Trailer Economy

Five long days of testing showed trailer aerodynamics and wide-base single tires are best bets to save fuel.

Tom Berg Senior Equipment Editor

What works and what doesn't among products that claim to improve fuel economy? Two Canadian fleets wanted some answers, so they employed a reputable institution and used scientific testing procedures, and got some interesting results after five days of intense activity last fall. They found that wide-base single tires and some aerodynamic devices yielded impressive fuel savings. Other products offer promise, they found, and still others didn't seem to work at all.

The "Energotest 2007" was done Oct. 1-5 at Transport Canada's Motor Vehicle Test Centre at Blainville, Que., on a 4-mile parabolic oval track. Runs were supervised by the Feric Division of IP Innovations, a non-profit research institution specializing in forestry but with some work with heavy trucks. This is what led the fuel-conscious fleets to approach the institution, according to Marius Surcel, a Feric researcher who participated in the tests and wrote a report on it.

Robert Transport and Cascades Transport, Quebec-based companies that have long sought fuel efficiency and reduced emissions, supplied tractors, trailers and personnel for the test. Transport Canada (the Canadian government transportation agency) put out a call to suppliers who might be interested in putting their products to an unbiased test. Those who did paid a fee to participate. Altogether, 19 products were installed on tractors and trailers and their results carefully measured.

Energotest participants followed Type II procedures established years before by The Maintenance Council (now the Technology and Maintenance Council) of the American Trucking Associations and adopted by the Society of Automotive Engineers. The procedures provide quick and reliable information about items being considered for use. Until they were designed, the only way for truck operators to find out whether something worked was to install it and run with it. But that can take many months and meanwhile, most of a fleet's trucks are still burning fuel at the old, less-efficient rate.

Under the Type II procedures, the fuel economy change resulting from an equipment installation is measured against that of an unaltered "baseline" vehicle. Both run the same course at the same speeds at the same time, eliminating variables caused by roads, traffic conditions and weather. Fuel in special tanks is weighed before and after each set of runs, and use calculated by weight; this is more precise than measuring use by volume, which fluctuates with ambient temperature.

Energotest was "a lot of work," said Lejean Laflamme, Robert Transport's technical support engineer, "but it was fun, too. It was long - five days, from dawn to dusk, 5 in the morning 'til 9 at night - very long days." But it was worth the time and effort because "we got 19 different answers" about that many products and operating methods right on the spot.

"We're a little bit tired of looking at numbers coming from Australia, Malaysia, other foreign countries," which is sometimes what suppliers offer for proof, Laflamme added. "I would like to meet some fleet managers from Australia and ask them if they are seeing numbers from Canada." Managers everywhere know that conditions elsewhere vary from their own, and the only useful numbers are those gotten first-hand right where they are. Type II testing at a 4-mile oval track in Quebec yielded believable numbers because variables were stripped away, baring the actual effects on fuel economy at a cruising speed of 100 kilometers per hour (62 mph).

Robert and Cascades supplied sleeper-cab tractors and 53-foot van trailers for the test. The tandem-rear-axle tractors were Volvo VN630s with Cummins ISX-450 diesels and Peterbilt 387s with Caterpillar C12-430s. All tractors had full fairing packages, though one was stripped of its tank skirts and run against another with the skirts in place to see how well they worked (the tank skirts improved fuel economy by 1 percent). Baseline rigs had standard dual wheels and tires, and trailers were stock so effects of equipment modifications could be measured.

No matter what kind of tires are run, the importance of proper inflation was confirmed by running a test rig with tires deflated to 85 psi and another at a recommended 100 psi. Done at the behest of Quebec's transport ministry, this test showed the rig with the soft tires got 3.1 percent worse fuel economy.

Another test showed that a double-trailer 10-axle B-train is 31 percent more efficient on a cargo-weight basis than a standard five-axle tractor-trailer and 8 percent better than a seven-axle tractor-trailer. This test was brief, literally done during a lunch-hour break in the scheduled proceedings, but seemed to confirm industry arguments that long combination vehicles can save fuel.

The greatest equipment gains were registered by Michelin wide-based single tires, which were run against standard duals, and by certain aerodynamic improvers. The tires' low rolling resistance improved fuel economy on test rigs by 9.7 percent, while aero devices applied to trailers bettered fuel economy by 5 to 9 percent. Included was a TrailerTail, comprising folding panels mounted at the rear of a van trailer to mimic a boat tail, plus trailer side skirts from FreightWing and Laydon Composites. Other aero devices also helped, but not as much, the track tests found (see list on following pages).

Some of the skirts were tested with panel extensions that covered trailers' wheels - a modification not likely to be used by many fleet operators. Effects of the wheel covers were not broken out in percentages in the Energotest report.

Alain Boutin, Cascades' director of risk management and compliance, said he was not surprised by the skirts' positive performance, because "we had done an in-house test with it, and saw it again in this test." Some of his in-service trailers have skirts - he won't say which brand - and they do save fuel.

In spite of the care that went into testing, participants figured there was a margin of error of plus or minus 2 percent. So anything showing a fuel economy improvement of more than that is worth considering and probably using, Laflamme believes. Something showing only a trace improvement or even a slight degradation might also be workable if it doesn't cost much. An example is a "cab space improver," a set of vertical metal panels bolted to a van trailer's nose. "It is cheap, only $35, so it might be worth it, even it there's only a trace of improvement," he said.

