With the geometry of the major components set, prototype assemblies began to be produced. Members of the engineering team were working 70-plus hours a week, channeling all of their energy into this project. "We've got a lot of emotion behind it," Mike Harrison told us of the personal touch everyone contributed.
The all-aluminum block, though it features 100mm bore spacing, bears little resemblance to its predecessor. Cast-iron four-bolt main-bearing caps with side bolts hold the forged steel crankshaft steady, even at 7,000 rpm. Large oil passages are built into the block to allow the oil to flow back to the pan faster and with less restriction. The coolant crossover is now built into the block, eliminating coolant passages in the intake manifold. This is good for performance because the hot coolant doesn't heat up the incoming air charge. The rods are a familiar forged powder metal with a floating pin, and the pistons are hypereutectic aluminum, but there are oil squirters to cool the pistons and help resist detonation. Compression ratio is a stout 11:1.
Though some would argue an aluminum intake manifold is preferable, the team opted for a composite plastic design. "The plastic is smoother, more consistent, and heat transfer is lower," remarked Adam Christian. Not only is the plastic intake lighter and less expensive to manufacture, it makes 1 to 2 percent more power than an aluminum version.
The all-new compact cylinder...
The all-new compact cylinder heads feature four valves per cylinder, vertical intake ports, and round exhaust ports.
The 10-liter manifold features long, shaped runners and an 83mm round inlet with "whoosh fingers" to direct airflow and control whistling at part throttle. It utilizes an 80mm round throttle body, which "flows better for its size than a twin," according to Christian. Intake specialists Dave Born and Nolan Dickey designed the intake with a front-mounted inlet, which required a new location for the alternator. As simple as that may seem, relocating the alternator was one of the greatest challenges.
The finished aluminum cylinder heads house two 37mm (1.46-inch) intake valves and two 31mm (1.22-inch) exhaust valves, compact roller fingers, and vertical 193cc intake ports. Port and Combustion Chamber Engineer Jim Froling perfected the chamber and runner design, complete with round exhaust ports, absent from the Three-Valve.
A new firing order forced the team to create a new design for the exhaust manifold. The team wanted to create a tubular header, but power loss, due to paired cylinders on each bank, disallowed use of a tri-Y design like conventional performance headers. With only two weeks left before tubular headers were scratched for cast manifolds, Christian thought of the idea of using a twin-T design. "I gave him a bunch of bent tubing, and he built the prototypes over the weekend in his garage," said Harrison. Though they look inefficient, we project long-tubes will only yield about 15 hp over these stock units.
The ballet of performance (power and driveability) and economy (emissions and cost) is not more prevalent than in the camshafts and Ti VCT, or twin-independent variable camshaft timing. The camshaft profiles, though not revolutionary, are completely optimized in efficiency. The new cam phasers use uneven torsional energy of the camshafts to index the cams, and the cam sprocket is machined in. Oil does flow through the new cam phasers, but only for cooling and lubrication duties. They are very quick to react, and can operate their full range of motion in one engine revolution. This infinitely adjusting timing and lobe separation (from 81 degrees to 131 degrees) is what makes this engine the animal that it is. Instead of waiting for 4,000 rpm to reach impressive torque numbers, "It pulls from 2,000 rpm all the way up to 7,000 rpm," Harrison says.
Aesthetically, the photos speak for themselves. The partial engine cover allows the intake to peek through but covers things like the wiring harness and injectors.