Keeping engines under control

March 1, 2004
HYDRAULIC POWER is the muscle that drives much of the equipment being installed on today's commercial trucks. Keeping that power under control is vital

HYDRAULIC POWER is the muscle that drives much of the equipment being installed on today's commercial trucks. Keeping that power under control is vital for the safe and effective operation of the equipment.

Distributors who assemble commercial trucks now have an array of options for controlling the speed of the engine — essential for regulating the power that drives the hydraulic system.

One option is to take the chassis — particularly larger trucks — to the local dealer. There, technicians can access the onboard truck computer with a laptop and program the engine control module to provide engine RPM targets to suit the customer's needs.

Engine idle speed of lighter duty trucks such as those manufactured by the “Big Three” are frequently controlled through PTO activation wires, add-on aftermarket controllers, or by programming the onboard computer.

Many upfitters are able to save installation time by making sure these options are included when the truck is ordered. If that step was missed, or if the truck is equipped with a transmission that does not have an opening for a power take-off, other options remain. Aftermarket suppliers are able to meet specific customer needs for items such as variable speed pendant controls for welding units, digger derricks, winch or fire trucks. Also available are controllers that work like a gas pedal but can be installed at the back of the truck or pump panel.

Here are some of the features and benefits typically provided when engine-speed control comes from the chassis manufacturer, according to Mike Pettigrew, senior marketing analyst with VMAC, a truck accessory manufacturer in Nanaimo, British Columbia:

OEM control capabilities tend to include:

  • A single adjustment speed setting or a fixed preset speed (1,250 rpm w/PTO activation).

  • Adjustment often requires a programming tool from dealership.

  • Charge protect. Some truck manufacturers offer this to prevent idling trucks from discharging the battery. When the controller senses that the battery is in discharge mode (electrical demand exceeds the amount of charge going into the battery), engine speed is increased.

  • Remote pendant capability.

Benefits of OEM controls include that they come with truck. In addition, safety issues like park/neutral are taken care of internally in truck computer.

By contrast, aftermarket controllers offer multiple speeds and charge protect. They also can be ordered with a remote pendant.

Benefits of aftermarket controls can include greater flexibility and custom functions. They can be installed and set up quickly, Pettigrew says, with no dealer programming required.

Manufacturers of idle up controls in the market each take a slightly different approach to accomplishing the same task. For example, VMAC controls the engine idle speed by mimicking the signal sent from the gas pedal so that the onboard truck computer receives the same signal as if someone were depressing the pedal.

“This provides for a quick and clean installation with the ability to provide three idle-up speed settings activated with a 12-volt signal from anywhere on the truck, from 900 rpm to 2,400 rpm,” Pettigrew says.

For trucks equipped with automatic transmissions, it is critical that the engine speed control does not take control of the engine until the transmission is in park, Pettigrew says. If the control is activated while the vehicle is in gear, serious injury or even death can occur.

To counter the possibility of the truck being left in gear while operating equipment, the controller should not allow the throttle control to operate if the transmission is in anything other than park, Pettigrew says. In the case of VMAC, the company uses the truck's park brake as the main safety system. Engaging the parking brake completes a ground circuit. Without the ground circuit, the control will not activate.

Pettigrew suggests that distributors consider speed controllers that tie into the foot pedal of the vehicle.

“On any hydraulic equipment, performance is directly related to engine speed,” he says. “To get optimum performance from your hydraulics, you want to have flexibility and accurate control. Systems that tie into the ECM (electronic control module) of the vehicle are restricted to a 1,200-rpm floor.”

Controllers that tie in at the foot pedal of the vehicle allow the user to go almost to idle (900 rpm) and can idle-up in any increment.

Other benefits provided by electronic engine controls include:

  • Reduced fuel costs. High idle settings consume unnecessary fuel.

  • Less noise. By operating the engine at just the speed required to power the equipment, excessive noise is eliminated. Pettigrew says that some states and many municipalities are implementing new regulations directed at idle times for work vehicles.

Words of caution

For distributors considering the use of aftermarket electronic engine controls, Pettigrew has this advice:

  • Match the truck with the controller

    “Trucks have gotten more electronically sophisticated,” he says. “Make sure that you match to the year, make, model, and engine each time you provide a control to your customers. With all of the running changes the manufacturers have been making during the last year, we often have to ask the build date of the truck before taking the order.”

  • Watch the wiring

    Be sure that electrical wiring is connected correctly and in the appropriate sequence, as per the instructions provided by the manufacturer.