C5 Exhaust

[04 Commemorative]

Why does the exhaust system have an "H" pipe or an "X" pipe instead of two seperate systems for each side of the engine?

 

[silver98]

The X or H pipe is required to balance the exhaust pressures between the 2 sides of the engine in order to present a 'common' back pressure to the engine. The pressure from combustion exits the engine in pulses, rather than as a stream. Each cylinder exhausts as the exhaust valve opens (form the Camshaft operation) and the pressure differential between the top of the cylinder and the tail pipe allows the gases from combustion to exit the cylinder. The quicker these gases are removed, the less energy the engine needs to expend on ridding itself of combustion gas. Since the cylinders produce combustion gas according to the ignition source, the spark plugs, the firing order of the spark plugs determines which cylinders generate exhaust gas when. With all of that established, our LS1's do not fire in an order that represents the physiczal location of the cylinders, in essence, it doesn't go Left side, right side, left side, etc. Therefore the waves, or pulses of pressure from exhaust gas must co-mingle with the other 'physical' side of the engine's cylinders to rpoduce an equal back pressure to the entire engine.


I hope I explained this correctly. I'm sure more technical folks will jump in on this to correct or complete the explanation. But I hope this helps a bit.

Joe

 

[Robert YellowVette]

The X or H pipe is required to balance the exhaust pressures between the 2 sides of the engine in order to present a 'common' back pressure to the engine. The pressure from combustion exits the engine in pulses, rather than as a stream. Each cylinder exhausts as the exhaust valve opens (form the Camshaft operation) and the pressure differential between the top of the cylinder and the tail pipe allows the gases from combustion to exit the cylinder. The quicker these gases are removed, the less energy the engine needs to expend on ridding itself of combustion gas. Since the cylinders produce combustion gas according to the ignition source, the spark plugs, the firing order of the spark plugs determines which cylinders generate exhaust gas when. With all of that established, our LS1's do not fire in an order that represents the physiczal location of the cylinders, in essence, it doesn't go Left side, right side, left side, etc. Therefore the waves, or pulses of pressure from exhaust gas must co-mingle with the other 'physical' side of the engine's cylinders to rpoduce an equal back pressure to the entire engine.

It also makes the exhaust quieter, so much so that GM had to restrict the size of the 'H' cross over pipe to about 3/4" from 2.5"...