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Road & Track wrote:Why a CVT Is Basically the Perfect Transmission
A dual-clutch gearbox is an automatic, and it isn't even the best one.
It was just over ten years ago that we lost my favorite automotive writer of all time, LJK Setright. A classical musician, law student, and accomplished photographer, Setright is probably best known for the forged-steel certainty with which he promoted his iconoclast and contrarian beliefs. In particular, he loved to chastise the auto industry for what he perceived as a reactionary attitude towards technology, turning his vitriol against targets as diverse as Mercedes-Benz (for retaining wooden wheels on some models well into the Thirties) and Jaguar (for "ruining" the aerodynamic stability of the 1994 XJ6 with the round-headlight 1995 re-style).
One of Setright's more controversial stances was his steadfast preference for the automatic transmission. This might not seem so outrageous in 2016, where everything from the BMW 3-Series wagon to the entire Ferrari lineup comes standard without a clutch pedal, but forty years ago the man stood more or less alone in the auto-journo world. He ridiculed the "antiquated" manual transmission while noting that the arrival of synchromesh gearboxes took all the skill out of driving a stick anyway. A major percentage of his book Drive On is dedicated to arguing the superiority of the self-shifting, planetary-geared transmission.
Yet even that arrangement didn't quite satisfy Setright, although he was unstinting in his praise of Porsche's Seventies-era decision to equip the original 928 with a PRNDL gate as standard equipment. The man saved his highest praise for what he considered to be the only truly proper transmission design on the market: the continuously variable transmission, or CVT.
If you, like most of the drivers out there, have only experienced the CVT as part of a relatively staid Japanese sedan like the Nissan Altima or Honda Civic, I doubt that you have any fondness for the idea. As implemented today, continuously variable transmissions are infamous for "rubber-banding" and for a sort of discombobulating disconnection of engine noise from forward progress. Even when all the electronic buttons are in their most sporting positions, as was the case when I drove a rental Altima around Circuit Of The Americas last year in preparation for my test of the Lamborghini Huracan there, today's CVTs are uninspiring and unpleasant in equal measure.
Yet this is the same transmission that was banned from Formula One before the first car so equipped, a 1993 prototype by Williams, turned a single lap in competition. It's easy to see why: when tuned for competition purposes, a CVT allows the engine to produce maximum power at all times. This is an advantage far more significant than the friction losses suffered by a CVT in comparison to a traditional gearbox.
There have been a few technical challenges standing in the way of using the CVT in sporting cars, but none of them could be considered even close to insurmountable. No, the reason your Porsche or Corvette doesn't have one has nothing to do with technology. Rather, it's human nature that poses the problem. "Car guys" want their sports car to sound like a sports car. They want the revs to rise and fall, they want the engine to audibly respond to their commands, and they want pretty much what they've always had in a performance car, with a wider cockpit and better mobile-phone integration.
Faced with the reluctance of privilege-car drivers to accept the CVT, but also faced with soaring emissions and fuel economy standards, the manufacturers have chosen to give us the DCT instead. As transmission choices go, it's the second most repugnant one available. (The first most repugnant is the automated single-clutch system found in cars like the Ferrari F355 F1 and many Aston Martins.) The DCT is an exercise in unjustifiable complexity, packed chock-full of computers and sensors and moving parts and actuators and the like.
I don't know anybody who thinks that he or she can service a modern DCT. The five-speed manual in my Neon race car—or the six-speed manual in my Porsche 993—can be taken apart and fixed by anybody with a service manual. But these new transmissions have the computing power of a modern Airbus and if anything goes wrong the best-case scenario is that the car just decides to sit in neutral and go nowhere. The payoff for this hideously unreliable electro-mechanical superstructure lowered unsteadily onto the century-old manual transmission? Well, you don't have to know how to use a clutch pedal, and you don't have to slow down while shifting.
