SEMA task force ensuring aftermarket parts maintain ESC performance

  • 15-Nov-2010 07:28 EST
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dSPACE simulator (left), running the company's hardware-in-the-loop software, is connected to a Ford F-150 with lift kit and special wheels and tires. Computers (center and right) running CarSim software provide signals to the F-150's ESC module, so parked vehicle electronics respond as if the truck were running FMVSS 126 on a proving ground.

The Federal Motor Vehicle Safety Standard (FMVSS 126) regulation that has been driving OE installations of electronic stability control (ESC) became final in September, and all light-duty vehicles must comply by 2012 model year. Although many vehicle makers have been phasing in their systems to comply over the last several years, much of the automotive aftermarket is just starting to pay attention.

FMVSS 126 applies to vehicles with GVWR (gross vehicle weight rating) of under 10,000 lb. It is based on a group of performance tests, primarily to measure lateral acceleration in a highway-speed lane change (with return to original lane) at speeds of up to 80 km/h (50 mph). Like many regulations, FMVSS 126 provides for self-certification by OE and aftermarket.

ESC systems measure yaw and respond to excessive steering input by the driver with computer operation of individual wheel brakes to maintain directional control. In addition to vehicle compliance with the performance requirements, FMVSS 126 also requires self-diagnosis with a warning light to indicate a malfunction.

The U.S. NHTSA (National Highway Traffic Safety Administration) believes the regulation-compliant OE installation of ESC will reduce single-car accidents from steering error, including rollovers from run-off-the-road. NHTSA estimates that rollovers account for 42% of single-vehicle crashes with fatalities and 56% of the total fatalities from such accidents.

Aftermarket affected, involved

Why would the aftermarket even have to be involved? The answer is that a host of the most widely installed aftermarket suspension, braking, and steering parts—from shocks, springs, sway bars, lift and lowering kits to calipers, discs and linings, wheels and tires each or in combination—may affect continued compliance with the regulation. The "performance"-oriented parts are those most likely to be brought into question.

SEMA (Special Equipment Market Association), the largest industry parts group, has had FMVSS 126 on its radar screen since 2004, when stability control became a NHTSA-recommended OE installation. It realized that its member manufacturers’ products eventually would have to satisfy a regulatory "do no harm" requirement. In addition, the makers of these aftermarket parts also would have to assure all OE, wholesale, and retail customers that their parts were engineered to be sufficiently "robust" to maintain safe handling through all normal operating conditions as well.

A panel of industry technical specialists, led by SEMA's John Waraniak, Vice President of Vehicle Technology, filled in many of the blanks for attendees at a special session held during the 2010 SEMA trade show in Las Vegas in November.

SEMA has a suspension task force developing a comprehensive plan, essentially based on a simulation program in a demonstration operation at Clemson University's International Center for Automotive Research (CU-ICAR). When fully operational, the program is intended to enable members to be confident their products comply, without the expense of the actual road test described in FMVSS 126. CU-ICAR is directed by Paul Venhovens, a BMW engineer who holds the university's BMW-endowed chair in systems integration in the automotive research graduate program.

The FMVSS 126 procedure is well-defined, from the preconditioning of the vehicle, its brakes and tires, to the specific performance tests, with steering precisely controlled robotically. The regulation requires certification of all vehicles, including every optional permutation and combination of steering, suspension, brakes, wheels, and tires. However, the time required and cost of each series at a proving ground makes individual testing impractical, even for vehicle manufacturers.

OEMs test some combinations, but because of the clear-cut requirements and test result specifications, they rely on engineering data and simulations to validate the majority. Although the OEMs offer performance upgrades, including larger wheels and tires, and special tire tread patterns, handling suspension, and steering packages, they do not make changes to the extent of some of the aftermarket ones.

Further, the aftermarket manufacturers' often are dealing with more than their own add-on kits and/or replacement parts, but with components from other companies, so their problem is more complex. Their parts and those of other manufacturers that they list as acceptable would altogether be expected to have no adverse affect and also require no modification to OE electronics.

For some of the aftermarket companies, their business model includes measurable sales volume to car dealers, which adds to the significance of valid FMVSS 126 data, because the parts typically must have OE approval. "If the MIL (malfunction indicator light) goes on, you probably won't get a second meeting," Waraniak told the SEMA session.

"Historically, there's been a tenuous relationship between OE and the aftermarket—a 'why do you want to change that' attitude," observed Ed Browalski, a former General Motors technical fellow and now a SEMA vehicle dynamics consultant on the project. The OEM typically hadn't taken advantage of technical feedback from the aftermarket, he said, but with today's smaller R&D departments, "the aftermarket can fill that void, and the OEM is starting to recognize that."

The main issue for many aftermarket suppliers seemingly would be avoiding litigation and/or loss of OE approvals. However, what could be of equal importance is that compatibility with FMVSS 126 is likely to become a selling point. Although most consumers are not tuned into federal standards, the more car-savvy buyers of aftermarket performance parts are likely to be aware and might regard compatibility as an indicator of superior engineering.

F-150 demonstration by CU-ICAR

The simulation program at CU-ICAR is CarSim by Mechanical Simulation Corp, explained Dr. Thomas Gillespie, the company's Director of Product Planning. CarSim is in use by some OEMs, Gillespie said, and it also has OE approvals for similar regulation in the European Community. "It can make the car electronics do all we want," he added.

Although CarSim could work with software that replicates the operation of the ESC control module, the ESC information is proprietary and closely guarded by all the suppliers. As a result, the actual vehicle module must be used, and that is done with a dSPACE real-time simulator, which connects into the ESC circuit of the test vehicle and uses dSPACE software to provide what is called a hardware-in-the-loop system.

The CU-ICAR demonstration project was exhibited at the SEMA Show. The vehicle was a Ford F-150 pickup equipped with a 6-in lift kit from Superlift Suspension Systems of West Monroe, LA, and a tire/wheel combination that Superlift suggested, the Extreme A/T tire from Pro Comp/Smittybilt of Compton, CA, and a 20-in wheel from American Outlaw of Brea, CA.

Superlift previously had run a successful FMVSS 126 proving ground test of its lift kit on the F-150, but the demonstration project is not a direct comparison simulation, so the data interchange does not complete the information loop between the two, Gillespie said. However, when anticipated final simulation results are in, the company will be using them to promote its compliance on the 2009-11 F-150. A key enabler was the strong cooperation of Ford Motor Co., which supplied considerable F-150 data that otherwise would have been time-consuming and difficult to obtain, Browalski explained.

Simulation also will enable aftermarket performance suppliers to develop group envelopes of acceptable companion products at a small fraction of the cost of proving ground tests, all members of the SEMA panel agreed.

At present, Superlift, Pro Comp, and Rancho/Dynomax of Monroe, MI, are the SEMA participants in the task force. Because tire data is so critical to the simulation, however, SEMA is actively recruiting tire manufacturers, and Waraniak said he has indications of forthcoming support.

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