With the recent exodus of Toyota and Honda, the Champ Car World Series, under the Championship Auto Racing Teams Inc. (CART) organization, was ripe for change. Enter Ford Motor Co. and Cosworth Racing Inc. Ford and CART entered into a two-year relationship, renaming the Series "Bridgestone Presents the Champ Car World Series Powered by Ford." Cosworth Racing, a wholly owned subsidiary of Ford, is the sole supplier of engines for the Series, presenting a detuned version of the tried-and-true XF engine, now called the XFE.
The XFE engine is the fourth evolution of Cosworth's X Series Champ Car engines. The XFE is a 2.65-liter turbocharged V8 that provides 750 hp at 12,000 rpm and a maximum torque of 400 lb-ft. The top speed for Champ cars is over 230 mph.
To level the playing field and cut costs, teams now lease the same engines from CART. One team carries three engines and can have 13 rebuilds during the 19-race season for $1.3 million. Compare that to last year's lease, which cost teams $4 million, and included nine engines and 35 rebuilds.
Evolution of X
Entering the scene in 2000, the XF is said to be the smallest, lightest, and highest-revving Champ Car engine, and is 2-in. shorter and 18% lighter than its predecessor. The 2003 XFE is the evolution of the XF. It contains several performance modifications to comply with new Champ Car rules regarding horsepower and engine life. According to Ian Bisco, vice president of Cosworth Racing, "Our XF engine ran 300 to 400 miles before a rebuild. Now we have tripled the life of the XFE and we're running it to 1,200 miles."
Two issues came up: lowering the usable power of the engine while maintaining efficiency and oil consumption. Basically, in the world of racing, high rpms equal more engine damage. "The biggest thing was to reduce the rpms from 16,000 to 12,000," says Bisco. Power range for the XF ranged from 11,000 to 16,000 rpm. Cosworth engineers brought the power band down to a range of 7,000 to 12,000 to get a 5,000-rpm spread that drivers could work with.
Pistons in the XF were extremely light with low friction to maintain high horsepower. For the XFE, engineers designed a stronger piston by increasing the weight using more of the same material in different areas. Also, another O-ring was added to ensure oil consumption didn't escalate over 400 miles. This adds more friction to the piston, but boosts durability. Other changes for strength and longevity include switching from titanium components in the valve train back to steel, although Cosworth won't get into specifics. The increased weight of the pistons meant that the crankshaft had to be balanced differently and weight added as well.
To get performance levels up, intake trumpet length increased from 1 to 3 in. Cam time and fuel-injection timing also were tweaked. But how to get the required horsepower? By increasing boost in the turbocharger. Over the past few years, as speeds rose, CART reduced the amount of boost from a whopping 45 psi down to 34, using pop-off valves. The valves are electronically monitored by sensors. The only way for teams to get power up was by increasing rpms, which was costly. "Part of the cost savings this year was our ability to reduce the rpms back to 12,000. But to bring the power back up again, we increased the boost," says Bisco. Currently, 41.5 psi blasts through the turbocharger, making 750 hp at 12,000 rpm.
The XFE carries a conventional commercial-type turbocharger that runs with bronze bearings with aluminum and iron housings. Previously, the XF ran an expensive, titanium and magnesium turbocharger with roller bearings. A ring of injectors around the outside of the turbo would spray alcohol into the inlet wheel before it was forced into the engine. "This was costly, and a service problem because the turbo was separate from the engine," says Bisco. "Also, it was a maintenance issue because the electronic injectors and wire harnesses wrapped around a very hot turbo. But in the days when you were looking for that last 2 or 5 hp, it was a necessary evil," he adds.
In the current turbo, Cosworth engineers reintroduced precompression injection (PCI) to the inlet runner and made it part of the engine. "The injectors now get serviced with the engine and there are no electrical wires around the hot turbo housing, which will help with maintenance," says Bisco. "The current turbo is $7,000 compared to $13,000," he adds. Garrett Corp., of Torrance, Calif., makes the turbo.
Other modifications to the powerplant include changes to the fuel pump and materials in the engine. Fuel pumps had to increase flow to coincide with the higher turbo boost. The rpm reduction forced the mechanical fuel pump to turn more slowly. This necessitated increasing the size of the pump rotors, ensuring the same amount of fuel at lower rpms. Magnesium and carbon-fiber-engine components switched to aluminum for longevity. Dynamometer tests after 1,200 miles show the XFE with only an average 10-hp power loss. The powerplant weighs about 240 lb, or about the same as a conventional four-cylinder engine.