Here's a repost of the article.
Here's the story from their site:
Car-hacking secrets
Computer hackers seem to be everywhere, even under the hood of Detroit's
latest automobiles. Since the California Air Resources Board and the
Environmental Protection Agency implemented automobile-emissions
restrictions, some car buffs have resorted to software patches in the
engine controller to restore missing horsepower.
Automotive engine and transmission controllers operate like standard
proportional, integral, and differential (PID) control algorithms
(Reference 1). The proportional term sets loop gain, the integral term
reduces the steady-state error, and the differential term improves
responsiveness and stability. Vehicle manufacturers store these PID terms
along with feedback filter coefficients in nonvolatile memory to allow for
system tuning and calibration. Manufacturers can tweak these control-system
parameters depending on the physical engine or transmission and the target
market. For example, in markets with high gasoline prices, fuel economy
might be more important than horsepower. In other markets, such as in
California, emissions regulations may dictate reduced performance.
But California car enthusiasts love high-performance engines. Much to the
chagrin of the automobile manufacturers and in spite of tight security,
computer hackers have been able to reverse-engineer the code for most
engine controllers within just a few months of the code's appearance. By
adjusting the control-system parameters, hackers can defeat the
California-emissions controls and increase automobile performance. For
example, hackers claim that with a controller-software change you can get
10 to 15 more units of horsepower from a Pontiac Trans Am. Hackers can also
adjust the shift points for transmission controllers to give the driver the
feel of a higher performance engine.
Meanwhile, manufacturers and emissions-controls regulators are working to
prevent hacking and to detect altered vehicles. Modified engines affect
automobile warranties and environmental pollution and may create a safety
hazard for other vehicles.
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