2-1 Exhaust thought

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Acke
Posts: 31
Joined: Fri Aug 12, 2022 10:13 am

2-1 Exhaust thought

Post by Acke »

Hey!

I've read several post of people asking if a 2-1 system would be ok and 9/10 it would result in a performance decrease.
Do we know why that is?
Is it because the total diameter of the 2 pipes=better flow than 1 pipe, if that's the case wouldn't a 2-1 system with an increase in the diameter that is the same as 2-2 from the split give the same result?

Or does it have to do with exhaust pulses?
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freeridenick
Posts: 1574
Joined: Fri May 23, 2014 1:30 pm
Location: Derbyshire

Re: 2-1 Exhaust thought

Post by freeridenick »

Exhaust tuning is about scavenging and waves, pulses, are important. Length and diameter of tubing effect the waves. So both questions are the same, just differently worded. That's about the limit of my knowledge but I think, yes, with a big twin 2-1 means worse scavenging and so lower performance. Even stubby cans make these bikes worse.

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tony.mon
Posts: 15943
Joined: Wed Jul 25, 2007 10:46 pm
Location: Norf Kent

Re: 2-1 Exhaust thought

Post by tony.mon »

It's certainly not simply adding to the exhaust's cross sectional area, because you have to balance gas in to gas out.
I tried a free flowing filter and gasflowing the ports with a "oops. I forgot to use wadding when I rebuilt the Migs" approach.

It took high comp pistons to make that combo work efficiently.
But interestingly, after I dropped the bike on ice and squashed the rh side can, I capped off the link pipe with a sawn-off Lynx can end and ran with just one can for a while, and although I didn't Dyno it. I felt that it developed more torque lower down in the rev range.

I went back to two cans fairly quickly, as I didn't often ride it low in the rev range, so it was of little benefit.
It's not falling off, it's an upgrade opportunity.
mik_str
Posts: 2149
Joined: Thu Apr 01, 2004 10:45 pm
Location: Montreal, Canada

Re: 2-1 Exhaust thought

Post by mik_str »

I tried it (used a stock header, cut off at the collector and mated a link pipe and can for a 98 R1). It ran ok but had a noticeable dip in the torque curve between 4800-6500 rpm. Some V-twins run 2-1 systems and do it successfully, but the only such systems I have ever seen for the VTR were by Arrows (early on and in very limited numbers), Hindle (Canadian builder, again, only ever saw one) and Yamamoto (all Ti, veeeeery nice, though I was never able to get info about power as it was sold only in Japan from what I can see).
99 VTR1000F Firestorm, a.k.a. The Carbon Express
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