Auto vs Semi-Auto

There been an interesting back and forth about non-manual transmissions over at The Truth About Cars. Says Robert Farrago:

The day F1 racing cars switched to paddle shift control, the clutch pedal was doomed. Only the paddle system's violence kept the left pedal from a date with old Sparky. Ferrari’s ground-breaking attempts at a passenger paddler were representative rubbish; the clunky F1 system transformed the sublime F355 into a herky-jerky one-track pony. Other early systems were equally obtrusive, equally foul. At the same time, style conscious high-end manufacturers added wheel-mounted button shifts and gate activated “tip shifts.” Although the technology simply handed customers slushbox control, computers eventually transformed the systems into a reasonably convincing halfway house between mindless ease and endless excitement.

Aston's Vanquish got closer to the real deal. If drivers tapped its over-sized plus paddle at the exact right rpm, the V12 GT rewarded them with a perfectly timed gear change. If not, not. Other systems followed: Ferrari, Maserati, BMW, Lamborghini, Aston Martin, even Toyota (MR2 Spyder). All of these paddle shifters downshift magnificently-- even blipping the throttle on your behalf-- but they either slur their upchanges like a drunk handing you a cigarette or smack you in the back of the head like a sadistic schoolteacher. And that’s without considering the challenges of around town ambling or, God forbid, reverse (a non-issue for F1, obviously).

And then BorgWarner and Volkswagen AG developed DSG. The direct shift gearbox (DSG) features two wet plate clutches: one engages the odd-numbered gears, the second the even-numbered gears. When the first clutch is putting down the power, a computer readies the second clutch to engage the next gear (pre-selected according to engine revs and speed). When the driver bangs the paddle for another gear or the automatic calls for another cog, the first clutch is released and the second engages. Gear shifts are fast, smooth and accurate; both up and down the ratios. The DSG’s computer-- complete with 12 sensors-- stands guard against “inappropriate” gear selection; an over-twitchy paddle shifter can’t stall or blow up the engine.

Not so fast my friend, Bob Elton replies:

Automotive pundits in these parts have lauded the new Audi DSG (Direct Shift Gearbox) as if it was the Second Coming of Dr. Ferry Porsche himself. In reality, the “dual clutch” design has long been discredited amongst most modern automobile engineers. Don’t get me wrong. BorgWarner and The Volkswagen Group have created a truly impressive version of a 50-year-old concept. But the dual clutch transmission is still nothing more than a wonderful toy, a mechanically elaborate dead end.

Paddle shifters-- and all the other excuses for avoiding a true automatic transmission-- remain a simple matter of stirring gears around in a box, like cars did nearly a century ago. The only difference between DSG and ye olde stick shift is how the gears are stirred. Hudson, Cord, Reo and others tried to make a manual gearbox shift by itself. None of these ideas were successful because the basic gearbox just didn't lend itself to the task. In fact, Audi's DSG traces its roots to the 60-year-old Chrysler transmission: the M-6. Chrysler developed the concept of overrunning gears, and almost made it work.

[...]

Again, it’s this 50-year-old overrunning gear principle that allows the Audi transmission to work as well as it does. Given the level of engineering ability at The Volkswagen Group, why didn't they apply it to the development of a truely modern automatic transmission? Ideally, an improved automatic transmission would keep the engine close to an ideal rpm range for the speed, load and performance of the car. It would accomplish this task with as little lost power as possible and not interfere with the driver's ability to drive. At the risk of reigniting the flame campaign against automatics, the world’s best paddle shift system is still a distraction, asking drivers to worry about gear selection when monitoring direction, traffic, available grip and speed should be their paramount priority.

He doesn't quite say it, but I think Mr. Elton would advocate CVT's. These transmissions make the most sense on paper, as you simply run the engine at it's peak power/peak efficiency speed, and adjust the tranmission's gear ratio to match the wheel speed. Removed from the need to rev, you would optimize the engine's power band, resulting in a strongly peaked output. Normally, this would be horrible to drive, but if your transmission can bridge that gap, that's how you should do it.

The problem with this, I think, is the feel. The engine speed won't change (much) when your driving, which will sound and feel weird. The car's response will heavily depend on how the transmission is programmed to respond to your inputs, which will likely be unsatisfactorialy.

Essentially, I think people want a transmission that works like Gran Tourismo 4, where you can blip up and down at will. I think this is the look and feel that Farrago likes about the VW system. But I suspect this is a result of programming and fine tuning, and not the mechanical design of the transmission. Personally, I think a CVT with a combination of a hybrid motor - electric motors for the low rpm's (electric motors make maximum torque at 0 rpm), gas for the high speed (especially with efficient high-boost turbocharging), switching over where their torque curves cross - would be ideal. You could make a AWD car with separated drivetrains - FWD gas, RWD electric, which could greatly simplify the drive train for that too.

I've only driven sticks my whole life. At the moment, I'm looking into a new car, and the prevalence of automatic transmissions on the lots makes negotiating on a manual transmission a little hard. Currently, my commute does not involve stop-and-go traffic, and the terrain around here is pannekoeken flat. But if I had to drive out of downtown Seattle and go North on I5 at 5 O'Clock each day, I'd get the automatic right away, even with a high-reving Acura four-banger. But I don't, so it's still an open question.