ANYONE GONE FROM LOUD PIPES BACK TO STANDARD?

My secondhand 2007 1250 S came with a locally (South African) made Stealth brand canister. I’ve no idea how the Stealth and the original compare. The Stealth’s tone isn’t bad, but for that pop-pop-pop noise on the overrun.

In a previous incarnation I experimented with BMW exhausts and found the whisper-quiet original BMW exhaust excellent, if heavy.

My Bandit being in for repair after a recent mishap, I’ve got the pleasant choice between repairing the Stealth, or repairing a secondhand standard silencer and getting the bike back to original.

Question: aural aesthetics aside, can anyone vouch for originals vs aftermarkets or vice versa? Does your aftermarket make that popping noise after you shut the throttle?
 
Regards
Stan L
South Africa

The original is a lot heavier than most aftermarket cans.  It has a lot more suppression packing to quieten down the exhaust.  The popping noise you hear is unburnt fuel being pushed from the combustion chamber into the hot exhaust system and igniting.  

When you overrun, the ECU and injectors haven't had time to cut the fuel flow thus making the exhaust mixture a lot richer than normal.  It is made worse by the PAIRS (Pulsed Secondary AiR Injection System) that allows fresh air into the exhaust to dilute the mixture so as to pass emission standards.  Never did understand the logic of PAIRS, there is still the same amount of hydrocarbons being dumped out the exhaust port, but they fudge the EPA reading by diluting the ambient mixture with more fresh air.

When you replace the can, the unburnt gas ignition is now heard even more due to the unrestricted exhaust.  

One way to eliminate the majority of this popping is to remove the PAIRS setup, either entirely of by plugging up some rubber tubes, if you search on here there is a how-to buried somewhere in here. 



In the above photos the black pipes and black alloy covers have been removed and the exhaust port is covered with the two plates with the red gasket goo on them.  The gold resistor imitates the PAIRS solenoid so as not to put up and alarm condition.

barry_mcki wrote:  Never did understand the logic of PAIRS, there is still the same amount of hydrocarbons being dumped out the exhaust port, but they fudge the EPA reading by diluting the ambient mixture with more fresh air.

My understanding of this was when  the air was injected into the can, it changed the fuel/air mixture and allowed the excess fuel to ignite and be burnt off, the original can's packing supressed the combustion sound.

Once the fuel has burnt off the hydrocarbons escaping the exhaust are reduced.

I may be wrong though .................................

Chook wrote:

barry_mcki wrote:  Never did understand the logic of PAIRS, there is still the same amount of hydrocarbons being dumped out the exhaust port, but they fudge the EPA reading by diluting the ambient mixture with more fresh air.

My understanding of this was when  the air was injected into the can, it changed the fuel/air mixture and allowed the excess fuel to ignite and be burnt off, the original can's packing supressed the combustion sound.

Once the fuel has burnt off the hydrocarbons escaping the exhaust are reduced.

I may be wrong though .................................

I'll second that, no air no ignition no burn off no pop.
Valve overlap also contributes to unburnt fuel in exhaust. 
Sensors either side of the cat continually monitor emission. 

Anything that was unburnt  in exhaust  would show up as a fuel rich exhaust emission and fail EU emission test.
At least this works full time, not like the system that VW used on it's cars that registered it was being tested and then altered fuel input to be super lean, then returned back after testing.

https://www.youtube.com/watch?v=_xMykbzJWiQ

Nothing wrong with a stock can , except weight  and maybe size . .In a small " get off " on rhs the large stock pipe can push against the swing arm and bend the swing arm . (unfortunately ) .

It is hard to hear popping with the stock can because it so so restrictive. Most aftermarket cans are a lot less restrictive with a straight through core thus you will hear the popping. Easiest and free way to stop the popping is to plug the air injection hose from the airbox at the junction. Otherwise remove the PAIR system which not only stops the popping but reduces weight and cleans up the top of the cylinder head thus giving easier access to maintenance items. Remember, if tuning with the air injection connected it is much more difficult to maintain ideal AFR. If keeping bike completely stock then it can be connected, if changing any items such as exhaust can, header or intake - a tune is definitely needed and the air injection should be blocked.

Ive  had stacks of after market exhausts but never had one that pops without being able to stop it . Normally its sucking air in at the muffler join on over run . Some people like the sound ,i detest it . It says to me ,some it wrong with the tune of the bike . A bike on over-run should sound Brrrrrrrr not Brrr-pop -brrr- fart -crackle -bang . Balance the carbs and turn in fuel mixture screws (or out )

gus wrote:A bike on over-run should sound Brrrrrrrr not Brrr-pop -brrr- fart -crackle -bang. 

My sentiment exactly. I've told the dealer to source a used original from a breaker.

I bought my bike with an unbaffled Ixil slip-on on the stock pipes, it was loud, farted and popped on like crazy on the overrun and droned annoyingly at highway speeds. Ordered a set of baffles for it and it’s about perfect now. If there’s a reduction in power it’s only at the top end and worth the trade-off in manners. And the popping is pretty much gone. I could easily open it up a little more by drilling some extra holes in the baffle tube too.

Don't think Ixil are umm, "legal" for the road.
Don't think they would pass the 4k rpm decibel test without a baffle.

GSX1100G wrote:Don't think Ixil are umm, "legal" for the road.
Don't think they would pass the 4k rpm decibel test without a baffle.

Where I live, noise is a non-issue. It's not the actual volume I'm concerned with, it's that popping noise.

Regards
Stan L
South Africa

GSX1100G wrote:Don't think Ixil are umm, "legal" for the road.
Don't think they would pass the 4k rpm decibel test without a baffle.

With the baffles I reckon it’s legal, it’s not loud at all now, just sounds a bit sporty for want of a better term. Without the baffles... yeah, it was definitely asking for it.

It wasn’t the general volume or popping that was the dealbreaker for me though, it was the drone. It just made highway cruising unnecessarily fatiguing, if I’m just cruising along at 80/100/120 I don’t expect to really hear my exhaust at all unless I crack the throttle to overtake. I bought the bike to do some big on rides on and I want them to be enjoyable.