The X-frame configuration on the ’61 made placing the cross-over up front all but impossible. This is a tight shot of the exhaust at the rear of a ’61 Impala built by Scott Sullivan where he has placed an X-pipe just ahead of the tailpipe exits. X-type cross-over pipes do not have to be located just aft of the collectors. A longer spread between the pipes will produce a larger volume in the cross-over pipe but is only of minor importance. The length of a typical H-pipe is more often dictated by the distance between the twin exhaust pipes. The more convenient location for the H-pipe is generally farther back in the system where the exhaust pipes are generally closer together. Don Lindfors, who until recently spent many years with Patriot Exhaust systems, told us that their experiments with H-pipes revealed that often the location of the cross-over pipe could result in slight additional power improvements, but that often this location was very close to (or under) the transmission, which is not only inconvenient but also reduces ground clearance. The original H-pipe is a simple 90-degree connector, usually of the same diameter as the exhaust pipe, placed in a suitable position between the two pipes. ![]() Reading more: High-Zoot Paint from Affordable Equipment This is a nice example of a SpinTech X-pipe crossover system with the X located behind the transmission and driveshaft loop to provide additional ground clearance. ![]() This contributes to minor improvements in flow. The idea behind an H- or X-pipe is to minimize the pressure spikes on both pipes by adding volume to the exhaust at that location. This indicates how one exhaust pipe between the header collector and the muffler experiences both high- and low-pressure areas. This is an indication of the high- and low-pressure pulses occurring in each exhaust pipe. At idle, if the pressure gauge is not heavily damped, it will display pressure spikes as the needle bounces irregularly between high and low pressure. If you want to see this for yourself, you can take an ordinary low-pressure gauge that reads 0-5 or 0-10 psi and tap into one exhaust pipe just behind the header collector with a -3 or -4 line to the pressure gauge. This uneven pressure spikes occur in both sides of a dual exhaust system and tend to increase backpressure in the separate pipes. Even with the X-pipe, this system is more than a bit loud with the two-chamber mufflers. ![]() This is a 2½-inch X-pipe–style dual exhaust system for an early Camaro that is part of the Flowmaster American Thunder series, using a pair of two-chamber, Super 44 welded steel mufflers. On the left (odd cylinder numbers) side of a small- or big-block Chevy, in the course of a 720-degree complete cycle of the firing order, there is a sequence when there is a 180-degree portion of crank rotation where no cylinder fires on that bank and another 180-degree sequence when two cylinders fire 90 degrees apart. Every time an exhaust valve opens, a pressure wave travels through the primary pipes of the headers into the collector and into the exhaust pipe.īecause of the uneven firing patterns of a typical V-8, these exhaust pulses do not occur evenly. The exhaust noise generated by an internal combustion engine is generally attributed to sound pressure that travels in pulses or waves through the exhaust system.
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