I've been hearing a lot about fords needing a certain amount of back pressure and that free flowing exhaust isn't good for them. On my 06 gt I have high flow cats, x pipe, and slp loudmouths. Anyone else know anything about this and if I should buy different mufflers?
well any car (unless turbocharged) requires a certain amount of backpressure to build some torque down low. if you increase the size of your piping and remove all restrictions you will see an horsepower increase (up to a certain extent) and torque diminishing. An exhaust system can really help you shape a power/torque curve.
Backpressure is bad regardless of application. When you put a too efficient exhaust on a car, you are moving the torque curve upwards which equates to a loss of low end torque. It is not really lost, it is moved upwards. You have to watch what you do to your exhaust mods that you don't shift it upwards unless you intend to. That said, with the exhaust mods from the original poster, you are fine...
well any car (unless turbocharged) requires a certain amount of backpressure to build some torque down low. if you increase the size of your piping and remove all restrictions you will see an horsepower increase (up to a certain extent) and torque diminishing. An exhaust system can really help you shape a power/torque curve.
Technically thats incorrect. With a correctly designed cam and exhaust (for the proper velocity curve) you dont really want back pressure. In fact you want negative pressure.
However what most people mean by backpressure is I want exhaust that is as restrictive at high rpm as I can get away with to make sure velocity doesnt collapse at low rpm resulting in flow reversion. The backpressure only occurs at higher rpm where it hurts power.
The ideal low rpm exhaust (assuming suitable cam timing) would be be
open headers with the correct primary and collector dimesion for that rpm.