I had done this in the past on my 2 BMWs. But i think there is a a good reason for this valve/servo other than limiting the exhaust sound at low RPM and Idle. At Under 5K RPM the valve creates more back pressure which benefits the low-midrange power/torque.

 

good work !!!!!

you can hear the deeper tone without the servo

thanks

 

Yes it sounds much better with the servo disconnected.



I will try it out today and see if the mid range feels any softer. I really dont think i will notice tho. The bike has more power then what i am used to so it will be hard for me feel the loss if any.

Im more happy with the sound over 1 or 2 hp anyway.

 

i dont think it would be 1-2 hp or some nm/pound foot of torque.......less

 

You're teasing me with that video. Sounds soo fine! I'll probably end up just taking the cables completely off, like I did my last bike.

 

I will take the cables off once i do the 600 service. I know im being stupid and the dealer wont care but i did pay for the extra warranty and want to keep it.

Once the dealer does the service the cables will come off.

 

Has anyone REMOVED the cables on the 2015 yet? BMW moved the servo motor into a completely freakin impossible to reach spot. I'm in the process of installing a full system and need these cables gone but cannot for the life of me figure out how to get to the servo motor. Short of removing the swingarm-which I have no desire to do-I'm stumped.

 

Just cut the cables, its always a PITA to get to the servos.

I have done this on all three of my s1000rr's.

 

Ill be in the garage tonight. Ill look at the bike and see if i can come up with something

 

Okay cool. And I'll be sure to post back if I get it figured out as well.

The servo is located on the right side, right above the swingarm and hidden behind the subframe.

 

Finally got the little bastard. The plastic housing for the servo slides down onto a thin bracket, which isn't visible to the eye. Easiest way I found was to unbolt the lower two subframe bolts, pivot the subframe up and out of the way, and then you'll be able to slide the servo off of its bracket, open it up and remove the cables.

Was actually fairly easy once I figured out just how the servo was mounted.

 

did it pivot with just the lowers loosened...I'm having a hell of a time with it. Also, what size wrench did you use for the nut? 16? My 17 is too big and my 15 too small...you remove tank?

 

Gents

Servos are there for a reason, even MotoGP and WSBK bike run servos

It's for back pressure

Check this out

Aprilia MotoGP Bike Exhaust Gate - Photo.GP

 

That may be, but all the full exhaust systems delete the valves so regardless of what they are originally there for they are no longer used when going to a full exhaust.

 

Yup, further....anytime you eliminate the factory Cat, you eliminate the servo and hence the cables are useless. At least that's been the case on every bike I've had where I installed a link pipe and ditched the Cat

 

Don't believe rear servo aids in back pressure, previously it was determined that the front was for management and the rear was for noise compliance....

I did this last night, but left cables on bike this time around, my advice would be to take care in positioning the loose cables because they still move, so don't constrict them when putting cover back on.

 

I did this last night, but left cables on bike this time around, my advice would be to take care in positioning the loose cables because they still move, so don't constrict them when putting cover back on.

Yup, second this. Hence why I decided it worth it to just go through the effort of removing them. It wasn't fun but I could do it again in a matter of minutes now that I have it figured out how to get to the servos.

 

The servo is to limit the DB level to pass noise laws. The bike is tested at certain RPM. Once over that rpm the servo opens the valve to allow better flow.
They have to pass a DB level at a certain % of max rpm or something like that.

 

But this is not an issue with MotoGP and WSBK bikes. So why would they have servos?

An additional point:

SAE J1287 specifies that dB level is measured 20" from the exhaust outlet at 45 degrees, engine RPM at 50% of "the engine speed in revolutions per minute at which the engine delivers its maximum Net Brake Power as defined in SAE J1349."

Assuming maximum horsepower is achieved at 13,000 RPM, test RPM is 6,5000 - well above when the servo exhaust valve is opened.

Thus, the servo is not there to meet noise regulations.

 

Exhaust Valve/ O2 sensor



Are their any aftemarket exhaust that keep the O2 sensors and Exahaust Valve?

