Exup?

[Ruggybuggy]

What is the purpose of the Exup system on the stock muffler? Why did Yamaha install it and how does it work? I'm going to install an aftermarket exhaust and this has to be removed and kinda wondering if it can be removed why was it used in the first place.

 

[a7x3797]

Its a 'butterfly' valve in the mid-pipe that rotates to different positions at different times in the RPM range. Yes it will have to be removed for aftermarket exhaust. There is a Youtube video by Copperdawg on how to do it, basically remove the cables, but leave the servo plugged in to prevent a code being thrown. simple job, took me 15 minutes. The function of this valve is to 1.) Lower the db level of the exhaust in the higher RPM and 2.) create necessary back-pressure based on the stock engines performance.

 

[WABBMW]

I was curious as to just when the EXUP butterfly valve ever opened or closed, on my Gen II, so I bolted an indicator "arm" to the unit. Rode the motorcycle at all RPMs, under every conceivable load/RPM combination. Discovered that it stayed wide open all the time. I believe the Gen I units did function somewhat, but I don't know how effective they are. So especially on the Gen II, why even have it in place?

I believe that Yamaha heavily advertised this device in years past, and is embarrased to say that it is ineffective. I hope I am wrong about this. Hear people talking about sound abatement. Perhaps there is something to this, but I simply never saw the EXUP move from the wide open position.

Anyway, it is easy enough to remove and to deal with the cables and solenoid. There are meny posts about this. Copperdog is excellent.

 

[Hellgate]

EXUP has been around for decades. Two fuctions, 1) reduce sound emissions at inspected rpms, 2) increase the torque spread over the power band. Many MFG's use an EXUP like system. Even MotoGP bikes.

My Aprilia has one too. Works great.

 

[eurban]

Plenty of info on this topic on both FZ sites. Search! . . .

The EXUP on the GenII has no significant performance benefit but rather functions to help reduce the sound output of the exhaust system.
You will not miss it at all when you install your slipon or full system.

On the GenI and certainly on many other bikes the system is effective at improving the "torque spread". Not so on the GenII . . .

 

[NJFZ1]

...
On the GenI and certainly on many other bikes the system is effective at improving the "torque spread". Not so on the GenII . . .

That is correct. If you look at the EXUP on both the Gen I and Gen II you'll quickly see that they are in two totally different positions within the exhaust.