Arrow Thunder db killer modify - MVAgusta.net
 
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post #1 of 10 (permalink) Old 12-15-2016, 10:51 AM Thread Starter
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Arrow Thunder db killer modify

Hi there,

I have just purchased an Arrow Thunder in carbon fibre,
very happy with the looks and the fitment BUT I need to try and quieten it down a bit.
Its starting to attract the kind of attention I don't want, you can now here me well before you see me !
I have purchased another db killer so that I can have a play around modifying it without ruining the original one, if you know what I mean.
I have attached a couple of photos to give you an idea of what it looks like in standard form.
There are 3 rows of "5 holes" - 15 holes in total drilled in to its length.
If I cover up 2 rows of holes - 6 in total, by what ever means. would this cause any troublesome problems for the engine, eg. back pressure.
Before you start saying that I do not know what i'm talking about, I don't, that's why i'm asking for your expert knowledge
I look forward to your help.

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post #2 of 10 (permalink) Old 12-15-2016, 12:45 PM
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how is the original one? an open pipe without holes?
The I would try first like this how noise is, holes can be closed later.
yes it will affect flow and therefor also mixture. so every mod might need adjusting mapping for optimum.
Like with or without db killer

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Last edited by hb88xx; 12-15-2016 at 12:49 PM.
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post #3 of 10 (permalink) Old 12-15-2016, 01:00 PM
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arrow sometimes delivers both typees of db killers
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post #4 of 10 (permalink) Old 12-15-2016, 04:16 PM
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Quote:
Originally Posted by brutale jockey View Post
Hi there,

I have just purchased an Arrow Thunder in carbon fibre,
very happy with the looks and the fitment BUT I need to try and quieten it down a bit.
Its starting to attract the kind of attention I don't want, you can now here me well before you see me !
I have purchased another db killer so that I can have a play around modifying it without ruining the original one, if you know what I mean.
I have attached a couple of photos to give you an idea of what it looks like in standard form.
There are 3 rows of "5 holes" - 15 holes in total drilled in to its length.
If I cover up 2 rows of holes - 6 in total, by what ever means. would this cause any troublesome problems for the engine, eg. back pressure.
Before you start saying that I do not know what i'm talking about, I don't, that's why i'm asking for your expert knowledge
I look forward to your help.

brutale jockey
Have you a machine shop near you.Those baffles would be easy to make.or you could have the holes welded up.


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post #5 of 10 (permalink) Old 12-15-2016, 04:17 PM Thread Starter
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Hi there,

I have not removed the original db killer, as the exhaust and spare db killer both turned up at the same time, I just thought they would both be identical.
I ordered the spare db killer from an official Arrow supplier and gave him the part number I got from the Arrow Italy website - spare parts for Arrow thunder exhausts.
I must admit that when I saw the "dome" welded on the end of the killer, I was surprised, I thought it would be straight through like the one you extracted from your Arrow thunder exhaust.
Any more info would be nice

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post #6 of 10 (permalink) Old 12-15-2016, 06:36 PM
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Quote:
Originally Posted by brutale jockey View Post
Hi there,

I have not removed the original db killer, as the exhaust and spare db killer both turned up at the same time, I just thought they would both be identical.
I ordered the spare db killer from an official Arrow supplier and gave him the part number I got from the Arrow Italy website - spare parts for Arrow thunder exhausts.
I must admit that when I saw the "dome" welded on the end of the killer, I was surprised, I thought it would be straight through like the one you extracted from your Arrow thunder exhaust.
Any more info would be nice

brutale jockey
The "dome" welded is pretty standard. Its the same on my MV Corse pipes. Just weld up some of the holes. Start with 1 row first.. the closest to the tail if you want to start somewhere?

Cheers, Simon


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post #7 of 10 (permalink) Old 12-15-2016, 08:09 PM
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So it looks like there are 3 different dB Killers

if your's with the 15 holes are too loud wrap a narrow strip of sheet metal around it and

secure with a hose clamp..... starting with the rear holes .....still too loud?

use a wider strip of sheet metal.....

ideally you'd want to stagger the blocked holes to disrupt the shock wave .....so you

have less back pressure......

Me ? my dB Killers are long gone.......no sound test/requirement in California



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post #8 of 10 (permalink) Old 12-16-2016, 04:53 PM Thread Starter
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Thanks for that Noel,

I have just told my other half that we are moving to California, great weather and NO sound tests !

That's a good idea about staggering the holes, thanks again

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post #9 of 10 (permalink) Old 12-17-2016, 08:26 PM
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Neil;
and everyone think of the pressure pulse as a line across the pipe......you want to break

this up mechanically if possible.....if you make 90 corners .....with the holes you're

getting the pulse edgewise not head on where the amplitude (pressure) is way higher

After thinking about it I think an angled cap would be better than a dome because it

makes the center of the pulse bounce around inside the can

and it doesn't increase back pressure....as long as the area of the exit doesn't get small


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post #10 of 10 (permalink) Old 12-18-2016, 06:05 AM
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Quote:
Originally Posted by theknurl View Post
Neil;
and everyone think of the pressure pulse as a line across the pipe......you want to break

this up mechanically if possible.....if you make 90 corners .....with the holes you're

getting the pulse edgewise not head on where the amplitude (pressure) is way higher

After thinking about it I think an angled cap would be better than a dome because it

makes the center of the pulse bounce around inside the can

and it doesn't increase back pressure....as long as the area of the exit doesn't get small

Maybe rifle the bore of the can, or add a twist to the db killer to speed the pulses along as well.

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