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Modern Trucking Techniques
The secret life of engines as told by ECMs

By Paul Abelson
senior technical editor

The escalation of fuel prices has made us all aware of the need to improve operations. The importance of anything we can do to save fuel is magnified with diesel lingering around the $3 per gallon mark.

At the Technology and Maintenance Council meeting in September, one fleet owner reported that in 2003, fuel for his trucks cost less than $3,000 per month. Between the new post-10/02 emissions-controlled engines and today's fuel prices, he is now spending more than $8,500 monthly.

Fuel use is the single most important item in operating profitably. While we can't control the price at the pump, we can control the rate at which fuel is used. But to squeeze the most out of each precious gallon, we need to know what we're doing that wastes fuel, where we can improve and how effective we are in our conservation efforts.

That's where mining the data stored in your engine's electronic control module, or ECM, can help.

Most of us don't realize the wealth of data that ECMs store. Maintenance service providers use some of the data to identify mechanical and electrical problems and to track maintenance. All ECMs retain far more raw data than that, and each enginemaker has hardware to extract data and software to turn that data into usable information.

Here is only a partial list of what can be learned:

  • engine rpm;
  • time in gear;
  • idle time and percent fuel use;
  • fuel used idling;
  • load factors;
  • PTO time;
  • PTO fuel used;
  • speed vs. rpm; and
  • engine load vs. rpm.

The ECMs also contain overspeed data, hard brake incidents, last stop information and other operational history.

To determine how to make the data usable for operations improvement, enginemakers have personnel whose primary job is to work with distributors and major customers, teaching them to use the available data to generate reports and graphs that communicate info to operators.

Get to know your ECM

Most ECMs record all actions, including speed, shifts, brake applications and acceleration or deceleration rates. The data is measured and stored continually, but only for a short while. In the event of a sudden deceleration to zero – a wreck – data is frozen for one to three minutes prior to the incident and 15 to 30 seconds after.

The data, according to several court decisions, belongs to the vehicle owner. However, a prosecutor or a plaintiff’s attorney can subpoena it. The good news is that in numerous cases, the data cleared the trucker of any fault or wrongdoing.

If you are in a wreck and have to hire an attorney, make sure he or she knows about the data in your ECM.

Cummins' Customer Performance Technical Manager Jason Owens describes his job as helping customers get the highest fuel mileage they can. Cummins has several programs that analyze ECM data and make it understandable.

Insite is engineering-based software, more suitable for fleets of 10 or more power units with Cummins engines.

PowerSpec software lets you download data to your laptop or PC. It includes free software, but, like all other enginemakers' systems, it requires an investment in hardware to connect to data ports using standards J1708 and J1939 from the Society of Automotive Engineers.

While unlicensed information-producing software is available free on Cummins' Web site, a license is required to enable the vehicle owner to use it to make changes in engine operating parameters, such as road speed limiting, gear-down protection to limit power if a wrong gear is selected, governor droop, and 16 other parameters listed in the PowerSpec tutorial.

 In real-world applications, fleets using PowerSpec to train drivers and optimize settings have realized

8 percent to as much as 12 percent fuel economy improvement, according to Owens. Even for a one-truck operation, that's more than enough to justify paying a few hundred dollars for any necessary hardware.

Cummins' QuickCheck service tool interfaces SAE J1587 or J1939 data links with Palm handheld devices. Properly programmed, the Palm can work with other brand engines.

 Bill Stahl, director of OEM service at Cummins, said that by using PowerSpec to analyze and change parameters, an operator can get more run time in the engine's "sweet spot," the most economical rpm range. That could mean changing gears in order to run more at partial throttle.

For those not ready to make the investment in hardware or for those without a computer, Stahl suggests going to your engine distributor. For a fee, data can be downloaded from your ECM and analyzed to determine where improvements can be made.

After a few months, a re-examination of the data lets you know how much actual improvement you've made. Remember, this may take shop time, so don't be surprised if there's a moderate charge for the service.

 Caterpillar's Jason Phelps, customer communications coordinator, suggested that the easiest way for owner-operators running Cat engines to extract data is through the Cat Messenger. It graphically displays and records fuel use and average fuel mileage so a driver can monitor individual progress toward achieving goals.

Cat's Pocket Tec provides additional capabilities. The kit contains special software, a plug-in Palm adapter and a vehicle connection cable.

Besides diagnostics, the Pocket Tec lets owners configure engine parameters, review engine operations including temperatures, pressures and engine load factors. Owners can observe driver behavior, which includes time in gear, idle time, load factors, shift patterns and vehicle conditions.