Both of those advantages also apply to the CVT, however, so the true reason for the DCT can only be that we wish to pretend to be stick-shift drivers. That we want to hear the revs rise and fall like we're calling the shots ourselves. To assuage our guilt at losing part of our control over the car, the manufacturers give us paddle switches which, in my experience, are only useful when you're trying to get the last half-second out of a lap time by trying to second-guess the transmission's automated choice of a gear for a particular corner.
Proponents of the automated manual, particularly proponents of the mandatory auto-manual as found in the Porsche GT3 and the Ferrari F12, like to remind us that "it's the Formula One transmission" and "stick shifts are slower around a track." True on both counts, but it's only the Formula One transmission because the CVT was banned from Formula One. It's the tame housecat to the CVT's mountain lion, if you will, and it's primarily chosen by people who are afraid of stalling their Porsche in traffic.
In any world where human beings made their choices on even remotely rational grounds, the CVT would be standard equipment on every car that had "going fast" as part of its mission statement. As things stand, I think the most sporting vehicle you can find with a CVT is either the Nissan Maxima or the Aprilia Mana GT, depending on one's willingness to ride instead of drive. Both of them indulge in the lamentable play-acting of letting the revs rise and fall as the transmission "steps" between arbitrarily-chosen ratios. That's a shame, because it's inauthentic enough to make your average Brooklyn hipster spit out his craft beer.
You know what would be a great car? A CVT-equipped Viper ACR. While it's true that the ACR's V10 is torquey enough to make shifts relatively infrequent, I like the idea of a Viper that never shifts but rather just UPS-truck drones at max volume while scattering Ferraris and the like in its wake. I think the CVT should be called TorqueFlite in honor of Chrysler's previous engineering accomplishments in self-shifting transmissions. I'm pretty sure that the TorqueFlite Viper would hold the (admittedly meaningless) Nurburgring record for a very long time. And it would be a true moral triumph of results over marketing.
Would LJK Setright approve of the Viper ACR TorqueFlite? Well, he approved of Bristol, and Bristol built a Viper-engined car called the "Bristol Fighter" a while back, so I think there's a possibility that he would have loved it. He certainly would have loved the speed; when praising the Honda CBX, he wrote that its power gave it "the effortless superiority which is the mark of the true aristocrat." Could a Viper be an aristocrat? Why not?
Jack Baruth
Rory Phoulorie wrote:I personally prefer a manual transmission over an automatic (my daily driver has a manual transmission). I recently drove a Qashqai for a few days which, according to the badge on the back, has a "fancy-shmancy" CVT, and I really could not tell the difference between how that "shifted" compared to a conventional torque converter automatic.
But if, as the above article says, a well designed CVT is equally as good, but less complex, than a dual clutch transmission (DCT), then the only advantage of the DCT over the CVT is the engine noise. I personally could not care for the engine noise in anything but a Lamborghini, Ferrari and Maserati (which really has a Ferrari engine these days), so if I had to go the automatic route in anything but the makes I listed, I would choose the CVT over the DCT.
What say you?
pugboy wrote: the cvt in my toyota fielder is very good, smooth acceleration and you don't realise how fast you going until you check.
drchaos wrote:Plenty CVT's still have torque converters and that is where most of the parasitic loss occurs from automated transmissions. Lock up torque converters have helped but still no where near the efficiency of a DCT or a manual transmission.
Allergic2BunnyEars wrote:drchaos wrote:Plenty CVT's still have torque converters and that is where most of the parasitic loss occurs from automated transmissions. Lock up torque converters have helped but still no where near the efficiency of a DCT or a manual transmission.
Read up on the Zf 8 speed auto when you get a chance. It real bad for an automatic.
markmaddness wrote:Did the badge by chance say CVTC or something along those lines? If so, that has nothing to do with the transmission but rather the engine. I believe it stands for Continuous Variable Valve Timing Control. I can be wrong.
To me, the most noticeable characteristic of CVT transmission is not feeling or hearing gear changes. Also, I noticed better fuel economy from CVT transmissions.
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