Popping and flames....

[Jumblemo]

According to Akrapovic on the NN website:

" 'popping' or backfiring on the overrun are due to air leaks in the system. On overrun a vacuum forms in the system and air will be drawn in through any gaps and may even cause flames to appear out of the back of the exhaust."

So the question I have is where is the best place in the exhaust system to create an air gap, and how?

 

[Timolgra]

The big hole at the end

 

[Fluffmeister]

The big hole at the end

:

 

[Timolgra]

t:

.....

 

[Wizard]

You need to be careful to do it properly. Mark the centre of the bottom of the collector box, and move 10mm to the FRONT OFFSIDE before drilling with 24mm hole cutter. It has to be exact, of the airflow won't be right and it'll sound like a dodgy Corsa

 

[Jumblemo]

You need to be careful to do it properly. Mark the centre of the bottom of the collector box, and move 10mm to the FRONT OFFSIDE before drilling with 24mm hole cutter. It has to be exact, of the airflow won't be right and it'll sound like a dodgy Corsa

Sounds risky. I might try it on the original BMW collector once my Akra version gets here to make sure I get it right on the Akra

 

[Wizard]

Sounds risky. I might try it on the original BMW collector once my Akra version gets here to make sure I get it right on the Akra

Well, it's not for the faint hearted, that's for sure. But if it all goes wrong, just slap a bandaid over it

 

[Bionicmunky]

Well, it's not for the faint hearted, that's for sure. But if it all goes wrong, just slap a bandaid over it

Nah, if you set the drill at a slow speed and use lots of lube, you can save the cutout from the hole saw and use J-B Weld to pop it back in if it all goes wrong.

Also, 24mm is a bit on the wide side in my opinion, if you go 18mm it'll create a turbo like whistle under heavy acceleration adding to the overall effect

 

[Wizard]

Nah, if you set the drill at a slow speed and use lots of lube, you can save the cutout from the hole saw and use J-B Weld to pop it back in if it all goes wrong.

Also, 24mm is a bit on the wide side in my opinion, if you go 18mm it'll create a turbo like whistle under heavy acceleration adding to the overall effect

Ooooh........... ELECTRONIC DUMP VALVE!

 

[duckspeed]

According to Akrapovic on the NN website:

" 'popping' or backfiring on the overrun are due to air leaks in the system. On overrun a vacuum forms in the system and air will be drawn in through any gaps and may even cause flames to appear out of the back of the exhaust."

So the question I have is where is the best place in the exhaust system to create an air gap, and how?

Am I missing the point here? There should not be any leaks in the exhaust system, and cutting a bloody great hole in it makes no sense at all !

 

[Jumblemo]

Am I missing the point here? There should not be any leaks in the exhaust system, and cutting a bloody great hole in it makes no sense at all !

I'm confused by your post???!? How else would you propose one enables the exhaust system to produce 'popping' and flames on the overrun without the introduction of an air leak? Modern engineering standards have all but eliminated these desirable features.

 

[autogs]

its like shooting fish in a barrel in ere

 

[Nutty]

 

[Count]

Does anyone know if CherryBomb are making exhausts for the GS ?

Back in the day, these had the desired impact.

 

[Engineer]

According to Akrapovic on the NN website:

" 'popping' or backfiring on the overrun are due to air leaks in the system. On overrun a vacuum forms in the system and air will be drawn in through any gaps and may even cause flames to appear out of the back of the exhaust."

So the question I have is where is the best place in the exhaust system to create an air gap, and how?

Both my 2005 and 2010 GS's popped on the overrun and neither had leaks in the exhaust system, so why did they do that?

 

[Deleted account 211025001]

What I miss most about EFI bikes is hitting the engine kill on the over run and the subsequent rifle shot out of the exhaust

Andres

 

[Count]

Both my 2005 and 2010 GS's popped on the overrun and neither had leaks in the exhaust system, so why did they do that?

My Ducati sounds like a full on artillery assault dropping through the gears coming up to a junction, I can also modulate the throttle and induce pops and bangs if I want to be a hoolie (I do this A LOT).

I am not aware of any leaks but will now drill an 25mm wide hole in the collector as suggested - what could go wrong?

While I get the older brigade would prefer not to be reminded of trench-time at the Somme, I much prefer a noisy exhaust. I'm curious if the fuel choice makes a big difference as well, I think running higher Octane that burns slower (albeit with a higher flash point), means there is more likely to be some fuel that subsequently ignites in the exhaust and hence noise and the odd flame.

My advice, run higher octane fuel for a start and maybe, lay off drilling inch-wide holes all over the exhaust, ymmv.

 

[Jumblemo]

I minded to take a cautious approach and start as low as a 2 or 3mm hole. It's easier to drill larger holes than to fill ones that are too big. And the collector sets are quite pricey so I'd hate to ruin one.

 

[Jumblemo]

Both my 2005 and 2010 GS's popped on the overrun and neither had leaks in the exhaust system, so why did they do that?

Those older bikes had much poorer engineering quality, tolerances were no where near as fine as your new WC. So though you thought they had no leaks the evidence suggests oxygen was getting mixed into the hot exhaust gas stream.

It's those weaker tolerances that was part of the reason why bikes like the 1150 wheezed and ran out of power before redlining. Sort of akin to Austin Allegro panel gaps.

 

[Ogmios]

Timolgra,
mind yourself!