Chevy Indy V8 Insights: Software

    DETROIT, Aug. 22, 2002 -- While one group of GM Racing engineers
is testing and developing the hardware for the all-new 2003 Chevy Indy V8
engine, a second team is compiling pages of computer code that will operate
a new engine management system for Chevrolet's next-generation Indy car
engine. In this age of electronics, the ones and zeroes that make up the
engine's digital software are as crucial to success as pistons and cylinder
heads.

    Ned Baker, GM Racing's resident electronics specialist, heads the
task force that is developing a new "brain box" for the Chevy Indy V8. GM
Racing first employed electronic controls in motorsports in 1986; since
then, the pace of progress has been rapid and relentless. The 2003 version
is GM Racing's fifth-generation system developed specifically for
competition.

    "The GM Racing system consists of two modules," said Baker. "The
engine control unit (ECU) calculates how much fuel to deliver and monitors
the ignition timing. A second module then processes the ignition signals.
We start with a 12-volt battery signal, charge the capacitor to 400 volts,
and then the transformer windings in the coils produce the 16,000 volts
that the spark plugs require to ignite the fuel mixture."

    The operating principles of electronic engine management are
similar whether you are commuting to work or racing at the Indianapolis
500. The flow of fuel into the engine is regulated by injectors that are
switched on and off by the ECU. The injectors function like supercharged
spigots -- but at a much faster rate than any kitchen faucet. The Chevy
Indy V8's eight injectors cycle more than 42,000 times per minute when the
engine is turning 10,700 rpm. That number will double in 2003 with the
introduction of two injectors per cylinder.

    The interval that the injector nozzles are open -- the "pulse width"
in engineering terms -- precisely determines the amount of pressurized fuel
that is sprayed into the intake ports. GM's sequential system synchronizes
this injection with the engine's firing order.

    The ECU is programmed with a profile of the engine's fuel and
ignition timing requirements throughout its operating range. Sensors are
the eyes and ears that provide information on engine rpm, throttle
position, atmospheric pressure and other operating conditions to the
digital "brain." Based on these inputs, the ECU then refers to its internal
calibrations to determine the optimum fuel delivery and spark timing.

    "The racing system functions like a high-speed version of the
management systems used in GM production vehicles," Baker explained. "The
biggest difference is that the competition system doesn't have to operate
emission controls, air conditioning, electric fans, fuel pumps and the
other equipment found on production vehicles. A production ECU has a lot of
work to do and it has to do it very quickly -- for example, it must monitor
every firing cycle to control emissions. We utilize that computing power to
run the racing engine at much higher speeds. Decisions on injection and
spark timing must be made in microseconds."

    IRL regulations strictly limit the role of electronics on the
racetrack. Changes in the engine calibration must be made manually by the
driver, who operates a rotary switch on the dashboard to select one of
eight settings. Typically there are different calibrations tailored for
maximum power, fuel conservation and yellow-flag modes.

    "Telemetry from the pits to the car is not allowed, so you have to
depend on radio communication with the driver to adjust the engine during a
race," Baker noted.

    One of the few IRL-approved automatic functions is the pit lane
speed limiter. When the driver engages this system, the ECU regulates
engine power to maintain the prescribed maximum speed in the pit lane. This
speed limit, which is set by IRL officials, varies according to the track
and pit lane configuration. Chevy IRL teams can also program the system to
disengage automatically after the race car travels a predetermined distance
from the pit box to the exit.

    While electronic engine controls have become more powerful, their
physical size has diminished. The fifth-generation ECU weighs less than two
pounds and is about the size of a paperback novel. Reducing the size and
weight of these electronic components allows Indy car chassis designers to
package the units more efficiently within the tight confines of a
single-seat race car. The wiring harness that connects the ECU to its
sensors and other electronic systems is only six feet in length, yet it
contains more than 500 feet of wire.

    New features of the fifth-generation ECU will complement the
introduction of a smaller, lighter Chevy Indy V8 next season.

    "Starting in 2003, IRL engines are allowed two injectors per
cylinder," Baker said. "Dual injectors are a more efficient way to deliver
fuel to the two intake ports that are standard on the four-valve engines
that are used in the IRL. Doubling the number of injectors will add to the
complexity of the system, but our initial dyno tests have already shown the
benefits of two injectors.

    "The IRL rules will also allow 'shift without lift,' or
full-throttle electronic gear changes," Baker continued. "The sequential
transmissions used in IRL race cars are shifted like a motorcycle -- the
driver simply pulls or pushes the shift lever to go through the gear
pattern. With input from sensors on the transmission and the shifter, the
ECU can be programmed to shut off the engine for a very precise amount of
time during the gear change and then turn it back on. Without this feature,
the driver has to manipulate the throttle to take the torque load off the
transmission gears during a gear change. Next year the electronics will be
able to do this automatically, which will reduce the stress on the
drivetrain.

    "We are also discussing safety-related items such as a throttle
pressure switch," Baker added. "The ECU will then be able to shut down the
engine if it detects a stuck throttle."

    GM Racing is preparing for increased competition among manufacturers
in the IRL series next season. The development of a powerful new
engine management is a key element in GM's plans to maintain Chevrolet's
leadership in the open-wheel series.

    "After you have covered the basics, the success of an electronic
engine management system comes down to how well it meets the needs of the
drivers and teams, the reliability of the hardware and the soundness of its
underlying logic," Baker noted. "If the engineers have done their job, you
reach the point where the driver makes the difference. It's ultimately the
hands on the steering wheel and the feet on the pedals that win races."