DOMINION

By Dave Coleman From www.sportcompactcarweb.com
An automatic transmission is by far the simplest, most efficient way to ruin a perfectly good car. We all know automatics suck, but have you ever stopped to think why? Ignore the fact that they usually launch slowly, absorb valuable horsepower, or insist on changing gears when you don't want them to. The fundamental problems with automatics are just two things: The torque converter and their long, slow downshifts.


The torque converter functions much like a bungee cord connecting the engine and transmission. Hit the gas and the engine starts accelerating without you. Then, as the bungee cord gets tight (or the torque converter approaches its stall speed), the car starts accelerating. This delayed response is frustrating enough on its own, but the really maddening part comes when you let off the gas. The engine slows, but what about the car? You can't push with a bungee cord. Automatics offer virtually no engine braking, making it difficult to control the car's attitude in a corner, or even just follow the flow of traffic. No wonder all those Buicks and Suburbans constantly flash their brake lights for no reason.

google_debug();Then there's the downshift. Let's say you're drifting into a tight turn (fumbling all over the brakes because the damn torque converter won't let you use any engine braking), you hit your apex, and roll onto the throttle. Then what? The car slows down! Then it thinks for a second, picks a gear and winds up the old bungee cord. By the time the car's ready to accelerate, you're almost to the next corner.

Frustrating or not, they're making more and more slush boxes every day. The sad fact is most Americans don't like driving in the first place, so a gearbox that isolates them from the driving experience just makes their misery sweeter. Luckily, there are a few automatic transmission options that don't suck. I've sampled three of them in recent months, and found there is hope for us in this automatic future.

Audi Multitronic
Audi's solution is unique in that it pleases everybody, offering both the seamless, uninvolving slush of an automatic, and the option of true responsiveness and control. Audi's Multitronic continuously variable transmission does away with gears completely, replacing them with a strong chain and two variators. The variators are simply big, V-shaped pulleys, but the two sides of the V can slide closer together or farther apart at the request of the transmission computer. The drive chain acts more like a belt than a chain, riding in these variators without any direct mechanical connection like the teeth you would see on a bicycle sprocket. This freedom from teeth is the key, however, as it allows the movement of the variators to effectively change the diameter of the pulley.

The chain, you see, is 37 mm wide, so it naturally sits on whatever part of the V happens to be that wide. Slide the variators all the way open, and the belt rides on the base of the variator; smash them together, and it moves to the outer edge. When what is effectively a small variator attached to the engine drives a large one attached to the wheels, you have a low gear, when they're the other way around, you have a tall cruising gear. Unlike any gear-based transmission, though, there are an infinite number of gear ratios available between the highest and lowest settings, and the gear ratio can be changed at any time without any interruption of the power flow.

This immediately eliminates the slow downshift problem. Regardless of how long it actually takes the transmission to select a lower ratio (it's actually quite quick) torque starts flowing the second you hit the gas, and continues to flow while the variators do their thing.

The other feature that makes Multitronic so responsive is its lack of a torque converter. Instead, the system uses a wet, multi-plate clutch. This works just like a normal, dry, single-plate clutch, but it's more durable, more heat resistant, and is controlled seamlessly by the computer, not your left foot. Let off the gas and the car actually slows. To make things even better, there's a manual mode that allows you to manually shift through six pre-selected ratios. The effect is just like a manual, but with power being transmitted constantly, even during shifts.

No bungee cords, no delays, no problems.

If this is the transmission of the future, I'll be happy.

Toyota Sequential Manual Transmission
The computer-controlled manual transmission in Toyota's MR2 SMT (tested on page 148) offers a glimpse at another future where enthusiasts and commuters might live in harmony. The SMT is simply a conventional manual transmission with a computer doing all the fun stuff. An electrically driven hydraulic pump, much like the one used for the MR2's power steering, provides the pressure needed to actuate the conventional dry clutch, and to move the conventional shift mechanism.

Because it's still a manual transmission, most of the automatic's annoying traits are eliminated. You get engine braking, throttle response, and no undue power loss, but the upshifts are still agonizingly slow. For no obvious reason, shifts take about 500 to 700 milliseconds, which is more than twice as long as a quick shift with a manual. In mellow, city driving this is fine, but the slow shifts are surprisingly disruptive when you're trying to have a good time.

Consider it a proof of concept, however, and it shows serious promise. Because it adds only a hydraulic pump, accumulator, three hydraulic cylinders (one for the clutch and two for shifting) and a computer, the cost is quite low compared with developing and building a whole automatic transmission. If whatever bit of Toyota conservatism that caused the slow shifting can be overcome, this too, is a promising automatic.

Prodrive NGT
Prodrive's NGT, or New Generation Transmission, is the one I would want in my car. In the most basic terms, the NGT is just like Toyota's SMT, a manual transmission under computer control, but instead of using an existing transmission, Prodrive started over. Conventional manuals are designed for human control. They have synchros, since we aren't precise enough to match gear speeds perfectly on each shift, and they're overbuilt to withstand abuses from simple clumsiness to outright mechanical hatred. The shift throws are long, so the driver doesn't get lost, and the shift mechanisms are large and elaborate to allow a single stick to do all the shifting. With computer control, none of this is necessary.

Eliminating the human allows Prodrive to stuff six or seven gears in the space of a normal five-speed manual, and as many as eight in the space of an automatic. Waiting through seven gear changes would be agonizing if they were as slow as Toyota's, but Prodrive has managed to shorten the entire shift, from the moment torque is interrupted to the moment you start accelerating again, to an amazing 50 milliseconds. That's so short you barely feel it. The concept was developed in its WRC Subarus, but now Prodrive is making a push to get the NGT into production cars. It's still a few years off, and there's no word when or where we'll see them first, but if we're lucky, this rally technology will take the place of the your grandmother's slushbox.