Electronics have managed engine speed for years now, but a sophisticated new wrinkle on the theme may have escaped your notice. Called “Load Based Speed Control,” it’s a patented feature that’s standard on Cummins 2002 ISM and ISX engines. Little noise has been made about it, and that’s a shame, because it works a treat and could raise your least efficient drivers to fleet-average fuel economy performance — or better.

I spent a day with a pair of LBSC-equipped engines operated by Concord Transportation in Concord, Ont. The trucks we drove — my colleague Jim Park and I — were Kenworth T2000s, both with 2001-model Cummins ISX 450 ST2 engines, one mated to an Eaton Fuller 13-speed, the other to an Eaton Autoshift box.

More on our drive later. First, let’s define “load.” The term incorporates literally everything the engine must overcome to move the truck-the rig’s gross weight, aerodynamic drag, tire rolling resistance, transmission and axle parasitics, and anything else conspiring to keep it stationary.

As the name suggests, LBSC continuously calculates that load and then adjusts the speed range of the engine so it operates at peak efficiency. It works in conjunction with the Cummins road-speed governor and “geardown protection” features to manage engine rpm not only in top gear and one down from the top, but in all lower gears as well. In a
13- or 18-speed, for instance, LBSC will be in charge (if you want it to be) up to sixth low. In a 10-speed, it handles gears one through eight.

The logic divides the engine’s operating range in two — a “normal” and “extended” range, with a dividing line or “breakpoint” you can have set anywhere between 1,400 rpm and the engine’s governed speed. The maximum rpm will vary between those points depending on fuelling demand. If the engine load is light, rpms will stay closer to the low breakpoint; if the load is 100 per cent, you’ll get the higher value. And you’ll get access to the extended rpm range if you add a grade or a headwind or some other such drama to the mix.

In a 2,000-rpm engine, as all ISX motors are now governed, both default breakpoints are 1,800 rpm, for a balance between economy and performance. In a fuel-sensitive application, the default gives you 1,500 rpm on the low side and 1,600 rpm on the high side. If performance is your game, you set both thresholds to the highest value and let ‘er rip.
If activated in that 1,800-rpm default setting, the feature will let drivers access the extended range above 1,800 rpm when there’s a serious load placed on the engine, but holds revs below that point when they’re not needed. Cummins heavy-duty product manager Mark Conover says you also get access to the extended range during any out-of-gear condition to facilitate early downshifts, and when the truck’s at rest to enable PTO use.

Sounds simple, but Cummins engineer Steve Bellinger says LBSC took two years of intensive work that had him road-testing up to 10 hours a week. Four patents were ultimately issued and a number of North American fleets had ISX engines re-programmed with the LBSC feature last year before it became a standard production offering.

Bellinger, who is also responsible for the Smart Torque feature on many Cummins motors, says he conceived LBSC while staring at an engine’s fuel map. Basic physics dictates that an internal-combustion engine will operate most efficiently at low rpm under heavy load and least efficiently with light or intermediate load and high revs. Why operate an on-highway engine in that least economical way? The driver gains nothing and the fleet loses money up the stack.

Bellinger says moving the engine’s governed speed around will enforce progressive-shifting habits while maintaining the flexibility to extend the engine’s operating range when the driver really needs it.

“This feature is designed to continuously compute the power demand or load on the engine and then move the high-speed governor around based on how hard the engine is working,” he explains. “When the engine’s not working hard, we pull the high-speed governor in and limit the usable speed range of the engine. Conversely, where loads are high and there’s a legitimate need for extending its operating range, such as when climbing a grade or dragging a multi-axle trailer around a tight turn, we allow it.”

The key is computing the load accurately and often. Bellinger and his comrades came up with an innovative way to actually estimate the gross weight of the vehicle while it’s being used-a dynamic calculation done in that little red or black electronic control module several times a second. It also takes into account a variety of load variables. The bottom line is a computation that not only yields an accurate result but is also very responsive to sudden changes in effective weight.

On the Road

That’s a lot of description, but how does it work? Mighty well, but it’s obvious right away that LBSC has more to offer the inefficient driver.

We were driving a simple 20-mile route on a two-lane highway, with short, sharp hills and a couple of long ones — a perfect test ground for LBSC. Jim took the wheel first, in the 13-speed truck with 1,500/1,600-rpm thresholds. A natural progressive shifter after years at the wheel, Jim shifts sooner than the computer assumes and had to will himself to bump against the artificial governor — it feels just like that — at 1,500 rpm on level ground with our light payload of some 25,000 pounds. LBSC wouldn’t help him.

Not having Park’s discipline or experience, I’ve never cared much about progressive shifting, except in theoretical terms, so me and the governor are pretty good chums.
When Jim hit the hills, the ECU gave him 1,800 rpm — he says he typically wouldn’t have let it go that high — and the switch from the normal to extended operating range was seamless. We also stopped at the base of a good hill and wondered how quickly LBSC would recognize the load when we started again. For an instant, but not much more than that, it held us to 1,500 rpm, then let us go.

When I did the 40-mile rounder up and down those grades, I knew only too well I was being held back on occasion. That makes me like many drivers, certainly like the least efficient ones.

Did I feel hemmed in, constricted? Not at all. After just a few shifts I was pretty comfy with LBSC. In fact, I was grateful to be given what I saw as “guidelines.” It made the driving job easier-the engine’s driveability didn’t suffer in the slightest and the engine speed was there on demand when I met a grade or wanted to launch a downshift high on the tach.

On that point, surveys of drivers who use LBSC show that most drivers actually prefer it to the open alternative, Bellinger says. Only a small minority want the traditional governor.

How did LBSC mate with the Autoshift? Not at all, in a sense, because the transmission’s own shift logic takes over in automatic mode and LBSC is shut down. Many drivers use these gearboxes in manual at least some of the time, however, and in that case LBSC is there to take charge of managing engine speeds.

Jim and I both ran the same route with the auto box, preferring to use it in manual to manage the hills ourselves. It was actually a pretty good combination if we let out fingers do the tapping on the up and down shift buttons.

The Real World

At Concord, fleet manager Derek Varley’s figures show remarkable gains after installing LBSC in these two long-haul, light-load tractors. We’re not claiming any rigorous fuel testing here, and we don’t know how many variables we’re dealing with — these are just company records. Nonetheless, the Autoshift tractor went from average monthly miles-per-gallon figures in the high sevens and low eights through 2001 and early 2002, then all the way to high eights and low nines with LBSC activated, through October. Its best month was September of last year, at 9.3 mpg, compared to 7.9 for the same month in 2001.

The 13-speed got as much as 10.3 mpg, in August of 2002, compared to 8.8 in the same month a year earlier. On average, the results went from high eights and low nines without LBSC to higher nines and low 10s with it.

Again, there’s nothing even vaguely scientific about these results, and in fact Conover and Bellinger are a little dubious because there are unknown variables at play. That said, we’re told that every fleet using LBSC has so far reported positive fuel results.

Assuming your drivers are more like me than like Park, which seems probable, it sounds like easy asset management.