When you're upgrading a V8 exhaust system for performance, you'll soon discover that several companies offer X-pipes. Ever wonder why?
"The firing order of all production V8s, regardless of make, has one cylinder in each bank that will fire within 90 degrees of crankshaft rotation of another cylinder in the same bank," says Hedman Manufacturing.
"This occurs twice during completion of the entire firing order. These two cylinders will be exhausting almost simultaneously into the same [exhaust] manifold system. Full-length four-tube headers help separate these pulses until the collector is reached. After the header tubes dump into the collectors, the two cylinders again are fighting each other for space in the collector and exhaust pipe. The result is reflected pressure waves traveling back up the exhaust system, backpressure, lost power and poor economy.
"At the same time two cylinders exhaust in one bank, there is no activity in the opposite bank. The traditional H-pipe equalizer allows some of the excess pressure to bleed over [to] the 'quiet side' of the exhaust system, resulting in some low and mid-range torque improvements. At high rpms, however, the gases cannot bleed across the H-pipe fast enough to help power significantly."
That's why Hedman created the X-Treme Equalizer Pipe, which features a tangentially siamesed crossover junction to synchronize exhaust pulses. The X-pipe "splits the flow in the crossover junction, so the pressures on both banks will be equal and pulse-free after the crossover, regardless of the rpm," according to the company. "Volumetric efficiency and power are therefore improved at all engine speeds."
