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#Post#: 1329--------------------------------------------------
EXUP
DIR By: KoosMT01
Date: August 6, 2021, 9:24 am
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Hi all,
I recently fitted DAM mufflers.
Now i notice something i dindnt notice with stock mufflers.
Looks like, when the bike is not moving, i can rev but its nog
so loud.
As soon when i start moving, sounds like the valve opens, even
at quite low revs already.
Can anybody tell me here when the valve opens? Has it to do with
the wheels turning, starting on certain rpms, or both?
Actualy i like it this way, not planning to change anything,
just curious what are the conditions to open up the EXUP valve.
#Post#: 1331--------------------------------------------------
Re: EXUP
DIR By: TimR
Date: August 9, 2021, 3:26 am
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Im guessing yours is an RP18 bike...?
Yamaha developed the original ExUp valve to affect a variable
exhaust back pressure to take advantage of the interaction with
valve timing and scavenging/overlap. The benefits are improved
intake/exhausting volumes, as I understand it. So called
volumetric efficiency. You'll learn that the ceiling to tuning
these engines arrives when you just cant get enough charge into
the chambers/past the valves....
By the time the RP18 was released, Yamaha had resorted to using
the ExUp valve to control aspects of the engine tune to satisfy
EU4.
ExUp is used to control noise levels so as to get past the
regs. They also limit the revs in certain gears, run it lean to
pass emissions by using the closed loop and O2 sensor and the
timing curve was (probably) tweaked...
You might think the ExUp is for the purpose of better
performance...It is. It just depends who you are performing for
I guess..!
Clear?
???
#Post#: 1333--------------------------------------------------
Re: EXUP
DIR By: omeo-mt01
Date: August 10, 2021, 6:46 pm
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wasnt it also something about improving torque, you know 'cause
the mt has so little of it.
Anyway its easy to wire open and should be.
#Post#: 1339--------------------------------------------------
Re: EXUP
DIR By: KoosMT01
Date: August 17, 2021, 2:29 pm
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--- Quote from: TimR link ---
>
> Im guessing yours is an RP18 bike...?
>
> Yamaha developed the original ExUp valve to affect a variable
exhaust back pressure to take advantage of the interaction with
valve timing and scavenging/overlap. The benefits are improved
intake/exhausting volumes, as I understand it. So called
volumetric efficiency. You'll learn that the ceiling to tuning
these engines arrives when you just cant get enough charge into
the chambers/past the valves....
> By the time the RP18 was released, Yamaha had resorted to
using the ExUp valve to control aspects of the engine tune to
satisfy EU4.
> ExUp is used to control noise levels so as to get past the
regs. They also limit the revs in certain gears, run it lean to
pass emissions by using the closed loop and O2 sensor and the
timing curve was (probably) tweaked...
> You might think the ExUp is for the purpose of better
performance...It is. It just depends who you are performing for
I guess..!
> Clear?
> ???
>
--- End Quote ---
Clear explanation.
Yes my bike is made 2007.
Is it also known when the valve exactly opens? a certain rpm?
#Post#: 1340--------------------------------------------------
Re: EXUP
DIR By: TimR
Date: August 18, 2021, 8:05 am
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ExUp was invented way before the MTO1 was even a twinkle in
Yamaha's R&D dept...
Mine's an RP12. A much better bike, obviously....!! ;D
As a stage 3 bike, it hasnt an ExUp, or O2 sensor (or closed
loop protocol) - meaning I long since stopped thinking about
it....
It is known. I would think the best person to ask would be
Micha, from the Donnermeister forum. He flashes these ECU's and
knows exactly what is , and isnt OEM ..
Im sure there are other's who also know, but there is,as you
have to expect on the internet, some common misconceptions
perpetuated online too...
HTH
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