The easiest part was the rear part of the exhoust system. We decided to build the whole system with stainless steel. ( TIG welded )
The absorber boxes are eliminating the higher frequencies without reducing the flow . Here in the middle is enough room for a 55ltr fuel tank with heatprotection. The H-pipe shall improve the free flow and the sound. ( Sound shouldl be like one V8 and not like two 4 cyl. )
The next step was buildig the headers with downpipes. This was the complicatest part- we did it two times ! Here I describe the second part only : Learning from BMW means understanding why they have done it the way it is at the donor. The result of this : Pipes for each bank in 4-2-1 with a view at the firing order. Shortest possible distance to the pre cats with sensors.
We used Exhoust parts from the E39 M5 ( close engine - first 3 inch. - its a split tube - the inner tube can´t be welded )
The catalysts are from HJS and should be good enough for EURO5. Heat protection was the next step - enough heat for effectve cats is also required !