CART: Simulating Racing Conditions Proving Successful
2 July 1999
MONTVALE, N.J. (July 2, 1999) -- As the competition for the checkered flag
gets tougher in the CART FedEx Championship Series, the ability to simulate
racing conditions to test a race package becomes a critical part of a
successful program.
While Mercedes-Benz provides its IC108E Phase III (E3) engine to five teams
fielding eight Champ Cars in CART, each team makes individual choices about
which chassis it will race, and how it will develop the package for
competition. Mercedes-Benz relies on sophisticated dynamometers ("dynos")
at its headquarters in Stuttgart, Germany, and at the Ilmor Technology
Center in Plymouth, Mich., to perfect the power and efficiency of the E3
engine. And while manufacturers of Mercedes-powered Champ Cars might have
different philosophies about race car design, they work closely with
Mercedes engineers in an effort to put the most competitive car possible on
the grid.
Chassis builders possess their own growing arsenal of technology, from
computer-aided simulations to wind tunnels. In fact, only hours after
completion of the Texaco/Havoline 200 at Elkhart Lake, Wis., Lola Cars
International -- which supplies its new B99/00 Champ Car to Hogan Racing
and Marlboro Team Penske -- will unveil its new seven-post dynamic test rig
at its facility in Cambridgeshire, England.
Reynard Motorsport, chassis supplier to PacWest Racing, Player's/Forsythe
Racing and Bettenhausen Motorsports, also employs high-tech simulation at
its facilities in Shrivenham, England, and Indianapolis. The company's new
Auto Research Center features a 50-percent-scale, open-jet/rolling-road
wind tunnel and a seven-post dynamic test rig. Reynard's fluid dynamics
research complements their aerodynamic data acquisition by allowing
analyses of internal flows -- for example, within braking systems and fuel
tanks -- and by providing thermal studies of engine cooling and exhaust
gases.
"Certainly our fans identify with the engines that power our Champ Cars,
because they can identify with the engine manufacturers' products on the
street," said Andrew Craig, CEO of Championship Auto Racing Teams (CART).
"CART is unique in that we have many engine and chassis combinations that
teams can utilize to go racing. The engine manufacturers have to work very
hard, and the chassis suppliers have to be very innovative as well. It all
makes for a very competitive series."
The Dynamometer and the Test Rig
Mercedes-Benz's test-bed is the transient dynamometer located at Mercedes'
Stuttgart research and development facilities. This dyno allows engineers
to simulate all the demands placed on the E3 powerplant, from shifting and
clutch operation to aerodynamic drag, using a full gearbox assembly and
data gleaned from actual race laps. Mercedes engineers then can
custom-tailor the engine map (the Magneti Marelli software code that
controls such parameters as fueling and ignition) to maximize performance
and fuel efficiency for specific ovals or road circuits.
"The Mercedes-Benz transient dyno in Stuttgart gives us an opportunity to
be more prepared when we arrive at a circuit," said Paul Ray, vice
president of Ilmor Engineering, Mercedes-Benz's race-engine design and
manufacturing arm. "If Lola and Reynard can be more prepared before
turning a wheel, their teams are likely to be more competitive as well.
But it's the work we do together that really maximizes the total package."
Rigorous in-house testing allow Reynard and Lola to perfect a setup before
arriving at the circuit because they can evaluate the performance of
suspension and chassis components under simulated track conditions. The
combination of data acquired from the race circuit and wind tunnel can be
used to replicate any race track in the world.
Engine and Chassis: Getting the Perfect Fit
Months before testing begins, chassis engineers must design their car
around the Mercedes E3 engine and its supporting systems. Mercedes-Benz's
V8 powerplant was designed to be smaller and lighter than other Champ Car
engines-a huge benefit for chassis designers.
"A large engine is better for stiffness, but in many ways, the lower,
lighter design is better," said Simon Marshall, design engineer for Lola
Cars. "We have to make up the weight in ballast, but the Mercedes design
lets us put that weight where we would like to produce optimal aerodynamic
performance. It gives us more flexibility. Some engines require extra
scoops that can negatively affect the car's aerodynamics, but the Mercedes
engine doesn't require those. It's a very neat system that wasn't hard to
package."
Reynard Motorsport found similar advantages from the E3 powerplant. "We
changed our gearbox design completely to make the best use of the engine's
lower center of gravity," said John Thompson, drawing office manager for
Reynard. "We were able to do some things with the undertray that helped
the car. We can achieve more downforce with the Mercedes-powered cars than
we can for the others."
SIDEBARS:
The Seven Post Test Rig: A Primer
The seven-post test rig consists of seven flat pads atop independently
controlled hydraulic actuators. Using race data, a test-car and a set of
tires, the rig can replicate the forces exerted on the car from any race
track in the world. The rig allows teams to analyze many variables,
including torsional load dynamics, component stiffness, the effects of
weight transfer and ride-height sensitivity. Thus, any combination of
aerodynamic and mechanical setup options can be customized, examined and
refined to maximize the car's performance under actual racing conditions.
A Huff and a Puff:
How the Wind Tunnel Works
Reynard and Lola utilize wind tunnels featuring 50-percent-scale models and
wind speeds up to 135 mph to optimize air flow over and around a car for
peak efficiency. The model is computer controlled from outside the tunnel,
allowing engineers to vary the angles of pitch, roll and yaw.
"In the wind tunnel, we work on reducing drag for more straight-line
speed," said Simon Marshall, design engineer for Lola Cars. "We measure
the power of an engine by speed on the straight, and the chassis can really
screw that up if there is too much drag. It's more efficient for us to
minimize drag than for the engine manufacturer to produce more horsepower."
In addition to CART, Mercedes-Benz defends its Constructor's Championship
in Formula One with the West McLaren Mercedes team.
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