While diesel engine development activity has been focusedfor many years on meeting emissions standards, there is little doubt thatengine electronics have also continued to evolve. Today, the advancedcapabilities designed into modern diesels are helping fleets achieve efficiencyobjectives and boost fuel economy.
Cummins
Cummins ISX engines, for example, are enabled withSmartTorque ratings. These engine calibrations deliver up to 200 lb.-ft. ofextra torque in the top gears, making it possible to run longer in gears wherefleets can reap the greatest fuel economy benefit.
Another Cummins engine feature that helps improve MPG isLoad-Based Speed Control (LBSC). The electronic capability on ISX and ISMengines automatically adjusts the engine’s operating range to match the loadand route.
LBSC optimizes engine RPM during normal driving conditionsby governing engine speed to encourage shifting in the most fuel-efficientrange. It also continuously monitors vehicle operating conditions and allowsaccess to an extended operating range every time it senses the need, such as ona grade exceeding 2%, during sharp turns when tire scrub may occur, or with aload in excess of 80,000 lbs.
LBSC does not limit engine speed when operating in the toptwo gears or during gear changes. It does, however, give fleets the option ofsetting low or high governed engine speeds that can be adjusted forhigh-performance driving or fuel-sensitive driving, or a balanced approachbetween the two.
Cummins also offers Gear-Down Protection (GDP) on its ISXand ISM engines. GDP promotes increased fuel economy by encouraging drivers tooperate as effectively as possible in top gear, where fuel consumption islower.
Under light loads, when downshifting would be unnecessary,Gear-Down Protection can be set to limit vehicle speed very noticeably,providing the driver with a strong incentive to remain in top gear. Whenlugging uphill or pulling heavy loads, the GDP feature allows access to thefull operating range of the engine in all gears. Therefore, under a heavy load,the driver can accelerate up to speed in any gear. This allows the vehicle toperform well under heavy loads, but still encourages the use of the mostefficient gear at all times.
To help improve fuel economy even further, Cummins offersits RoadRelay 4 in-cab monitor. A related capability that can be enabled when avehicle is equipped with RoadRelay 4 is the Driver Reward feature. Thisfunction of the engine’s electronics seeks to improve MPG performance bymonitoring trip fuel economy and idle percent time, and provides the driverwith customer programmable rewards once desired thresholds are met.
Detroit Diesel
Detroit Diesel Corp.’s newest engines incorporate anamplified common rail system (ACRS) that optimizes each injection event tominimize fuel consumption. ACRS works in unison with the DDEC VI electronics’motor control module (MCM) to deliver the exact amount of fuel that is neededfor a particular speed, acceleration, altitude, and grade.
DDEC VI electronic controls promote fuel economy in DetroitDiesel engines, including DD13 and DD15 models, in several ways. For example,an advanced cooling system is set up to decrease fan-on time, minimizing fuelconsumption.
Prolonged idling also wastes fuel so the DDEC VI optimizedidle system maintains engine temperature, battery voltage and cab temperaturewithout continuously idling. By automatically starting and stopping the engine,the optimized idle feature cuts fuel use.
On Detroit Diesel DD13 engines, electronic controls areenabled to provide ample power down to 1,100 RPM so drivers can spend more timein top gear. With the DD13 as well, an extremely wide and flat torque curvemaintains the power need to eliminate downshifting. The controls also providedrivers with a wider sweet spot that makes it easier to cruise in the mostfuel-saving range.
On the larger Detroit Diesel DD15 engine, there is anelectronically controlled wider torque curve throughout the RPM range sodrivers need to shift less to maintain speed up and down small hills, or ingusty conditions. Less shifting leads to better fuel economy.
The DDEC Reports feature of Detroit Diesel’s DDEC VIelectronic controls can also help save fuel. This capability lets fleetmanagers monitor every facet of engine operation, including comparingroad/engine speed to RPM.
Mack Trucks
Mack Trucks engines incorporate the Mack vehicle managementand control system (V-MAC IV), which provide an electronic way to help savefuel on the manufacturer’s MP Series engines. Integrated Temp-A-Start has alsobeen incorporated into V-MAC IV electronics. This feature cuts fuel use byallowing drivers to automatically stop and start the engine while idling tokeep the engine warm, the batteries charged, or the sleeper cabin comfortable.
V-MAC IV electronics monitor and control critical enginefunctions that impact fuel use, such as electronic fuel and timing control. Thesystem also gives fleet managers a choice of an automotive or all-speed styleengine governor, driver-programmable low-idle speed, and programmable shutdownoptions.
V-MAC IV has a multiple programmable engine settings featurecalled VLS (vehicle limiting speed). When enabled, this program can rewardand/or penalize a driver if the vehicle does not meet the predetermined fueleconomy standard set by a fleet manager.
For example, if the VLS is set at 68 MPH and the fueleconomy target is 6.5 MPG and the driver meets that objective, the electronicsallow additional speed as a reward. In this case, the extra speed could be setto 3 MPH, or a new VLS of 71 MPH –– as long as the driver continues to meet the6.5-MPG threshold.
The VLS feature on Mack engines will also penalize driverswho do not attain the fuel economy target over a chosen 50-, 75- or 100-milerange. In this case, the VLS would then be reduced by a customer-set valueuntil the target is met. The factory andfield-programmable feature can be disabled, used as an incentive only, orenabled with the penalty and reward capabilities at the fleet’s discretion.
Mack also offers an optional new Co-Pilot cluster driverdisplay that provides drivers with over 50 screens with real-time fuel economyand trip data. Drivers can also access indicators for the engine sweet spot toensure the vehicle is being operated at peak efficiency. A Fuel EconomyIncentive Program that helps fleet managers reward drivers for saving fuel canalso be enabled when coupled with the Co-Pilot display.
Achieving MPG goals
Many factors, from vehicle design and specifications todriver competence, can impact fuel efficiency in today’s over-the-road trucks.For their part, engine manufacturers are also enabling advanced electronics tohelp achieve the goal of improving fuel economy and cutting costs.
For more information about the products and capabilities inthis article, visit the following websites:
Cummins Inc.: www.cummins.com
Mack Trucks Inc.: www.macktrucks.com
