Why MILLIONS of Cars Have The WORST Transmission Ever

you probably hate continuously variable Transmissions or cvts and that's because they're terrible which is weird because in theory CVT should make cars better the CVT was once banned in Formula 1 because it was too good now it's the worst transmission ever built that's a bit of a mystery so let's get into it the way cvts work isn't especially complicated Transmissions transmit rotation from a car's engine to its Wheels in a normal transmission that happens through gears which have a small all number of set ratios a typical first gear might have a ratio of 3 to one where the input gear rotates three times for every one rotation of the output so if the engine is spinning at 3,000 RPM the output from the transmission would be 1,000 RPM that's an underdrive ratio a modern car also has gears that increase the transmission's output speed called overdrive gears cvts are different instead of a set of 5 to 10 gear ratios cvts transmit engine rotation through an input pulley to an output pulley via a belt or chain the size of the pulley determines the ratio so if the input pulley is a third the size of the output pulley that provides a 3:1 ratio the pulley are where the genius of the CVT happens they don't have a fixed size each pulley is made from two conical halves when those halves move closer together that pushes the belt away from the center of the pulley increasing the pulley's effective size essentially turning it into a bigger gear because the pulley are connected by a belt which can't change in length when one pulley increases in size the other decreases and vice versa when the size of the pull is changed that also changes the effective gear ratio in other words cvts provide a variable gear ratio by not having gears they also provide an infinite number of possible ratios limited only by the largest and smallest positions of the pules now that we know how cvts work it's easier to to understand why they should be good if you've ever looked at a power output from an engine on a dino graph you know that engines make different amounts of power at different engine speeds or RPM and there's one sweet Peak where max power is achieved and at every other engine speed power is less with a normal transmission the gear ratios dictate the relationship between the engine's RPM and wheel speed for each ratio there is just one specific vehicle speed where the engine speed is making maximum power at every other vehicle speed the engine is at some other RPM and producing less power the CVT with its variable gear ratios solves that problem mash the throttle the engine will jump to the perfect RPM for maximum power and the CVT will vary the gear ratio to keep the engine in that sweet spot as the vehicle speed increases the Williams F1 team tested a CVT in 1993 because of that Ideal Power delivery there are no official recorded lap times but David colard one of the few people who ever drove the CVT equipped Williams estimated the benefit to be half a second a lap or more and that's a lifetime in Formula 1 then the FIA banned cvts all together they never explained why but there was speculation that the CVT was simply too good the Williams car would have just been too difficult to be in a car without one the result would have been an expensive arms race between the teams to develop their own it's weird that cost concerns might have made the FIA ban cvts a big reason why modern cars use cvts is because they save money in a couple of ways first cvts are simple that's one reason why they're popular in small applications like scooters cvts are also old technology they were first used in cars in 1896 technology that is both old and simple tends to be cheap and that's true for cvts cvts also save money by conserving fuel generally the faster an engine is spinning the more fuel it uses that's why normal Transmissions have OverDrive gears to reduce engine RPM at high vehicle speeds cvts choose among infinite gears to provide the perfect ratio for maximum engine power or minimum fuel use at any speed even though they old technology manufacturers only recently turned to cvts because they improve fuel economy and that helps car makers satisfy regulations combine that with cvts being simpler and cheaper to make and you can see why they should be good so why aren't they better fuel economy also makes those cars more appealing to buyers but only on paper because most people hate how cvts feel to drive and that's not just car snobs it's nearly everyone everyone knows how acceleration is supposed to sound young children can perfectly replicate this we know that when a car is accelerating the engine speed shouldn't just sit at a constant RPM and we're bothered when a car's acceleration is so disconnected from the engine [Music] sound after 100 Years of geared Transmissions being the most common type CVT equipped cars feels like there's a huge delay between pressing the throttle and the car accelerating because they sound wrong the perceived delay is in addition to the actual delay between the engine spinning up and the CVT getting into the correct ratio which is a whole another problem and to solve these problems manufacturers have actually made cvts worse to make cvts feel better most of our program to simulate the gear changes of a regular transmission the engine revs up and down as though the car is shifting gears and that seems to provide some comfort but those fake shift points prevent the CVT from doing the one thing it's really good at keeping the engine at the ideal RPM for power or for fuel economy in other words fake shift points reduce acceleration and increase fuel consumption once you take that Advantage away the case for CVT starts falling apart because they're all fragile cvts are based around Simple Technology but that doesn't mean they're reliable they've been widely criticized for breaking more than normal Transmissions One Source even describes the CVT as the worst transmission ever built the belt and pul system creates a lot of friction and that produces a lot of heat and in some cases cvts require additional external coolers that means more complexity and more cost eliminating even more of the theoretical benefits of cvts that friction also means a lot of wear on the Belt when the FIA banned cvts back in 1993 Williams didn't seem all that upset partly because Williams were already winning but they also knew a CVT attached to an 800 horsepower engine would wear at its belt long before finishing a Grand Prix that power limitation is likely the final nail for cvts if you put one on a scooter it'll be fine but on a race car probably not so should a CVT be in a road car well that all depends on how much power it makes the Mercedes m139 engine is just 2 L and makes 42 feet of torque completely stock and current cvts can't keep up one of the most widely used cvts is designed for 2 L engin and has a torque limit of just 1885 feet that's nothing for many modern cars it's possible that cvts will improve as they're developed more but why bother when there's already better Alternatives one of the most popular automatic transmissions ever is the zf8hp it's in over 3.5 million cars across a dozen brands with versions capable of handling up to 885 feet of torque so will the theoretical potential of the CB ever be realized or are cvts destined to be terrible forever so let me know what you think in the comments and thanks for watching

Channel: OVERDRIVE

Views: 258,273

Keywords: Automotive, Cars, Racing, engineering, CVT, CVTs, Continuously Variable Transmissions, Williams, Williams FW15, FW15, FW15c, transmissions

Id: 1RnrTDxgur4

Length: 8min 7sec (487 seconds)

Published: Tue Mar 12 2024