As there's currently a hole rusted through my exhaust, I figured I'd buy an OE replacement pipe thinking it would be close to the same.

I purchased the walker exhaust pipe Walker P/N: 54699 for about $50. (Dealer wanted over $300 for Mazda P/N: N3H140600B). 54699 wasn't carried/stocked at Walker, so I spent a few weeks trying to find a shop that had it in one of their warehouses.

The pipe itself is pressure bent / crimp bent, which may introduce a 1/4 inch or so obstruction in the diameter already, though the bends aren't overly large - it's still a slight reduction in flow which I could have dealt with...

But the problem lies with the pipe diameter being only 2 inches! It's flared out to 2.5 at the end in order to mount to the muffler, but the pipe is severely restricted at 2 inches vs OEM 2.5 all the way.

I believe it's about a 44% decrease in flow if my calculations are correct?

Area of exhaust flow based on circle diameter:
(2.5 inch) 3.14 x 1.25 x 1.25 = 4.91 sq/inches
(2.0 inch) 3.14 x 1.00 x 1.00 = 3.14 sq/inches

Percent difference between the two:
( (4.91-3.14) / ( (4.91+3.14) /2) ) * 100 = 43.9752%

If we were to factor in say a 1/4 inch flow reduction for crimp bending (on the 2.0 pipe), we'd be looking at an overall reduction of 68.7% from OEM.... yikes!

(1.75 inch) 3.14 x 0.875 x 0.875 = 2.40 sq/inches

( (4.91-2.40) / ( (4.91+2.40) /2) ) * 100 = 68.6731%

If there are any alternatives in being able to purchase just an aftermarket pipe that's cheaper than the dealer, without getting a full cat-back, please feel free to chime in. Otherwise I just thought I'd post this for people wondering about the walker pipe... I wouldn't recommend it.

 

Thanks for the heads up.

 

contact mazmart, they should have it at a good price.