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The $30 WRX Uppipe Project

The uppipe, or up pipe, on the factory Subaru is very restrictive, so I wanted to replace it with a higher-flowing pipe. I wanted a stainless steel and a flex section, but the aftermarket options were limited and expensive. I decided to make my own.

The most interesting and surprising part of this project was the negative response I got from other WRX owners on the message boards. Make your own uppipe? "Only an idiot would do that, when there are perfectly good aftermarket pipes you can buy! I bet it will fall apart on you."

It hasn't fallen apart after 50,000 miles. This was a rewarding and worthwhile DIY experience, and at $30, it was very cheap.


You can get some mandrel bent tubing and a flex section and convert your factory uppipe into one that flows as well as the aftermarket pipes (and won't crack from stress). You don't have to gut your cat. You don't have to spend a fortune. The new, fabricated pipe is pictured to the left.


Even if you gut the stock cat, you're left with a very narrow pipe which expands to twice its size and back down to under 1.5", right before entering the turbo's exhaust housing inlet which is 1.75".

Purchased items:

1.75" I.D. flex section (J.C. Whitney 47US175OU, $20)

180 degree mandrel bent 1.75" I.D. tubing section (Speedway Motors 910-13851, $9).

It's also a good idea to buy a used factory uppipe as a spare in case things don't work out. You can always sell it to someone else later.

Equipment used: chop saw, angle grinder, die grinder with carbide burr, rotary wire brush, fiberglass cutting wheel, air hammer with chisel attachment, and welder.


Remove the heat shields from the factory pipe by cutting the welds.
A crude welding fixture made from 2x4s guarantees the bolt flanges on the finished piece will perfectly match the placement and angles of the factory pipe.
The mandrel bent tubing and flex section after cutting.
After cutting the flanges from the factory pipe, some cutting and grinding is needed to clean them up. An air hammer with a chisel attachment helped to knock out the old sections of pipe still attached to the inside of the flange's hole.
The flanges require a little grinding to open them up, so that the new pipes will fit inside as shown.

Next, weld the tubing sections together, and to the flex section

Using the fixture, the flanges are welded to the tubing.

The factory heat shields can be re-attached to give a stock appearance, or you can leave it as-is.