Hey there, as some of you know I just recently boosted my 94 CD7 and am getting it tuned on the 4th of June. I just need to get it to my standards before I get it on the rollers.

My downpipe consists of all 2.5" stainless tubing. I have a four bolt flange to a mandrel bent downpipe piece that bends underneath the turbo, to a mandrel bent 90deg piece, 12" flex pipe, to a pipe that consists of my 3-bolt cat delete flange and two O2 bungs for ease of installing a wideband.

I currently have the pipe that swings underneath the turbo to the 90deg held together by a 2.5" coupler/clamps. It has a nasty exhaust leak and I don't want it to mess with my tune, not to mention its loud and noisy and sounds like an old man farting. Problem is I have no way of aligning it off the car ACCURATELY and its between the subframe and the front of the block. I can TIG steel and Aluminum, but getting a welder in there is basically impossible.

How would you guys suggest going about this? Here's how its setup off the vehicle with the clamp.

 

JB spot weld it? Then pull it out and weld it correctly. Or just spot weld, fit, adjust until perfect.

 

leave the clamp on it, pull it off the car and take the wrap off.
weld it and then take off the clamps.

your going to want better fitup than what you have there. maybe make a relief cut where that tube is bubbling off the other and tighten it down to a tight slip-fit before you weld it up.



When building downpipes from scratch for a one off system out of a fixture, you do one peice of the system at a time, tack it, plan the next peice and look at the end goal, weld your tack and then start over.

 

Either tack it in the car, pull it out, and finish weld.

or

Use a sharpy to mark 3 lines, take everything out, tack, refit to make sure it's correct, and final weld.

 

weld brackets or tabs to the "would be" pieces to keep them in place and then cut and weld in the new piece you need.

 

x2 to this method. Draw a line around it where the two pipes meet, then put a few marks to orientate it once its off the car. Weld, reinstall, and be on your merry way

 

I think everyone has this pretty much covered. I'm not proficient in TIG welding yet, but I cut/fit everything myself.

To get a piece setup, I'll fit it together on the car and mark in several places with a sharpie. Off the car, I tape the pieces together in four places around the diameter with painters tape (once held together I usually use this as an opportunity to clean off my old marks and make new, cleaner, and numbered marks). Then my assembly goes back on the car one more time to double check my fit. Once all is said and done it gets driven out to my welder.

For your situation, I'd remove the wrap, reinstall, mark, tack weld, double check then fry it up. I'd imagine having a slip fit might make it a little easier for you, plus you have the advantage of welding it on site.

 

Dont tape your joints.

I hate when people bring me taped up parts for welding.
Especially when they use packing tape.

 

Any particular reason? I can see packing tape leaving behind adhesive. Blue painters tape comes off clean and neither of my welders have every complained. I also don't wrap the joint (around the circumference), I tape across the joint leaving spaces in between for a tack.

 

Alright cool. I actually used a sharpie with multiple markings to align my flex pipe with the main 2.5" tube that goes back to my cat back when I welded that. I can also remove the clamp, align it with the 4-bolt section, make my markings and then tack. Appreciate the input.

 

Painters tape is better than other tape, esp the automotive designed stuff. I just find that often times it doesn't really hold the tubes perfect, and when I'm done welding everything is just a little bit off. Often times enough that it doesn't fit.

One of those things that I prefer to just let me do all of that work, instead of having someone give me pre-mocked up parts. However, I have had people give me a "form" made from bent piping or cobbled together pieces that I can make a part from, which is fine.

 

Ive had someone come in with a PVC part they made themselfs for me to copy. lol

 

Alright, so I removed the clamps and left the crimped coupler on and then used a piece of 1" angle iron to mark five different spots on the two pipes. After they were marked I used a 1/4 die grinder to remove the coupler and extended the lines with the same angle iron as before. Worked like a charm! A lot easier than I made it.. Now I don't have that obnoxious old-man-fart sound coming from the clamp, and I was able to completely wrap the length of it with one strip.

Thanks!