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Hi all.
knew to this forum so pleasure to be here, have a new purchase a 2005 R1. It’s more of a project to mod and play with. Wanted to ask as not seen anything regarding this. If I remove the Exup, does that have any bearing on the mot and emission tests. Also is there any good videos or explanation how to do the mod, been looking but not much out there.


again thanks and great to be here
 

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Hi all.
knew to this forum so pleasure to be here, have a new purchase a 2005 R1. It’s more of a project to mod and play with. Wanted to ask as not seen anything regarding this. If I remove the Exup, does that have any bearing on the mot and emission tests. Also is there any good videos or explanation how to do the mod, been looking but not much out there.


again thanks and great to be here
I've got an 04 and honestly couldn't say. My immediate thought is that it would. Fortunately I don't have to deal with emissions in my state.
 

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Registered
Joined
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58 Posts
Hi all.
knew to this forum so pleasure to be here, have a new purchase a 2005 R1. It’s more of a project to mod and play with. Wanted to ask as not seen anything regarding this. If I remove the Exup, does that have any bearing on the mot and emission tests. Also is there any good videos or explanation how to do the mod, been looking but not much out there.


again thanks and great to be here
PEG Grinder however wrote this a while ago.
Nov 25, 2006

EXUP Explained. The EXUP valve found in Yamaha's sportbikes has nothing to do with emission or noise control.

What it is. - It is a rotating guillotine valve (like a big petcock valve) that increases or decreases the amount of exhaust flow through the exhaust system and is controlled by engine rpm.

Why it's there. - To increase the speed of exhaust flow during low to mid-range rpm operation. Using Bernoulli's equation that states that a gas flowing through a restriction in a pipe will both decrease pressure and increase velocity the EXUP valve provides an adjustable "orifice" to keep the exhaust gas velocity higher at low rpms.

Because of the overlap between exhaust and intake valves necessary for efficient high rpm operation, at lower rpms there is a tendency for exhaust gasses to be drawn back through the exhaust valve as it is still open during part of the intake stroke. This reduces combustion efficiency because part of the air/fuel charge is contaminated with exhaust gas (which doesn't burn because it already has burned on the last cycle)

By providing a restriction after the header pipes the EXUP valve increases the velocity of the exhaust gasses and tends to suck them through the pipes and away from the combustion chamber reducing the amount of gas drawn back in. By the time the motor is at 8000 rpm the valve is fully open and it's as if it weren't there.

Removing the EXUP will only effect low-mid range operation, some torque will be lost and surging will occur as the stock map tries to make adjustments for the loss of combustion chamber efficiency due to the exhaust gas contamination.
 
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