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post #1 of 7 (permalink) Old 09-08-2014, 05:18 AM Thread Starter
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Why??

Okay, I have a 2004 750 Brutale running on standard (as far as I am aware) ECU and chip. Following a chance purchase of link pipe and arrow silencers, I fitted them to the bike removing the standard (but gorgeous) silencers and the cat/collector box.



The crackle from the arrows was quite impressive and after a few runs I noted that although the bike initially seemed more responsive above 6K, it would occasionally cut out as I dropped the revs when approaching junctions. It also felt a increasingly woolly between 2-5 K revs. In fact it got to the point where I though I'm going to put the standard silencers back on

As I was using the bike for work yesterday and would be heading out early I dropped in the DB killers that came with the silencers (I like my neighbours) . On the run into work, it felt like a different bike. Okay more muted but it felt smoother, the woolliness had disappeared and no cutting out when coming off the revs. Just to be sure I took it out again today for about 80 miles and it definitely performs better with the DB killers in

Is it possible that the open silencers upset the fuelling?? I know with my T509 Speed Triple I have to alter the map to suit whichever silencer I am running and the bike is incredibly sensitive to the issue.

Anybody else experienced this??
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post #2 of 7 (permalink) Old 09-08-2014, 05:34 AM
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Open silencers usually will make the motor lean out. If your too lean, it's possible to melt a piston or two. So I'd be careful in your case. I'm not sure by what you mean by the bike acting "Woolley", but a lean motor has too crisp of a throttle response, better gas mileage and could run hot.

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post #3 of 7 (permalink) Old 09-08-2014, 05:50 AM
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Bottom line is...YES.....the open pipes require different ECU mapping. The dB killers essentially put the pipes back close to stock in performance (lighter and sounds a bit better, some would say looks better).

Contrary to popular belief, sometimes open pipes will actually make a bike run more rich. There is a lot more to exhaust system design then sound.

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post #4 of 7 (permalink) Old 09-08-2014, 06:18 AM
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Also Back pressure is effected,Fueling will be out by miles.Some people live with it,I cant ,I actually have mine Dyno tuned once a year.so I know my fuel mixture is correct.

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post #5 of 7 (permalink) Old 09-08-2014, 06:26 AM Thread Starter
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Thanks all for the quick responses, you have confirmed my suspicions, I'll leave the DB killers in as I also like the sound with them fitted.
I have a microtec ECU which I want fitted in the near future so I'll be getting the bike dyno'd at that point anyway.

Are the free-flow air filters that I see advertised eg DNA, BMC, worth the money??
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post #6 of 7 (permalink) Old 09-08-2014, 08:35 AM
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Quote:
Originally Posted by Fentible View Post
Thanks all for the quick responses, you have confirmed my suspicions, I'll leave the DB killers in as I also like the sound with them fitted.
I have a microtec ECU which I want fitted in the near future so I'll be getting the bike dyno'd at that point anyway.

Are the free-flow air filters that I see advertised eg DNA, BMC, worth the money??
Definitely. I had a BMC one fitted and when Chris installed and set up the Microtec he couldn't get it as he wanted. There was a slight dip in the mid-range no matter what he tried.

He tried an MWR filter instead and it lifted the mid-range up perfectly.

Obviously every bike is different with unique set ups so probably worth discussing with your Dyno guy first.
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post #7 of 7 (permalink) Old 09-08-2014, 10:50 AM Thread Starter
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Originally Posted by biaggi View Post
Obviously every bike is different with unique set ups so probably worth discussing with your Dyno guy first.
Thanks for the heads up Biaggi, its Chris I will be taking the bike to anyway.
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