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Discussion Starter · #1 ·
I remember switching my stock exhaust for an aftermarket exhaust and I swore that the bike had less jerk off the line. I didn't have access to dynos so couldn't confirm, but when I switched back to the stock exhaust with the exhaust valve, it felt like my low end torque was restored.

Anyone doing dynos that has seen this. I've heard from some mechanics that the back pressure will increase low rev power and limit higher rev performance.

Any else have any insight?
 

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Discussion Starter · #2 ·
Answered my own question with some youtube videos. It's not back pressure but more about exhaust velocity, laminar flow, and scavenging, all of which are hard to predict. A larger diameter pipe may trigger a slower exhaust velocity and less exhaust scamvenging.

That may be why my original aftermarket didn't perform as well at low RPMs, slower exhausts velocity, less laminar flow, and less exhaust scavenging from stock.
 

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Answered my own question with some youtube videos. It's not back pressure but more about exhaust velocity, laminar flow, and scavenging, all of which are hard to predict. A larger diameter pipe may trigger a slower exhaust velocity and less exhaust scamvenging.

That may be why my original aftermarket didn't perform as well at low RPMs, slower exhausts velocity, less laminar flow, and less exhaust scavenging from stock.
Were you tuning your fueling to the exhaust changes ?
 

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Discussion Starter · #4 ·
Not at that time, I didn't have access to a tuner. It was a Revo 6'. Not sure if it would have made a difference. I never have seen a dyno for a reco exhaust system.
 

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2008 M109R, 2016 FJR1300, 1999 VMax
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I rember people discussing 2 into 1 pipes long ago, and it was mentioned that collector design is extremely important.
Also, the stock exhaust is 2 into 1 into 2. Aftermarket dual exhaust will not perform as well as a 2 into 1, due to the lack of scavenging. Having said that, I have heard that Big shots perform reasonably well (IF they are still available.)
The best performing pipes for the 9 are no longer available, although I have never seen a Dyno run with the Revo exhaust.
 
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