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 Post subject: Re: Catching a Wave?
PostPosted: Mon Apr 20, 2020 12:09 am 
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Joined: Fri May 08, 2009 1:13 pm
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Current ride: XB9SX
Today l could choose between making a cut down badass tail light housing from my spare, or start tweaking my spare XB9 header. ;)

Looking again at the two headers l have and other factory 9 collectors from pictures on eBay, l was shocked to see how much variation there is in welding and shape on supposed to be identical spec headers. :?

Some are very neatly welded and have a pronounced V shaped valley on each side of the Y shaped moulding to blend in with the two incoming pipes, other examples have crude welds and hardly any valley to the sides. :? Where l measured a cross section of 26.5cm2 on my spare header, the sides of the Collector were almost bulging outwards! :shock: I estimate that the variation at this point can be as much as 18%, which is a lot in anyone’s book! Is this why every XB9 feels so different to ride?

As l have explained at length elsewhere this void in the Y of an XB12 would be much less significant as those incoming pipes are much bigger in section. The ratio of incoming to the space in the collector is significantly less than on a 9. So what are the gases likely to do under those conditions? :?

I was also surprised to see by comparison that the headers that came with my XB were actually beautifully welded and that the Y collector looks to be very well contoured. It’s just inside where the incoming pipes appear to have a big step at the weld point. In almost the opposite fashion, my spare header looks more streamlined inside where the incoming pipes are welded, but with badly shaped blending from twin to single pipe there after. :roll:

As above l measured the spare collector cross sections as 22, 23.9, 26.5, 20 and 14.7 cm2 over a length of transition of about 92mm. By correction of pressing or hammering in the side valleys of the collector the profile should be 22, 23.9, 21.8, 19.4 and 14.7 cm2. Note the big change in the middle. ;) If l could clean out the pipe innards with a long brush, l could try lead filler to the back of the weld then shaping with a long grinder or file! That might even make my Venturi redundant! ;)


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 Post subject: Re: Catching a Wave?
PostPosted: Mon Apr 20, 2020 9:16 am 
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Current ride: XB9SX
Doh! Lead won’t stay there.....would have to be higher melting point like brazing! :roll:


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 Post subject: Re: Catching a Wave?
PostPosted: Sun Aug 16, 2020 9:37 am 
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Joined: Fri May 08, 2009 1:13 pm
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Current ride: XB9SX
Having done pretty much everything else needed to my City X, I returned to the tweaks to my spare XB header.
l have heated the Y collector with a mini blowtorch till it glowed and used a cold chisel to ‘gently’ hammer in the sides in a key area to as close to the above profiles as l can get to obtain more consistent gas flow.

The header collector now looks much more like a ‘pro-race’ collector! 8-)

The only problem is the welded header pipe stubs inside. One of these is not even fully round on one side. It looks like a real Friday after being down the pub job! :? I was hoping to find a tapered carborundum stone grinder of around 35mm to fit to an extended bar to grind this out, but no luck so far. I might have to get a 40mm grinding wheel and grind that down just to get it to fit inside the pipe! Hand held files just won’t dent stainless at that reach. Short of cutting the collector open and doing major surgery, l may have well have had a complete new Y collector fabricated by Albert and welded back on. :? I have not gone down that route as the motive for doing my own experiments is to learn which theories about my XB actually work....or not. lOl

My next move could be to get some 38mm steel bar, grind a taper on the end then use it as a ram to splay the header pipe stubs in the Y collector open, or at least to a more round shape....if l can get them hot enough! At least butane canisters are still relatively cheap! ;)


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 Post subject: Re: Catching a Wave?
PostPosted: Sun Aug 16, 2020 10:31 pm 
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proff. patpending
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Current ride: Victoria Sponge
Location: Bristol - Gateway to all things good
When all this is finished, will you declare it to your insurance? Asking for a friend...

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 Post subject: Re: Catching a Wave?
PostPosted: Mon Aug 17, 2020 7:41 am 
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Joined: Fri May 08, 2009 1:13 pm
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Current ride: XB9SX
Good question.......but!

Declare what exactly? I returned a pipe shape closer to the factory blueprint? With a grind and polish there is nothing to see! ;)

Is there an insurance assessor clever enough to even be able to identify my current Venturi insert from all the other stock pieces of metal? I would then argue that it was a restrictor insert to reduce speed and extend the life of the engine. lOl


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 Post subject: Re: Catching a Wave?
PostPosted: Mon Aug 17, 2020 8:46 pm 
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Joined: Fri May 08, 2009 1:13 pm
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Current ride: XB9SX
....or the Venturi sleeve is just a metal sleeve to reduce exhaust blowing from the joint without the need for sealing paste! ;)


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