seen some spec sheets claim this engine tops out at 39.8%, 00:11:49.108 --> 00:11:50.976 so it might not quite hit 40. 00:11:50.976 --> 00:11:53.446 But either way, it's quite good. 00:11:54.080 --> 00:11:56.015 For an engine: no matter what you do, 00:11:56.015 --> 00:11:59.485 the internal combustion engine remains not that great at its job, 00:11:59.485 --> 00:12:05.925 but the Atkinson cycle is a substantial efficiency improvement over a standard Otto cycle engine. 00:12:06.425 --> 00:12:13.799 So if all it takes to make an engine significantly more fuel efficient is to tweak the intake valve timing, 00:12:14.200 --> 00:12:20.172 well, you might wonder why we aren't putting modified Atkinson cycle engines into every car on the road. 00:12:21.207 --> 00:12:24.376 Well, with the advent of variable valve timing, 00:12:24.376 --> 00:12:26.879 we kind of are a little bit. 00:12:26.912 --> 00:12:29.882 But when it comes to the engine itself, 00:12:29.949 --> 00:12:32.685 you still have to make design compromises. 00:12:33.119 --> 00:12:35.087 Remember, we're expecting this thing 00:12:35.121 --> 00:12:38.257 to move the car from a stop and accelerate quickly. 00:12:38.390 --> 00:12:42.361 Yet we also want it to run efficiently when at cruising speed. 00:12:42.628 --> 00:12:47.433 And whenever you try to optimize for one of those two things, 00:12:47.600 --> 00:12:49.802 you make the other one worse. 00:12:50.336 --> 00:12:52.538 This is the crux of the problem. 00:12:52.571 --> 00:12:56.909 The Atkinson cycle maximizes fuel efficiency at cruising speeds, 00:12:57.343 --> 00:13:02.081 but it's pretty lousy at delivering large amounts of power when you need it. 00:13:02.414 --> 00:13:06.218 And, well, that kind of lousy engine 00:13:06.218 --> 00:13:09.755 is exactly what's sitting in this van’s engine compartment. 00:13:09.855 --> 00:13:15.094 While this 2.5l four cylinder can produce 186 horsepower... 00:13:15.494 --> 00:13:20.699 well, first of all, that's not a lot for a vehicle this large or an engine that large. 00:13:20.699 --> 00:13:24.236 But also the engine delivers power in a way 00:13:24.236 --> 00:13:27.373 which many people would find incredibly annoying. 00:13:27.406 --> 00:13:30.943 So if all this minivan had was that engine, 00:13:30.943 --> 00:13:35.815 it would be a very slow turd which nobody would enjoy driving. 00:13:35.815 --> 00:13:38.984 It would be very fuel efficient! 00:13:38.984 --> 00:13:40.986 In fact, with the right transmission 00:13:41.020 --> 00:13:43.622 not far off from what this thing can manage, 00:13:43.622 --> 00:13:47.960 but it would be an unacceptable driving experience for most people. 00:13:48.227 --> 00:13:55.301 This engine is extremely compromised by being designed for fuel efficiency above all else. 00:13:56.268 --> 00:14:00.606 However, the van doesn't just have that engine. 00:14:00.606 --> 00:14:04.743 And that, dear viewer, is the point of hybrid cars. 00:14:05.010 --> 00:14:07.179 See, here's the thing about cars. 00:14:07.246 --> 00:14:11.183 They only need large amounts of engine power to accelerate. 00:14:11.483 --> 00:14:17.423 Sure, having 300 horses under the hood can make car go vroom real fast, but once you're up to speed, 00:14:17.456 --> 00:14:20.826 you don't need any where near that much power. 00:14:21.227 --> 00:14:26.165 This minivan only needs about 30 horsepower to maintain 70 miles an hour. 00:14:26.432 --> 00:14:29.034 You can get that out of some lawnmowers. 00:14:29.034 --> 00:14:35.641 So rather than give the car a huge V6 engine just to make highway on-ramps a little easier, 00:14:36.542 --> 00:14:41.447 what if we gave it a little four banger optimized for amazing efficiency at cruising speeds, 00:14:41.447 --> 00:14:46.218 and we used some electric motors to give the engine a boost when accelerating? 00:14:46.585 --> 00:14:50.756 We can power those motors using some stored energy in a small battery pack, 00:14:50.756 --> 00:14:55.127 and then, whenever we get a chance, we'll recharge what we took from the batteries 00:14:55.127 --> 00:14:58.998 and we'll get them ready for the next time you need to pass someone or whatever. 00:14:59.498 --> 00:15:03.402 That's really what hybrid drivetrains have always been about. 00:15:03.435 --> 00:15:08.140 They’re an exercise in solving the edge case of rapid acceleration 00:15:08.140 --> 00:15:14.313 without resorting to the brute force option of equipping a car with a bigger, thirstier engine. 00:15:14.780 --> 00:15:17.483 The electric motors and battery pack in this thing 00:15:17.483 --> 00:15:20.719 are only there to be an auxiliary source of energy 00:15:20.719 --> 00:15:24.723 which can be borrowed from and replenished whenever it makes sense to do so. 00:15:25.190 --> 00:15:29.228 Sometimes that will be for increasing total system power output. 00:15:29.261 --> 00:15:33.799 While the engine in this minivan tops out at 186 horsepower, 00:15:33.799 --> 00:15:38.003 its electric motors can add about 60 horsepower on top of that, 00:15:38.037 --> 00:15:42.341 bringing the total to 245 horsepower whenever you floor it. 00:15:42.408 --> 00:15:49.315 Incidentally, that's five horsepower more than the 3.5l V6 in a 2002 Honda Odyssey, 00:15:49.381 --> 00:15:53.052 a minivan which could barely manage 20 miles per gallon. 00:15:53.285 --> 00:15:56.588 But the drivetrain in this van will also borrow energy 00:15:56.588 --> 00:16:00.426 from the battery pack during mild acceleration, if it makes sense. 00:16:00.526 --> 00:16:05.364 For instance, if the throttle pedal is pushed down enough to request 80 horsepower, 00:16:05.364 --> 00:16:11.804 but the car's computers know that the engine is more fuel efficient when limited to 60 horsepower or less... 00:16:12.571 --> 00:16:16.175 well, then the car is just going to have the engine produce 60 horsepower 00:16:16.175 --> 00:16:21.280 and fill in the remaining 20 using the electric motors and energy stored in the battery pack. 00:16:21.914 --> 00:16:26.418 Now here's where I need to take a break and explain what I meant by the video title. 00:16:26.952 --> 00:16:29.621 Obviously, “nobody” is hyperbole. 00:16:29.655 --> 00:16:34.026 The engineers designing these things sure do get the point of hybrid cars! 00:16:34.026 --> 00:16:40.265 But when the broader public discusses how hybrid cars attain their better fuel economy, 00:16:40.332 --> 00:16:45.304 discussions tend to focus on the cool new stuff a hybrid drivetrain can unlock, 00:16:45.304 --> 00:16:50.309 like regenerative braking or the ability to move the car without using the engine. 00:16:50.709 --> 00:16:53.178 But what I'm trying to get across here 00:16:53.178 --> 00:16:55.981 is that that's all just icing on the cake. 00:16:56.115 --> 00:16:59.218 The actual cake batter is the engine. 00:16:59.718 --> 00:17:02.621 Yes, hybrid cars need those electric motors 00:17:02.621 --> 00:17:08.394 to make the engine not seem like the wheezy, compromised slow turd of a thing that it is, 00:17:08.394 --> 00:17:12.297 but that engine is the only thing which consumes energy. 00:17:12.297 --> 00:17:15.234 And that's why it's the special sauce. 00:17:15.734 --> 00:17:19.138 Since James Atkinson died in 1914, 00:17:19.171 --> 00:17:22.941 we could have had this special sauce in cars the whole time. 00:17:22.941 --> 00:17:26.612 But the engine on its own is miserable. 