Nissan 370Z Forum - View Single Post

chops · 03-10-2011, 09:59 PM

Quote:

Originally Posted by Jessobear

I have the Nismo OEM exhaust with FI resonated HFC's and I can definitely tell you that my car does not have any noticeable exhaust rasp.

I also find it funny that everyone really gets on the piping diameters of the H pipe. Having stepped piping sizes is actually totally normal and can actually aid in the scavenging effect of the exhaust system. Think about this in terms of total cross-sectional area: passing the exhaust through two 2" diameter pipes is a greater cross-sectional area than passing through a single X or Y pipe.

The advantage of an X pipe has nothing to do with cross sectional area. It has to do with easier flow between the two sides of the exhaust due to a smoother transition compared with an H pipe. An X pipe will also have the effect of making the exhaust quieter from noise cancellation due to the easier cross flow of the two legs. The H pipe configuration is not a bad design in essence, which is why people have only seen small gains from other exhaust systems.

Here's a decent link about putting an X pipe exhaust system on a car:

Exhaust System Installation H-Pipe, X-Pipe,- Car Craft Magazine

Quote:

For any performance exhaust system, some type of crossover connecting the two sides of a dual exhaust system is important because it acts to balance the two banks of the engine. The common H-style crossover is good at balancing sound pulses between the two halves, but does little to promote scavenging because the exhaust gases tend to follow the path of least resistance, which is straight through each pipe rather than taking the 90-degree turn through the H-pipe into the other half of the system. In an X-pipe system, however, where the two sides of the system intersect, the gasses have no choice but to intermingle as they pass through the junction. This promotes improved scavenging effects by smoothing out uneven exhaust pulses from the engine’s firing order. It also helps quiet down the exhaust, resulting in a mellower, less raspy tone. According to Magnaflow, the faster acceleration of the gasses through an X-pipe causes them to flow in a linear fashion parallel to the walls of the tubing rather than tumbling. This “laminar” flowing gas is much quieter than tumbling gas, resulting in an exhaust tone up to 8 decibels quieter than a traditional H-pipe.

this is fine by me! more power, less rasp, cant go wrong with the X-pipe..