by Jim Kerr
In the quest for fuel economy, the auto manufacturers use all the tricks – lighten whenever possible, use smaller displacement engines, control fuel more accurately, and reduce aerodynamic drag. Another area that has been redesigned for economy is the transmission. Automatic transmissions have refined gearing, lock-up torque converters, and variable displacement oil pumps to improve efficiency and fuel economy. CVT (continuously variable transmissions) are another step in improving economy because of their capability of allowing the engine to operate at optimum rpm’s. Now, another form of automatic transmission is hitting the market, and it offers even better economy – the automatic/manual transmission.
Formula 1 race cars use them. Ferrari is using one. BMW is introducing one this year on the M3 model. Big highway trucks and industrial equipment have used them for several years. GM has been working on one, as I am sure many others have, and I have driven a Ford Focus with one installed. The automatic/manual gearbox offers advantages of both the manual and automatic transmissions.
In reality, the automatic/manual transmission is a manual gearbox with computer-controlled shifting and clutch operation. A manual gearbox has less internal friction, no power-robbing torque converter, and doesn’t have to pump a large volume of oil through the transmission. Increased transmission efficiency means less fuel consumed and more power to the drive wheels. The traditional disadvantages of manual gearboxes, the constant shifting in traffic and having to operate the clutch, are removed by using smart computer logic controls.
All you need to do is put it in Drive and step on the gas. The faster you try to accelerate from a stop, the faster the computer releases the clutch, just like an experienced driver would. When it is time to upshift, the computer releases the clutch, shifts the gears with electric solenoids, and re-engages the clutch. Need to pass? The computer downshifts just as easily for quicker acceleration.
Because the transmission is computer controlled, the roll of the shifter has changed. It could still be mechanically linked to the transmission gears, but now all it really needs is a few electrical contacts to sense the driver’s input. Ferrari decided to use steering wheel shift control. BMW uses the conventional shifter for selecting the gears, including reverse, but also uses paddles like the Formula 1 cars behind the steering wheel for sequential shift control. The Ford Focus I had a chance to drive used a console-mounted shifter much like an automatic transmission – place it in Drive and go. Move it sideways into the up/down gate for manual gear selection.
I found the prototype unit in the Focus worked well, but needed a little refinement in the computer programming. In automatic mode, I could feel a little “jerk’ each time the transmission shifted. It was similar to driving with someone that needs more practice with the clutch pedal. It was most acceptable to drive, and a little more refinement should offer an excellent alternative to the automatic transmission.
BMW call their unit a second-generation SMG (Sequential M Gearbox). Advantages of the unit include quicker shifts than even an automatic transmission. It takes only 80 milliseconds to make a shift! During a shift, engine power is reduced, so the driver doesn’t even have to lift off the gas pedal. When downshifting, the computer automatically double-declutches, but if a downshift would over rev the engine, the shift is prevented. Similarly, if a downshift causes the wheels to slide on a slippery surface, the clutch is disengaged to take full advantage of the car’s stability control system. Driver error, of which none of us ever makes (!), is virtually eliminated.
Finally, automatic/manual gearboxes offer more relaxed motoring. Stop and go traffic isn’t a hassle. Starting out on an incline is simple with no clutch pedal to operate. Any driver can use the car. But if you like performance, then the manual shift selection capability still allows you all the performance (and more) that you would find with a conventional manual gearbox. Economy, performance, and easy to use – what more could you ask of a transmission?