FAST’s interchangeable runners push horsepower ceiling

Words And Photos: Brandon Flannery

The aftermarket industry had a bit of a learning curve when Chevrolet introduced the LS platform. The all-new, “clean sheet” design addressed weaknesses found in previous generations and had little in common with its predecessors, other than the bore spacing and rod bearings. Updated versions have added to the engine’s robustness, and its outer limits are still being explored. With time and experimentation, LS power levels and rpm redlines are now hitting numbers previously unheard of — and hitting them reliably.

One of the first to forge a path into higher horsepower was the engineering group at Fuel Air Spark Technology (FAST). An early project included a patent for interchangeable runners within a new intake manifold of multi-piece composite design with a larger throttle body. Many hours went into developing the internally-mounted runners for optimum performance.

These molded air horns capture the incoming stream of air through the throttle body and funnel it into the head through an optimized rectangle tube. The resulting airstream maintains high velocity that is ideal for low-end torque and increased horsepower. Testing on a near-stock LS7 produced gains of nearly 20 hp.

The original goal was to maximize power throughout a standard, street-friendly 2,500-6,500 rpm operating band. Hence, the runners needed to be as long as could be packaged inside the LS space constraints for proper wave tuning, especially in the mid-range.

“For 95 percent of customers, the standard FAST LSXR manifold is tuned perfectly for their operating rpm,” says Billy Godbold, longtime COMP Performance Group engineer. “Of course there is always that 5 percent that takes things to the next level, and the interchangeable system is designed to help them get there.”

Godbold says anyone who isn’t turning over 7,000 rpm probably wouldn’t see any benefit to upgrading intake runners. In fact, they’d probably see a slight dip in low-end torque, which would offset any gains above 6,000.

“You really don’t want to trade 10-15 lb-ft at your shift recovery point for 5-10 hp at peak in a street application,” he says. “However, the shorter runners love rpm and really wake up in the 7,000-8,000 rpm window.”

High rpm applications (especially those engines used in competition) place unique demands on the intake system. First, you need less air flow restriction to just supply the demand. Second, optimum intake runner length is not only dependent on rpm, but also the cam timing.

These new FAST runners — two versions are available — take full advantage of larger-duration camshafts and larger displacements typical in race-type applications.

This is good news for those going “beyond bolt-on” or with high-stall automatic cars and stick-shift cars.

The mid-length “High HP” runners have proven to average more than 20 additional horsepower between 6,000 and 9,000 rpm over the original LSXR manifold. The shorter “Race” runners can top the best four-barrel race intakes and offer 30-plus more horse-power on average between 7,000 and 9,000 rpm than the original LSXR manifold, with a 500-1,000 upward shift in peak horsepower for “top of the tach” performance.

The High HP runners do not sacrifice as much torque as the Race runners, which can be a plus for those not needing a max-rpm scenario. As builders continue to explore new options, the runners can even be mix-and-matched between the High HP, Race, and even Standard runners to dial in the torque and horsepower peaks for a specific application. The possibilities are numerous. The doors to new technology are also opened.

“Everything works as a system,” says Godbold. “If we can improve one component, like the intake, it then inspires us to alter the other components. Once we have a manifold that is set up to go 9,000 rpm, we can then design a camshaft to compliment it or make upgrades to elements of the fuel system. Operating in the 9,000 rpm range safely opens up a new realm of possibilities and package options.”

At the time of these photos, the prototypes were being put through their paces. The engine was a mild 6.0L with a stock crank and H-beam rods and pistons from Lunati. Camshaft grinds were also tested, and the data will be analyzed and integrated into a new camshaft customers can purchase.

Where will the rpm craze end? Time will tell, but for now, those surfing the outer limits of the LS platform have a range of options when it comes to getting enough air and fuel to help them achieve their goals.

Source

Fuel Air Spark
fuelairspark.com