Postby davery » Thu Aug 06, 2015 1:40 am
This is a really interesting thread. So it would appear whether the header is a 4-2-1 or a 4-1 the area of the collector will be less than the total area of each of the four pipes leading into it. If the collector is 1.75" then the area of a cross section is about 2.4 sq in. Divided by 4 would be .6 sq in. This would mean each of the 4 pipes would be a diameter of less than 1/2 in. That can't be right, so the collector does restrict the flow. How much? I have no idea what the inside diameter of each pipe is, but assume it is 1". That would mean the area of a cross section would be .785 sq in. Since there are 4, that would mean the total area of all four cross sections would be 3.14 sq in. So through the header the total area decreases by about 20%. This would be a gradual decrease, so I assume this acts as a merge collector to create back pressure. The question is after the pipe goes to a 2.25" pipe after the merge collector, is any additional decrease in area of of the cross section (say at the converter) really needed? For example, would a straight pipe provide the most horsepower? I'm probably missing something or making this too simple. I'm just trying to understand the mechanics of the exhaust system.
Last edited by
davery on Thu Aug 06, 2015 1:49 pm, edited 1 time in total.
Don Avery
Dayton, OH/Sarasota,FL
1985 Pininfarina
2011 Eos
2012 Mercedes E550 Cabriolet