Exhaust Flow Control Valve (Twin Cam 2013)

[David.]

Recently purchased some Plusgas, http://www.plusgas.co.uk/about-plusgas/

Plusgas quote, "It breaks the grip of rust, scale, carbon, paint and gum.", thought the carbon bit might be appropriate for the exhaust system.

[Beagle]

Recently purchased some Plusgas, http://www.plusgas.co.uk/about-plusgas/

Plusgas quote, "It breaks the grip of rust, scale, carbon, paint and gum.", thought the carbon bit might be appropriate for the exhaust system.

By gum that brings back memories. Used this in the 60’s as a freeing agent. ( like wd40) It will burn off quickly though.

[LAF]

Well I just put a Akrapovic header on my 17 GS.  I used a Servo Buddy https://www.skutr.net/servo-eliminators/ and it eliminates any issue with the servo. Everything is gone. 

I ran my GS-911 on it and it passed the two Servo Tests so the Servo Buddy works for sure. 

[David.]

Whilst at Hilltop, it was reported that the Exhaust flap servomotor fault code is currently present again. Their advice was not to remove the flap, it helps with exhaust back pressure at low engine speeds.
Having just paid £320 for re-mapping, I'm happy to follow this recommendation.

The bike is booked in tomorrow (Wednesday) at Cooper Sunderland for them to have a look at it. My objective is to hopefully have the flap replaced under warranty.
The flap is £320, plus labour for fitting, my warranty excess is £100.

I took the silencer off and checked the flap, is it indeed not cycling from full open to fully closed & back, only going partially closed.

Looking back at this thread has provided valuable evidence that the fault existed 12 months ago.

[Rick B]

Im on my 2nd set of headers due to the flap seizing up,all done under the warranty.

[David.]

Fortunately for BMW the exhaust flap on a TC is not part of the headers.

[simbo]

Whilst at Hilltop, it was reported that the Exhaust flap servomotor fault code is currently present again. Their advice was not to remove the flap, it helps with exhaust back pressure at low engine speeds.
Having just paid £320 for re-mapping, I'm happy to follow this recommendation.

The bike is booked in tomorrow (Wednesday) at Cooper Sunderland for them to have a look at it. My objective is to hopefully have the flap replaced under warranty.
The flap is £320, plus labour for fitting, my warranty excess is £100.

I took the silencer off and checked the flap, is it indeed not cycling from full open to fully closed & back, only going partially closed.

Looking back at this thread has provided valuable evidence that the fault existed 12 months ago.

What was the outcome at the dealers David?

[David.]

What was the outcome at the dealers David?

Having spent hours washing & polishing the bike, based on the weather forecast, decided to re-schedule for Tuesday next week.

[LAF]

The flap does NOTHING for performance in any of the PRM range. 

It is there strictly for noise reduction.  if you start you bike with the muffler off you can see and watch the flap at a few throttle positions.  It never closes more then 2/3rds of the way and is full on open at 3500 RPM. 

And as to the TC there was a slip on pipe made to eliminate that flap pipe that was a inexpensive way to get rid of it.  Now built into the headers makes it a very expensive replacement.

Me I just put a set of Akropovic SS headers on and called it a day.

[David.]

KS Motor give the following tech-info for exhaust gas flaps on motorcycles,

"Reduces the flow area in the low to medium engine speed range for increased dynamic pressure. This increases the cylinder charging and therefore also the torque.

Releasing the full tube cross-section in the upper engine speed range for maximum performance and sporty sound."

[simbo]

KS Motor give the following tech-info for exhaust gas flaps on motorcycles,

"Reduces the flow area in the low to medium engine speed range for increased dynamic pressure. This increases the cylinder charging and therefore also the torque.

Releasing the full tube cross-section in the upper engine speed range for maximum performance and sporty sound."

9 out of 10 cats prefer whiskers cat food too

[David.]

Here's what was written in BMW Motorcycle Magazine about the similar flap on the HP2 Sport (where this first appeared):

"This constantly adjusts the internal diameter of the exhaust system to suit engine revs and ensures good low to mid-range performance for a linear power output all the way to the rev limiter."

[simbo]

Here's what was written in BMW Motorcycle Magazine about the similar flap on the HP2 Sport (where this first appeared):

"This constantly adjusts the internal diameter of the exhaust system to suit engine revs and ensures good low to mid-range performance for a linear power output all the way to the rev limiter."

The HP2 probably has a free flowing exhaust to allow for more top end performance, hence the need for a valve to close it up a bit to give it some bottom end torque. The RT not so much, it's for noise regulations and nothing else.

[David.]

This video of an R1200R https://www.youtube.com/watch?v=kECJwihAW6w shows the exhaust flap going from full open, to full closed & back to full open when the ignition is switched on.

[David.]

Decided to re-schedule for Tuesday next week.

Off to Cooper BMW Sunderland this morning, will report back later.