Basically with a turbo, if you fit an exhaust that is more free flowing e.g. less number of cats, then you will reduce back pressure, which will give an uplift in performance.
The decatted option will give the most power, then 100 cell, then 200 and so on.
Reducing backpressure will effectively move the entire power curve to the left so the total power under the whole curve will be greater.
People get hung up on xx gain from a modification. Imo it is better to have 10hp increase across the whole power curve than have 20hp which is from 5000rpm to the red line.
You will see some manufacturers of exhaust claim their exhaust gives 40hp for example. That can be true, although not on a stock turbo car - as an example on a 9e20 which runs 20 seconds or less to 300kph, if I run with the flaps closed (more restrictive) the car will run 23 seconds versus 20 seconds. That is probably a 50hp difference alone. So the more powerful the car, the more a better flowing exhaust will contribute.
Cheers ken, and thanks for your advice on the phone the other day!!!
Ken
p.s. I should add that the design of the exhaust will also reflect any power increases, although I have tested some that actually reduce power through poor design, despite having less cats.