00:17:26.612 --> 00:17:29.114 And until we had perfected the electronics 00:17:29.114 --> 00:17:32.918 and control systems necessary to develop hybrid drivetrains, 00:17:33.052 --> 00:17:36.555 nobody was going to buy a car with an Atkinson cycle engine. 00:17:36.789 --> 00:17:38.357 Not even a midwesterner. 00:17:38.857 --> 00:17:45.064 But even though an Atkinson-cycle engine is much more fuel efficient than an Otto cycle engine, 00:17:45.297 --> 00:17:49.902 it is still a reciprocating piston engine with many of the same problems. 00:17:49.935 --> 00:17:53.338 This engine still has friction losses and pumping losses, 00:17:53.372 --> 00:17:57.976 meaning it's only at its peak fuel efficiency under certain conditions. 00:17:58.010 --> 00:18:04.550 So the other thing we can do with a hybrid drivetrain is keep the engine in those conditions 00:18:04.550 --> 00:18:11.623 under many more circumstances than would be possible without some batteries and motors to fill in usability gaps. 00:18:12.324 --> 00:18:16.428 And now here's the other thing I meant by the video title. 00:18:16.662 --> 00:18:22.734 If you're not familiar with how Toyota's hybrid system works both mechanically and operationally, 00:18:23.702 --> 00:18:29.174 you should probably hold off on writing that comment explaining how you think hybrid cars could be improved. 00:18:29.174 --> 00:18:32.811 Because I promise you, Toyota is already doing that. 00:18:32.911 --> 00:18:35.247 Okay, I've got a lot to unpack here. 00:18:35.514 --> 00:18:38.684 First, I don't mean to sound like a shill for Toyota. 00:18:38.684 --> 00:18:42.788 For one thing, they've really been dragging their feet on battery electric vehicles 00:18:42.788 --> 00:18:45.591 and are still playing with hydrogen for some reason. 00:18:45.591 --> 00:18:48.093 So, you know, there's that. 00:18:48.093 --> 00:18:52.498 Also, their user interface software is... well, it could be better. 00:18:52.498 --> 00:18:56.401 But when it comes to the engineering of hybrid drivetrains 00:18:57.202 --> 00:18:59.037 they kind of nailed it. 00:18:59.104 --> 00:19:01.507 There's a reason they are the standard bearer 00:19:01.507 --> 00:19:03.542 and they've earned that distinction. 00:19:03.642 --> 00:19:08.280 But before I explain the mechanical parts of their Hybrid Synergy Drive 00:19:08.280 --> 00:19:12.551 and dispel some of the various misconceptions about hybrid cars that are out there, 00:19:13.418 --> 00:19:16.688 let's first look at what the thing is actually doing as you drive it. 00:19:16.688 --> 00:19:18.790 And with the help of this scan tool, 00:19:18.790 --> 00:19:21.927 I can graph some parameters which will help us make sense of it. 00:19:22.194 --> 00:19:26.131 We begin our journey at a gas station in Hammond, Indiana. 00:19:26.165 --> 00:19:32.070 I've set the scan tool up to log vehicle speed in blue, engine RPM in red, 00:19:32.137 --> 00:19:37.176 the accelerator pedal position in black, and the hybrid battery state of charge in green. 00:19:37.409 --> 00:19:41.580 Not graphed, but shown below is the target engine power in Watts. 00:19:41.580 --> 00:19:44.616 And for those who would like to convert that to horsepower, 00:19:44.650 --> 00:19:47.286 divide that number by 746. 00:19:47.686 --> 00:19:49.254 Before we get on the road, 00:19:49.254 --> 00:19:54.259 I'm going to take the car through a car wash, and I want you to notice that the car does not need 00:19:54.259 --> 00:19:56.595 the engine to be running in order to move. 00:19:56.828 --> 00:19:59.965 Right now, it's simply using one of its two electric motors 00:19:59.965 --> 00:20:02.701 to spin the front wheels and drag itself along. 00:20:03.068 --> 00:20:08.473 When I started logging, the hybrid battery was at 52.5% state of charge, 00:20:08.473 --> 00:20:10.976 and by the time I had parked it in the car wash, 00:20:10.976 --> 00:20:13.212 it was down to 49%. 00:20:13.612 --> 00:20:15.981 Now the car is on this whole time. 00:20:16.315 --> 00:20:19.351 The reason the battery state of charge is slowly dropping 00:20:19.351 --> 00:20:21.987 is because the car has a lot of electronics running, 00:20:21.987 --> 00:20:26.825 including the HVAC system which has an electric air conditioning compressor. 00:20:27.192 --> 00:20:33.632 That's one of the fun side benefits of having a hybrid drivetrain with a lot of stored electrical energy on board: 00:20:33.699 --> 00:20:36.401 if you make all the accessories electric, 00:20:36.435 --> 00:20:40.005 the car can be fully functional while the engine is shut down. 00:20:40.739 --> 00:20:44.509 The car let the state of charge get down to just below 40%, 00:20:44.509 --> 00:20:47.045 and then it decided to start the engine. 00:20:47.179 --> 00:20:50.749 This happened just before the end of the car wash. 00:20:50.882 --> 00:20:57.422 But I want you to notice as I pull out that it's not really working to charge the battery. 00:20:57.456 --> 00:21:02.628 Instead it simply maintaining its state of charge around 39%. 00:21:03.195 --> 00:21:07.032 I will explain why it's not charging the battery in due time. 00:21:07.032 --> 00:21:08.667 But now that I'm actually moving, 00:21:08.667 --> 00:21:13.839 I want you to notice that the engine speed is entirely decoupled from the vehicle speed. 00:21:14.106 --> 00:21:17.676 This cars engine can be used as an electrical generator, 00:21:17.676 --> 00:21:20.245 to push the car forward with the front wheels, 00:21:20.245 --> 00:21:26.885 or indeed both at the same time, which is actually the only way the engine can push the car forward. 00:21:26.918 --> 00:21:28.520 But more on that later. 00:21:28.787 --> 00:21:31.156 As I accelerate to this traffic light, 00:21:31.189 --> 00:21:35.027 you'll see the engine speed up to produce more power to accelerate. 00:21:35.027 --> 00:21:40.999 But then the light was turning red and I had to let off the gas so the engine revved right back down. 00:21:40.999 --> 00:21:45.637 And notice that here the battery state of charge went up rapidly, 00:21:45.637 --> 00:21:49.207 but only as vehicle speed was decreasing. 00:21:49.474 --> 00:21:54.446 That's because the car was using regenerative braking to charge the battery pack. 00:21:55.180 --> 00:21:57.182 Again, I'll explain that more later. 00:21:57.182 --> 00:22:00.652 But now the light turning red was a problem for me 00:22:00.652 --> 00:22:05.357 because I need to take that entrance ramp up there and I'm in the wrong lane. 00:22:05.424 --> 00:22:08.994 So I had to practically floor it to get around this truck next to me, 00:22:08.994 --> 00:22:10.595 and I felt very bad about that maneuver. 00:22:10.595 --> 00:22:13.231 But look at the data we got out of it! 00:22:13.332 --> 00:22:18.437 Here we see the hybrid battery state of charge quickly drop back below 40% 00:22:18.437 --> 00:22:24.343 as the car used some of its stored energy to assist the engine during this sudden need for power. 00:22:24.843 --> 00:22:27.512 But as soon as I let off the accelerator, 00:22:27.579 --> 00:22:29.881 the state of charge stopped dropping. 00:22:30.182 --> 00:22:34.553 I was nowhere near highway speeds yet and still had to do quite a lot more accelerating. 00:22:34.553 --> 00:22:38.924 But now I don't need to exceed what the engine can do by itself. 00:22:38.957 --> 00:22:42.627 So the car simply lets the engine do all the work. 00:22:42.694 --> 00:22:47.099 In fact, the hybrid battery state of charge is increasing slightly, 00:22:47.099 --> 00:22:49.835 indicating that the engine is producing more power 00:22:49.835 --> 00:22:53.071 than is actually required to move the car right now, and it's 00:22:53.071 --> 00:22:56.241 using that excess power to charge the battery back up. 00:22:56.675 --> 00:23:00.078 Now here's something which is very important. 