Let Electronics do the Shifting

Seventy-five cents: Go to the little filling station on the corner of Van Born and Wayne roads outside of Detroit and it's what you'll pay for a gallon of gasoline. That's a third the price of milk and a quarter that of orange juice, on a gallon-for-gallon basis. It's even less than the price of bottled water, for that matter.

But in Europe - where folks pay upwards of $5/gallon on per capita incomes at least 30% below that of the U.S. - and it's easy to understand why Europeans demand a measure of fuel savings from every piece of the automotive puzzle.

Of course that means looking beyond the engine for fuel savings. Manual transmissions, for example, are inherently more efficient than automatics - the problem is, fewer and fewer drivers want to hassle with self-shifting.

Enter Hydraulik Ring GmbH, a division of Siemens Automotive AG. The company offers up a means of eking an additional 7% efficiency out of a conventional manual transmission through the creative use of electronics. The result is a system called an automated shifting manual (ASM) transmission.

Siemens begins with a manual transmission, eliminates the clutch pedal and replaces the mechanical shift linkages with hydraulic lines. The hydraulic lines terminate at actuators that control the actual shift operation, and it's to these actuators that the electronics send their commands.

The electronics are programmed to shift the gears at the optimum rpm for fuel savings. They work on a principle similar to that applied to engine control modules (ECMs), though a couple of factors prevented the system's full development until fairly recently.

The trickiest part to tackle, says Glenn A. Barton, Siemens' marketing manager of diesel systems, was how to deal with the zero torque point. In a conventional automatic transmission, the torque converter always transfers some amount of torque to the wheels, and transmission and engine rpm remain in sync. In a manual transmission - as with the ASM - at the point at which the clutch disengages the gear, no torque is being fed to the wheels, and the transmission and the engine cease matching revs.

"The touchiest part of the shift is clutch engagement. It's the area that's most noticeable to the customer," says Mr. Barton.

The ASM solves this with a fuel cutoff, as in a diesel application, or by adjusting the throttle feed to re-engage the transmission without jolting the vehicle. This calls for the use of electronics with a measure of additional sophistication over conventional ECMs.

Volkswagen AG attributes a full 0.2L of the rated fuel economy of its 3L Lupo, unveiled at the Paris Motor Show last September, directly to the use of the Siemens system. The automaker says it would not have achieved the benchmark 78-mpg (3L/100 km) fuel economy figure without it.

For optimum space, weight and cost savings, the ASM's electronic controls can be integrated directly into the existing ECM, or the system can be added to a manual transmission by linking the ASM's electronics with the vehicle's ECM.

ASM's are attractive for future high-efficiency hybrid electric vehicles; New Venture Gear produced its own version last year for DaimlerChrysler's ESX 2 hybrid concept car. And truckmakers are interested, too, because "clutch pedal efforts have been creeping up for years," says Mr. Barton.