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PIT Reveals Aero Testing Results

Trailer skirt fuel savings averaged 6.69%

MONTREAL -- The Performance Innovation Transport (PIT) group, a not-for-profit engineering and research enterprise that's part of FPInnovations, made useful news this week. During its biannual Energotest event at the Transport Canada test track in Blainville, QC, it announced the results of five years of performance evaluations on trailers equipped with side skirts and undercarriage aerodynamic devices. The skirts won.

The test results show that trailers with side skirts consumed an average of 6.69% less fuel than similar vehicles without skirts. Trailers with undercarriage aerodynamic devices consumed 1.43% less fuel on average than similar units without the deflectors.

“The goal of these trials was to identify the real value of each technology so fleet operators can focus their implementation efforts where they get the best value and can more easily justify their capital investment,” said Yves Provencher, director of PIT. “Our controlled test-track fuel efficiency studies accelerate technology implementation and provide the commercial vehicle industry with the information it needs to make sound technology choices.”

For the fuel economy evaluations, PIT tested side skirts from Freight Wing, Laydon Composites, Ridge Corporation, and Transtex Composite. Fuel savings with these devices ranged from 5.2% to 7.45% compared to similar vehicles without skirts.

Trailer undercarriage air deflectors tested by PIT were supplied by AirFlow Deflector, Airman, and SmartTruck. Fuel savings ranged from 0% to 2.2%.

The PIT testing was performed in accordance with SAE J1321 Fuel Consumption Test Procedure - Type II. For each test, unmodified control vehicles and test vehicles had the same general configuration, were coupled to the same trailers for base and test segments, and maintained load weights the same throughout the entire test period. All vehicles were in good working condition and set to manufacturer's specifications.

Fuel consumption for the tests was measured by weighing portable tanks before and after each trip. The testing consisted of a baseline segment using non-modified vehicles followed by a segment using the control vehicle and test units equipped with the aerodynamic devices. For baseline and final segments, results were presented as the ratio between the average fuel consumed by the test vehicle and the average fuel consumed by the control vehicle. The values for fuel savings reflect the changes resulting from the modification of test vehicles.

The Energotest event was to feature fuel-consumption tests comparing North American and European trucks as well, but the two Volvo tractors imported from Sweden for the duel couldn't beat bureaucracy. They were held up by Canada Customs, so that testing has yet to be done.

The 2014 Volvo Globetrotter tractors are spec'd with Volvo engines set to the current Euro 5 emissions standard. They're rated at 460 hp and 1696 lb ft of torque, mated with I-Shift transmissions and 2.57 rear axle ratios.

They'll go up against two North American Volvo tractors. One is a 2014-model VNL 630 with an EPA 2010 emissions spec on its 425-hp Volvo engine developing 1650 to 2050 lb ft (an Eco Torque version), plus I-Shift direct-drive transmission and a 2.64 rear axle ratio.

The other domestic tractor is a 2009 Volvo VNL 630 with EPA 2007 emissions equipment. It's a 375-hp/1450-lb-ft Volvo engine with an I-Shift transmission and 3.36 rear axle ratio.

The testing will make the following comparisons: Volvo EPA 2007 vs. Volvo Euro 5; Volvo EPA 2010 vs. Volvo Euro 5; and Volvo EPA 2007 vs. Volvo EPA 2010.

Fuel efficiency will be evaluated using the SAE J1526 Type III fuel consumption tests, which compares the fuel consumption of one component of a combination vehicle to the same component in another combination vehicle, using portable tanks and the gravimetric method. The compared tractors will be switched between the semi-trailers at mid-test.

The tractor-trailer combinations will be optimized to allow the best fuel efficiency, such as the smallest tractor-trailer gap, and matching tractor roof deflector height with trailer height.

The results will be announced at the 2013 American Trucking Associations Management Conference & Exhibition in October.

Based in Montreal, PIT was formed in 2008. It's an unbiased, neutral testing organization to help manufacturers evaluate and refine prototypes and to assist fleet managers in selecting the best technologies to reduce costs and environmental impact. PIT works in cooperation with the U.S. SmartWay Transport Partnership, Natural Resources Canada, and Environment Canada. The latter has selected PIT as the benchmark facility for testing green transportation technologies.

Membership in PIT has grown to include 26 fleets, 16 municipalities, and four federal and provincial government agencies. Fleets pay an annual membership fee based on fleet size, as little as $35 per vehicle. Manufacturers pay to have their products evaluated.

FPInnovations, the mother ship, is among the world’s largest private, not-for-profit forest research centers, helping the Canadian forest industry develop technologies that promote efficiency and sustainable development. PIT is a logical extension of its work developing technologies for logging trucks.

Email Editor

What is the impact of redirected airflow away from brakes on the trailer axles when side skirts are utilized? Do brakes --- linings and drums --- run hotter?

Good question re brake heat. As far as I'm aware this wasn't measured but it seems inevitable that the lack of ram air would have an effect. Will see what we can find. The question has come up before but I've never seen a solid answer.

How can the Smart Truck System be between 0 - 2.2% as stated in the article and yet the Smart Truck System web site is reporting 5.5 % for the basic UT 1 system using the same SAE test procedure. The issue seems to be in testing not the results.

When did this test take place ?

Good question. We asked it too. PIT says it first did the test 2 years ago, then again this past summer. Same results. SmartTruck disputes the findings but hasn't commented further yet.

How can two different testing organizations come up with such a difference in final numbers? I would look at the testing organizations first. Smart truck used a third party to test. What third party did PIT use?

Does this mean the Smart Truck system is not CARB approved for California ?

Not at all. SmartTruck's UT1 and UT6 were CARB- and SmartWay-approved before the PIT testing was done. They paid for Canadian testing to help them win over Canadian customers.

Doesn't the article inform the reader that the Smart Truck UT 1 system had at most 2.2% fuel savings? That number does not qualify for CARB approval for the Smart truck UT 1 or for that matter any Smart Truck system.
Do you agree that the Smart Truck numbers on the Smart Truck web site are correct and that PIT numbers are wrong? OR the PIT numbers are correct and the Smart Truck web site numbers are wrong?

Mr. Anonymous, it seems like you want to argue. If so, please sign your name. But I have no axe to grind either way with this story. I'm just a reporter.