00:23:00.245 --> 00:23:03.048 It is unusual that this is happening 00:23:03.048 --> 00:23:07.285 and the car doesn't ever want to do this if it can be avoided. 00:23:07.519 --> 00:23:11.356 It's only using the engine to charge the battery pack right now 00:23:11.356 --> 00:23:19.297 because the battery fell below 45% state of charge from the car sitting in the car wash parked for a good five minutes. 00:23:19.898 --> 00:23:25.404 45% is as low as the car ever wants the battery to be when it's being driven, 00:23:25.437 --> 00:23:28.173 because if it's lower than that, the car 00:23:28.206 --> 00:23:33.245 can't sustain the power boost function of its electric motors for very long at all. 00:23:33.912 --> 00:23:39.785 When getting around that truck, we saw it lose three percentage points in just six seconds 00:23:39.785 --> 00:23:41.420 and I wasn't even flooring it. 00:23:41.686 --> 00:23:45.857 So now that the car is in drive and in motion, 00:23:45.857 --> 00:23:53.498 it wants to quickly get the battery back to its target minimum charge to prevent an apparent loss of available power to the driver. 00:23:54.032 --> 00:23:59.404 But, and this is something I really want to make sure everyone out there understands, 00:23:59.438 --> 00:24:01.973 in all other circumstances, 00:24:01.973 --> 00:24:09.815 the car goes out of its way to avoid charging the battery pack using the engine, and for a very good reason. 00:24:10.315 --> 00:24:13.418 If you'll permit me, one of the things I'd like to unpack 00:24:13.418 --> 00:24:17.255 is what I have found to be a very common, but I would argue 00:24:17.322 --> 00:24:21.860 misplaced fixation on the concept of the diesel-electric locomotive 00:24:21.860 --> 00:24:26.465 and how that technology could potentially be deployed in hybrid cars like this. 00:24:26.898 --> 00:24:30.802 I'm not going to get too deep into this, because what follows will hopefully explain why 00:24:30.802 --> 00:24:33.839 I believe the fixation is very misplaced. 00:24:33.839 --> 00:24:37.909 But one of my goals with this video is to help more people realize 00:24:37.909 --> 00:24:45.116 that it is not good to convert one source of energy to another unless you actually need to do that. 00:24:45.383 --> 00:24:47.285 Now, I know this might sound odd 00:24:47.319 --> 00:24:52.023 to the many people out there who know that a diesel-electric locomotive does just that: 00:24:52.057 --> 00:24:57.796 They use a generator to convert the mechanical output from their diesel engine into electricity, 00:24:57.796 --> 00:25:00.999 which will then power electric motors to move the train. 00:25:01.566 --> 00:25:04.069 But what I've never seen discussed 00:25:04.069 --> 00:25:08.206 is that efficiency is not the point of that process. 00:25:08.206 --> 00:25:13.345 And in fact, trains would be more fuel efficient if they weren't doing that. 00:25:13.979 --> 00:25:17.716 See, no electric generator is 100% efficient. 00:25:17.716 --> 00:25:21.953 And likewise, no electric motor is 100% efficient. 00:25:22.187 --> 00:25:28.927 By converting the mechanical energy from the diesel engine to electricity and then back to mechanical energy, 00:25:28.960 --> 00:25:32.063 a two-step conversion process is happening 00:25:32.063 --> 00:25:39.070 in which a significant percentage of the power output from the engine gets wasted in conversion losses. 00:25:39.437 --> 00:25:46.511 Those losses mean that more diesel fuel gets burned than if that two-step conversion process wasn't happening. 00:25:46.945 --> 00:25:48.513 But that's the thing. 00:25:48.780 --> 00:25:55.387 Locomotives need to get tons of material moving from a dead stop by themselves. 00:25:55.554 --> 00:25:58.957 That requires a gargantuan amount of torque, 00:25:59.057 --> 00:26:03.795 an amount which a piston engine is not capable of producing on its own. 00:26:03.862 --> 00:26:10.669 But it can do it in a roundabout way if you... do precisely what a diesel electric locomotive does. 00:26:10.802 --> 00:26:17.042 Locomotives actually need to do that two-step conversion in order to perform their function. 00:26:17.075 --> 00:26:23.381 But it is not the most fuel efficient way to move a vehicle using an engine. 00:26:23.815 --> 00:26:27.118 Now, what I think is a pretty major source of confusion here 00:26:27.118 --> 00:26:31.122 is that many people know trains are very fuel efficient, 00:26:31.489 --> 00:26:34.893 but that's nothing to do with the drivetrain. 00:26:34.993 --> 00:26:37.562 Trains are inherently fuel efficient 00:26:37.562 --> 00:26:40.432 because they have steel wheels running on steel rails 00:26:40.432 --> 00:26:43.735 and a middle finger to the concept of aerodynamics. 00:26:44.336 --> 00:26:48.206 They're so energy efficient, by virtue of being trains, 00:26:48.206 --> 00:26:51.443 that the conversion losses of the diesel-electric drivetrain 00:26:51.443 --> 00:26:54.212 essentially don't matter to that use case. 00:26:54.346 --> 00:26:56.247 In short, what I want to stress 00:26:56.281 --> 00:26:59.284 is just because it's a good idea for a train 00:26:59.317 --> 00:27:02.287 does not mean it's a good idea for a car 00:27:02.287 --> 00:27:04.589 where aerodynamics do matter a lot, 00:27:04.589 --> 00:27:08.159 and it has rubber tires running on a road surface. 00:27:08.159 --> 00:27:10.562 And if you're thinking, “Well, fine, 00:27:10.562 --> 00:27:13.832 but trains don't have that battery pack to store energy. 00:27:13.832 --> 00:27:17.268 So what if the engine could stay in its most efficient 00:27:17.335 --> 00:27:18.870 operating profile no matter what, 00:27:18.870 --> 00:27:22.307 and whenever it's producing more power than is needed to move the car, 00:27:22.474 --> 00:27:25.844 we'll just shuffle that power over to the battery pack to use later?” 00:27:26.778 --> 00:27:28.680 Well, that sounds like a good idea, 00:27:28.680 --> 00:27:32.283 but charging a battery is another kind of energy conversion, 00:27:32.283 --> 00:27:36.755 which is also inherently lossy and thus should also be avoided. 00:27:37.155 --> 00:27:41.092 That is why the car doesn't charge the battery with its engine 00:27:41.092 --> 00:27:43.395 unless the battery is too low. 00:27:43.895 --> 00:27:46.898 When the car is parked as it was in the car wash, 00:27:46.898 --> 00:27:50.702 it does use the battery pack like a buffer to power its accessories, 00:27:50.702 --> 00:27:53.171 and will run the engine for a few minutes at a time 00:27:53.171 --> 00:27:55.106 to charge it back up when it gets low. 00:27:55.106 --> 00:27:57.709 In fact, here's exactly what that looks like: 00:27:57.709 --> 00:28:01.613 with the vehicle stationary, once the battery pack dips below 40%, 00:28:01.746 --> 00:28:05.583 the engine switches on and charges the battery up to about 48%, 00:28:05.650 --> 00:28:07.218 a process which takes three minutes. 00:28:07.218 --> 00:28:13.491 And then it will shut the engine back off and use the energy it just stored until it's too low again. 00:28:13.892 --> 00:28:18.496 But that's just a fancy kind of idling this drivetrain can do 00:28:18.530 --> 00:28:21.332 thanks to its fully electric suite of accessories. 