| 2. Custom Centre-Exit Exhaust | A complete centre-exit exhaust system was fabricated by Graham at Exhaust-by-Design which is located near Finmere in Oxfordshire. I gave Graham the brief to make up a 3in diameter straight through stainless steel system from the turbo back, exiting in the centre with twin 3in slant-cut chrome end tips. There is very little room to get the 3 in bends and some silicencing in a centre-exit system. We were also unsure how much silicencing we would need. Our first attempt resulted in a system that was 105 dB at 4000 rpm. I had to drive it home and could only bear to rev to 3000 rpm in central Oxford. It was like a Nascar. I took it back the next week and Graham introduced a second straight through silencer box.
So far I am very pleased with this version and it is bedding in nicely, the tone is good and the noise level is very acceptable. produces a good burble on the overrun.
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Our research has shown that moving up from a 2.5in to a 3in exhaust system is a major jump. In terms of exhaust gas flow you have an increase of 44% in flow efficiency. That will improve turbo response but also gives you more sound to deal with. In addition, the larger pipe diameter does lower the overall exhaust note.
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