exhaust popping
- Thread starter birdseye
- Start date
- the bike. A 2008 in bog standard trim, a backfire when I go onto a trailing throttle at low speed / revs. For exampl, stopping at traffic lights.
Dave Barrett
Registered user
Yes, this is normal and part of the charm of the earlier 1200s. It's caused by a small remainder of fuel being ignited by the hot catalyst.
I'm running standard on my 58 adv and it pops away 
My 2011 twin cam does it.
Me to 54 plate.
Roymondo
Registered user
On my 2011 twin cam it is a sign that the exhaust flap has seized (yet again)
chipsonfriday
Registered user
My 2006 GS did it until I installed an "Accelerator Module".
Chips
Chips
My 2008 gs does it a lot 
superglide
Registered user
My 2011 twin cam does it, so do I have a problem?
Deleted account Cooperman
Registered user
Enjoy 
Bendy toy
Registered user
Mine did it gently with the standard exhaust and louder with a free flowing exhaust. I'd not be surprised if it flashes at night
Do people worry about this sort of stuff? 
Deleted account 210516001
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The best popping is available if you close the throttle completely then open it just a tiny amount again and hey ho it pops like a merlin engine rolling inverted on a spitfire.
Easy
Registered user
I found the same on my 2008 GSA, so much so that I'm thinking of taking the module off as I miss the popping and farting.
...Thought I'd lend a hand here.
Yes, my 2009 GSA (with R1200S engine and 'box) does exactly the same.
Except that because the S engine has higher compression (12.5:1, as opposed to the GS and GSA's 12.0:1), and this particular bike has what can most politely be described as a 'full race' exhaust, the engine note is much sharper and more strident, and the overrun Rice Krispie sound effects are more like a series of rapid-fire thunderclaps.
If I'm not wearing earplugs, the noise - even at 160 Km/h+ - can be loud enough to hurt.
I'm told that not all BMW engine-management programming is created equal, and that some bikes (particularly those which backfire on the overrun) run leaner than others.
Good for fuel consumption and emissions - not so good if, taken to extremes, you get elevated combustion temperatures and your exhaust valves start to burn.
The 'Accelerator Module', and other such devices that plug in between the IAT sensor and wiring harness, are nothing more than a simple resistor.
The principle is that introducing more resistance into the IAT sensor line forces the entire engine-management map up the enrichment scale by 'fooling' the ECU into thinking that the engine is running in colder air than it actually is. The ECU compensates by lengthening the injector pulses (and on our engines, possibly increasing the fuel pressure), thus richening the mixture.
It's a trick that's been used on race bikes and cars for years. In fact, prior to closed-loop emissions-control systems becoming widespread, many Bosch injection-equipped vehicles had a little potentiometer under the bonnet which a mechanic could turn to richen or lean out the mixture - standard procedure at service time.
I found the same on my 2008 GSA, so much so that I'm thinking of taking the module off as I miss the popping and farting.
Yes, my 2009 GSA (with R1200S engine and 'box) does exactly the same.
Except that because the S engine has higher compression (12.5:1, as opposed to the GS and GSA's 12.0:1), and this particular bike has what can most politely be described as a 'full race' exhaust, the engine note is much sharper and more strident, and the overrun Rice Krispie sound effects are more like a series of rapid-fire thunderclaps.
If I'm not wearing earplugs, the noise - even at 160 Km/h+ - can be loud enough to hurt.
I'm told that not all BMW engine-management programming is created equal, and that some bikes (particularly those which backfire on the overrun) run leaner than others.
Good for fuel consumption and emissions - not so good if, taken to extremes, you get elevated combustion temperatures and your exhaust valves start to burn.
The 'Accelerator Module', and other such devices that plug in between the IAT sensor and wiring harness, are nothing more than a simple resistor.
The principle is that introducing more resistance into the IAT sensor line forces the entire engine-management map up the enrichment scale by 'fooling' the ECU into thinking that the engine is running in colder air than it actually is. The ECU compensates by lengthening the injector pulses (and on our engines, possibly increasing the fuel pressure), thus richening the mixture.
It's a trick that's been used on race bikes and cars for years. In fact, prior to closed-loop emissions-control systems becoming widespread, many Bosch injection-equipped vehicles had a little potentiometer under the bonnet which a mechanic could turn to richen or lean out the mixture - standard procedure at service time.
Bendy toy
Registered user
Running along with another GS both with aftermarket pipes we sounded like a WW2 bomber as the engined notes hummed and throbbed. No other bikes sound like that.
My Akra system now has a fairly open baffle in one can and a full fat dB killer in the other. It still pops like a goodun but now doesn't wake people in the next village.
My Akra system now has a fairly open baffle in one can and a full fat dB killer in the other. It still pops like a goodun but now doesn't wake people in the next village.
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