00:28:21.566 --> 00:28:24.569 Otherwise, when the vehicle is being driven, 00:28:24.669 --> 00:28:29.407 the battery pack is charged almost exclusively with regenerative braking. 00:28:30.041 --> 00:28:33.278 For those who may not know what regenerative braking is, 00:28:33.278 --> 00:28:38.083 well, the electric motor which can propel the car forward via the front wheels does that 00:28:38.083 --> 00:28:40.985 when we put electric current through its stator windings, 00:28:40.985 --> 00:28:45.757 which in turn generate a rotating magnetic field which spins the motor. 00:28:46.024 --> 00:28:51.029 But if the motor is spinning because of something else, it creates 00:28:51.062 --> 00:28:56.167 a rotating magnetic field, which we can draw power from using those same stator windings. 00:28:56.634 --> 00:29:01.406 That was a long winded way to say “electric motors are also electric generators,” 00:29:01.406 --> 00:29:04.075 and when using the motor as a generator, 00:29:04.075 --> 00:29:08.980 it will actually slow down the rotational speed of whatever it's attached to. 00:29:09.114 --> 00:29:11.349 In this case, the wheels of the car. 00:29:11.816 --> 00:29:16.488 In other words, it functions like a brake when generating electricity. 00:29:16.488 --> 00:29:18.923 And that's what regenerative braking is. 00:29:19.023 --> 00:29:23.995 It's a way to capture energy from the vehicle slowing down and charge the battery pack. 00:29:23.995 --> 00:29:29.467 And since you need brakes anyway, this is a free source of energy. 00:29:29.467 --> 00:29:33.404 And when the energy is free, conversion losses don't matter. 00:29:33.938 --> 00:29:38.409 And so as I drive on the open road where I'm not using the brakes much at all, 00:29:38.710 --> 00:29:42.881 the battery pack is just sitting there at about 45% state of charge. 00:29:43.281 --> 00:29:47.786 The car doesn't want to dip into that energy because there's no point! 00:29:47.786 --> 00:29:50.421 It all came from the engine anyway. 00:29:50.989 --> 00:29:56.060 There are only two reasons for this car to use that stored energy: 00:29:56.060 --> 00:30:01.699 One, the driver has floored it and wants all 245 horsepower this system can offer. 00:30:01.699 --> 00:30:09.107 Or two, the current load on the system causes the engine to go so far outside of its efficiency band 00:30:09.107 --> 00:30:16.881 that it would save fuel to borrow from the battery pack and replenish what was borrowed when the engine is no longer under such a heavy load. 00:30:17.448 --> 00:30:20.351 But, because of conversion losses, 00:30:20.385 --> 00:30:24.422 that second scenario is much rarer than people think it is. 00:30:24.689 --> 00:30:28.059 The engine has to get way outside of its efficiency band 00:30:28.059 --> 00:30:31.496 for borrowing energy from the battery pack to make any sense, 00:30:31.496 --> 00:30:35.366 and that's why the car is not really using the energy in there at all 00:30:35.366 --> 00:30:39.204 when it's cruising on the highway, or even during mild acceleration. 00:30:39.337 --> 00:30:43.041 If the engine is able to do it by itself efficiently, 00:30:43.041 --> 00:30:46.044 that is always the best course of action. 00:30:46.511 --> 00:30:49.848 Around town is a completely different story though. 00:30:50.148 --> 00:30:53.284 When you're on the highway, a car is constantly working 00:30:53.318 --> 00:30:56.154 to push itself forward, but off the highway, 00:30:56.187 --> 00:30:59.691 you're going to keep switching back and forth between accelerating and braking. 00:31:00.124 --> 00:31:06.564 In a traditional car, friction brakes reduce vehicle speed simply by converting energy into heat. 00:31:06.764 --> 00:31:11.002 That works great for stopping the car, but that's all it does. 00:31:11.569 --> 00:31:14.906 The battery pack in this car is able to absorb 00:31:14.906 --> 00:31:18.309 what would be wasted as heat through regenerative braking, 00:31:18.309 --> 00:31:22.146 and since that process doesn't use the engine at all, 00:31:22.447 --> 00:31:26.851 whatever energy it can absorb from the vehicle slowing down is free. 00:31:27.185 --> 00:31:34.192 So when regen breaking gets the battery pack above 45%, then the car will use that energy to... 00:31:35.159 --> 00:31:36.828 help the engine. 00:31:37.428 --> 00:31:39.163 This is what I keep getting back to, 00:31:39.197 --> 00:31:41.666 and what I'd really like to hammer home today. 00:31:41.733 --> 00:31:44.435 If you've been imagining hybrid cars 00:31:44.435 --> 00:31:47.372 to use their battery packs something like a bank account 00:31:47.372 --> 00:31:52.710 which gets paid into when there's excess energy and borrowed from when there's excess power demand, 00:31:53.645 --> 00:31:56.281 this is only kinda sorta of true. 00:31:56.648 --> 00:32:04.756 The gasoline in this thing's fuel tank and that engine remain the only source of input power this system has. 00:32:04.756 --> 00:32:08.927 So the engine is always going to be the primary propulsion device. 00:32:09.093 --> 00:32:15.400 And that's why this minivan almost always starts the engine just after you begin moving. 00:32:15.733 --> 00:32:19.704 You have to treat it very gently if you don't want the engine to start 00:32:19.704 --> 00:32:26.844 because there just isn't that much energy or power to be had from its small battery pack sitting underneath the front seats. 00:32:27.211 --> 00:32:32.150 That battery is not really there to push the car forward when it's got a full charge. 00:32:32.150 --> 00:32:38.089 It's just there to augment this engine’s output so the engine itself can stay entirely 00:32:38.089 --> 00:32:42.627 within its most efficient operating range in as many circumstances as possible. 00:32:42.760 --> 00:32:46.798 In that way, this thing is like the diesel-electric drivetrain 00:32:46.798 --> 00:32:49.434 many people imagine hybrid cars should emulate. 00:32:49.434 --> 00:32:53.504 And that's why I said “Toyota's already done that.” 00:32:53.805 --> 00:32:57.308 But the most efficient way for an engine to run is for it to not. 00:32:57.308 --> 00:33:00.945 So when the car has an opportunity to shut the engine off, 00:33:00.945 --> 00:33:03.448 it almost always takes it. 00:33:03.481 --> 00:33:08.486 For example, pretty much whenever you let off the accelerator, the engine shuts off. 00:33:08.586 --> 00:33:11.155 You're no longer commanding forward power, 00:33:11.322 --> 00:33:13.758 so there's no point burning any gasoline. 00:33:14.158 --> 00:33:19.030 If the car has enough free energy stored in its battery pack from regen braking 00:33:19.030 --> 00:33:21.766 and you're commanding only light throttle, 00:33:21.766 --> 00:33:26.004 then it might decide to keep the engine off for a good while. 00:33:26.237 --> 00:33:30.875 But once your accelerator request exceeds the power output of the battery pack, 00:33:31.042 --> 00:33:33.811 the car has to start the engine to keep up. 00:33:33.945 --> 00:33:35.246 So it does. 00:33:35.747 --> 00:33:39.350 Still, if there's free energy left in the battery pack, 00:33:39.384 --> 00:33:43.287 the car will sometimes kind of flip the script and use the engine 00:33:43.287 --> 00:33:47.892 to augment the limited power from the electric side of its drivetrain. 00:33:48.192 --> 00:33:51.062 Here you can see the battery state of charge dropping 00:33:51.062 --> 00:33:53.297 even though the engine is running. 