The tricky world, with haves and have-nots, of CVTs

The 2016 Honda HR-V and the 2016 Nissan Maxima demonstrate all you need to know about the potential and pitfalls of the continuously variable transmission.

One company understands that the only way a CVT will be successful in North America is if the transmission is invisible to consumers. That is, it has to perform like a regular, geared automatic transmission; it can’t make strange noises; and it can’t let the engine rev up to the point of raucousness.

The other company seems to have simply dumped a CVT into its vehicle to claim better fuel economy. It’s as if little or no attention was paid to managing unpleasant engine noises, buzzes and vibrations, or whether acceleration is smooth or even adequate.

The CVT has a checkered past in North America. It has come and gone more times than Brett Favre. Ford and GM tried building their own a decade ago and were forced to drop them after quality and other problems surfaced. Fiat Chrysler Automobiles’ Jeep division dumped the CVT from the Compass three years ago, replacing it with a traditional six-speed automatic, and U.S. sales of the stubby crossover took off.

CVT technology has continued to improve as companies such as Japan’s Jatco figure out ways to make CVTs handle more power. A torque converter added smoothness. Faux shift points made them feel familiar to drivers who prefer step-gear automatic transmissions.

The CVT has just one forward gear and does not shift. Instead of gears, two movable pulleys connected by a metal belt transmit power to the wheels.

Now, led by Nissan, the CVT is making inroads in North America. The CVT offers several huge advantages over the traditional automatic: It has far fewer moving parts. It’s smaller, and it weighs less. It’s also less expensive to build, says AutoPacific analyst Dave Sullivan.

But while the CVT has those advantages, it’s a bit tricky to get the refinement just right, says Jim Zizelman, managing director of powertrain systems for Delphi’s Americas unit.

Delphi doesn’t make CVTs or parts for CVTs, but the giant supplier does make the engine management systems for vehicles equipped with CVTs.

“In the end, it comes down to the engine itself, how you combine it with the CVT, and the power-to-weight ratio in a vehicle,” Zizelman told me. “Depending on what that is, in some cases, you may have to run the engine at fairly high rpms to get that vehicle to respond normally to a driver’s input.

“So, if you have a lower-powered engine and you have to run that engine to fairly high rpm to get the torque you need, it can feel a little bit louder or rougher than what you’d be used to in a conventional, multispeed transmission,” Zizelman explained.

That is exactly the problem with the HR-V’s raspy, 1.8-liter, 141-hp four-cylinder. When you merge onto a busy highway, the engine is like the big bad wolf from the fairy tale. It huffs and it puffs (and it buzzes), but it doesn’t blow anything down. It’s an unrefined racket and feels a bit like the engine is not connected to the wheels.

Nissan, which started replacing traditional automatic gearboxes with CVTs in 2006, has more experience, and it shows.

The Maxima is smooth, quiet, refined and very fast. As the engine winds up, it makes a symphony of sultry sounds. Acceleration is seamless.

Powertrain matching -- that is, selecting the proper size engine for the vehicle’s weight and duty cycle -- and calibration, Zizelman says, is very important when using a CVT.

This year, Ford’s product development chief, Raj Nair, said the company’s powertrain engineers are taking another look at the CVT. GM recently, and quietly, reintroduced the transmission in the tiny Spark subcompact.

The CVT’s time may now have arrived. With fuel prices down and demand for small, fuel-efficient cars plummeting, automakers are going to have to double down and control costs in their smallest, least profitable vehicles.

But if engineers don’t get it right, some perfectly good vehicles, such as the HR-V, are going to get tattooed with poor ratings. Luckily, Honda offers the HR-V with a manual transmission.