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Offline anubisss

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Exhaust servo questions and what happens if I remove it
« on: March 17, 2017, 12:29:25 AM »
So this exhaust servo thing is new to me.  I am assuming it is for pollution regulation.  But, waht does it doe and how does it do that?  I avhe been lookin g at my stock header wondering why I can can't cut out toe entire cat portion of the pipe and weld in two pieces to take the pale of teh cat.  Sure, I want the Akra head pipe but no more until the current ones are paid for. 

Can someone that understands this explain this valve please.  Next, what happens if I remove it?  I have read the otehr threads but am still confused.  Do I get some sort of error if I remove it?  I assume it is not used when you change the head pipe?  Oh, and where are the 02 sensors in the head pipe and what happens if you remove them and add a tuner?  Computer errors or not?

Lastly, how does this all affect warranty?  Thanks for the help. 

Offline Winger

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Re: Exhaust servo questions and what happens if I remove it
« Reply #1 on: March 17, 2017, 08:45:08 AM »
Jeeze that's a complicated question and to answer is properly I'd be typing for hours,BM build a bike which is restricted by the TUV and the number crunchers so what us customer get is the best BM can do within the confines of the former somewhere in the BM vaults is a real unrestricted XR :002:

Take the servo out and it will say nothing on the instruments but plug a GS911 and it will show a fault.

Start cutting things out of the exhaust system and that carefully built Motor will be all over the place,I currently have a set of Akra headers to go on my bike they the manufacturers state that you need a 3rd party fuelling mod my preference is a Rexxer map and they currently still do not do one.

I  run other bikes with Power Commanders but piggy back is not the way I want to go I've even looked a the Rapidbike option but I'm not familar enough with it.

Take the lamba's out and you prevent the ECU from adjusting the fuelling that In it's self is not a bad thing if you live at sea level start climbing high up and you will understand what they do,there are factions that set engines up both with and without my K1200r that has a Rexxer map in doesn't run with lamba's connected but can get a little woolly high up in the Alps.

I'm sure there loads I have missed  :084:
« Last Edit: March 17, 2017, 08:47:49 AM by Winger »

Offline anubisss

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Re: Exhaust servo questions and what happens if I remove it
« Reply #2 on: March 17, 2017, 11:00:35 AM »
Thanks for teh quick abridged version.  So basically this is for pollution control but the bike is tuned so that it runs best like this and when changed it SHOULD be remapped to make up for the change in AFR due to the lack of the valve.  So, as far as the 02 sensors go (what americans call them) are the closed loop,open loop, or both?  I have a Power Vision on my EFI Harley and understand this kind of stuff pretty well but the vavle is not something Harley does.  Rule of thumb there is if you change exhaust system only no need for a remap, but if you change the a/c too (add more air to the system) then you need a tuner and a proper tune.  My bagger has 73K miles on it and it has a Power Commander when I bought it which I replaced with a Power Vision as the Power vision is so much more usable.  The vision allows the ECM to be flashed whereas the Power Commader is merely a piggyback device that "tricks the ECM" to alter the fuel tables. 

Next question is when are the 02 sensors automatically adjusting and when are they not?  IF I put a PC with a dyno tune map on teh bike does it allow the entire rpm range to be tuned or will there be a point when the bike is still using the stock map or adjusts by itself?  This bike has plenty of power for me in stock form but I have alwyas found a proper Dyno tune will make a world of difference in how a bike runs.  Cooler, more power, etc.  I don;t mind paying for a Dyno tune but would much prefer to wait and buy a power vision (Can Bus Version Obviously) as my otehr is not a can bus version than use a Power Commander.  On my bagger the PC went bad around 50k miles and ti started running weird.  I took it off and the bike ran fine.  So, I dislike PC.  And lastly, I am in the US, specifically California.  Lots of great Dyno tuners here but wonder if anyone is proficient with this BMW. 

And to sum it up, if I disconnect the servo it will be seen by the dealer if there is warranty issue but won't throw a code on the dash.  I am more concerned about the dealer than what it says on the dash just in case there is an issue. 


Offline S1000XR

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Re: Exhaust servo questions and what happens if I remove it
« Reply #3 on: March 17, 2017, 11:22:19 AM »
Why mess with it for the sake of a few hp that you probably won't even notice in real world riding  :027:

Offline Winger

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Re: Exhaust servo questions and what happens if I remove it
« Reply #4 on: March 17, 2017, 12:00:14 PM »
I'll work backwards this thread isn't about HP if folks think it is then their not on the right wave length even with a pipe/filter/fuel map your talking 6/7hp max and probably less but how the motor ran was a world away from stock because it doesn't have the restriction of a TUV map in the midrange.

