Gauge Check

| December 12, 2008

Advances in electronics are reducing the need for a cockpit full of needles. Make sure the gauges you choose give you the data you need.

The trucking industry is polarized when it comes to gauges, says Kenworth’s Gary Ziebell, a project engineer. “Sometimes it seems as if owner-operators don’t care what information the package imparts, as long as it looks retro,” he says. “Unless it can be packaged as an analog gauge with a needle, they don’t want it. On the other hand, the fleet guys want no gauges at all.”

“And this means fleets don’t have enough information on the dash for the good driver,” interjects Kenworth’s assistant chief engineer Dan Farmer. “The problem,” Ziebell says, “is that neither party sees the value of gauges.”

For the owner-operator who wants to operate as efficiently as possible, there is plenty of value in knowing what’s going on with everything from the radiator to the rear axles. While only so many gauges can be crammed onto any given dash, certain digital gauges offer improvements over analog versions, and new developments in electronics make it possible to run multiple sources of data through one display unit. A smart choice of gauges, whether in spec’ing a new truck or installing aftermarket products, can help you head off problems before they happen.

Aftermarket gauges can often replace original equipment gauges in their positions or fit into unused circles in the dash. A replacement must be of the right diameter – often 2/-inches – and might require a mounting bracket.

Peterbilt’s owner-operator customers have a keen interest in taking the pulse of all their truck systems, says Todd Acker, Peterbilt’s over-the-road brand manager. “These truckers are accustomed to scanning every gauge, and many could close their eyes and tell you the location of every one on their dash. They also are likely to want a dashboard that reflects their individuality.”

Mack customers prefer analog gauges, says Mack Powertrain Division’s Wayne Wissinger. However, he believes “all drivers will approve of Mack’s coming digital display, located on the B-panel to the right of the driver. It will be high resolution and easier to read, and you can put lots of information there.” A display consisting of a drivetrain diagram with the fluid temperature for each component shown next to it replaces an array of gauges that would take up much more room. The system automatically warns the driver if something goes wrong.

With Freightliner’s digital system, “The engine messages are all on a common data bus, and we display them separately on the dash,” says Paul Menig, chief electrical engineer. The engine messages include the inputs for the speedometer, voltmeter, and oil pressure and coolant temperature gauges.

For International, “With electronic engines, the speedometer, tachometer, coolant temperature, and oil pressure information are transmitted over the ATA data link from the engine’s electronic control module to the speedometer/ tachometer module,” says Ron Welch, a marketing manager. International’s gauges feature warning lights and audible beeps to alert drivers of trouble.

On Volvos, the entire instrument cluster is multiplexed, which means many signals are sent on a common wire in encoded form, says engineer Jon Quigley. Each gauge then reads only the signal meant for it. The Volvo cluster connects with just three plugs and operates entirely via solid-state electronics, which “eliminates all problems with air sources or binding mechanical parts,” Quigley says.

Not only are gauges themselves changing, but because many engine and drivetrain functions are better controlled, some gauges have become less important. Critical ones are often managed by the engine’s electronic control module.

Take the oil pressure gauge. “To reduce parasitic losses, oil pressure’s regulated by a spring in the filter head discharge that dumps excess pressure,” says Kenworth’s Ziebell. “It doesn’t tell you when you’ve got the wrong viscosity oil or when the oil temperature is way up, either. So the reading has less value than in the past.” Besides, he adds, if oil pressure gets critically low, the ECM will give you a warning light and ultimately shut the engine down.

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