In Defense of the Most Despised Transmission
The continuously variable transmission, or CVT, is one of the biggest points of contention in the modern automotive world. On the one hand, you have the car manufacturers who love the simple, lightweight nature of the CVT, not to mention the better fuel efficiency it affords over the cars and trucks fitted with standard automatic transmissions. On the other hand, you have performance-minded consumers who will never accept the CVT and hate it with a burning passion. While both parties’ arguments have their merits, the CVT is, without a doubt, here to stay and will likely be the transmission of choice in the not so distant future.
To understand why the CVT is hated as much as it’s loved, it helps to know how it works. The most common setup used in cars today is a belt and pulley system, with the belt running around two pulleys. The pulleys themselves expand and contract to allow the belt to move towards and away from the pulleys’ centers. This effectively gives the CVT an infinite amount of gears within the parameters of the pulleys, taking the place of physical gears and stepped gear ratios. The result is seamless shifting and an engine that always stays at optimal speed.
Now, this should excite the performance community — an engine which stays in the powerband when you need it. When you don’t need high performance, a CVT reverts to saving fuel with a ridiculously high gear-ratio, perfect for highway cruising. Indeed, if optimized completely for performance, a CVT is a near perfect transmission. Back in 1993, the Williams F1 team tested a CVT in the FW15C car, and the technology was banned before the season even started because it was almost too good at its job. It removed shifting duties entirely and, combined with the onboard computers, always kept the engine speed exactly where it was needed. The unhappy result of the CVT’s operation, since it always stays at an optimal engine speed while accelerating and decelerating, and without defined gear changes, is a dull, lethargic sound, identical to a single-speed gearbox.
To give a CVT some semblance of traditional performance and control, and to try and eliminate the characteristic aural drone, manufacturers build in a “manual mode.” Even though there are no defined physical gears, a CVT with a manual mode allows drivers to select defined gear ratios with either steering wheel-mounted paddles or shift buttons. But, masquerading the CVT as something it’s not instead of leaning into its strengths only makes the situation worse. “Gear changes” on CVTs don’t involve a cut in power, noticeable change in sound, or cause weight transfer — all things engineers look to eliminate, but enthusiasts and purists cling to the notion like the troglodytes they are.
The irony of the situation is traditional automatic and manual transmissions are heading down a development path resembling poor imitations of a CVT. There’s a reason the early transmissions only gave drivers between two and four gears, while newer transmissions feature many more, like the seven-speed manual in the Porsche 911 and Ford’s newest 10-speed automatic. The more gears a transmission has, the more optimized it can be balancing power input, engine speed and vehicle speed. A CVT cuts to the chase and technically gives the engine infinite gears (between the maximum ratios).
In that respect, the CVT (and slight variations of it) will be the only mechanical transmission able to keep up with electric car performance. Electric motors (like in the Tesla Model S and Rimac electric supercar) use single- or two-speed gearboxes and provide an instantaneous and linear power curve that never loses oomph. The CVT, then, is the gas-powered engine’s best hope to remain competitive. As electric cars start to crowd the roads and trickle into track days, CVT naysayers will be left in the rearview.