Re the tech questions there's little point in me giving my view point because each tuner you speak to will give a different opinion or be it only slightly depending on their preference be it a PC or a remap and if I was in the States I'd be talking to Bren Tuning.

As for warranty!!! You can't have your cake and eat it you'll be kissing goodbye to that and just as a thought I'm getting an increasing number murmurings from guys in the trade about top ends on these XR's and RR's going Clak Clack Clack is it bad lube or soft cams I don't know because BM's solution is to put a new motor in and I know someone personally with an RR that has had that done so it's not Internet hear  say.

All I will say is when Rexxer have a map for the XR I'll fit the headers and crack on with the job because there is much to be gained away from the poxy TUV map which really applies to any bike.
« Last Edit: March 17, 2017, 12:03:01 PM by Winger »

Offline skapan

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Re: Exhaust servo questions and what happens if I remove it
« Reply #5 on: March 17, 2017, 12:11:55 PM »
The oxygen sensors are always adjusting (after warmup). Removing them requires a dyno tune and ECU flash to install it. Or a Power Commander.  The rear servo valve is more for drive by noise control than emissions, and you can remove it and leave the servo box connected to the wiring or plug in a "servo buddy".  Personally I wouldn't mess with it, but if you do be prepared to spend $2500 or so to get it right. And say byebye to your warranty, regardless of Moss-Magnuson.  Just my opinion, I'm sure there'll be lots more.

Offline Winger

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Re: Exhaust servo questions and what happens if I remove it
« Reply #6 on: March 17, 2017, 12:25:12 PM »
Picture is worth a 1000 words  :002:



My K1200 that in fairness was transformed because the BM map was just crap but still good enough to run the legs off my XR over 120 mapped 4 years ago and not been touched since.


Offline ogden

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Re: Exhaust servo questions and what happens if I remove it
« Reply #7 on: March 17, 2017, 12:57:59 PM »
*Originally Posted by anubisss [+]
Can someone that understands this explain this valve please.  Next, what happens if I remove it?

It's just like the Exup valve* Yamaha started putting on their bikes almost 30 years ago. It's not for emissions control, it's used to vary resonance in the exhaust, control back pressure, and effectively allow the exhaust to be tuned for higher torque at both higher and lower revs. Without the valve, the exhaust is only tuned for one or the other. Think of it a bit like a crude version of variable valve timing, as it's kinda doing a simlar job, just in a different part of the bike.

Race exhausts don't have them because they're tuned entirely for peak power at high revs. Road systems do have them because you want a good spread of power, not just outright top-end. Frankly, anyone sticking a full race system on an XR probably bought the wrong bike for the job, and would have been better off with an RR in the first place.

So is there a reason to remove it from a road bike? Not really. Will it give you any benefit? Unlikely. Will it save weight? Not a significant amount on a bike as heavy as the XR. Is it worth the effort removing it? Doubtful. I think the valve is permanently open if you put the bike in Dynamic mode anyway, which is why it sounds a bit louder at lower revs. But at least if it's still there you have the option of having it closed in other modes.

* https://en.wikipedia.org/wiki/Four-stroke_power_valve_system

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Offline anubisss

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Re: Exhaust servo questions and what happens if I remove it
« Reply #8 on: March 17, 2017, 02:12:49 PM »
Thanks for the answer.  I read everything the servo buddy people wrote.  I ride on the streets and highways and more power on this bike is so not necessary for either of those.  I have a better understanding now but I really want to get ride of that cat in the stock head pipe as I am convinced it will run cooler and flow better without that huge cat under the bike. More Power?  Not a requirement for me as I wlil never be able to ride this bike to its full potential in stock form. 

I rarely use Dynamic mode and rode one of my Harley's to work today so next time I ride the S1000XR I will check Dynamic mode and see if I can notice the differences aside from the wheel coming off the ground easier.  Really, i want the bike to be louder so I don;t get run over.  On my Harley's this is never an issue.  ;)  and in fact most people hear me coming and get out of the way before I get there which is really nice and what I was used to before the S1000XR. 

Offline Troppo

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Re: Exhaust servo questions and what happens if I remove it
« Reply #9 on: March 18, 2017, 12:52:27 AM »
If you remove the valve as others have said, it will more than likely stuff up the fuelling....

It isn't a Harley....

You haven't ridden in Dynamic mode? 

It makes more noise on the overrun in Dynamic - it pops and bangs.