While a shorter length pipe can improve top-end power and longer pipe can increase low-end horsepower, each of them has its own pros and cons depending on the vehicle.
What does a smaller exhaust pipe do?
When your engine is at low RPM, the amount of exhaust gases leaving is low, so the velocity it exits the exhaust is low. You can increase this velocity by using a smaller pipe, but this will create a restriction for higher RPM.
Does exhaust pipe size affect sound?
If you are too lazy for the details, bigger exhaust pipes do make the exhaust louder – but only by a little. Exhaust pipes are made bigger to allow better exhaust flow. Instead, aftermarket exhaust also equips a less restrictive muffler – which is responsible for the much louder sound.
Is a smaller exhaust pipe better for an engine?
Again engine efficiency is improved. Smaller exhaust pipes present a greater resistance to steady state flow. So smaller isn’t necessarily better either. It’s a compromise between resistance to flow and flow velocity.
What do you think about drag pipes on motorcycles?
Drag pipes and large open pipes look and sound “cool” but are definitely tuned for larger engines, thus giving up alot of lower end torque where most daily riders need the power.
How many pipes equal one pipe of a given size?
It is frequently desired to know what quantity of pipes of a given size are equal in carrying capacity to one pipe of a larger size. At the same velocity of flow the volume delivered by two pipes of different sizes is proportional to the squares of their diameters; thus one 4″ pipe will deliver the same volume as four 2″ pipes.
How is the size of the exhaust pipe determined?
Pipe diameter is determined by engine displacement (bore and stroke), compression ratio, valve diameter, camshaft specifications (lift, duration and timing), and the cuticle rpm band. If pipe diameter is too small, backpressure increases. Backpressure is defined as flow resistance created in the exhaust system.
