Packed Like Sardines

14 Nov Packed Like Sardines

Sometimes we’re working in spaces where extra real estate isn’t exactly prevalent. Today is one of those days.

Last time we looked at Tim’s 911, we drove it over to fabrication and put it up on the lift in preparation for the custom exhaust we’d be developing. First, however, we knocked out two relatively easy pipes that needed to be made. You see, heat in this car comes from tubing that runs through a chamber built into the exhaust manifold. As the header is hot from the exhaust gas, it warms the secondary chamber in the manifold as well, and air rushing through there collects that heat to use for the cabin’s HVAC system. With a motor that’s not supposed to go in this specific car, we had to make custom tubing to run from the manifolds to the rest of the heating ducting. Some aluminum piping and welding later, and we’ve got them both in place.

As one of the pieces of tubing was just a little closer to a metal oil line than we liked, we set about making a small brace that will separate the two, preventing any sort of nasty rattling noises from occurring.

With that out of the way, it’s time to address the 400-lb gorilla in the room, the custom exhaust for the 993-swapped O.G. 911. The 993 motor has two headers, one per bank, each with an exhaust outlet that dumps towards the other. Ideally, both pipes would meet in the center and jump off to each side, exiting through two exhaust cutouts in the rear bumper. Well, it’s a different story with the vintage 911, as it only ever had one outlet on the driver’s side of the vehicle. In an attempt to keep this car as close to original as possible (and to avoid cutting into the bumper), we’ll be maintaining that single outlet. Now, this makes things a little trickier. We already secured a 2-into-1 muffler that will provide us with the sound we’re looking for (as running a straight piped setup will get a little old, relatively fast), it’s just a matter of running both the header outlets to that muffler. Again, space isn’t exactly sitting around in massive quantities, so we need to snake the pipes around a bit. The passenger side will start twisting from the outset, whereas the driver’s side will benefit from a bit of a straight section to start.

And then it turns into a pretzel.

You may notice that there’s a good deal of tape covering up small segments of pipe. Well, seeing as how these bends are rather tight and slightly angled in non-traditional ways, we won’t be able to replicate them with any piece of pipe that we normally order. Therefore, it’s pie cut time. And with pie cuts come a good deal of welding. Craig tallied up the welds and figured this exhaust would have about 3 dozen individual welds involved in it. For something that’s relatively short on length, it’s not going to be a smaller job by any means. Once the pieces were test-fitted with the tape on, we went about taking them to the welding table and tacking them together.

With this many welds necessary, the piping will be subject to a good amount of heat. This heat, even if it’s spaced out over the course of several welding sessions, can still cause the piping to warp a bit. Obviously, with such tight space constraints, this isn’t going to bode well for our fabrication department. As a result, we used some steel bar we had lying around in order to help maintain the exhaust piping’s shape during welding. The excessive amount of tape is used to cover up the ends of the pipe, with just enough space left over to insert the inert gas used for backpurging during welding. This keeps the insides of the pipes as smooth as, well, the outsides of the pipes.

From there, we set about welding a few rings at a time, allowing it to cool while working on the other piece of piping. Having two pieces being welded simultaneously is great, as one can cool while the other gets worked on. No wasted time here.

In what seems like no time at all, we had two mostly-welded pipes hanging out in front of the fan, waiting to cool before the final welds are applied and the pipes are taken back to the 911 for further test-fitting and tacking to the rest of the system.

Now wait just one minute. You didn’t think we’d let you get away from this blog post without showing off some of our TIG welding, did you? Well, we won’t inundate you, as we have in the past. Instead, we’ll throw up three quick pictures. It’s much less fun when you let a robot do all the work, don’t you think? As always, we take pride in our welds and love showing them off to readers and customers alike.

And that’s about it for the 911 exhaust thus far. Once the pipes are tacked into the muffler, we’ll start working on the piece of the exhaust that goes from muffler to bumper. This isn’t the only custom exhaust we have lined up at the moment, either; remember that V12 SL600? You should be hearing something wicked coming from that beast very soon, also. Stay tuned and we’ll keep you in the know.