00:33:53.464 --> 00:33:56.734 It's doing that because it's got some free energy to use up, 00:33:56.734 --> 00:34:00.304 so it might as well do that and take some load off the engine, 00:34:00.304 --> 00:34:05.309 which has the side bonus of keeping the engine in a really energy efficient operating condition 00:34:05.343 --> 00:34:08.913 even though the vehicle is accelerating and climbing a hill. 00:34:09.614 --> 00:34:14.685 If you'd like to see in data and hear from a microphone what the powertrain of this vehicle 00:34:14.685 --> 00:34:17.488 does under a wide variety of circumstances, 00:34:17.555 --> 00:34:21.526 you can check out this Sights and Sounds video I've released on my second channel. 00:34:21.659 --> 00:34:26.197 I put an audio recorder in the engine compartment of this thing on my way to Hammond, 00:34:26.197 --> 00:34:31.502 and being able to hear the engine and motors so clearly revealed some interesting things 00:34:31.502 --> 00:34:35.039 about how the system makes decisions and how it works in general. 00:34:35.640 --> 00:34:37.408 But to wrap this video up, 00:34:37.442 --> 00:34:41.846 now it's time to talk about the mechanical details of Toyota's hybrid system, 00:34:41.846 --> 00:34:48.019 because what I've talked about so far might very well make it sound fragile and dauntingly complex, 00:34:48.119 --> 00:34:51.923 when in fact the system is so mechanically simple 00:34:52.256 --> 00:34:54.392 it almost hurts to think about. 00:34:54.826 --> 00:34:59.797 So, here's the wildest thing about how Toyota designed their hybrid system: 00:35:00.098 --> 00:35:05.436 The engine in this vehicle is not actually connected to the front wheels. 00:35:05.436 --> 00:35:08.639 And yet, the engine in this vehicle 00:35:08.639 --> 00:35:12.009 is permanently coupled to the front wheels. 00:35:13.211 --> 00:35:17.081 To explain that apparent contradiction, let's put the Cube up on the lift 00:35:17.081 --> 00:35:20.685 and let its engine spin the front wheels while it's off the ground. 00:35:21.185 --> 00:35:23.588 With the engine running and the car in gear, 00:35:23.588 --> 00:35:26.691 both front tires are turning at equal speed. 00:35:26.824 --> 00:35:32.263 But because the car has to navigate turns where one wheel will be rotating faster than the other, 00:35:32.563 --> 00:35:38.069 the power coming from the engine and transmission is delivered through what's called a differential. 00:35:38.469 --> 00:35:41.239 It's not important to know the mechanical details of that, 00:35:41.239 --> 00:35:47.078 but the differential is designed to split the power output of the engine between the two wheels, 00:35:47.111 --> 00:35:50.148 while also allowing them to spin independently. 00:35:50.348 --> 00:35:54.185 And the ordinary differential has a bit of a quirk: 00:35:54.318 --> 00:35:58.589 I can easily stop one of the two wheels with my hands, 00:35:58.589 --> 00:36:03.394 and now that I've done that, the other wheel has sped up. 00:36:03.861 --> 00:36:06.631 Note that the engine didn't get any faster, 00:36:06.631 --> 00:36:10.568 it's still just idling. But by preventing one wheel from moving, 00:36:10.568 --> 00:36:13.704 the other wheel is now spinning twice as fast. 00:36:14.005 --> 00:36:15.873 But it gets even weirder. 00:36:16.107 --> 00:36:19.510 If I start to rotate the wheel I'm holding backwards, 00:36:19.510 --> 00:36:22.980 the free spinning wheel on the other side spins even faster! 00:36:22.980 --> 00:36:28.753 And if I then start pushing the wheel forward again but faster than the engine wants to spin it, 00:36:28.786 --> 00:36:31.622 the wheel on the other side starts to slow down. 00:36:31.622 --> 00:36:34.525 In fact, if I can spin the tire fast enough, 00:36:34.525 --> 00:36:37.995 I can get the other tire to come to a complete stop. 00:36:38.729 --> 00:36:40.831 What's this got to do with the Sienna? 00:36:41.299 --> 00:36:43.000 Well, believe it or not, 00:36:43.034 --> 00:36:46.871 this phenomenon is at the heart of Toyota's hybrid system. 00:36:46.871 --> 00:36:51.409 But rather than use the engine to spin a pair of wheels through a differential, 00:36:51.742 --> 00:36:55.846 the engine spins the rotors of two electric motors. 00:36:56.314 --> 00:37:00.451 I'm only going to give you a very surface-level explanation of this, but look. 00:37:00.484 --> 00:37:01.986 That's it. 00:37:02.320 --> 00:37:06.224 Watch this video from the Weber Auto YouTube channel if you want the full explanation. 00:37:06.224 --> 00:37:09.794 But those parts on the table are the whole thing. 00:37:09.994 --> 00:37:13.064 That is Toyota's Hybrid Synergy Drive. 00:37:13.064 --> 00:37:17.201 It's just two electric motors and a planetary gearset. 00:37:17.268 --> 00:37:18.469 That's it. 00:37:18.636 --> 00:37:24.075 The only parts not shown are the stators and wiring which actually drive the electric motors 00:37:24.075 --> 00:37:26.844 and the case which holds all this stuff together. 00:37:27.545 --> 00:37:28.946 Oh, and also in reality, 00:37:28.946 --> 00:37:32.049 this would all be covered in oil for lubrication and cooling. 00:37:32.283 --> 00:37:37.421 But when it comes to the spinny bits which connect the engine and motors to the wheels of the car, 00:37:37.555 --> 00:37:40.324 there are literally just three: 00:37:40.758 --> 00:37:43.160 the parts of a planetary gearset. 00:37:43.628 --> 00:37:48.766 The crankshaft of the engine spends the planet carrier of the planetary gear set, 00:37:48.966 --> 00:37:55.773 a small electric motor generator unit known as MG1 spins the sun gear of that gearset, 00:37:55.773 --> 00:38:01.212 and a larger electric motor, MG2, spins the ring gear of that gearset, 00:38:01.212 --> 00:38:05.583 which is itself coupled to the wheels of the car through a conventional differential. 00:38:06.317 --> 00:38:06.784 Okay, 00:38:06.784 --> 00:38:10.554 it's time to get out the whiteboard because I need something to point at 00:38:10.554 --> 00:38:12.990 as I explain the details of how this works. 00:38:12.990 --> 00:38:15.226 This drawing is not at all accurate 00:38:15.226 --> 00:38:18.696 when it comes to how these three parts are arranged and fit together, 00:38:18.696 --> 00:38:23.000 but that's kind of the whole problem with describing Toyota's system. 00:38:23.034 --> 00:38:26.337 What each part by itself does is very simple, 00:38:26.337 --> 00:38:29.540 and how they're coupled together is also very simple. 00:38:29.540 --> 00:38:33.978 But the choreography of the dance they're performing to make the car go 00:38:34.078 --> 00:38:35.179 is not. 00:38:35.179 --> 00:38:37.882 Here is my best (and revised) attempt 00:38:37.882 --> 00:38:39.984 at painting the complete picture for you. 00:38:40.484 --> 00:38:42.053 So here's the engine. 00:38:42.053 --> 00:38:44.855 Here's MG1 and here's MG2. 00:38:45.156 --> 00:38:51.329 What connects this all together is that planetary gearset which acts to split the output power 00:38:51.329 --> 00:38:55.366 from the engine between the rotors of MG1 and MG2. 00:38:55.966 --> 00:38:58.602 What I think is the most confusing thing 00:38:58.636 --> 00:39:02.640 to wrap your head around here is that all three of these devices 00:39:02.640 --> 00:39:04.809 can move under their own power. 00:39:05.676 --> 00:39:08.479 MG1 and MG2 are both electrical generators, 00:39:08.479 --> 00:39:11.449 but they are also both electric motors. 00:39:11.649 --> 00:39:15.886 The engine burns fuel to spin and the motors use electricity to spin, 00:39:15.886 --> 00:39:20.291 but the car is in direct control of all three of these things 00:39:20.291 --> 00:39:23.427 and can spin them at whatever speed it desires. 