The success of Ford Nextel...
The success of Ford Nextel Cup teams in the '05 Nextel Cup season was plain to see. One of the prime attributable factors was the D3 head. Seen here is a specially lightened Dirt Late Model derivative.
Finding the power to win big-time races is sometimes no more difficult than looking in the right place. When top teams find a source of power, they attempt, at almost all costs, to keep such a source secret. So far, a major factor in most Ford Nextel Cup, Busch, and Craftsman Truck series wins, namely the cylinder heads, has seemingly been kept below the radar for more than 18 months.
If you think we're about to reveal some front-running Cup car teams' key technologies, you're wrong.
That's the bad news. The good news is we can tell you about the subsequent generation of heads in question, those based on the D3 casting, that are too advanced in specification for NASCAR to approve. How good are they? Well, consider this. The Nextel Cup heads are good enough to make over 840 hp from a 355-inch, single four-barrel endurance engine-and the derivative heads we are about to look at are better yet.
The Cup car UPM D3 derivative...
The Cup car UPM D3 derivative that was tested had the intake port angled about 5 degrees at the manifold face. This improves overall intake flow over that seen on a Nextel-legal intake port.
No quantum step forward in racing ever happens by itself. There always has to be somebody who is prepared to push the envelope. In the case of the Cup car D3 castings, the guy who went out on the limb to make Fords significantly more competitive is Don Losito. Losito is the boss of Ultra Pro Machining. Although it's a sizable company, it is little known outside the ranks of top professional racers, especially in NASCAR classes.
The D3 head came into being as a substantial evolution of Ford's SC1 casting. Although it's something of a simplification, we can say it is essentially a high-port (intake and exhaust) version of the C3 head. Prior to the introduction of the D3 head, the C3 head was, from 1992, the approved Nextel Cup head. The intent of the C3 head was to service the needs of ARCA, Sprint cars, Midgets, Dirt Late Models, and drag racers, as well as the NASCAR classes. Although good for its day, by 1998 the C3 head was beginning to suffer from aging technology, and we all know what that means in a competitive sport such as racing.
In 1999, Losito set about developing some-thing better with future NASCAR approval in mind. Starting with the SC1 Ford casting, he juggled valve angles, port locations, and chamber forms in an attempt to get a more optimal overall design. But outlining what was done in one sentence really trivializes the effort involved. The reality is that every one of the many relevant aspects considered was first tried on the com-puter. If it passed muster there, it went on to the flow bench, and finally the dyno.
In the D3 casting, the exhaust...
In the D3 casting, the exhaust port is long enough for it to morph into a round shape at the manifold face without loss of flow. This helps to make header production easier.
Most of the computer time went into analyzing situational geometry delivered by various valve angles, sizes, and positions, and the effects and interactions produced with the piston crown and cylinder wall. An issue of some importance was the effect valve pockets could have on the ring package. The better the resulting low lift flow, the wider the optimum cam lobe centerline could be. This would allow the valve to be open less at and around TDC, thus requiring shallower valve pockets, meaning the ring pack could have a higher and more optimal placement.
Computational Fluid Dynamics (CFD) also crept into the picture here, though there is reluctance to say to what extent as it is a cutting-edge F1-type technology. What is CFD? It's a method of computing airflow through and around objects. The beauty of this is it allows you to not only see where the air is flowing, but also local velocities and pressures. We have seen some of this applied, and trust us, CFD is the head development tool of the future. The only problem at present preventing its widespread use is its complexity and need for huge computing power.