johnc Posted June 13, 2007 Share Posted June 13, 2007 Some people wonder why I charge $850 and more for an exhaust system... http://e30m3performance.com/installs/installs-2/exhaust/exh1.htm FYI... I did not write this article and its not an exhaust system that I've built. Quote Link to comment Share on other sites More sharing options...
JIM73240Z Posted June 13, 2007 Share Posted June 13, 2007 great read. with a hi performace motor, say tims car, would a dual exhaust be more benificial than a single. say 2 2" pipes vs a single 3"? jimbo Quote Link to comment Share on other sites More sharing options...
ARZ_ Posted June 13, 2007 Share Posted June 13, 2007 No the single 3 inch would be better for less back pressure. one, two inch tube with a wall thickness of .040" has an inside area of 2.89in/sq X 2 equals 5.78 in/sq one three inch tube with a wall thickness of .040" has an inside area of 6.69in/sq I guess I shouldnt knee jerk this response (because I didnt read the whole article yet) but, if more flow is the goal then 1 three inch diameter exhaust tube would flow more than 2 two inch tubes. Quote Link to comment Share on other sites More sharing options...
johnc Posted June 13, 2007 Author Share Posted June 13, 2007 As the article says, once you're past the X or Y pipe, the size or style of the exhaust only matters if it impedes flow. A 300hp V8 engine would be fine with a dual 2" exhaust system past the X pipe or a 3" exhaust after the Y pipe. A 600 hp V8 engine would have trouble with a 2" dual exhaust system after the X pipe or a 3" exhaust after the Y pipe. The basic points of the article are: 1. An X or Y pipe is mandatory in a high performance exhaust. 2. The position of the pinch point is critical and must match the header and the cam. 3. Everything after the X or Y pipe must be as free flowing and smooth as possible. I made a mistake regarding secondary pipe length between the header and the Y pipe on an M3 exhaust and we ended up with a big hole in the powerband between 2500 and 3500. Re-doing the secondary pipes and making them 2" longer eliminated the hole and woke the bottom end up. Quote Link to comment Share on other sites More sharing options...
johnc Posted June 13, 2007 Author Share Posted June 13, 2007 This is an example of the work that has to be done to get a racing exhaust right. This customer of mine paid over $1,000 for porting work on the stock exhaust manifold, custom secondary pipes, Y pipe, and straight through 2.5" exhaust for his Spec944 Porsche. This is for a "low buck" spec racing series. This exhaust work alone got him 6% more horsepower and 5% more torque. Quote Link to comment Share on other sites More sharing options...
SHADY280 Posted June 17, 2007 Share Posted June 17, 2007 speaking of header design, has anyone tried to build a "180" style of header for our l6 engines? they seem to work well on chev engines. Quote Link to comment Share on other sites More sharing options...
johnc Posted June 18, 2007 Author Share Posted June 18, 2007 L6 headers are already 240 degree (Chevy 180) style headers. Its inherent in their design. Quote Link to comment Share on other sites More sharing options...
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