Equalizing exhaust pressure
Ultimate HDF Member
Joined: May 2008
Posts: 7,439
Likes: 884
From: 'Noke, VA
Problem is that then you're choking the system. Yes, you'd increase flow through the left side, but you'd be reducing it through the right (the easy way out) which would lead to increased back pressure, increased exhaust temperatures, and a pressure wave which would make reversion more likely.
Tourer
Joined: Feb 2011
Posts: 434
Likes: 2
From: Wisconsin
I have the fuelmoto pipes and header, the mufflers have different baffles. The left side is more restrictive then the right unless I use the quiet baffle (which I was told to run in the right). Using these mufflers, you could switch the baffles, but doubt that you could feel a difference in doing so.
Elite HDF Member
Joined: Jun 2006
Posts: 3,572
Likes: 5
From: Templeton California
My old Dyna had a Thunderheader with damn near equal length head pipes and it worked real well.There are a couple more 2 into 1s out there that are similar and the stock 2 into 1 into two pipe on the Fat Bob is also damn near a straight copy of a thunderheader from the collector up.Not sure if any of this can transfer to a touring bike though.
Extreme HDF Member
Joined: Jun 2007
Posts: 12,653
Likes: 18
From: Broken Arrow, Oklahoma
Nope.
The left side outlet is longer, there's a vicious crimp in the crossover, and there's two 90-degree bends in the pipe. The exhaust follows simple physics which means it takes the path of least resistance.
I went with a Jackpot header and full-sized crossover. That helps a bit, but that won't overcome those two turns and the length.
The left side outlet is longer, there's a vicious crimp in the crossover, and there's two 90-degree bends in the pipe. The exhaust follows simple physics which means it takes the path of least resistance.
I went with a Jackpot header and full-sized crossover. That helps a bit, but that won't overcome those two turns and the length.
the line from header to rt exhaust is a straight line
the lft exhaust takes a couple of 90ş turns.
think of the left side as an "overflow" when the flow exceeds the ability of the rt side, the left side will flow more.
on my exhaust system I swap the lft and rt side tips to equalize "wear" so they look more similar.
some systems are set up so that the 2 pipes are different- the left side may be smaller internally so as to keep velocity high
the key with exhaust is not just "flow" but also the velocity of the gasses.
high velocity is good
ike
the lft exhaust takes a couple of 90ş turns.
think of the left side as an "overflow" when the flow exceeds the ability of the rt side, the left side will flow more.
on my exhaust system I swap the lft and rt side tips to equalize "wear" so they look more similar.
some systems are set up so that the 2 pipes are different- the left side may be smaller internally so as to keep velocity high
the key with exhaust is not just "flow" but also the velocity of the gasses.
high velocity is good
ike
I've read that a lot on this forum. And, it makes all the sense in the world. Now if I could just figure why my left side flows more than the right. Did it with the stock slip-ons, with the American Custom (stock slip-ons with baffles cut out), and now with my V&H Monster Rounds. Head pipe is stock, and still has the cat. You can put your hand down there and feel the difference, and you can really see it on a cool morning.
So what gives??
Ultimate HDF Member
Joined: May 2008
Posts: 7,439
Likes: 884
From: 'Noke, VA
I've read that a lot on this forum. And, it makes all the sense in the world. Now if I could just figure why my left side flows more than the right. Did it with the stock slip-ons, with the American Custom (stock slip-ons with baffles cut out), and now with my V&H Monster Rounds. Head pipe is stock, and still has the cat. You can put your hand down there and feel the difference, and you can really see it on a cool morning.
So what gives??
So what gives??
Road Warrior
Joined: Jun 2006
Posts: 1,993
Likes: 20
From: Southeast GA
When I'm behind my bike with it running, I can't tell which side is making more noise. I don't see what the big deal is.
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Ultimate HDF Member
Joined: May 2008
Posts: 7,439
Likes: 884
From: 'Noke, VA
I can tell when riding that the right side is louder. I will say that since I changed out the crossover, the difference is less pronounced.
Seasoned HDF Member
Joined: Feb 2008
Posts: 22,999
Likes: 11,439
It is called scavenging and it one of the best ways to get a Big Vtwin to run right and tune well. So called True duals are not the answer