---Backpressure in exhaust; good for city bad for highway!---

[basslover911]

What i have been thinking;

Backpressure is good because it increases torque, so that is good for city driving where you need to constantly accelerate and decelerate.

But what about for constant cruising? When you dont need that torque... Wouldn't less backpressure be the best since air would flow out much better?

[Duffman]

Backpressure isn’t good for anything except when used for sound attenuation.

[markweatherill]

On a production car, 'back pressure' in the exhaust is factored into the cam timing. The exhaust valves can begin to open earlier than if an open exhaust was used, a benefit at lower engine speeds (i.e. in everyday driving).

[Ryland]

It's not about back pressure, it's momentum! the exhaust is exiting in pulses not a constant flow, if it was a steady flow then larger would be better, but your engine is not a turbine... and even with a turbine you have to tune your exhaust to keep the momentum to help the engine run better (at least the books on turbine design seem to say so), so what it boils down to is if you believe in physics a properly sized exhaust is going to treat you best, if you are 16 and were given a car, and failed math class then go with a larger exhaust.

[eco_generator]

Originally Posted by basslover911

Backpressure is good because it increases torque

You have some more reading to do...