What is the real reason they fit a airflap in the induction pipe and a exup valve in exhaust. Surely its more than just for noise reduction. Please only answer if u know the real answer as im having a debate with a couple of ppl.
^what peggy said^ I used for a red car manufacture and they had a variable inlet tracks which helped with torque. But that's different to the flap in a 675 since it change the inlet track length.
its all about power/efficency at different parts of the rev range the exup is closed at low revs and opens up higher up at low revs it creates a little back pressure any one with exup remooved and no remap will notice a little less power on inital pull away then when the get up the revs slightly its fine as for the flap im only sort of guessing here but again low revs the flap will be cloosed as not a lot of air will be needed so its cloosed untill higher revs to allow more charged air into the airbox to get the fuel/mix right and also force the air through the throttle boddies
