The Collector

Soon I realized I needed to keep things quite compact, and thus the collector was going to be my biggest problem. How does one cram four 38mm (1.5") OD runners into one 55mm (2.2") ID turbine inlet flange?
Oh, and *equally* please. I don't want to lean out the (slightly favored intake-wise) #2 and #3 cylinders even more. (the latter has proved to be the weak link at HIGH boost) I would've made things a lot easier by going with a log-style manifold, but that would again give #2 and #3 the advantage.

So I started designing a compact collector. Something like the "bucket style" collector outlined on the SDSEFI tech page just wouldn't do. Bulky and dodgy.

I came up with this.

Four 45 degree bends...

... sliced in a vertical plane ...

... until they all fit in the turbine flange together.

Marking and cutting was the hardest part. I set each 45 degree bend upright and eyeballing alongside a ruler I was able to mark the two vertical cuts (at a 90 degree angle to eachother.) To allow four of these to fit in my turbine flange, I made the cuts so that the length of the arc left at the bottom of the bend would be 1/4 of turbine flange inner circumference. Still with me? Good.

Cutting these pieces is not easy. Make sure, when marking, that near the top of the bend you end up at the same height on both sides of all four pieces. That's more important than having the cuts exactly vertical or exactly straight. Be precise when cutting - go 1mm off and due to the angle you may end up 1/4 inch higher or lower and end up with gaps.

In case you're wondering : I've done the cuts bottom-up. First part is easy, in a vise using a hacksaw. Then the pipe will weaken and become too weak to clamp in the vise. This is where it gets tricky. I solved this by clamping it by one of the parts I was going to remove anyway. Now the hacksaw would hit the vise so I flipped the blade.

And this is one of the pieces I ended up with.

I think these shots show what I have in mind.

Done!

After cutting my fing..I mean cutting four of these pieces, I took the whole thing to Bjorn and spent a while with a welder. Never mind the not-so-clean CO2 welds - looks is not a concern, strength is. So the resulting V-grooves on top were basically filled up.

After tacking the pieces together near the top, we cut down the bottom a bit until the whole thing fit snugly in the flange, making sure each bolt could still be reached with a box end wrench.

Note that the resulting collector is only 3 inches high including the ~1/2 inch flange! With pipes exiting in all directions at a 45 degree angle, routing the runners to it will not be a big problem with the design I have in mind.