Robert Transport is now using wide-base single tires and side skirts on some of its trailers. There are 1,200 trailers in the fleet, and the equipment is best employed on those in long-haul service where speeds are high enough to allow the devices to work, he said. The manager's task is to identify such trailers and outfit them appropriately.

"Some of our trucks and trailers have the big single tires," said Boutin of Cascades Transport. "In the United States, we don't have any (weight) restrictions on wide tires, and we have some on regular routes, but we don't haul the same loads" as the same rigs in Canada. "In Quebec you have to use a special permit if you want to use the same weight" with singles as with dual-tired vehicles which put more width of tread to pavement. That province allows 91,000 pounds gross for a five-axle semi (and a payload of about 55,000 pounds), compared to 80,000 pounds (and a 45,000-pound payload) in the U.S.

"The TrailerTail is a very nice device, but needs some improvements to make it workable," Laflamme said in explaining why Robert is not yet using that product. The panels on the prototype tested last fall were too thick and "a little heavy, and it would fold itself" while running. "They're making changes; the new version might have those."

Advanced Transit Dynamics, TrailerTail's maker, said the product it subsequently unveiled in March at the Mid-America Trucking Show is lighter and its folding framework more secure so the device works effectively. Would Laflamme therefore consider using it? "We will use it if it meets our needs," he said. "For a 5 percent improvement - why not?"

One product that surprised Boutin, LaFlamme and Surcel was the Econoco, a device about the size of a filter that's installed on a tractor's fuel line. It applies an electromagnetic field that its maker says changes the fuel's molecular properties and makes it burn better - 3.4 percent better, according to test results.

The device is reminiscent of simple magnets that when strapped to fuel lines are said to improve fuel economy. This down-on-the-farm trick dates to the 1930s, and commercial versions have popped up every so often in recent years, to the derision of mechanical and petroleum engineers who testified that there's no reason magnetism should have any effect on fuel, much less make it burn more efficiently. But "it worked," said Laflamme said of the Econoco. "The representative at the test was disappointed; he was hoping for 15 percent. But 3 percent for me was good, really good."

"We have made some in-house tests, in real-life trucking, double-checking the test result," said Boutin. "We still have one in the truck and the result is the same. The result (at the track) is a little bit better than when we got from the in-house tests."

"It seemed to work for the test," confirmed Surcel. "It magnetizes the fuel molecules. We checked the device on the truck and we checked the fuel system, the injectors and everything else, to make sure everything with them was normal. Scientifically speaking, I am not able to explain why it works. But it's not my problem," he chuckled. "It did work in test conditions."

Several other products that claimed to improve engine efficiency actually reduced it in most runs, at least on the test trucks. Among them was a motor oil friction reducer, a hydrogen generator-injector, and free-flow mufflers for pre-2007 diesels.

Given the test's Canadian sponsorship, most of the products tested are produced in that country. But two are made in the U.S., and most of them are sold in both countries. Feric's report (at www.feric.ca, under Program Activities) names the tested products and their results, which we've listed here as they were applied to trailers and tractors:


Trailer Products

Advanced Transit Dynamics TrailerTail, folding rear drag reduction device, +5.1%

Freight Wing Trailer skirts, +7.2%

Laydon Composites Trailer skirts, +6.8%

Michelin North America (Canada) X-One wide-base single tires (also run on tractors), +9.7%

Transtex Composites BoatTail, rear drag reduction device, +2.6%

MinistPre des Transports du Qubec, impact of tire pressure (85 vs. 100 psi), -3.1%

Cascades Transport, in-house tests of cab space shield-trailer, -0.3%

Cascades Transport, in-house tests of cab space deflector on Manac trailer, +1%

Robert Transport and Cascade Transport, load-efficiency comparison of B-train (tractor with two trailers on 10 axles) versus tractor with single two-axle trailer (B-train was 31.4% more efficient) and tractor with four-axle single trailer (B-train was 8% more efficient).

Feric, in-house tests of open doors versus closed doors on an empty woodchip trailer; operators have long contended that leaving the doors open improved air flow, and they are apparently right, because this trick improved economy by1.6% versus running with the doors closed.


Tractor Products

Doggett Enterprises XADO anti-friction engine oil additive,-4.2%

Dynamic Fuel Systems Jetstar, on-board hydrogen gas generator and injector, -0.2%

Econoco, a device applying a low-intensity electromagnetic field on the fuel line, +3.4%

Meka Form road tractor fenders, +1.4%

Passing Lane Liberator muffler, trailer with 48,000-kilogram (105,600-pound) load, Cummins ISX engine, -0.7%

Passing Lane Liberator muffler, trailer with 25,000-kg (55,000-pound.) load, Cummins ISX engine, +1.1%

Passing Lane Liberator muffler (load not specified), Caterpillar C12 engine, -0.4%

Cascades Transport, in-house tests of tank shield, +1.0%

Cascades Transport, in-house tests of decoupled rear differential on tractor, +0.1%

Each of the products was tested separately, and no rig was run with more than one product, the participants explained. So the effects of using more than one of the tested products on a rig were not determined in the Energotest. However, previous studies with tractor-only devices in the U.S. showed that the percentages of two or more products do not add up to a final result. For example, a 5 percent improvement from low-rolling-resistance tires and a 5 percent improvement from a roof fairing do not equal 10 percent better fuel economy; the combined result might be a 7 percent improvement. The Canadians said they hope to run another test series this summer, and will try to combine products to see what happens.