A change in the U.S. Environmental Protection Agency’s testing programs won’t be the only consequence for automakers in the wake of the Volkswagen emissions-cheating scandal.
Powertrain control strategies, including the ability to adjust engines with aftermarket devices, may also be revised, experts note. They also expect government regulators in the U.S. and Europe to more strictly enforce existing rules and tighten emission-testing protocols, close gaps between laboratory and real-world testing, and perform more spot checks that can catch abuse after new vehicle models are approved for sale.
Overall, industry engineers should expect greater oversight over automotive testing and validation in the aftermath of what some are calling “TDI-gate.”
Shortly after the EPA said VW was using illegal engine-control software that reduced diesel tailpipe emissions during dynamometer calibration testing, the agency announced it would begin performing on-road tests. That quick response came as VW’s CEO resigned, investigations began, lawsuits by vehicle owners flooded in, and the company’s market value plummeted.
While VW’s deception may be the largest such event, it’s far from the first. In 1998 EPA levied a $1.1 billion fine on seven heavy-duty diesel engine makers—the largest civil penalty ever imposed for violations of an environmental law—for using "defeat devices" in the engines’ controllers. This software altered injection timing and boosted fuel efficiency while illegally bypassing the emission control equipment on 1.3 million trucks.
Some industry insiders, speaking on background only, said that such strategies using a control map created just for testing, were once fairly common for both diesels and gasoline engines. Other OEMs, including Ford, GM, and Honda, have also been fined for cheating.
Real-world vs. lab: 4x higher NOx levels
The practice of using different engine-control software for testing and actual driving, is known as “dual mapping.” The control map written solely for emissions tests usually kicks in when the engine’s running but the steering wheel isn’t moving.
“A lot of companies probably did similar things with gasoline engines in the 1990s, but most of them stopped in the late ‘90s,” said a technologist at a leading semiconductor company who requested anonymity for this article. Like many industry executives, he was reluctant to talk with Automotive Engineering publicly about the embattled OEM.
He said the trickery is now conducted primarily in diesels “because you’ve got more parameters to control,” he continued. “Diesel fuel burns in bursts, depending how you manage things like tumbling as unburned fuel moves in the cylinder; you can end up with way more particulates.”
Regulators have found it difficult to monitor emissions comprehensively and consistently. The U.S. upgraded its tests a few years ago to make lab tests closer to real-world driving conditions, but in Europe tests are comparably benign. European diesel vehicles’ highway performance is nowhere near the levels found in regulatory labs, according to experts at Emissions Analytics, a U.K. company that performs on-road emissions tests.
“In real world tests of about 700 cars in Europe, we found NOx levels four times above the government test levels, CO2 was 31% above official levels, and fuel economy was 24% worse,” said Nick Molden, Emissions Analytics' CEO. “The twist is that in Europe, that’s probably all legal, it’s more a factor of inadequate testing in Europe.”
He noted that current European tests don’t have hills, rapid acceleration or tests used in the U.S. including cold starts. Many observers feel that the EPA’s announcement that it would begin running on-highway tests is only one of the changes that will occur in response to the VW scandal.
“This may have a big impact on the aftermarket and security,” the semiconductor expert said. “Car buyers can fairly easily use off-the-shelf tools to adjust the engine; carmakers haven’t gone out of their way to prevent this. Going forward they may not want to let these things happen. This could also impact who’s able to reflash the controller.”
The ongoing controversy over dynamometer vs. real-world testing, and criticisms of government standards protocols, have spawned various solutions aimed at closing the gaps. See http://articles.sae.org/12610/ and http://articles.sae.org/7094/.
Control strategy revisions expected
Experts noted that it’s also possible that automakers will revise their engine control strategies. If new software took advantage of everything that today’s microcontrollers can do, it would be simpler to create controls that meet emissions and fuel economy mandates while still delivering performance, according to John Mills, CEO at SimuQuest Inc., an Ann Arbor, MI, software development company. However, that may not happen soon.
“Companies could move to use a better representation of physics and start adopting more parameterization [model-based optimization of engine controls],” he said. “But a lot of companies have legacy strategies that they’re afraid to change because they know it works.”
Demands that new engines must reliably exceed 150,000 miles is one reason for this reluctance to change from software that’s been proven on the road. Another factor is the large volume of software needed to control an engine.
“The amount of code varies widely; some OEMs have one code base used for every engine, using only a segment of it for each vehicle,” Mills said. “Other OEMs have separate strategies for different engines. Some have hundreds of thousands of lines of code. A lot of that is fairly verbose, but there are tens of thousands of lines of code that are critically important.”
The rising capability of microcontrollers is among the reasons that engine developers can create separate programs for emissions tests and normal operations, experts explained. Engine control programs only do one thing, adjusting engine parameters, so the processing speeds and memory requirements of engine controllers are small compared to consumer devices like phones and laptops.
“The low-end engine control units have processors that run at about 100 MHz at the low end, going up to around 300 MHz,” the semiconductor technologist said. “The processors have up to six Mbytes. In the fairly near future, that will go up to seven or eight, maybe even 16 Mbytes.”
The complexity of engine controls, along with their importance in providing reliable vehicles with good performance and fuel economy, means that software gets close attention. Some observers believe that because of this, VW’s engineering management, and perhaps higher level executives, likely knew that regulators knew that additional software was being used to mislead those who tested the vehicles.
“This is quite troubling,” observed a Tier 1 engineer. “Some people say that this might be the work of a few people. But these aren’t the type of metrics the full team would miss—nor are they activities that the group would not observe.”