 

What does an exhaust servo motor do?
exup systemAn exhaust servo motor is one component of the exhaust valve system (sometimes called the ex-up or power valve system) found on almost every modern sportbike including all Honda, Kawasaki, Yamaha, Suzuki, BMW, Ducati, Triumph and a few others. The system consist of a few parts, the first is the valve assembly inside the exhaust pipe. This is a simple butterfly valve that can open or close to change the amount of exhaust flow. Connected to this valve is a set of cables that run to the other part of the system, the servo motor. This motor, which is controlled by the engine control unit, has a pulley on top that rotates the cables to open and close the valve in the exhaust. The cables are used to isolate the motor from the hot exhaust and allow it to be placed in a more convenient place on the bike.

The purpose of this system according to the motorcycle manufacturers’ marketing departments is to create back-pressure at lower RPM’s to increase torque. Unfortunately, this probably isn’t the real reason; the true purpose of the exup valves is to meet noise and emissions regulations. The exhaust valves are partially closed at idle and low rpm to reduce noise, and closed again at the upper RPMs to meet peak noise and emissions regulations. The proof of this has been shown on the dyno where removing the valves and retuning the engine creates a flatter better torque curve. Additionally, in the USA, most bikes close the valve again at the upper RPM range, but in Europe they do not (different regulations) and the European bikes typically create a few more HP on the top end as a result.


Exhaust valves and servo motors explained

 

As for moto gp and other race classes and why do they have them! I would say that their bikes are so far ahead of ours does it matter???? If i had to actually pick a reason i would say its mostly due to noise as well. i know on many tracks they have a noise level (DB MAX) im not sure if the rules bend for top level racing classes or not. My second opinion would be to gain every single tiny little bit of torque they can. Maybe in a certain corner they can lug the engine more to get more drive out of the corner. Or open it up and get a higher top speed in a long corner.

 

I appreciate the speculation, here and elsewhere, that it is to meet noise regulations - but the testing is done at an RPM where the valve is open. Thus, keeping the noise down to meet the reg cannot be the reason.

After market exhausts delete the valves to reduce complexity and weight, and because the primary reason we buy them is for the sound.

MotoGP bikes scream at low RPMs and scream louder at high RPM. While there are noise regulations at various tracks (I do not know if there are any where MotoGP is run), an exhaust valve would need be set to close at the location where sound is measured - not at a given RPM.

And, as you indicate, MotoGP bikes are special critters and the valve use there may well be used to extract the last bit of power. As may well be the case for our bikes.

It is an amusing topic, always rife with speculation and competing links that support multiple theories.

My guess is the closed valve assists low RPM throttle response and tractability, more than with peak torque at these RPMs.

 

For the S1000RR, BMW refers to the valve in question as an "acoustic flap" and the one in the headers as the interference valve.

https://rideapart.com/articles/2010...rticles/2010-bmw-s1000rr-most-powerful-liter-bike-ever-finally-unveiled-in-full

* The "Technology in Detail" PDF for the 2015 further explains that the valve in the crossover tubes is only active after 11,500 RPM for a "uniform cylinder charge".

 

Thanks! Great bit of info.

 

Does doing this or removing baffle affect warranty? Taking it for first service upcoming week...

 

so the 15 is the right size, however sub frame won't pivot...need confirmation on what bolts need to be loosened...I'm guessing top two as well in order to pivot. Servo is tucked in there good...bolt in pic is one of the ones that hold it in place..

 

Here you can see inside the servo housing and get a look at the cables. Once disconnected the cables will slide out of the plastic cover.

 

^ lol...kind of figured it was more to it than just two bolts once I started messing with it. that's why I asked about tank. at that angle, tank would have to be off.

I don't feel like dealing with the hoses (particularly accidentally damaging the quick disconnect on fuel line), but I'm going to have my tank painted anyway so I will do it then or try to disconnect them without lifting subframe. Looking at your pic, it may be possible....Thanks.

 

Kinda forgot about this thread. Oops.

Disconnecting them without lifting the subframe is possible, but getting the now disconnected cables actually popped loose from the servo housing is another story, because of the way they slide out. The hoses and fuel line all came off super easy, I wouldn't worry about damaging them.

Picture does make it look like a huge job but it's not bad. More time consuming than anything.

 

thanks for the information

 

Here she is boys. Like delivering a newborn.