by 6000 SSEi

Ever thought what a good size for exhaust pipe might be? This is for anyone wishing to improve performance by changing the factory exhaust.

The exhaust system should have minimal restriction to the exhaust flow that is being released in order to create the most amount of power from the engine. With restriction present, backpressure is developed, making the engine work much harder to release the exhaust out of the engine cylinders.

The standard for exhaust diameter is to not run too large of exhaust, for the engine needs a certain amount of backpressure. This is correct in the sense of one should not run too large of diameter exhaust tubing, but the statement of the engine needing backpressure is not. You need to have the least amount of backpressure possible to produce maximum power. Too large of diameter exhaust will cause a power loss and loss of low end torque because a larger pipe has less exhaust stream velocity than a smaller pipe. If the exhaust pipe is too large, then the exhaust flow will be slowed with less velocity. There are exceptions, forced induction or high-volume race engines require a larger diameter exhaust due to the flow characteristics of the engine. Supercharged and turbocharged vehicles can have an exhaust gas volume of 1 to 2 times more than an equivalent displacement naturally aspirated engine. In this case, one is able to use a larger diameter of exhaust for greater performance.

Below is a general rule of thumb when selecting a diameter for your exhaust:
  • 100ci - 150ci motors = 2 inch exhaust tubing
  • 150ci - 220ci motors- 2.25 inch exhaust tubing
  • 220ci - 350ci motors- 2.5 inch exhaust tubing

For supercharged and turbocharged vehicles, one should use no less than a 2.5 inch exhaust system. Forced induction vehicles with a 220ci or larger engines can use 3 inch exhaust.

This information is from Exhaust Back-Pressure - Is Bigger Always Better? (Right click, open in a new tab)
- 7/8/2003 by Axxel Performance Exhaust Tech