00:39:23.961 --> 00:39:28.165 Now for a moment, I want you to forget that these are motors, 00:39:28.165 --> 00:39:30.401 because you can think of this arrangement 00:39:30.401 --> 00:39:33.070 as equivalent to a diesel electric drivetrain. 00:39:33.070 --> 00:39:36.907 But rather than connect an engine to a single electrical generator, 00:39:36.907 --> 00:39:40.177 it's been connected to two of them at the same time 00:39:40.211 --> 00:39:42.313 through that planetary gearset. 00:39:42.546 --> 00:39:44.949 We refer to that gearset generically 00:39:44.949 --> 00:39:48.119 as a power splitdevice, because that's what it does. 00:39:48.152 --> 00:39:52.256 And it operates exactly like the differential in a typical car. 00:39:52.590 --> 00:39:55.159 That is why I used the Cube as a demo. 00:39:55.159 --> 00:39:57.495 And just as I can make one of the Cube’s 00:39:57.495 --> 00:40:00.531 tires speed up just by stopping the other one, 00:40:00.598 --> 00:40:04.402 a Toyota Hybrid can make one of its two generators speed up 00:40:04.402 --> 00:40:06.904 just by slowing the other one down. 00:40:07.438 --> 00:40:09.140 Now, that might seem trivial, 00:40:09.140 --> 00:40:11.709 but what I haven't drawn into this diagram yet 00:40:11.709 --> 00:40:14.445 is that one of those generators, MG2, 00:40:14.445 --> 00:40:17.481 is also coupled to the wheels of the car. 00:40:18.015 --> 00:40:23.921 So this one is not actually free to spin at whatever speed it wants to. 00:40:23.988 --> 00:40:27.091 Its rotational speed depends on how fast 00:40:27.091 --> 00:40:29.760 the wheels and thus the car are going. 00:40:29.827 --> 00:40:34.064 And in fact when the car is stopped, this can't spin at all. 00:40:34.465 --> 00:40:37.468 But that doesn't mean the engine can't spin. 00:40:38.202 --> 00:40:40.137 MG1 is always free to rotate. 00:40:40.137 --> 00:40:43.140 So if MG2 cannot, what will happen 00:40:43.140 --> 00:40:46.010 is that all of the engine's rotational output 00:40:46.043 --> 00:40:50.381 gets sent to MG1 and this will spin really fast. 00:40:50.414 --> 00:40:53.784 It's just like me holding this tire stationary. 00:40:53.818 --> 00:40:59.089 The engine output is all going to the other tire or in a Toyota hybrid, 00:40:59.089 --> 00:41:03.060 if the wheels are stopped and MG2 cannot spin, 00:41:03.060 --> 00:41:06.630 then all of the engine output will go to MG1. 00:41:06.997 --> 00:41:11.535 But of course, MG1 isn't a tire, it's an electrical generator. 00:41:11.535 --> 00:41:15.639 And MG2 isn't just an electrical generator, 00:41:15.639 --> 00:41:17.875 it is also a motor. 00:41:18.175 --> 00:41:22.213 So whenever a Toyota hybrid wants to move forward, 00:41:22.213 --> 00:41:27.418 it will simply use the engine to spin the rotor of MG1 really fast, 00:41:27.418 --> 00:41:31.322 which will generate electricity. And then it will shuttle that electricity 00:41:31.322 --> 00:41:35.159 over to MG2 in order to make it spin. 00:41:35.392 --> 00:41:38.128 Since MG2 is connected to the front 00:41:38.162 --> 00:41:40.664 wheels, that's going to push the car forward 00:41:40.664 --> 00:41:43.400 or indeed backwards. 00:41:43.400 --> 00:41:45.936 Reverse gear is accomplished simply 00:41:45.936 --> 00:41:49.673 by spinning the rotor of MG2 backwards. 00:41:49.807 --> 00:41:52.443 But, when the car is moving forward... 00:41:52.743 --> 00:41:55.379 well, you may notice that what I've just described 00:41:55.379 --> 00:41:58.082 here is a diesel electric locomotive. 00:41:58.082 --> 00:42:01.685 And earlier I went on a tirade about why that is a silly way 00:42:01.685 --> 00:42:04.455 to move a car because of conversion losses. 00:42:04.688 --> 00:42:09.360 Well, that is the brilliant thing about the powersplit device. 00:42:09.593 --> 00:42:12.897 If the engine is running at a fixed speed 00:42:12.897 --> 00:42:18.502 and one of these two motors slows down, then the powersplit device 00:42:18.502 --> 00:42:22.540 will mechanically force the other one to speed up. 00:42:23.173 --> 00:42:25.676 Now, to explain why this is important, well, 00:42:25.709 --> 00:42:28.312 remember how regenerative braking works? 00:42:28.479 --> 00:42:30.548 When we use a motor as a generator, 00:42:30.548 --> 00:42:34.752 It creates an opposing mechanical force on the thing which is spinning it. 00:42:34.752 --> 00:42:38.489 And that force acts to slow the spinning thing down. 00:42:38.756 --> 00:42:43.060 During regenerative braking, the slowing rotor of MG2 00:42:43.160 --> 00:42:46.597 slows down the wheels of the car, acting like a brake. 00:42:46.697 --> 00:42:52.736 But the same thing happens as MG1 generates electricity using the engine. 00:42:52.937 --> 00:42:57.875 As the stator windings surrounding MG1's rotor harness power 00:42:57.875 --> 00:43:03.013 from the rotating magnetic field the engine is producing by spinning this rotor, 00:43:03.013 --> 00:43:08.519 an opposing torque is generated which will try to slow the rotor down. 00:43:08.519 --> 00:43:13.691 But because of the powersplit device coupling all of this together, 00:43:13.757 --> 00:43:21.365 even if the engine is running at a constant speed, MG1 slowing down causes MG2, 00:43:21.365 --> 00:43:25.436 and thus the wheels of the car to speed up. 00:43:26.003 --> 00:43:31.775 The fact that the relative rotational speed of the engine and wheels can be altered on the fly 00:43:31.809 --> 00:43:38.215 simply by speeding up or slowing down the speed of MG1 is what makes this system functionally equivalent 00:43:38.215 --> 00:43:40.551 to a continuously variable transmission. 00:43:40.884 --> 00:43:44.421 And that's why Toyota calls it an eCVT. 00:43:45.189 --> 00:43:49.360 Personally, I don't think they're doing themselves any favors using that term, 00:43:49.360 --> 00:43:56.166 since most people who know the term CVT associate it with horrible things which are mechanically fragile 00:43:56.166 --> 00:43:58.769 when this is anything but. 00:43:58.769 --> 00:44:04.341 The powersplit device has no gears to change, or clutch packs to wear out, or weird 00:44:04.375 --> 00:44:07.811 belt chain things to move between two cones. 00:44:08.078 --> 00:44:11.148 It's as mechanically simple as you could possibly imagine, 00:44:11.148 --> 00:44:14.084 and all of its parts are permanently coupled together. 00:44:14.151 --> 00:44:17.087 Yet it does all the stuff we've been talking about. 00:44:17.321 --> 00:44:20.124 And what's really remarkable to me about this system 00:44:20.124 --> 00:44:23.727 is that it all fits into a package which doesn't even look 00:44:23.727 --> 00:44:26.263 that different from a traditional transmission. 00:44:26.263 --> 00:44:28.132 That's why nothing under the hood of this car 00:44:28.165 --> 00:44:31.301 looks all that out of the ordinary, except for the fact that the gearbox 00:44:31.301 --> 00:44:34.204 has some beefy wires coming out of it. 00:44:34.638 --> 00:44:35.773 Now, in reality, 00:44:35.773 --> 00:44:39.810 and this is another thing which makes holding all this together in your head pretty difficult, 00:44:39.910 --> 00:44:43.580 We don't actually need the rotational speeds to change 00:44:43.580 --> 00:44:47.017 in order to transmit power from the engine to the wheels. 