Mid pipe diameter ?


Hi guys - I get my new '03 LE "Busa on Friday and want to know the diameter of the stainless mid pipe of the exhaust so I can get some custom pipes made up to match some Scorpion mufflers that I have ?
I hope I understood you correctly. The outside diameters of the header X-pipe ends (that the mid pipes slip onto) are 49mm by my dial gauge calipers.

But, it might not be so simple. The Busa mid pipes have a liner (that looks like a catalyst/muffler) so the actual inside "flow" diameter of the Busa mid pipes is considerably smaller than 49mm. Of course, this doesn't mean that you can't make custom mid pipes that run from the X-pipes to your Scorpions. It does mean that 49mm ID mid pipes will decrease exhaust gas VELOCITY which will probably decrease torque at low-to-mid range RPM. :super:
Thanks very much Warbaby -a good intelligent answer - (hard to find here some times !)
My idea is to sleeve the 52mm custom mid pipe (which is the Scorpion entry size ) down to the measured 49mm just at the last moment before the junction - basically it will negate the restriction in the factory pipes - sound good ?? :)
If you were keeping the stock cans, the pipe change might be noticable. But the scorpion cans you're trying to mount are going to decrease backpressure anyway, so I say go for it!

tlronny > What I was trying to say is that the stock Busa mid pipe I.D. is SMALLER than 49mm because of the built-in liner. If your new mid pipe is 49mm there will be drop in gas flow VELOCITY at all RPM in the new mid pipe. That USUALLY causes a torque loss at lower RPM. Conversely, it should flow better at high RPM. That may be good or not so good depending on what results you want from the exhaust mods. ;)
I get what your saying - the mid pipe itself will be 52mm but there will be a 1" long sleeve (internally welded) at the end to connect to the original collector - hopefully the loss at low revs wont be too bad at the expense of a better top end ( and a rorty sound of course !)

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