Are CVTs The Best (Fastest) Transmissions?

Align:start hello everyone and welcome in this video we’re going to be talking about why CVTs are actually pretty awesome transmissions and a lot of people love to hate on CVTs and say they’re soulless and I do agree I think they are but I don’t think any more so than any of the other automatic transmission styles out there so you know a manual transmission it’s a lot more involved and as a result people like it they say it’s more fun to drive but things like dual clutch transmissions these are justified as being acceptable in these high-end sports cars because you know they’re quicker so they posted faster lap times faster acceleration times they shift much quicker and so they’re considered better because they’re faster and so by that same logic that’s why I want to talk about CVTs and people hate on CVT is because they can sit at you know a constant engine rpm and so as a result of this marketing departments have told manufacturers we can’t have these constant engine RPMs we have to have stepped gears and so you know now they sound just like every other transmission out there except they’ve completely defeated the purpose of the CVT transmission and doing that that’s not the manufacturers to blame that’s their consumers consumers don’t understand it they don’t like it they complain and then so as a result manufacturers have to change it this is a long rant that’s pointless but anyways see metis today they’re marketed in a way where they’re engineered kind of in the wrong way and so that’s what we’re going to get into here so in a given gear this is our first question to kind of explain why cvts are actually really cool in a given gear where does maximum acceleration occur and so here we have kind of a torque curve of a 2008 zo6 of course does not have a CVT transmission and the question is very simple where does maximum acceleration occur in a gimmick gear it’s of course going to occur at peak torque and if you’re curious about the math there is a math right there but the point is you’re going to have a bunch of different variables all of which because you’re in one gear will be held constant except for torque which is right here so your gear ratios constant your final drive is constant the rate as you retire and the mass of your car is constant so the only thing affecting acceleration that changes is torque and as you can see when it’s at its peak that’s when acceleration will be the highest so that means your maximum acceleration in a given the gear is at peak torque and that’s okay but what we want to know is at a given vehicle speed whereas maximum acceleration because that’s where you want to sit at and we’ll explain why so here’s kind of the the come in math portion of this video but we know that power is equal to force times velocity that’s one of our given equations another one of our given equations is horsepower is a function of torque and rpm so we can set these two equal to each other now of course there would be a five – five – divided underneath these if you’re using the imperial system but regardless horsepower is a function of torque and rpm so we can say that force times velocity setting these two equal to each other power equals power is equal to torque times the engine rpm so then we can divide velocity on the other side F equals T times W divided by V we know also that force is equal to mass times acceleration we can set these two equal to each other and now we have an equation with acceleration in it so we can find out what max acceleration is so that gives us acceleration equal to torque times your engine speed divided by velocity times the mass and so we’re at a given speed so V is going to be constant M is going to be constant the max the mass of the vehicle T times W of course is equal to horsepower so our maximum acceleration is going to occur at maximum horsepower right here and so it’s not going to occur at peak torque at a given vehicle speed so so why is that and this is kind of the interesting part so let’s say we’re in this Corvette we’re in third gear and we’re at this peak torque right here but if we were to downshift we could be at our peak horsepower so you’re going to be at less torque but you’re using a lower gear ratio or a higher gear ratio rather and as a result of that you’re going to have more wheel torque because as our equation shows right here your force at the wheel as a result of your gearing through your transmission okay if you’re still following which hopefully none of this math is very complicated it’s just simple algebra that you know you divide a bunch of different equations so we have 505 horsepower is equal to 6,500 rpm times torque the torque at that divided by five – five – so that’s how we can figure out torque and so we have 408 pound-feet of torque right here versus 475 which is our peak so we’re at less torque but we’ve got a greater ratio so what’s the gear ratio difference well if you divide 6500 by 4800 that would give you your gear ratio difference one point three five four so a thirty five percent more aggressive gear ratio so we take 408 pound-feet of torque which is what we produce right there we multiply that by that gear ratio one point three five four that gives us 552 pound-feet which is going to be you know going to the wheels versus 475 from the engine and so you know this is assuming you go through the transmission and this would be a one-to-one this will be at one point three five four to one ratio so 552 divided by four seventy-five one point one six so what that means what all of this math here is demonstrating is that if you were to be in this gear right here at this point in time accelerating you would be accelerating sixteen you’d have 16 percent more torque at the wheels a 16 percent greater force at the wheels than you would if you were in a gear that put you at peak torque so that’s the critical thing the critical thing is that you always want to sit at peak power if you want maximum acceleration so you know a lot of people will look at their torque curves and say okay when should I shift gears that’s not what you should be looking at you should be looking at how do you keep yourself at maximum power because you know your torque can taper but you’ll still have more wheel torque as a result of the gear ratios okay so we’re we’re putting this all together and getting back to the reason why cvts are awesome is looking at wheel force versus vehicle speed okay and so maximum acceleration would be if we were to just follow peak horsepower and change the gear ratio accordingly but because we’re in this Corvette which has a six-speed transmission or whatever it has you’re going to have this here’s going to be your first gear right there that’s what your force at the wheels is going to look like you’ll hit peak torque and then it’ll start to taper down but you’ll get into peak power so you’ll follow that curve as you’re getting into those higher rpms and then you know you go into second gear so your wheel torque is going to drop and then you’re going to go over here and then you’re going to drop it as you go into third year and then you’ll start to follow the curve again drop as you want to fourth gear start to follow the curve again and so a manual transmission and automatic transmission a dual clutch transmission anything with gears you’re going to have this step where you lose a bunch of wheel torque instead of following the ideal curve and that’s why I CVT is so awesome because what a CVT does is it just adjust the gear ratio that’s all it does and by just adjusting the gear ratio you can sit at maximum acceleration so the car can accelerate as fast as is humanly possible humanly probably isn’t the right word but physically possible for that car to go through it because it just sits right on that curve and so kind of a problem with CVT s is they haven’t really been developed for very high torque applications other used more economically that’s probably a demand thing I mean nobody really wants a supercar with a CVT but if you were to have a supercar with the CVT it would be quicker than what the supercars are currently using with their dual clutch transmissions so hope you guys learned something from this hopefully just a slight ounce more respect for CBTs because they actually are really cool in how they work I also do have a video illustrating how they work which you may want to check out and one final thing a lot of the math from this video came from this book physics for gear heads it’s a pretty cool book if you actually do like math if you don’t like math you’re probably going to be a little disappointed but it breaks down the math of a lot of cool ideas a lot of different automotive concepts and makes it kind of easy to understand so a pretty cool book and I’ll include a link to this in the video description thank you all for watching and if you have any questions or comments feel free to leave those below