Cadillac LMP 02
Technical Insights: Northstar Engine Development
SEBRING, Fla. - Pose the question, "What's
new?" to GM Racing engineer Ed Keating, and you get a succinct reply:
RACE-PROVEN NORTHSTAR LMP ENGINE IS
REVISED FOR 2002
Keating leads the team of engineers and technicians that produces the prime
mover for the Cadillac LMP 02 - the twin-turbocharged 4.0-liter (244ci)
Northstar V8 racing engine. While the changes in the body and chassis of the
second-generation Le Mans Prototype are apparent, the modifications to the
heavily revised powertrain are virtually invisible.
"We have made substantial changes in internal
components and specifications for the 2002 season, but the engine's external
appearance is generally unchanged," Keating said. "After evaluating the
alternatives in displacement, induction systems, maximum boost and air
restrictor sizes, the engine group decided to continue development of the
turbocharged Northstar V8 that has proven itself over the last two seasons
ACO RULES SPECIFY MAXIMUM BOOST AND INLET
RESTRICTORS FOR LMP ENGINE
The Automobile Club de L'Ouest (ACO) rules that govern the 24 Hours of Le
Mans and the American Le Mans Series (ALMS) achieve performance parity among
different types and sizes of engines by specifying inlet air restrictors and
maximum turbocharger boost. Under the ACO formula, the 4.0-liter Northstar
V8 is limited to 1500 millibars absolute manifold pressure (equivalent to
7.5 psi boost pressure) and its air intake is regulated by two 32.4mm
(1.28-inch) diameter orifices.
"The ACO regulations do a very good job of
producing equivalency between naturally aspirated and turbocharged engines
with a variety of displacements," Keating said. "However, turbocharged V8
engines have enjoyed great success at Le Mans in recent years, and the
architecture of both the production Northstar V8 and its racing derivatives
is well suited to this particular configuration.
PROVEN ENGINE ALLOWS TEAM CADILLAC TO
FOCUS ON CHASSIS DEVELOPMENT
"Another factor in the decision to continue development of the turbocharged
Northstar V8 was time management," Keating continued. "There are already
enough variables with the introduction of an all-new chassis. The Northstar
V8 is a proven, reliable powerplant that will allow the team to focus on car
development rather than powertrain issues."
The Northstar LMP engine is a product of GM's
global motorsports program. It has close ties to the 4.0-liter naturally
aspirated engines used by Opel in the German Touring Car Masters (DTM) road
racing series and to the methanol-burning naturally aspirated 3.5-liter
Chevy Indy V8 engine that is being introduced in the Indy Racing League (IRL)
oval-track series in 2002. All three racing engines are based on GM
Powertrain's Premium V platform.
NORTHSTAR V8 BENEFITS FROM IRL AND DTM
"In 2001, we introduced a 180-degree crankshaft in the Northstar LMP engine
that was based on a design originally developed for the IRL series," Keating
reported. "This year we are incorporating cylinder head and valvetrain
developments from the Opel DTM program that suit the operating range of the
Northstar LMP engine.
"We are also pursuing improved performance
and fuel efficiency through friction reduction, induction system tuning,
refinements in engine calibration and enhancements in oil scavenging to
minimize parasitic windage losses," Keating added.
GM PREMIUM V ENGINE FAMILY PROVIDES
PLATFORM FOR LMP, DTM AND IRL RACING ENGINES
The LMP, DTM and IRL racing engines share their fundamental design with the
family of production Premium V engines that power Cadillac Seville, Eldorado
and DeVille models. The production and racing engines have similar
attributes, including lightweight aluminum block and cylinder head castings,
four-valve combustion chambers, chain-driven dual overhead camshafts and
electronic engine management. They also share the same architecture,
including a 90-degree V angle and 102mm cylinder bore centerlines. In the
Cadillac LMP and IRL applications, the engine is a fully stressed chassis
member that is subjected to suspension and aerodynamic loads.
COMMON ENGINE ARCHITECTURE IS KEY TO
EFFICIENT USE OF RESOURCES
"The Premium V engine program demonstrates how General Motors is able to
marshal its global resources to adapt a common engine platform to the unique
requirements of three different racing series," said Joe Negri, GM Racing
IRL/Road Racing Group manager. "Using a common engine architecture in
several racing series allows GM Racing to respond quickly to new
opportunities while controlling overall costs.
"The common elements in the ALMS, DTM and IRL
engine programs also promote synergy between GM operating units in North
America and Europe," Negri added. "This engine program demonstrates how GM
uses motorsports to achieve its business objectives in specific markets."
NEW SIX-SPEED SEQUENTIAL TRANSMISSION
The Northstar LMP engine is paired with a new six-speed sequential gearbox
in 2002. Paddles mounted on the steering wheel activate gear changes through
a pneumatic shifting mechanism. This system allows the driver to shift gears
without moving his hands from the wheel.
"The pneumatic shifter is completely
self-contained," said chassis designer Nigel Stroud. "Unlike many
hydraulically operated systems, it does not require oil pressure from the
engine. Consequently we believe this air-operated system offers advantages
in both reliability and maintenance."
Two years of continuous engine development
have pushed the Northstar V8's output to 600+ horsepower.
ENGINE DEVELOPMENT PROGRAM FOCUSES ON
POWER, RELIABILITY AND FUEL EFFICIENCY
"The Northstar engine program has made impressive progress, and we fully
expect this steady improvement to continue," said Cadillac LMP Program
Manager Jeff Kettman. "Working with our development partners, Ed Keating and
his group have produced an extremely reliable engine package. With the
enhancements that they are introducing this year, we anticipate further
improvements in outright speed while maintaining the reliability and fuel
efficiency that are absolutely essential in endurance racing."