NHRA Pit Crew Runs a CNC Shop

It has been a long time since a Ford has ranked high in the NHRA (National Hot Rod Association) Pro Stock Car Racing standings.

In its quest to do something about that, Cunningham Motor Sports turned to CAM software to squeeze more horsepower out of standard Ford engines. Jim Cunningham is a die-hard Ford enthusiast, driver, and co-owner with Gloria Cunningham of the Cunningham Race Team. They have embarked on an aggressive program of engine modification to increase the horsepower and rpm output of standard Ford 500 in.3 (8194 cm3) engines to levels competitive with today's dominant GM and Mopar products.

With that objective in mind, an engine shop was built in 2005 on the premises of the Cunningham-owned and operated Capitol Raceway (Crownsville, MD). Until recently, however, things were not going that well. As of the fall of 2007, the Cunningham shop had not produced an engine combination that would hold together without some significant component breaking.

Head porting with the Millport CNC mill is the most sophisticated machining task performed in the Cunningham shop.

Marcus Bowen, who divides his time between being crew chief and working in the engine shop, characterized the situation perfectly: "You have to get something that holds together, because you can't learn if you keep breaking it."

Over-reliance on outside shops with long lead times was one of the biggest problems. "If we wanted to change something, we had to make a phone call, set it up, ship it out, and wait for it to come back," Bowen explains. "When it came back, we had to put it back on the engine and back on the Dyno. That could take several weeks. And when you got it on the Dyno, you may not like what you see and have to take it apart."

Early in 2007, the team purchased a five-axis Millport CNC mill with a Centroid controller from Millsite Engineering (Ravenswood, WV) for head porting and a four-axis RMC V-30 machining center with a Milltronics controller from RMC Engine Rebuilding Equipment Inc. (Saginaw, MI). To develop toolpaths for both CNC systems, Cunningham chose Mastercam X3 software from Mastercam/CNC Software Inc. (Tolland, CT) with Mill, Multiaxis, Solids, Router, and Art modules.

The pit crew was now in the unique position of having to run its own CNC machine shop for engine-component R&D without having any CNC experience. The pit crew spends half of its time for ten months a year on the racing circuit. But the team was undaunted. Team members had visited with Mastercam at the Performance Racing Industry trade show in Orlando. They were convinced that they could master the necessary skills. Developing relationships with other customers they met at the Mastercam booth also proved to be a confidence builder and an invaluable resource.

Mastercam five-axis program digitizes the new head-port geometry, and generates a CAD model that can be used to create toolpaths for machining eight identical head ports.

Bowen's teammate Joe Greenwich took about three months to get acclimated to Mastercam to create toolpaths for head porting and other surfacing applications. Bowen, who had begun working in the shop in November 2007, took on all the fouraxis work. Doug Ewart, head engine builder, who had spent his 30 years in the business doing manual drafting and manual machining, picked up on Mastercam in about two months and "has never looked back."

The aggressive R&D program to improve engine power is producing a rapid turnaround on component availability, with 90% of these components being manufactured in the Cunningham shop to control lead times and costs.

Although the three users are new to CNC programming, the specialized nature of the parts they manufacture is actually a big help. They only have to know a fraction of Mastercam's capabilities, and the userfriendliness of the software allowed them to learn these quickly.

"You don't worry too much with Mastercam, because with its solid modeling and backplotting, when you run the program on your computer screen, what you see is what you get when you then run it on the CNC machine. You don't have to worry about the machine going down because you have misprogrammed something," Bowen explains.

A small number of machining activities have the greatest bearing on improving engine power, so the team has focused on head porting, intake manifolds and runners, the valve train, and pistons. Bowen says, "It's one big puzzle to get the combination put together right."

Piston work provides a telling example of fast turnarounds. Bowen says that the lead time for a set of pistons machined to specification by an outside vendor is 3–6 weeks. Cunningham can machine them on the team's CNCs and have them installed in less than three days.

Head porting is the most sophisticated machining task performed in the engine shop. The CNC is used to rough the port to near-net shape. Then desired port geometry is created with hand tools and tested on the dynamometer until power is believed to be optimal. A Mastercam five-axis program is used to digitize the new head port geometry by automatically collecting 3-D data from the part with a spindle probe. The subsequent CAD model can be used for creating five-axis toolpaths for machining eight identical head ports.

So even if it's not an actual race week, the pace of work at Cunningham Motorsports is always fast. Components are manufactured, tested, and installed in Ford engines, and the engines are then tested on the track a stone's throw away.

The team has gone from having no viable combinations in November 2007 to three reliable engines that have resulted in significant engine performance improvements. Horsepower has been increased from a peak of 1220 to 1360 hp (910.1015 kW). Engine speed has improved from about 9400 to more than 10,000 rpm.

Improvements have been so dramatic that Jim Cunningham has had to alter his driving style a little bit to adjust to the new power at his command.

"We've just got to keep working at it, constantly making changes," Bowen says. "We learn something every day. If the learning ever stops, we are out of a job."

"Maybe we can squeeze out another 50 hp [37 kW] in the next few months. Of course, now that Ford has committed to upgrading its engine block design, we will essentially be starting all over again when the new engines arrive," Bowen concludes.