Don’t Be an Idle Fool

One of the top priorities for fleet managers is to reduce fuel consumption. In fact, when it comes to fuel consumption, they are facing a perfect storm. They are being told to reduce carbon emissions because of greenhouse gas concerns, they need to reduce the use of imported petroleum for national security reasons, and finally, they need to reduce the amount of money they are spending on fuel in order to make our budgets.

There are various means of reducing fuel consumption, including right-sizing of vehicles, vehicle weight reduction, powertrain optimization and various other means of increasing overall vehicle efficiency such as the use of high-efficiency components and improved aerodynamics. All of these items are important, but when it comes to reducing your vocational fleet fuel consumption that means vehicle idling.

Reducing Engine Idle Time

Several years ago, the Center for Transportation Research at the Argonne National Laboratory did an analysis of commercial truck idling. The report states 6.7 percent of all fuel used by commercial (non over-the-road) trucks is consumed by idling. However, this figure is somewhat misleading. If you look at the data for trucks that drive 40,000 miles or less, this figure increases to almost 20 percent, with some specific categories such as utility and dump trucks running over 40 percent. To make matters worse, the study does not count the fuel consumed while a truck is operating in power take-off (PTO) mode since the truck is considered to be “performing productive work.”

Obviously, there is a great potential for reducing fuel consumption through idle control. If your fleet was composed of nothing but full or even partial hybrid vehicles, the incidental idling associated with normal traffic flows (stop lights, congestion, etc.) would not be an issue. However, we all know this is not a realistic scenario, so the question facing today’s fleet managers is: “How can I reduce unnecessary engine idling?” Unfortunately, the answer is not a simple one. Before you can address this issue, you need to understand that engine idling time can be divided into three different categories.

Idling in Stop-and-Go Traffic

The first category is the idling associated with stop-and-go traffic conditions on congested roadways. There is not much you can do about this type of idling other than to install extended idle shutdown systems, typically timed for five minutes, on your engines. Note that these systems are now required by law in some areas and for certain applications (primarily commercial). Even if you have installed (or enabled) idle shutdown systems, drivers can usually find a way to get around them in order to maintain heating or air conditioning. Unless you either have drivers buy into a no-idling policy or an effective no idle enforcement procedure, incidental idling will continue to be a problem.

Off-the-Road Idling

The second (probably overall most wasteful) category is the off-the-road idling of engines. Drivers may allow their trucks to idle for a number of reasons including the desire to: maintain cab comfort; maintain battery charge when trucks are parked near the road and operating safety warning lights; and operate various electrical drive accessories such as computers, radios and other electronics. There are several systems currently available to address these issues. Cab heat can be maintained by using electric pumps to circulate engine coolant, as well as electric heaters. A short-term solution to this issue is to install fuel-fired heaters to keep the coolant warm (used in conjunction with a pump). The electric systems also have the ability to provide air conditioning. Finally, if the heating and cooling loads are large, you can use an auxiliary engine system which still uses less fuel than what would be consumed by allowing the main engine to idle.

Electrical loads (lighting, electronics and the systems mentioned above) can be supported by the use of auxiliary batteries and the installation of systems that monitor the battery charge. These systems will automatically start and stop the truck engine as needed to maintain battery charge. In addition, they take advantage of the alternator’s ability to rapidly charge the truck’s batteries to an adequate level to maintain the electrical loads being applied. By properly matching the battery pack and alternator performance curve to the stationary demands, you can achieve a significant reduction in engine idle time.

Non-Productive Engine Operation and PTO

Finally, there is the issue of non-productive engine operation time in conjunction with PTO operations. The most basic solution to this issue is to install a remote engine start/stop system. These systems may include a load sensing system to control engine RPM, depending on the application. The major drawback to these systems is that you are still depending on the operator to start and stop the engine as required. Recent developments in the areas of automatic demand engine start systems and electric PTOs (E-PTO) can generate significant reductions in non-productive engine idle time.

The Bottom Line

By evaluating your vehicle drive cycles and applying the proper technologies, you can achieve major reductions in vehicle idle time without incurring the cost of complete hybrid vehicle drive systems. In some applications, you can achieve as much as 80 percent of the fuel savings associated with full hybrid vehicles for less than a quarter of the cost. Take the time to evaluate your drive cycles and take advantage of new technologies to reduce both your fuel costs and your vehicle maintenance costs.

Bob Johnson is the fleet relations director for the National Truck Equipment Association (NTEA), based in Farmington Hills, Mich.

Weight and See

Four Factors to Calculate Before Hauling Crews and Equipment

1. Gross Combination Weight Rating (GCWR) — The GCWR is the maximum allowable weight for a truck and trailer combination, including: the tare weight of the truck; any cargo being carried on the truck; and the weight of the trailer, the driver, passengers and fuel (basically everything that moves with the vehicle).

2. Gross Axle Weight Rating (GAWR) — The GAWR is the value specified by the vehicle manufacturer as the load-carrying capacity of a single axle system. Each axle on a truck (and trailer) has a maximum allowable weight capacity. The GVWR of a truck is usually less than the combined GAWRs of all of a truck’s axles. The GAWR is limited by the weakest link in the axle system, which also includes the suspension and the tires. For example, an axle with a design rating  of 21,000 lbs may be rated lower due to the rating of the selected suspension (springs) or tires. When calculating the design load on an axle, make sure to take into account any weight transferred to the axle from a trailer (tongue weight) and the potential placement of cargo.

3. Maximum Trailing Weight (Trailer) Rating — Lighter trucks (classes 1 through 5) usually have a maximum allowable towing weight rating. This rating limits the weight of any trailer being towed regardless of the GCWR, GVWR and individual GAWRs assigned to the truck. Simply put, if a trailer weighs more than the allowable trailer rating, the truck is considered to be overloaded no matter the other values.

   

4. Highway Weight Ratings and Truck Registration — All of the above conditions represent the physical overloading of a vehicle. A vehicle can be legally overloaded if the weight of the vehicle exceeds the maximum allowable loading limits for a highway as established by (a combination of) state and federal regulations or if the weight of a vehicle exceeds its registered weight limit. When registering a vehicle, don’t forget that in most states the towing vehicle must be registered for the maximum GCWR at which you plan to operate.