Beefing up the Peugeot 407: Phase 2

Phase 1 of my Peugeot 407 upgrade was the complete package of third party bars to strengthen the chassis at strategic points. The torquey exhaust system represents Phase 2 of my Peugeot 407 upgrade. It consist of a 4-2-1 extractor, a mid and rear muffler, all customized from scratch because there was none off-the-shelf in the local automobile industry. The 4-2-1 rather than 4-1 version was preferred for torque rather than power. The more efficient release of the exhaust gas showed weakness in the stock mid muffler with an irritating resonance between 1,500-2,500 rpm. A  tougher custom stainless steel rear muffler was fabricated based on the size and design of the original mid muffler. This solved that issue but the irritating resonance shifted to the stock rear muffler. Again, a  tougher custom stainless steel rear muffler was fabricated based on the size and design of the original rear muffler and that put an end to the resonance issue. These modifications will definitely auto-calibrate the oxygen reading as suggested by the exhaust lamda and it usually requires a full petrol's tank consumption to normalize the car's response. Driving the car in the usual style as I do in town, I found I got better fuel consumption because I usually do 2 return trips to Kuala Lumpur and back in 1/8 tank but can now I can 3 return trips with the same 1/8 tank. All this means I should get better mileage if I were to use the car outstation. However, based on the fabricator's feedback and experience, he does not expect so because the improved performance will be too difficult to resist footing the accelerator pedal. 

Conclusion: Although the car is now more torquey, what I really like about the car now is a much smoother and quieter engine throughout the powerband making it a new pleasure to drive with  more grunt in the exhaust note when I floor the accelerator pedal.