A Slick New Composite Manifold

Tuners really want three things from the aftermarket components they use to soup up their cars. They want more horsepower, less weight and good looks. "Carbon-fiber composites can deliver all three," says Bob Miller, president of Diaphorm Technologies.

Diaphorm recently delivered these three tuner virtues in the form of a carbon-fiber-reinforced thermoplastic air intake manifold made from nylon-12 and a biaxial stretch-broken carbon fiber. "We call it pseudo-continuous reinforcement because the fiber has been stretch broken to allow us to mold the material more aggressively," Miller explains.

Designed for the Honda H22 engine, the 18- × 8- × 12-inch manifold weighs just 4.5 pounds, or about 11 pounds less than the stock manifold. And that weight includes its aluminum base plate and ports.

The finished parts also fit the bill in the aesthetics department. "Carbon fiber has that 'bling' factor," says Miller. "It's hot among tuners right now."

But CFRP's biggest advantages relate to its strength-to-weight ratio. While much of the carbon fiber manifold's weight advantage comes from a lower density than aluminum, Miller notes that the strength of the composite also permitted a thin wall design (0.080 inches), saving even more weight.

	Using proprietary composites’ manufacturing techniques, Diaphorm Technologies has created an air intake manifold made from nylon-12 reinforced with continuous carbon fiber.

Even at that wall thickness, the manifold holds up to some aggressive pressure testing. Diaphorm subjects the manifolds to 60 psi at 200F. "The OEM seals fail before our manifolds do," Miller says.

The manifold's thin walls and the design freedom offered by composites also contribute to a horsepower increase — by bumping up the internal volume of the manifold and enabling free-flowing, optimized air passages. Miller cites dyno results that show a 13 hp gain over one popular aluminum aftermarket manifold. "We didn't test against the stock manifold, but we'd do even better against it," he says.

Making manifolds

To make the manifolds, Diaphorm relies on one of its proprietary composites manufacturing processes. Working with a variety of thermosets, thermoplastics and reinforcing fibers, the company specializes processes that have low-pressures and low-tooling costs. These processes occupy a middle ground, in terms of suitable production volumes, between hand lay-up and compression molding. Miller estimates that the company can turn out parts that cost 20 to 70 percent less than compression molding at low to medium production volumes — typically from a few dozen to several thousand parts.

The company pioneered a molding process that uses a rubber diaphragm to press the molding material into a single-sided mold at low pressures — as low as 30 to 45 psi versus 1,000 or more tons for a comparable compression molded part. These single-sided tools can be built from aluminum or composites — materials that help keep tooling costs low.

The manifold, however, relies on a different process. Miller describes it only as a "closed-mold process that uses an internal pressure mechanism." Diaphorm uses this process to make the manifold in two halves, which it joins with an adhesive to form the finished shell.

According to Miller, this closed-mold process still uses low-cost aluminum tools and low-pressures, so molding costs have remained low. From a technical standpoint, it also supports geometric complexity not possible with compression molding. For example, the manifold features aspect ratios up to 8:1. It also has compound 3D angles with corner radii down to 1/16 inch — without cutting fibers or darting the reinforcing fabric. "You usually find such intricate shapes only in hand lay-ups," Miller notes.

Diaphorm will market the new manifold under the Fiber-Tuned brand name. And while the first product targets just the H22 engine, the company plans to introduce other sizes soon — something made easier by Diaphorm's use of adjustable tooling. Other automotive parts will likely follow this year, including a carbon-fiber cap that's still in development.