Thursday, 19 September 2019

Yamaha XV single carb manifold (part 1)

So, I've been to a bit of a vacation (thanks for asking, yes it was lovely) and then instantly fell ill and since have spent a bit too much time my bathroom porcellain. As such there's not quite the progress to show, that I wanted to show you, i.e. a finished first manifold.

As I have a good friend, who is (like me) strongly opposed to single carburettor manifolds on Yamaha V-twins, we decided that I would build a few different ones, ideally test them on his dyno and work out what works and what doesn't, with the intention of building a n/a setup for the turbo TR1, so I can (every now and then at least) use it on the road and not only as a very decorative coat hanger and also distribute the other remaining ones among some people I know.

So this is my Mk.1 design, an idea which I actually built (and used) on my very first turbo-setup. It's a rather elaborate design that starts off with a y-piece that is turned 45 degrees to allow for better fitment. Both runners are off the same length. It's not the shortest runner-length design possible, but at least on the first turbo it worked quite nice. (But then again, turbo's aren't particularly picky about flow, they just cram stuff into the engine and that's the end of it really.)

It sure does look a wee bit elegant with all those sweeping curves, doesn't it?

So why is this not done already? Well, I changed tubing suppliers and this one sold me bends with a different radius, i.e. standard 90ies and not "tight" 90ies for wastegate use. So I have to come up with a fixture to shorten the tubes in the bandsaw and then weld it in with the flanges.

This is the setup I built a while ago with bends with the correct radius:

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