When were the silencers changed?

[Engineer]

My April 05 bike has a different silencer to the earlier bikes, i.e. black end cap is now silvery and that 'funny round bit' at the front is no longer there.

Excatly what changed and why? Just curious.

 

[Deleted account 211025001]

In the UK it would seem the change over occured at roughly March/April 05. However these are not hard and fast dates.

Do a search on the subject and you'll find loads but the generall consensous is that the 'funny round bit' is a Power Valve of some description.

Whether it's there to improve power caracteristics or open the pipe up above 5500 revs (or where ever the EC measure exhaust noise) to give a 'fruitier' tone I don't know but I suspect the later as 'normal' power valves are usually situated in the mid section of the exhaust, not the silencer.

Who knows

Andres

 

[John Armstrong]

The power of the search function:

http://www.ukgser.com/forums/showthread.php?t=40598&highlight=power+valve

 

[Piggers]

Silver/Black Ends

I thought that the Stainless Systems (Optional Extra) had Silver Ends and the Standard Exhausts had the Black ends !!!!!

Not sure about the valve thingy mentioned in many of the threads !1
I am going to look at my bike tonight to check if it has one..



Cheers, Piggers

 

[Mouse]

All the exhaust systems are stainless steel. The optional extra some people seem to like is for a chrome coating on the header pipes, as far as I know.

From my observations, there's no connection between chrome pipes and the design of the silencer. Seems to be, as suggested above, that early in 2005 BMW started supplying a different design of silencer. Until someone cuts one open, or maybe dynos a bike alternately fitted with the different units, we can only speculate about the difference.

 

[plasmatron]

I thought that the Stainless Systems (Optional Extra) had Silver Ends and the Standard Exhausts had the Black ends !!!!!Cheers, Piggers

that'd be a negative there Piggers... Mine is a Sept '04 build with chrome headers, with "mystery valve", with black end cap...

the factory chrome option means everything from the headers up to where the can bolts on is chrome plated, the cans do not differ between chrome / non chromed options... but all the bikes I've seen so far that have silver end cap don't have the "mystery valve" whilst the black end cap ones do...

 

[birdseye]

Probably the same moive as the keys and tool kit changes?

 

[geojunkie]

What the exhaust silencer valve does

Was bored waiting on some service on my 1200GS today and the mechanic handed me a technician training guide to the 1200GS. Full of full color cutaways of just about every system on the bike and supporting text explaining the features and benefits.

The exhaust valve on the silencer is said to respond to pressure and time. In other words, it it forced open by exhaust pressure, but has some kind of dashpot type setup that slows its time response in opening or closing down. That can is probably a spring and some kind of damper setup. The valve itself opens in internal bypass inside the silencer that sends the exhaust (after a couple of gyrations back and forth in the can) to both of the outlet pipes. When the valve is closed, the exhaust is also forced out through an annular space within the silencer that would cut sound and looks like it would add restriction too.

The text said its only purpose was to reduce noise in city type driving, but allow more sound on the highway. It must alter performance to some degree because just looking at it, the backpressure must be higher when it is closed. This may help the bottom end or hurt it, I don't know. Given how it works, it takes a whack of throttle and some time before it opens, so you could not say for sure what RPM it comes in at. Probably higher on quick romps up through the gears, and lower at sustained cruising.

It might be an improvement just to have it open all the time, as that is more like what most aftermarket cans would be, even moreso, because they are straight through and not back and forth. Anyway to change it takes cutting and welding.

Dan