sorry studio just thought i would point out that 2" bore is actually too big for the commer,it has still got the 1 5/8 hole at the manifold exit,its the larger bore in the silencer that is making the difference as its less restrictive.
the bigger downpipe will slow down the gas speed causing more pulse reversal at low revs, most people dont realize that exhausts flow in both directions, the mini is a good example as the exhaust port actually flows more in the reverse direction [:0] (take note panky). this causes more exhaust gases to go back into the cylinder to contaminate the incoming charge and raise its temperature which means a drop in low end torque
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on my BSA i had 5 stratigically placed dams that prevented gases reversing in the pipe, it was very noticable the way it came on the cam sooner and pulled harder from zero revs.
one 90 degree bend is equivalent to 22 feet of extra pipe,so twisting the pipe everywhere is a no no as well.
i am sure bessie is feeling much better for it though
"you were only supposed to blow the bloody doors off"
the bigger downpipe will slow down the gas speed causing more pulse reversal at low revs, most people dont realize that exhausts flow in both directions, the mini is a good example as the exhaust port actually flows more in the reverse direction [:0] (take note panky). this causes more exhaust gases to go back into the cylinder to contaminate the incoming charge and raise its temperature which means a drop in low end torque
.on my BSA i had 5 stratigically placed dams that prevented gases reversing in the pipe, it was very noticable the way it came on the cam sooner and pulled harder from zero revs.
one 90 degree bend is equivalent to 22 feet of extra pipe,so twisting the pipe everywhere is a no no as well.
i am sure bessie is feeling much better for it though
"you were only supposed to blow the bloody doors off"
