CVTs are Like a Disease

By Chris Haak

04.28.2009

As David Wright pointed out yesterday in his piece on the Honda Fit vs. the Honda Civic, we do not commute to work or run errands on paper – we do so in cars made of metal, plastic, rubber, and glass.  What sounds like a good idea on the spec sheet sometimes just isn’t the same thing when the proverbial rubber meets the road.  Today’s example:  the continuously variable transmission, or CVT.

For those who are unfamiliar with CVTs, they are generally an automatic transmission that features an infinite number of gear ratios rather than, say, five or six fixed ratios as on a conventional transmission.  Once you shift a CVT into drive, its computer determines the optimal operating range based on the engine’s power characteristics, throttle application, engine load, and other factors.  The transmission continuously varies its gear ratio during vehicle operation, usually by changing the distance between two V-shaped pulleys.  As this distance changes, the belt connecting them rides higher on one pulley and lower on another pulley, changing the effective diameter of each pulley and therefore altering the gear ratio.

On paper, the advantages of a CVT are numerous.  As a conventional automatic spools up during acceleration from one beginning of one gear ratio to immediately before it shifts, the engine will find itself out of its peak powerband immediately following a shift.  A CVT can get the engine to its peak power-producing speed and just stay there, altering the ratio so that the engine never runs out of revs.  This theoretically improves acceleration.  Further, the ability to keep the engine at its peak operating speed also allows the CVT to keep the engine at its most efficient ratio when cruising at a steady state, which improves fuel economy and emissions.  Some higher-end cars with CVTs, such as Nissan’s offerings, even allow a set number of pre-programmed fixed ratios that can emulate a conventional automatic transmission.  When coupled with shift paddles, these CVTs with a manual feature offer lightning-fast shifts and, at least theoretically, the best of both worlds.

As far as I’m concerned, though, the advantages end there.  In terms of driving feel, CVTs – even the best ones – give the sensation of a transmission that is slipping and not working properly.  Since CVTs generally have lower torque capacity than do conventional transmissions, most CVT applications are with four cylinder engines, which can give a tiresome drone without the momentary break in the sound that a conventional automatic that just shifted could bring.  The limited torque capacity also means that many companies restrict torque output during initial acceleration, so stomping on the accelerator pedal from a stop will not bring instantaneous acceleration.  Even my wife, who is the furthest thing from a power-hungry driver like me, complained about the perceived lack of power in several CVTs that she’s driven.

A close-ratio six-speed automatic (or even now a seven- or eight-speed automatic, as Infiniti and Lexus have begun rolling out) offers a much more compelling alternative to a CVT.  The conventional automatic offers full torque output at low speeds, no weird sounds or sensations, and such a minor dropoff in RPMs between gears to make it nearly negligible.  For example, when I was in high school, I drove a Pontiac Grand Am SE with a four cylinder and three-speed automatic.  The Quad 4 engine, in spite of its complete lack of refinement, made good power above 6,000 RPMs, but once it shifted, it dropped completely out of its powerband because the ratios were so far apart.  In contrast, when I tested an Infiniti FX50 for a week with the new seven-speed automatic, it was always in the proper gear.  It shifted quickly and often because there were so many ratios, but shifts were a much less jarring experience than they would have been in a three- or four-speed automatic.  Even a Chrysler Town & Country minivan with the 4.0 liter V6 and six-speed automatic impressed me by dropping down only about 1,000 RPMs between gears as it shifted.  The mommy-mobile could hold its own on a dragstrip (full disclosure:  I’m allowed to make fun of minivans because our family vehicle is a Sienna – which by the way has a five-speed automatic).

And yet, in spite of consumer and enthusiast compliants, CVTs continue to proliferate the automotive landscape.  As automakers scramble to improve fuel economy in the face of both consumer and regulatory demands, they see CVT inclusion as a relatively simple, low-cost way to add a mile per gallon or two.  Every Nissan-badged car and crossover with an automatic now has a CVT; the Mitsubishi Outlander and Galant have CVTs.  And yet several automakers have tried CVTs only to abandon them; the Saturn Vue had a CVT and no longer does; the Ford Taurus (nee Five Hundred) did early during the first few hundred of its Five Hundred days and now only offers a conventional six-speed automatic.  Previous-generation Mini Coopers had CVTs, but now offer six-speed automatics instead.  I wonder if we’ll see a pendulum of CVT applications swinging in favor of them presently, only to see the dissatisfied customers upon whom they’re foisted staging a revolt with their wallets and running away from them.  One can hope, at  least.

I’ve now spent the last three weeks testing press vehicles with CVTs – the Nissan Altima 3.5 SE Coupe, the Mitsubishi Outlander SE 4×4, and the Nissan Sentra 2.0 SL.  The Altima, because it had a V6 and shift paddles, was the most enjoyable, but I would have loved the car twice as much with the available six-speed manual instead.  The Outlander had shift paddles and a sport mode, but didn’t have the sporty feel of the Altima because it was a heavier vehicle hamstrung by a four cylinder.  The Sentra has no manual mode or sport mode, and offers only an overdrive off button and a low gear setting, so it’s the least-enjoyable of the three.  After three weeks of CVTs, I’m excited to drive a “normal” car again tomorrow when , and then Nissan drops off an XTerra for the next seven days.

If I were king of the automotive world, I’d ban CVTs.  Unfortunately, I’m not, and it appears as if the CVT disease is spreading across the automotive landscape.  I hope we never get to a day when nearly all desirable vehicles offer only CVTs as a transmission choice, because I can only tolerate so much buzzing during my ear while accelerating before going crazy and writing another editorial complaint about them.

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