Any chance of a ball park figure for the cost of the BF system please guys? Just an idea of cost as this is quite high on my to-do list.
It's also a bit of a myth that back pressure = low end torque... It's all to do with the scavenging effect within the exhaust pipe. At lower RPM with a larger exhaust, exhaust gas velocity it lower meaning the pressure waves moving through the exhaust are less powerful. This is more of problem at lower RPM because at higher RPM, the pulse frequency is much higher and the gas flow is closer to constant. The scavenging effectively sucks exhaust gas out of the engine rather than leaving the engine to push it out. By reducing this effect you are making the engine work harder, hence the apparent drop in low end torque. It's still there, but less is being transmitted to the wheels.
However, having said all that, it's less of an issue with turbo car's as the turbo vanes are in the exhaust stream meaning the pulses are diminished somewhat and there is less scavenging effect in the first place, therefore less to loose. So in theory, on the GTi, you shouldn't really notice much drop in low end torque (especially with a turbo anyway). Infact, it's almost win-win because you aren't loosing low end torque because you weren't relying on the scavenger effect in the first place (as with a N/A engine) but you are lowering back pressure with means more power at higher rpm due to less of a pressure drop over the length of the system.
Sorry for my rambling/thinking out loud... quiet day in the office. I thought it might be relevant.