"My dad was a truck driver," Phelps said. "He always used to tell me, 'Listen to the engine.' Now, I can do more than listen. I can use the Cat Messenger to tell me exactly what is happening."

An example Phelps gave was engine temperatures. Five degrees can make a difference. Diesels run better when they're warm, but if temperature parameters are exceeded, the fan will run excessively, using as much as 50 horsepower.

Detroit Diesel's ProDriver also provides driver information through a dash-mounted programmable reader. Targets can be set for the parameters monitored, such as idle time; fuel economy; current instantaneous and average mpg; trip data including driving time; percentage in cruise; fuel use and mpg in cruise and in top gear; maximum vehicle and engine speeds; over-rev time and percentage and engine load.

Using DDEC software, data can be processed to create activity reports. Chuck Blake, Detroit Diesel's manager of customer fuel consumption analysis, suggests using the reports as training tools.

"We can observe changes made in driving habits or even gearing changes. Diagnostic Link, a combined diagnostic tool and trip-reporting library, is fairly expensive for small fleets of less than 12 trucks. If the operator is truly interested, a Detroit Diesel distributor may provide trip activity reports for minimal labor costs," Blake said.

He suggested looking at same-month reports year-to-year so the effects of temperature are minimal. A 10-degree temperature change can be worth 2 percent in fuel efficiency because of air density and its effect on aerodynamic drag.

Wayne Wissinger, Mack's manager of product strategy, discussed ways to use data in the V-MAC system. DataMax is the on-board data logger that captures, among other things, trip summaries; GPS log; driver event log; maintenance and fault log; and incident log.

The system will produce information for fleet management, service and maintenance personnel and, of course, drivers. Like the others, it can create histograms - charts that graphically present reports.

Driver information can be presented through the CoPilot, Mack's dashboard readout. In order to change any parameters, an owner would need Mack's PC-based fleet management software, InfoMax. Service tools can look at data, but cannot make changes.

The newest version of Mack's engine software was just introduced in October - VMAC IV will allow programming of more than 200 parameters. CoPilot works with VMAC IV.

No matter which engine you operate, several things are common to all. Differences are in the details.

The overwhelming majority of engines built in the past decade have electronic engine controls with data memory. Dashboard readers provide processed information in a useable form. Software is available for PCs and laptops to allow data analysis. Cable sets interface with SAE-standard data posts.

Because each engine has unique characteristics, you should work with your engine's dealers or distributors to determine your best operating parameters.

Paul Abelson may be reached at

ECM data reliability

There are many issues affecting engine ECM data accuracy that truck owners and fleet managers must understand when using ECM data to make business decisions. The most important issues are:

1. There are many fleet-specified parameters to program correctly.

2. There are many variables to consider and understand when analyzing ECM data.

3. There are no standards for data collection or calculation methods. ECM data gathering and calculation methods vary significantly among engine models from a single manufacturer; they vary even more significantly among engine manufacturers themselves.

4. ECMs create data sets with varying degrees of accuracy. Accuracy of fuel measurement, mileage, and other parameters varies greatly. Errors of up to 10 percent are not unusual.

5. Fleet managers must invest a significant amount of time to ensure ECM data accuracy.

Source: The Technology and Maintenance Council’s Recommended Practice 344.

What can your ECM do for you?

In general, here are some ways you can use your engine's data to improve your operations. If you have two or more trucks - create driver profiles. Monitor how they shift, how they brake, how long they operate in each gear and how much they idle. In short, gather as much information on each driver as possible.

Compare drivers, but not with each other. You can compute optimum figures for each piece of equipment and compare driver performance with the ideal for each truck. If you drive, analyze yourself as well as others. Establish targets for each driver or for yourself. Use periodic downloads to compare results against those targets.

By comparing against the ideals, you may find that by splitting a gear and slowing down or increasing speed one or two miles an hour, you can operate in your engine's sweet spot, so fuel mileage can increase.

With a used truck, you may want to change tire sizes to help in getting optimum gearing. Remember to reprogram the ECM for the new tire size. If you have regular customers or regular runs, collect information on individual trips. You may find that because of weight, shape of a load, terrain or regional climatic conditions, some loads may not be as profitable as you may think. Others could be more profitable. Adjust rates or your customer base accordingly.

 The data exists. It is there for you to use. Why not use it to your advantage? With fuel hovering around the $3 mark, the time you spend may yield a high return.

Paul Abelson may be reached at