Chevrolet Racing Press Releases:
04-14-2007: GM Racing White Paper: Inside the New Chevrolet R07 Small-Block V-8
Source: GM Media
Technical Insights on GM's First Purpose-Built Small-Block V-8 NASCAR Racing Engine
DETROIT – For the first time since 1955, Team Chevy is introducing an all-new small-block V-8 engine in the top tier of stock car racing. The new Chevrolet R07 is the first purpose-built engine designed and developed by GM Racing specifically for NASCAR Nextel Cup competition. This purebred engine is the successor to the production-based powerplants that have made Chevrolet the most successful manufacturer in NASCAR history. This white paper highlights the Chevrolet R07's development and summarizes its technical features.
Design and Development
The Chevrolet R07 is succeeding the championship-winning SB2 (Small-Block/2nd Generation) engine that has been used by GM teams in NASCAR Cup racing since 1998. NASCAR approved the Chevrolet R07 for competition in 2007, and it is expected that the R07 small-block V-8 will become the exclusive Chevrolet powerplant in the Nextel Cup series as teams turn over their inventory of SB2 engines and components.
Work on a successor to the SB2 began in earnest in 1999, and several variations of the conventional small-block V-8 were designed, tested, and evaluated. In 2004, NASCAR held discussions with the au tom otive manufacturers about a possible "Engine of the Future" that paralleled the Car of Tomorrow body/chassis program. Although the Engine of the Future did not become reality, the meetings did establish a framework for future NASCAR engines.
"The discussions with NASCAR and the other manufacturers about the Engine of the Future were extremely productive," said Jim Covey, NASCAR engine development manager for GM Racing. "Although the Engine of the Future program was put on the shelf in 2005, NASCAR Nextel Cup Series director John Darby developed a list of parameters that define the envelope for all manufacturers, thus giving Chevrolet an opportunity to develop the R07 engine. This 'box' set the boundaries for specific design features and minimum and maximum dimensions for key engine components.
"We had already started to lay the foundation for a future Chevrolet engine, and we were able to adapt that design to the Chevrolet R07," Covey continued. "That was the key to designing, testing and submitting the engine for approval on a very tight schedule. A prototype R07 engine was running durability tests on a dyno six months after we kicked off the program. The R07 engine development team included Ed Keating and Ron Sperry, who focused on cylinder heads and intake manifolds, and Ondrej Tomek, who was responsible for the cylinder block. We also worked with our key Chevrolet teams, GM Powertrain, and our suppliers."
Just as in all forms of motorsports, the rulebook defined the basic engine package. GM Racing's objective was to produce the most competitive and reliable engine within the boundaries established by NASCAR.
"NASCAR's box provides considerable latitude for manufacturers to design their engines, and there are many parameters that have to be balanced," explained Pat Suhy, GM Racing Group Manager, Oval Track. "If a manufacturer maximizes one aspect of the engine design then it may limit what can be done in another area. Our goal at GM Racing was to find the optimum point for all of them. We relied on our computer-aided engineering and design tools, our experience, and input from our affiliated teams to make informed decisions on the engine configuration. It was all about balancing those tradeoffs to produce an engine that would produce competitive power with exceptional reliability while also improving safety and reducing costs for Chevy teams."
Many of the advanced technical resources used by GM Racing engineers to develop the Chevrolet R07 racing engine are also used to develop GM production engines. By employing technology such as computational fluid dynamics (CFD), finite element analysis (FEA), and solid 3D modeling, GM Racing engineers were able to evaluate and analyze various designs in computer simulations. This extensive use of computer modeling also accelerated the production of prototype parts after the specifications were finalized.
While CFD is commonly associated with aerodynamic development of race cars, it can also be used to analyze the behavior of fluids such as the coolant flow through the Chevrolet R07's block and cylinder heads. FEA was used to analyze the strength and minimize the weight of the R07's block and cylinder heads.
"Although we use many of the same engineering tools, the timeframe for racing engines is much shorter than it is for production engines," Suhy noted. "The rapid turnaround in racing allows us to get feedback on the accuracy of GM's computer simulations and models very quickly. The same programs can then be refined to make them more accurate when used to develop future production engines."
