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Bigger tubing loses power?

1K views 2 replies 3 participants last post by  mcm95403 
#1 ·
Hey guys I'm thinking of changing my muffler to valvetronic one, but before I think of getting it, the inlet and diameter is 3" and on my SXT it's 2.25" I believe. Now the piping before and after my magnaflow mufflers are 2.5", so will replacing the mufflers with 3" inlet and outlet mufflers to a 2.5" piping affect the torque or power in any way?
 
#2 ·
Proper exhaust pipe size is a function of both engine output and displacement. Unless an engine is really modded for more horsepower, the stock size is perfect for it. Going too large can over scavenge an engine and actually decrease engine output, as well as efficiency.

A 3 inch diameter pipe is typically used on larger engines of 350-450 cubic inches that produce between 350 to 450 hp.

Here are two articles that provide further explanation. The second one provides a formula for determining the exact size pipes for an engine.

https://www.hotrod.com/articles/what-exhaust-pipes-work-best/

How To Calculate Muffler Size and Exhaust Pipe Diameter | Exhaust Videos
 
#3 ·
Larger tubing does NOT "over scavenge". Rather than maintaining velocity, it allows the exhaust pulses to slow down in the tube, "stacking up" and causing back pressure - above and beyond the 14.7 psi of atmospheric backpressure (at sea level) all exhaust systems must over come.
 
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