May 01, 2013

Downpipe Revisited

Sometime in February I discovered that the downpipe wasn't quite done yet.


Embarrassingly, I had a bit of an oversight with my placement of the oultet v-band flange when I originally fabricated the thing. As I found it, where it ended up next to the oil pan, was too tight to get the v-band clamp on. How I didn't see this the first time I'm not sure, but after a face-palm, some choice words, and removing the wastegate/dump tube assembly the downpipe was back out again. To remedy the problem involved extending the length by 6" to push the flange out into a more open area. Fortunately I had plenty of spare material kicking around, although it meant sacrificing the v-band flange that was on there. The extra length did create another situation however. In the same fashion as a stock Saturn downpipe, I had wanted to add a bracket to secure the exhaust against the two rearward most mounting points of the transaxle-motor brace. Originally I was going to save this additional bracket for the next length of exhaust, but since the downpipe was now passing under these points I would be adding it to the extension.


After mocking up my extension the downpipe went back in another time so I could make some crude templates to work off of. I designed the bracing to be two piece with an l-bracket bolted to the motor and another bracket welded to the downpipe, the idea being two separate pieces would help compensate for any shifting during my travels from the shop to the welder. My templates then made the transition from cardboard to AutoCAD where I cleaned up my geometry before sending the files out to be lasercut as part of batch in the previous post. With the downpipe being troublesome to snake in out of the car, I included two bolt holes on the piece destined to be fixed to the downpipe while I left the l-bracket blank. Since the l-bracket was going to be easy enough to get at I just assumed I'd lay out the two remaining holes after everything was welded up and bolted into place.


The downpipe made a trip to the welder during my wait for the laser cut items. When I had everything back in one place, the downpipe went back in the car again to mock up the brackets. Now the following feat I am strangely proud of - with the l-bracket bolted into place and the second bracket clamped to that, I realized that the latter was neither parallel or perpendicular to any surface on the downpipe, so I was going to have to make a jig to hold it into place. Pawing through the scrap box yielded me a piece of thin gauge angle aluminum that I snipped in a few place so I could bend it around the 3" tubing. Some searching around the shop turned up a large enough hose clamp and two miniature c-clamps to hold the bracket in place. I was so amused I even took a picture, plus I got a laugh out of the welder.


My jig worked though, and with the downpipe in (hopefully for the last time this season) everything lines right up the way it is supposed to. Now I just need to layout and drill some holes!

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