00:44:47.284 --> 00:44:49.853 What matters is the opposing torque 00:44:49.887 --> 00:44:52.790 MG1 is putting on the engine crankshaft, 00:44:52.790 --> 00:44:57.594 and that torque can be constant while the speeds are constant, too. 00:44:58.295 --> 00:45:01.665 Remember, it's really easy to stop this spinning tire 00:45:01.665 --> 00:45:06.170 because an ordinary open differential will send all the engine power 00:45:06.203 --> 00:45:09.640 over to whichever tire has the least traction. 00:45:09.807 --> 00:45:11.041 It's kind of a bummer, really, 00:45:11.041 --> 00:45:13.777 and that's why limited slip differentials are a thing. 00:45:13.777 --> 00:45:18.415 But luckily for us, a similar thing happens with the planetary gearset. 00:45:18.415 --> 00:45:23.454 So if MG1 is producing an opposing torque on the engine, 00:45:23.454 --> 00:45:29.426 rather than actually slow the engine down, that torque just gets shuttled over into MG2. 00:45:29.426 --> 00:45:33.864 And thus the act of using MG1 as a generator 00:45:33.864 --> 00:45:38.569 actually causes the engine to push directly on the wheels of the car. 00:45:38.902 --> 00:45:41.939 This is why the Toyota hybrid system, in my opinion, 00:45:42.005 --> 00:45:47.644 can't neatly be classified as either a series hybrid or a parallel hybrid. 00:45:47.845 --> 00:45:49.913 It's actually somewhere in the middle. 00:45:50.547 --> 00:45:55.419 While there is a mechanical connection between the engine crankshaft and the wheels, 00:45:55.586 --> 00:45:58.522 the engine can't actually push the wheels forward 00:45:58.522 --> 00:46:03.160 unless the hybrid system is doing something to slow down MG1. 00:46:03.527 --> 00:46:07.431 Otherwise, it's equivalent to a car with one tire off the ground. 00:46:07.598 --> 00:46:11.602 All the engine will do in that case is spin that tire really fast 00:46:11.602 --> 00:46:13.537 and the car won't actually move. 00:46:14.304 --> 00:46:20.344 Now, this means there are some conversion losses happening in Toyota's system, but 00:46:20.377 --> 00:46:25.582 how much and exactly where they're occurring is way above my pay grade. 00:46:26.083 --> 00:46:30.354 My mental model suggests the car doesn't have to do very much work 00:46:30.354 --> 00:46:34.158 to cause the engine to mechanically contribute, so the losses are minimal, 00:46:34.158 --> 00:46:36.860 but I have no real basis for that 00:46:36.860 --> 00:46:42.099 other than the stellar real world fuel economy most Toyota hybrids have historically attained. 00:46:42.599 --> 00:46:45.969 Now, that was the first time I've even mentioned the terms 00:46:45.969 --> 00:46:49.173 series hybrid and parallel hybrid in this video. 00:46:49.173 --> 00:46:53.277 And that's because to the end user, the difference doesn't really matter. 00:46:53.977 --> 00:46:58.582 But at the same time, the difference is kind of the heart of the point 00:46:58.582 --> 00:47:00.551 I'm trying to make in this video. 00:47:01.118 --> 00:47:04.221 Toyota's hybrid system is a parallel hybrid system, 00:47:04.221 --> 00:47:08.091 because the engine can mechanically contribute to the movement of the car, 00:47:08.091 --> 00:47:12.062 and I hope by now you understand why this is a good thing. 00:47:12.896 --> 00:47:14.998 Series hybrids are different. 00:47:15.065 --> 00:47:18.268 Series hybrids have an engine which can only power 00:47:18.268 --> 00:47:21.638 an electrical generator, and the electricity which is generated 00:47:21.638 --> 00:47:23.574 that way will be used to charge a battery 00:47:23.574 --> 00:47:26.176 or power electric motors to move the car. 00:47:27.311 --> 00:47:32.549 But unless you have a very good reason to design a system that way, 00:47:32.783 --> 00:47:35.319 this is not a good idea. 00:47:35.652 --> 00:47:38.455 Diesel electric locomotives have a very good reason 00:47:38.455 --> 00:47:41.758 to decouple the engine from the motors: for torque. 00:47:41.859 --> 00:47:45.295 And in theory, a future extended-range electric vehicle 00:47:45.329 --> 00:47:48.198 might benefit from separating the engine and generator 00:47:48.198 --> 00:47:49.466 from the rest of the car. 00:47:50.434 --> 00:47:51.869 But I promise, 00:47:51.869 --> 00:47:57.474 such a future vehicle is not going to benefit from that from a fuel efficiency standpoint. 00:47:57.674 --> 00:48:01.879 There could very well be a good packaging reason to design the vehicle that way. 00:48:01.912 --> 00:48:05.816 But if you're insisting on using the engine primarily as a generator 00:48:05.816 --> 00:48:10.420 for any other reason, I would argue you're making a mistake. 00:48:11.021 --> 00:48:15.659 And we have a perfect example of such a mistake with my previous car, 00:48:15.859 --> 00:48:17.861 a Gen1 Chevy Volt. 00:48:18.262 --> 00:48:22.366 For reasons which are unclear but probably rhyme with General Motors, 00:48:22.366 --> 00:48:28.505 that car was designed explicitly to operate as a series hybrid in most driving conditions. 00:48:29.006 --> 00:48:31.708 Well, after its battery charge had been depleted. 00:48:31.708 --> 00:48:33.844 The whole point of the Chevy Volt was to be 00:48:33.844 --> 00:48:37.214 an electric car first with a small electric range, 00:48:37.214 --> 00:48:40.517 but which also had a gas powered range extender 00:48:40.517 --> 00:48:43.053 to give it unlimited range for road trips. 00:48:43.220 --> 00:48:46.990 But once you had run out of charge and it started up its engine, 00:48:47.591 --> 00:48:49.593 you discovered that the car wouldn't 00:48:49.593 --> 00:48:53.063 keep the engine running when you were cruising at moderate speeds. 00:48:53.063 --> 00:48:56.099 Instead, it would run the engine in spurts 00:48:56.099 --> 00:48:59.002 where it was producing way more power than the car 00:48:59.036 --> 00:49:02.539 actually needed to drive, say, 40 miles an hour, 00:49:02.639 --> 00:49:05.309 and then it would send the excess power 00:49:05.309 --> 00:49:07.544 into the battery pack to use later. 00:49:07.544 --> 00:49:11.615 So after a while it would shut off the engine and use up that energy. 00:49:11.882 --> 00:49:16.253 But because there were four steps of energy conversion going on there: 00:49:16.253 --> 00:49:19.790 engine to electricity, excess electricity to charge the battery, 00:49:19.823 --> 00:49:22.159 discharging the battery to get electricity out of it, 00:49:22.159 --> 00:49:25.162 and then using that electricity to spin an electric motor, 00:49:25.462 --> 00:49:28.966 It got surprisingly mediocre fuel economy. 00:49:29.333 --> 00:49:32.469 The Gen 1 Volt, on premium gas to boot, 00:49:32.469 --> 00:49:37.574 could only manage 35 miles per gallon city 40 highway. 00:49:37.874 --> 00:49:42.112 So that car, which was a lot smaller than a minivan, 00:49:42.412 --> 00:49:45.882 got basically the same fuel economy as this minivan. 00:49:45.949 --> 00:49:49.987 Worse, from a dollars perspective, if you actually used premium fuel. 00:49:51.088 --> 00:49:52.589 That's pretty terrible! 00:49:52.589 --> 00:49:57.594 But given how that car was designed to operate, that's to be expected. 00:49:57.861 --> 00:50:06.103 Even with the flexibility of electric motors and fancy electronics, series hybrids are just less efficient than parallel hybrids. 00:50:06.136 --> 00:50:09.740 If you can use the engine to push the wheels of the car, 00:50:09.873 --> 00:50:13.343 you should be doing that to avoid conversion losses. 