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Discussion Starter #1
I am stripping an 08 R1 to put engine and associated bits into a car.
Got a question about the ex-up valve.
What is its true purpose? Back pressure mapping? Sound deadening? Emissions?
Any help would be great.
Ideally would probably delete but need to know all the facts.

R1.. The fast kind
1,018 Posts
According to Yamaha its purpose is to improve low and midrange torque.

I guess there's people out there that can vauge for that.

Others think it's a kind of sound dampening device to pass noise regulations.

When i got my ECU flashed with YEC/YMS software i removed the entire EXUP butterfly assembly since the servomotor isn't supported anyway, i also fitted linkpipe (decat) and slipons.

Thanks to the unrestricted software the low and midrange improved even though the EXUP was gone..

Many years ago i made a simple investigation of the -07 EXUP and found it was only responding to rpm and it opened 100% before 4000rpm

To be honest i can't say how important the EXUP is since i havn't tested it on a dyno...

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