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Discussion Starter #1
Hi all,
just wanted to know what the best option is for deleting the cat on my bike. From my understanding, there is no link pipe? So I would have to cut and weld? Is it a difficult job to do myself and if I opt for someone else to do it, how long should it take them so I can estimate the labour cost?
 

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Discussion Starter #2
UPDATE spoke to my MV dealer. His opinion is that it’s not worth work considering it’s a high flow cat anyway and the sound wouldn’t change so much? Is this true?
 

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High flow yes but still restrictive. I've de-cated a few.

Not difficult to do. I can send some pics of where to cut. Then if you are lucky you can drive the Cat out. If not then it a cut and remove. Then just Tig it back up.

Certainly sounds different after.
 

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Discussion Starter #5
High flow yes but still restrictive. I've de-cated a few.

Not difficult to do. I can send some pics of where to cut. Then if you are lucky you can drive the Cat out. If not then it a cut and remove. Then just Tig it back up.

Certainly sounds different after.
So you think it is a good option for now so I can see what it sounds like and if it doesn’t change the sound enough, I order the inox manifold (considering it will cost me $1400AUD and the cat delete will cost maybe 10% of that)?
Also you say it changes the sound? A lot louder or just enough to notice?
 

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So when I de-cat headers its £80, you are on the wrong side of the planet to me. But yes 80 to 120 would be about correct for a de-cat, assuming you add in a 18mm boss (do this) for a WB sensor. You can always take a second hand set of flee bay, and mod those. Any set from 2010 will fit. The only difference is the pre 2013 has an 18 not a 12mm lambda sensor mount, you you would need to add a 12 mm sensor to these headers

Sound, well its a little louder, although this will be impacted by the end can(s) you have. The tone also changed, it mad mine sounds a little more aggressive or edgy if that's make sense. Additionally you remove the large thermal mass that the Cat creates right next to the brake master cylinder.

From a CFD perspective, the Cat is Quite restrictive, I'll measure the resistance to flow later SRT(pressure drop) / Flow, but at 5000 to 5500 L/min the pressure drop will be quite large.
 

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Discussion Starter #7
So with my 2015. If I opt for a decat, I just use the same sensor and that’s it. Just a cut, remove cat and weld back up whereas if I was to buy the Inox manifold I would need to add a 18mm boss to it? Or am I totally off?
I have the Arrow RG4 end cans. Are they that much different to stock end pipes as far as sound is concerned?

So when I de-cat headers its £80, you are on the wrong side of the planet to me. But yes 80 to 120 would be about correct for a de-cat, assuming you add in a 18mm boss (do this) for a WB sensor. You can always take a second hand set of flee bay, and mod those. Any set from 2010 will fit. The only difference is the pre 2013 has an 18 not a 12mm lambda sensor mount, you you would need to add a 12 mm sensor to these headers

Sound, well its a little louder, although this will be impacted by the end can(s) you have. The tone also changed, it mad mine sounds a little more aggressive or edgy if that's make sense. Additionally you remove the large thermal mass that the Cat creates right next to the brake master cylinder.

From a CFD perspective, the Cat is Quite restrictive, I'll measure the resistance to flow later SRT(pressure drop) / Flow, but at 5000 to 5500 L/min the pressure drop will be quite large.
 

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So with my 2015. If I opt for a decat, I just use the same sensor and that’s it. Just a cut, remove cat and weld back up whereas if I was to buy the Inox manifold I would need to add a 18mm boss to it? Or am I totally off?
I have the Arrow RG4 end cans. Are they that much different to stock end pipes as far as sound is concerned?
@antovujica hey bro, you actually have the Arrow RG-7 exhaust. The RG-4 is an older version. I know because I have the RG-7 on my F4.

I had it installed after the first service and honestly I personally don't think there is any difference in sound compared to the stock exhaust.
And to be honest I was very pissed off because I paid $2,500 for it. It even has the same markings underneath stating it's the same decibel level as the original.

De-catting will definitely give you a slight increase in sound (loudness) but not as much as you would probably be hoping for.
476514
476515
 

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@antovujica hey bro, you actually have the Arrow RG-7 exhaust. The RG-4 is an older version. I know because I have the RG-7 on my F4.

I had it installed after the first service and honestly I personally don't think there is any difference in sound compared to the stock exhaust.
And to be honest I was very pissed off because I paid $2,500 for it. It even has the same markings underneath stating it's the same decibel level as the original.

De-catting will definitely give you a slight increase in sound (loudness) but not as much as you would probably be hoping for.
View attachment 476514 View attachment 476515
Yeah right! I noticed the markings too and wasn’t 100% sure if it was just stock pipes with the arrow end caps because it doesn’t sound as good as the bike looks. Have you had your cat deleted? I think I might just buy the inox manifold to get the results I want.
 

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@antovujica I still have the cat in, I am going to buy inox manifold as well, it's recommended that you buy the ECU to match or get your current ECU set to full system specific tune.
You already have ECU studio if I remember correctly? That's perfect for your set up.

Plus grab a hi-flow BMC air filter and it will definitely improve all round.

How is everything going with your quick shifter? Did you get it sorted?
 

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Discussion Starter #11
Yeah I have ECUstudio so I’ll be sweet. Couldn’t recommend the company more. They’ve been great with everything. Quickshifter works perfectly up and down. Has to modify the rod and buy a shift arm from an R1 so it wouldn’t hit the sprocket cover but that’s all irrelevant. I have all ROMs available to me plus I’m pretty sure it already has a race rom on it which assumes that you have an aftermarket exhaust. I’ll definitely look into the air filter as well. Will be ordering the inox manifold as soon as the heat from the current situation tapers off. Evolution bike got back to me and said they’ve had no issues with shipping though...
 

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Discussion Starter #13
So when I de-cat headers its £80, you are on the wrong side of the planet to me. But yes 80 to 120 would be about correct for a de-cat, assuming you add in a 18mm boss (do this) for a WB sensor. You can always take a second hand set of flee bay, and mod those. Any set from 2010 will fit. The only difference is the pre 2013 has an 18 not a 12mm lambda sensor mount, you you would need to add a 12 mm sensor to these headers

Sound, well its a little louder, although this will be impacted by the end can(s) you have. The tone also changed, it mad mine sounds a little more aggressive or edgy if that's make sense. Additionally you remove the large thermal mass that the Cat creates right next to the brake master cylinder.

From a CFD perspective, the Cat is Quite restrictive, I'll measure the resistance to flow later SRT(pressure drop) / Flow, but at 5000 to 5500 L/min the pressure drop will be quite large.
sorry mate, just wanted to make 100% sense of this. So if I de cat the stock pipes it’s just a cut and weld? And if I buy the inox headers from evolution bike I’ll have to mod the O2 sensor?

heavily contemplating just doing the de cat, considering the inox headers are stainless steel and not titanium. Surely not that different to a decatted stock pipe?
 

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Yep just a cut remove and reweld. not difficult at all

The headers on the MV's are disappointing when you compare weights to a GSXR etc. The aftermarket might be a little lighter and look nicer too, the only difference is that CAT area. I welded in a new tube inside the CAT to control the gas flow and expansion, most people don't bother. That's the only area of real difference for me. Reality is +/- 2 bhp or so between decat and full headers matched to your end can etc. On a big bike, its not that much to worry about IMO
 

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Discussion Starter #15
Yeah fair enough. And if all I’m looking for is a little more aggressive note from the exhaust, then a decat isn’t a bad option? Would the sound be THAT different between a decat and the inox headers?
 

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Discussion Starter #17

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Deleted because link didn't work.
 

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@antovujica sorry try this.
 
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