00:50:13.810 --> 00:50:20.384 Nissan, for some reason, is supposedly about to release a new series hybrid drivetrain with the Nissan Rogue, 00:50:20.384 --> 00:50:22.819 and I don't really understand why they're doing that, but 00:50:22.886 --> 00:50:26.023 we'll see what kind of fuel economy they can get out of it. 00:50:26.089 --> 00:50:29.726 My guess is, like the Volt, it's going to be decent, 00:50:29.726 --> 00:50:31.862 but far from exceptional. 00:50:32.462 --> 00:50:38.568 By the way, it's very possible there's a patent reason that GM chose to build the Volt the way they did. 00:50:38.635 --> 00:50:42.439 Their Voltec drive system was actually remarkably similar 00:50:42.439 --> 00:50:45.008 in many ways to Toyota's hybrid system. 00:50:45.008 --> 00:50:48.979 It, too, fit two electric motor generator units into a package 00:50:48.979 --> 00:50:52.249 which replaced the conventional transmission, and in a layout 00:50:52.249 --> 00:50:55.752 which was really similar to what's in this minivan. 00:50:56.186 --> 00:51:00.791 They could very well have gotten into legal trouble had they made the design any more similar. 00:51:00.791 --> 00:51:04.628 And Ford ended up licensing Toyota's hybrid technology 00:51:04.628 --> 00:51:08.398 because Ford also ended up making a very similar design. 00:51:08.398 --> 00:51:13.370 In fact, the hybrid Ford Maverick is basically a Prius, but truck shaped. 00:51:13.837 --> 00:51:17.507 By now, most of the original Toyota patents will have expired, so 00:51:17.541 --> 00:51:21.945 I don't know how much this matters in 2026, but I wanted to mention it. 00:51:22.312 --> 00:51:23.447 I'm about to wrap up, 00:51:23.447 --> 00:51:29.019 but in case any of you out there need another reason to see this as a really cool way to do things 00:51:29.052 --> 00:51:32.055 well, remember how this van is all wheel drive? 00:51:32.355 --> 00:51:35.392 Toyota made that happen in a really fascinating way, 00:51:35.392 --> 00:51:39.129 which is only possible because this is a hybrid electric vehicle. 00:51:39.296 --> 00:51:42.732 They just slapped a third electric motor on the rear axle. 00:51:43.133 --> 00:51:44.468 This thing's not very powerful. 00:51:44.468 --> 00:51:46.203 It's only about 40 horsepower. 00:51:46.203 --> 00:51:48.772 But that's plenty to get the car unstuck 00:51:48.772 --> 00:51:52.609 or to give it some extra traction in wet, slippery conditions. 00:51:52.676 --> 00:51:56.513 And because this thing normally just tootles along without doing anything, 00:51:56.546 --> 00:52:00.117 there's virtually no efficiency penalty to having it. 00:52:00.183 --> 00:52:02.652 The EPA rating between the front wheel drive 00:52:02.652 --> 00:52:06.156 and all wheel drive versions of this car varies by exactly 00:52:06.289 --> 00:52:10.961 one mile per gallon, so doing it this way is pretty clever. 00:52:11.261 --> 00:52:16.633 And Toyota’s hybrid drivetrain design has another pretty huge trick up its sleeve: 00:52:16.633 --> 00:52:22.139 It can be tweaked to make a car a plug-in hybrid trivially. 00:52:22.139 --> 00:52:28.411 This van's main electric motor, MG2, can actually produce 180 horsepower. 00:52:28.678 --> 00:52:31.047 The reason the hybrid system can only provide 00:52:31.047 --> 00:52:34.518 about 60 horsepower of boost power to the engine 00:52:34.551 --> 00:52:37.754 is a limitation of the battery pack it's been equipped with. 00:52:37.821 --> 00:52:41.892 If it had a larger battery pack capable of delivering more power, 00:52:41.925 --> 00:52:46.696 this thing could operate in all-electric mode with pretty decent power on tap. 00:52:46.696 --> 00:52:52.936 And that's why many of Toyota's plug-in hybrids really are just their standard hybrids. 00:52:52.936 --> 00:52:54.671 But with a larger battery pack 00:52:54.671 --> 00:52:57.741 which can be recharged using off board power. 00:52:58.375 --> 00:53:01.811 However, something I want you to know is that plug in hybrids 00:53:01.811 --> 00:53:05.749 only make sense for those that can reliably charge them at home 00:53:05.749 --> 00:53:08.518 or at work with cheap electricity, 00:53:08.885 --> 00:53:12.322 because when plug in hybrids switch to gasoline power, 00:53:12.355 --> 00:53:15.225 they have a pretty significant fuel economy penalty 00:53:15.225 --> 00:53:17.861 compared to their non plug in counterparts. 00:53:18.228 --> 00:53:21.998 This is mostly due to the fact that they're carrying more weight around with them, 00:53:21.998 --> 00:53:24.968 since they have a much larger and heavier battery pack, 00:53:25.035 --> 00:53:31.274 though changes to the drivetrain design to prioritize engine-less operation can also make fuel economy worse. 00:53:31.541 --> 00:53:35.445 So if you're not able to charge your car every day, 00:53:35.478 --> 00:53:38.682 either at home or at work with cheap electricity, 00:53:39.149 --> 00:53:41.084 don't consider a plug in hybrid. 00:53:41.117 --> 00:53:45.689 There's no point having those extra batteries unless you can actually use them. 00:53:46.289 --> 00:53:49.025 Personally though, as I'm sure many of you already know, 00:53:49.025 --> 00:53:52.062 I'm over the internal combustion engine. 00:53:52.162 --> 00:53:54.497 Since I can charge my car at home, 00:53:54.497 --> 00:53:58.668 I’d much rather that car just have more batteries 00:53:58.668 --> 00:54:01.304 and not have such things as a catalytic converter 00:54:01.304 --> 00:54:06.543 or a transmission, or a fuel tank, fuel pump, fuel injectors, or fuel. 00:54:06.943 --> 00:54:09.713 But while we are still figuring out how to undertake 00:54:09.713 --> 00:54:15.218 the monumental task of getting wires from buildings to parking lots, 00:54:15.719 --> 00:54:18.521 well, charging a car will be less convenient 00:54:18.521 --> 00:54:20.090 than refueling for many people. 00:54:20.090 --> 00:54:22.826 So if you're going to have a car with an engine, 00:54:23.093 --> 00:54:25.929 why not make the smarter choice and get one with an engine 00:54:25.929 --> 00:54:28.698 designed to burn as little fuel as possible? 00:54:29.199 --> 00:54:33.703 Gas costs money, you know, and sometimes it gets very expensive very quickly. 00:54:34.638 --> 00:54:40.010 Making choices which lower your ongoing costs, I think, should always be in fashion 00:54:40.343 --> 00:54:43.780 because your future self is worth treating, too. 00:54:45.415 --> 00:54:47.851 ♫ losslessly smooth jazz ♫ 00:54:49.052 --> 00:54:49.853 whoop 00:54:50.020 --> 00:54:53.390 And because this thing normally just tootles along without doing anything, 00:54:53.423 --> 00:54:57.661 There's virtually no penalty to having it. The miles per gallon - 00:54:57.761 --> 00:54:59.129 Oh, I'm looking at my face. 00:54:59.162 --> 00:55:00.030 That's silly. 00:55:00.030 --> 00:55:03.466 There are still, woo. hoo. hoo! 00:55:04.501 --> 00:55:07.037 And I backed the teleprompter up too much. 00:55:07.637 --> 00:55:08.838 Farts. 00:55:08.872 --> 00:55:10.607 Farts. Farts! 00:55:10.607 --> 00:55:14.911 ...replenished whenever it makes sense to do so from an efficiency perspective. 00:55:15.445 --> 00:55:16.913 Why did you add that line? 00:55:16.913 --> 00:55:20.717 I should have written that differently and I just figured out how. 00:55:20.850 --> 00:55:21.718 That. 00:55:21.718 --> 00:55:23.086 Why'd you stop? 00:55:23.119 --> 00:55:25.021 You weren't supposed to stop, you turd. 00:55:25.188 --> 00:55:26.556 this line could use a revision. 00:55:26.556 --> 00:55:27.957 I'm doing it on the fly. 00:55:27.991 --> 00:55:29.426 This may be a mistake. 00:55:29.626 --> 00:55:32.128 with a larger battery pack capable of.