Akra slip on - What is the inside diameter on exit side? - KTM Forums: KTM Motorcycle Forum
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post #1 of 18 (permalink) Old 04-12-2019, 12:12 PM Thread Starter
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Akra slip on - What is the inside diameter on exit side?

Folks - Would anyone be so kind to measure the inside diameter of the Akrapovic 1290 Super Duke R slip-on (DB killer removed)? It has to be measured in a certain way as the tip is "slash cut" so you need to place the caliper a certain way ...or as in the pictures....you gear heads would understand....

I may have an interesting project ...
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post #2 of 18 (permalink) Old 04-12-2019, 12:22 PM Thread Starter
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I may make my own carbon silencer for the 1290....I picked this brand new authentic Akrapovic (looks absolutely stunning in person) locally however it was for a different bike - I hope to make it work with some work on the inlet side for a fraction of the cost of new powerports titanium slip on..
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post #3 of 18 (permalink) Old 04-13-2019, 07:27 AM
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just do it , ive pulled a few akra open now , nothing alien inside, standard geometry.

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post #4 of 18 (permalink) Old 04-13-2019, 12:03 PM Thread Starter
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Quote:
Originally Posted by cors187 View Post
just do it , ive pulled a few akra open now , nothing alien inside, standard geometry.
Thanks...I've confirmed my suspicion that my carbon fiber silencer inside diameter is the same as the one offered by KTM power parts (makes sense from Akrapovic's use of economies of scale) however they are doing something funky on the inlet side.

I've done a lot of reading on threads of people wanting to do what I'm planning but they were shot down as they were told you cant put on a silencer slip on that has an internal diameter less that the collector outlet... Well folks, that's exactly what KTM Powerparts is doing when you buy the titanium slip on ...the internal diameter is ~54mm.

The outlet of the cat/collector is ~60mm outside diameter (not sure if the internal diameter - in the process of verifying this) ....so there appears to be some slight reduction..anyone with an Akrapovic slip-on handy ? kindly post some pictures of the inlet...
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post #5 of 18 (permalink) Old 04-13-2019, 12:11 PM Thread Starter
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This is the inlet of the OEM silencer - no internal diameter reduction on the inlet....would love to see the equivalent picture for the Akra slip on...
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post #6 of 18 (permalink) Old 04-13-2019, 01:28 PM
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Wasn't sure what you reffered to as I'm on mobile. But often and I think it's normal to have header size, then collector size which is bigger and then back to something in between header and collector.
@AusPete loves to talk pipes. @augiedoggie prolly in his workshop with a welder right now.. @sparty is prolly drunk but has had his finger in more holes that the 4 of us.
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post #7 of 18 (permalink) Old 04-14-2019, 10:22 AM Thread Starter
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I can't wait to put this on the SDR......

Here are some measurements in case anyone needs them.

The silencer is the same length as the Akrapovic slip-on offered through Powerparts - I may shorten it by 5cm to be the same length as the silencer included with the full system..

I will need to source/make and adapter/coupling and have it precisely welded on ..once that's done I'll consider shortening the silencer.
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post #8 of 18 (permalink) Old 04-14-2019, 12:56 PM
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noise patrol checking in

i received pm and link but unable to study it properly yet. i wanted to check in on public forum in the interest of sharing your worthy experiment. i had a slight misconception regarding original focus of your modifications goals. brief study indicated the inlet size would neck down/reduce muffler inlet from inlet pipe. this is not an uncommon practice. exhaust velocity is sometimes deliberately increased by reducing a muffler inlet size. muffler baffle screen size affects exhaust flow differently than a solid pipe. sound control is affected by baffle screen size and reduced diameter is sometimes required for softer exhaust note. diameter of insert and length of canister are both critical to restriction/back pressure and exhaust note. larger insert makes it more throaty sounding. shorter canister makes exhaust note a bit more raspy. changes to either size in the smallest amount can make huge changes to performance but sometimes do very little to change exhaust sound level. dont be afraid to put a smaller muffler inlet on and experiment. you may find the result surprising. i would offer most riders would prefer a quality exhaust note/sound more than worry about extracting every ounce of power from motor. as long as power is not reduced anywhere and sound level is pleasant to the rider it should be considered a success.

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post #9 of 18 (permalink) Old 04-14-2019, 02:56 PM Thread Starter
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Quote:
Originally Posted by augiedoggie View Post
i received pm and link but unable to study it properly yet. i wanted to check in on public forum in the interest of sharing your worthy experiment. i had a slight misconception regarding original focus of your modifications goals. brief study indicated the inlet size would neck down/reduce muffler inlet from inlet pipe. this is not an uncommon practice. exhaust velocity is sometimes deliberately increased by reducing a muffler inlet size. muffler baffle screen size affects exhaust flow differently than a solid pipe. sound control is affected by baffle screen size and reduced diameter is sometimes required for softer exhaust note. diameter of insert and length of canister are both critical to restriction/back pressure and exhaust note. larger insert makes it more throaty sounding. shorter canister makes exhaust note a bit more raspy. changes to either size in the smallest amount can make huge changes to performance but sometimes do very little to change exhaust sound level. don't be afraid to put a smaller muffler inlet on and experiment. you may find the result surprising. i would offer most riders would prefer a quality exhaust note/sound more than worry about extracting every ounce of power from motor. as long as power is not reduced anywhere and sound level is pleasant to the rider it should be considered a success.
Thank you for your timely advice!

I will source/create a suitable adapter to mount this silencer on to the OEM collector and will keep the original length to start.
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post #10 of 18 (permalink) Old 04-14-2019, 04:44 PM Thread Starter
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Went to my local automotive/hardware store and was pleasantly surprised to find an adapter with dimensions that could be used... this would be cut down significantly on both sides...

Now I need to find a high quality one in stainless steel!
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