Last year I asked for someone to donate a stock dp elbow. Thanks to a really awesome well known member/performance shop, I was able to get a donated stock elbow for my custom do it yourself 3" downpipe project. Over the fall and winter, I was able to get caught up on some of my own projects. I finally got around to building a 3"dp for my We4. Keep in mind that I am a very experienced fabricator and welder. The dp on our cars are pretty basic. At least much less complicated than some headers I have built. So anyone with decent welding a fab skills can probably save themselves about $400 by doing this project themselves.
Step 1: Cut a flange out of a stock DP elbow.
Note: You have the option to buy these from RJS with larger pucks, but if you don't have a huge turbo or over 100 bucks for a simple flange, then follow these steps with your stock elbow.
Draw a line around the flange of the stock elbow as pictured and use a cutoff wheel and a grinder to cut around. Be sure to cut around the waste gate puck and lever so that it remains attached to the flange. (unless you have an external wg).
You should end up with a flange that looks like the one in this photo. Bolt your flange up to the turbo. That is the foundation for all the work to come.
Step 2: Buy a 3" Mandrel bend pipe. (I got mine from Summit Racing) You will need at least 1 180deg bend and a 45deg bend. You will also want some thick 3-bolt flanges for the test pipe and an o2 bung if you run a wide band.
Step 3: Start at the turbo and make your first cut for the 90 coming out of the turbo. (It needs to be tight, I used the cut on the left in the photo below.
Step 4:Once you get that cut, fit it to the flange and angle it back toward the opening in the firewall. Mark the position with a sharpie and tack it in place.
When you get the angle you like, work from there with more pieces of tube. Keep marking reference points with a sharpie so you can reposition it when tack welding. I like to build as you go. Too much pre- planing will get you into trouble.
A trick I like to use when cutting tube bends is to take time and plot out straight dotted lines around the bend. I normally eyeball it, but you can use a rubber band if that helps.Then you can use them as a guide when cutting anywhere along the bend. If you cut at an angle, you will end up with oval shaped openings and the mating piece of pipe wont fit.
Making reference points like this helps when holding it under the car and trying to duplicate it when welding.
Step 5: Use something to space the pipe above your control arm. I used a socket in this picture to ensure that I left enough space for the dp.
Below is a photo as to how it snakes through the opening below the firewall. Make sure you have plenty of clearance.
By now you should have something that looks like the photo below.
Step 7: Waste gate integration.
Use cardboard to make a template for the wastegate. Remember to fully open the puck and make sure that it clears. Once you have your template, cut a piece of scrap tube and trace your template to it. You can reshape it with a hammer to make it fit snug. I built mine in 2 pieces.
To be continued: hit my photo limit for this post
Step 1: Cut a flange out of a stock DP elbow.
Note: You have the option to buy these from RJS with larger pucks, but if you don't have a huge turbo or over 100 bucks for a simple flange, then follow these steps with your stock elbow.
Step 2: Buy a 3" Mandrel bend pipe. (I got mine from Summit Racing) You will need at least 1 180deg bend and a 45deg bend. You will also want some thick 3-bolt flanges for the test pipe and an o2 bung if you run a wide band.
Step 3: Start at the turbo and make your first cut for the 90 coming out of the turbo. (It needs to be tight, I used the cut on the left in the photo below.
Step 4:Once you get that cut, fit it to the flange and angle it back toward the opening in the firewall. Mark the position with a sharpie and tack it in place.
When you get the angle you like, work from there with more pieces of tube. Keep marking reference points with a sharpie so you can reposition it when tack welding. I like to build as you go. Too much pre- planing will get you into trouble.
Step 5: Use something to space the pipe above your control arm. I used a socket in this picture to ensure that I left enough space for the dp.
Below is a photo as to how it snakes through the opening below the firewall. Make sure you have plenty of clearance.
By now you should have something that looks like the photo below.
Use cardboard to make a template for the wastegate. Remember to fully open the puck and make sure that it clears. Once you have your template, cut a piece of scrap tube and trace your template to it. You can reshape it with a hammer to make it fit snug. I built mine in 2 pieces.
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