Cooley On Cars
Your Emails: What's the tech behind continuously variable transmissions?Brian Cooley explains the tech of CVTs and why they're not used for more performance applications.
[SOUND] I'm Brian Cooley from c/net ONCARS, taking another of your emails about high tech cars and modern driving. And this one comes in from William V. who asks, could we explain the technology behind a CVT, continuously variable transmissions, and why they're not used for more performance cars. He says, one would think the ability of a CVT to maintain an ideal engine power band at all time Would make it a perfect gear box for sports performance and racing equipment. It absolutely would seem that way William. And I'm with you on that. Being able to keep an engine in that RPM sweet spot is one of the holy grails of performance. But there's a problem. CVTs don't have really strong positive engagement, because they are not made up of cogs. And keep the way traditional transmission is for really hard-locking clutches and torque converters. They're kind of constant slipping mechanism. As a result, they don't really handle high power all that well. That's not where they've found their main role. Though they do maintain the sweet spot in engines, but mostly to seek economy, not to seek maximum power and torque output. A CVT, as you probably know, is made up of a bunch of pulleys and belts. A variable pulley, metal steel. belt that is able to slide between these varying pulley flanges all the time. That's the nature of its slightly slippery technology. We did a whole episode on transmissions back in May of 2013. I think it was episode 18 that explains this really well. I'll put a link in the show note so you don't have to go hunting for it. The show notes for this episode are over at CNET on Cars.com Another issue around CBTs and performance cars, is that they don't sound the same. A care with a CBT tends to constantly be in about the same rev range, more or less. It doesn't run all the way down, and all the up, the way a gear transmission can, or could. And there fore it's not going to be very satisfying to the performance driver, who likes the sound. Of running through the gears in a real transmission. [NOISE]