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Discussion Starter · #1 ·
I just bought the 04 R1 and was wondering how to hollow out the catalytic converter.

Has anyone done this yet? Any noise difference?
 

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The `Shocking` Truth
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Why not just switch to an after market pipe? What you really need to do is ditch the EXUP system to bring up the torque curve.
 

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Drinking Colt 45's with Lando
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Beat it out with a screw driver. There is a post on this, I will try to find out. I think there are some good diections in it.
 

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technobug said:
Why not just switch to an after market pipe? What you really need to do is ditch the EXUP system to bring up the torque curve.
This is not correct. The EXUP is there to boost torque at lower RPM. Removing the EXUP will gain you some top end HP at the expense of torque.
 

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Insanity Please
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cranky1 said:
This is not correct. The EXUP is there to boost torque at lower RPM. Removing the EXUP will gain you some top end HP at the expense of torque.
I agree Cranky1, I don't think the rocket scientists at Yamaha put the EXUP there by accident, as I won't be removing mine. Why get rid of Titanium when you already have it. Slip-ons for me eventually, that is when my :bow 04R1 :bow turns up....:dunno
 

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cranky1 said:
This is not correct. The EXUP is there to boost torque at lower RPM. Removing the EXUP will gain you some top end HP at the expense of torque.
That is the stated theory! However, there is another explaination that states the purpose of the valve it to quiet the exhaust so that a stock bike can pass noise testing and also have a louder exhaust (with less back pressure) at higher revs. Regardless, all full systems that eliminate the EXUP system seem to also fix the dip! So, the EXUP system is probably the culprit.
 

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Insanity Please
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Speaking of power dips, some dyno guys have said that the CAT could be the culprit for the 5-6,000 mid-range dip. Interesting point about the EXUP though.
 

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The `Shocking` Truth
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Thanks for the comments Cranky and Warp, but you guys have obviously bought into the marketing hoopla. Wait a little while until all the pipe manufacturers start posting dyno curves. There are some SERIOUS improvements made by ditching the EXUP. Rideability may suffer but power gains are large.

Lion- percisely!
The EXUP prolly tames the injection mapping down low to give better throttle feel, and smooth out any hesitation. However it does this by putting a large hole in the torque band. With EXUP is prolly the better choice for street riding though.
 

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Discussion Starter · #9 ·
Do you just hammer the screwdriver into the cat? Won't you restrict any flow if this is not done properly?
 

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I'm just guessing, but Im thinking, the exhaust is coming out so fast, at the point right before the dip, the exhaust gets trapped before the catalytic converter and pressure builds. Finally, after the dip is over, the exhaust gas, of course gets through the restrictive cat, and the powerband looks normal again. Try and visualize the airflow in the pipes, from what I am trying to explain.
 

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Insanity Please
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What surpirses me, is that you can get high flow/volume CAT's in aftermarket situatiions, one would think that the same be possible in this situation or is alreayd fitted....

I'll raise the flag for streetability as well, when it comes to the EXUP, but time will tell..

Cheers, Warp
 
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