In this way, the Chevrolet R07 racing engine will lead to better production GM powerplants. "The concepts and processes that are used to improve the performance of our racing engines are shared with the production engine designers to improve the efficiency of our production engines," said Tom Stephens, group vice president of GM Powertrain.
The Chevrolet R07 retains the pushrod/two-valve layout that has been the mainstay of American motorsports since the introduction of the first-generation GM small-block V-8 in 1955. This classic design has now evolved into a highly advanced racing engine.
Per NASCAR specifications, the Chevrolet R07 displaces a maximum of 358 cubic inches with a maximum cylinder bore diameter of 4.185 inches. The block is a precision iron casting with integral oil and coolant passages that eliminate the need for most exterior lines. The distance between the Chevrolet R07's cylinder bores is 4.500-inch (vs. 4.400 inches in the SB2 small-block). This wider bore spacing improves coolant circulation around the cylinder barrels. In conjunction with a targeted cooling system, the R07 block design minimizes temperatures at critical locations.
The R07 block has a new six-bolt head bolt pattern instead of the small-block's traditional five-bolt design. The revised head bolt pattern improves head gasket sealing and reduces cylinder bore distortion.
The R07's camshaft is located higher in the block than the camshaft in the SB2. The raised cam operates pushrods that are correspondingly shorter and stiffer, thereby improving valvetrain dynamics at high rpm. The raised cam also provides clearance for inboard piston squirters that spray the underside of the pistons with oil for cooling. The camshaft tunnel is isolated from the crankcase to minimize windage losses caused by oil falling onto the rotating crankshaft assembly from the cam and to contain the valvetrain parts in the event of breakage.
In contrast to the SB2's "mirror port" cylinder heads, the Chevrolet R07's aluminum cylinder heads resemble production LS-series small-block cylinder heads with alternating intake and exhaust valves. The R07's shallow valve angle produces a compact, efficient combustion chamber design that produces the required compression ratio with a lightweight flat-top or slightly domed piston. GM Racing engineers optimized the R07's intake port layout for the single, centrally mounted four-barrel carburetor mandated by NASCAR.
The aluminum intake manifold has an extended plenum to equalize fuel distribution among the cylinders. The manifold is dry; a separate valley cover carries coolant from the cylinder heads. The R07's distributor is located at the front of the engine to facilitate adjustments in ignition timing.
The Chevrolet R07 rocker covers are rigid cast aluminum with O-ring seals. The covers incorporate integral valve spring oilers that are pressure fed from passages in the cylinder heads, eliminating the need for external oil lines. GM Racing also designed a high-efficiency water pump and a carbon fiber front cover that shields the aftermarket camshaft belt drives used by NASCAR teams.
The R07 has provisions for driving a conventional diaphragm fuel pump off of the camshaft. A remote-mounted mechanical fuel pump can also be driven via a cable from the rear of the camshaft. When using the cable drive, the fuel pump can be relocated to the rear of the car near the fuel cell. This enhances safety in an accident by mounting the fuel pump in a less vulnerable location.
"Chevy NASCAR teams were deeply involved in the design of the Chevrolet R07," said Suhy. "We meet monthly with representatives from our four key partners – Hendrick Motorsports, Richard Childress Racing, Joe Gibbs Racing and Dale Earnhardt, Inc. – to get their input on how we can make Chevrolet racing engines more reliable and easier to build and service. Many of their ideas were incorporated in the R07's final design, such as the integration of the oil and cooling systems.
"It's not about helping our affiliated teams to build the most powerful engine because each of them has developed their own proprietary parts and processes," he noted. "GM Racing's role is to provide premium quality, easy-to-use components. We want Chevy teams to be able to devote more of their energy and resources to winning races and less energy to preparing engines."
The introduction of the Chevrolet R07 small-block V-8 represents another milestone in the continuous evolution of the small-block V-8 engine. GM's first purpose-built NASCAR racing engine was designed, built and tested to continue Team Chevy's winning tradition in NASCAR.