Modern Champ Cars are defined by their chassis. All Champ Cars share the following characteristics:
- They are single-seat cars.
- They have an open cockpit.
- They have open wheels -- there are no fenders covering the wheels.
- They have wings at the front and rear of the car to provide downforce.
- They position the engine behind the driver.
The chassis of a Champ Car is an amazing thing -- formed almost completely out of carbon fiber and aluminum honeycomb, a Champ Car chassis is extremely strong and lightweight. The entire chassis of the PacWest Motorola car weighs only about 1,000 pounds (455 Kilograms) when it arrives from the factory. The team then begins mounting things like the engine and electronics onto the chassis.
The chassis for the Motorola PacWest car is made by Reynard in England. Reynard supplies the chassis for a number of the teams. Other teams use chassis from Lola. Every year, the manufacturers release a new chassis and all of the teams start from scratch, attending testing sessions to try to gain a competitive advantage with their new chassis.
One reason that a new chassis comes out every year is because the rules evolve with each season. For example, in 1999, the CART rules reduced allowable aerodynamic downforce by 500 pounds, and all of the chassis manufacturers took this rule change into account in their designs. (The Information section of the CART Web site contains the complete rule book for Champ cars.)
When it arrives from the factory, the chassis comes complete with the body of the car, the suspension, the steering system and the transmission, and is called a rolling chassis. The team's job is to add things like the engine and electronics to the rolling chassis and tune it to the driver's style for maximum performance.
All Champ Cars have similar components:
The Motorola PacWest team uses engines supplied by Mercedes-Benz. Ford, Honda, and Toyota also supply engines to other teams.
One incredibly interesting characteristic of the chassis is the fact that the engine and transmission are actually a part of the chassis -- they are known as stressed members. You can see that the only thing connecting the tub to the transmission and rear wheels is the engine, and the rear wing bolts directly to the transmission.
The chassis of a Champ Car as described here weighs approximately 1,110 pounds (500 kg). Adding the engine and other components brings the weight up to the official 1,550 pound (700 kg) running weight for a Champ Car. At race time, the driver and fuel bring the car's total weight to between 1,900 and 2,000 pounds (860 to 910 kg).
One of the most important features of a Champ Car is its aerodynamics package.
The most obvious manifestations of the package are the front and rear wings, but there are a number of other features that perform different functions. A Champ Car uses air in three different ways:
- The wings on a Champ Car work opposite to the way they work on an airplane (see How Airplanes Work for details on airplane wings). On an airplane, the wings provide lift. On a Champ Car, the wings are mounted upside down so that they provide downforce. The downforce keeps the car glued to the track with a downward pressure provided by the front and rear wings as well as the body itself. The amount of downforce is amazing -- once the car is traveling at 200 mph, there is enough downforce on the car that it could actually adhere itself to the ceiling of a tunnel and drive upside down! In a street course race, the downforce aerodynamics have enough suction to actually lift manhole covers -- before the race all of the manhole covers are welded down to prevent this from happening.
- The engine in a Champ Car creates an incredible amount of heat. The car is burning a gallon of methanol fuel every 30 seconds or so, and that process releases approximately 100,000 BTU of heat per minute that the car must dump through its radiators (one Champ Car produces enough heat in 10 hours to heat a 2,000 square-foot house all winter!). The side pods are designed to move a huge amount of air past the radiators to help this process.
- In this photo you can see how the radiator and its plumbing mounts to the air tunnel beside the driver. At race speeds, this tunnel moves approximately 10,000 cubic feet of air past each radiator per minute -- enough air to fill a 2,400 square foot house every minute! The engine also needs spot cooling provided by small air scoops like the one you see in the picture below. On road and street courses, the brakes use special cooling ducts to bring more air over the rotors.
- The engine needs air to breath. An air intake at the rear of the car provides a stream of air directly to the turbocharger. The screen keeps debris out of the air intake -- debris can be a real problem at 240 mph!
One thing that you can see by looking at them -- Champ Cars definitely are not streamlined, aerodynamically perfect vehicles. You've got the wheels and suspension system sitting out in the open, the huge wings grabbing the air and converting it into downforce, the vents and protrusions on the body, and even the driver's helmet sitting out in the slipstream! It takes a great deal of power to overcome all of this drag, and that's one reason why Champ Cars need such amazing engines.
One part of the aerodynamics package that is not visible is underneath the car. A single carbon-fiber panel covers the entire underside and provides a completely smooth surface for the air to flow past. There are two air tunnels formed into this panel, underneath the two side pods. The tunnels taper so that the Bernoulli effect creates suction underneath the car. Both the wings and these tunnels contribute to the downforce.