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Discussion Starter · #1 ·
Went out for a quick blast tonight and decided that I'm fed up with coarse throb........throb and excessive noise of the Dakar, with the Staintune on (baffle in)

The bike sounds nice..............but the noise gets on my tits (and everyone elses, I suspect)

Does the bike run better with the stock set up on..........I suspect so and read/heard somewhere, that the 650GS was faster on the stock pipe, than any aftermarket set up.

Does the 650GS run leaner with an aftermarket pipe...........any evidence?
 
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Johnnyboxer said:
Does the 650GS run leaner with an aftermarket pipe.
Because the F650GS and F650CS are electronically fuel-injected it doesn't matter what you put on there as the system copes with changes of pipe, air-pressure, temperature etc.

There is a sensor in the exhaust which measure the oxygen output. That sensor will tell the EFI to richen or unrichen as the case may be.

With carburetted bikes you often need to rejet the carbs, when using different pipes or when running at different altitudes.
 

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Discussion Starter · #3 ·
Are you definitely sure Trevor?

Just cos it's EFI and has a sensor (knew that already) doesn't mean it can't run lean!

Most 1150 GS's (yes I know it's a Twin, but the principles are the same as thay have a sensor and EFi) fitted with a Remus and Y Piece - ie - a straight through system tend to show that they are running lean and a plug check confirms this.

There have been instances of Piston damage too.

So I wouldn't be to sure that your F650GS is ok with a straight through system, with minimal baffling to create back pressure.

Anyway, back to the orginal question.............do they go better AND faster with the stock pipe set up???
 
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Johnnyboxer said:
Just cos it's EFI and has a sensor doesn't mean it can't run lean!
As soon as it leans off, say by using an open-pipe, it puts too much O2 into the pipe, the sensor detects it and tells the EFI to give a slightly longer injection pulse to richen it back to the correct level.

That happens dozens of times per second contiinually as you are riding the bike. If in practice it does lean off (showing plug colour changes) then there's summat wrong with the sensor (or EFI)

There's a 1.5 Megabyte pdf file to explain all about it (Page 6 & 7)
Here -> http://www.trevorgeorge.myby.co.uk/f650gs.pdf
 

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The EFI can only work within certain limits, and can only richen the mixture so far, so you could be operating outside its variable limits.
I ran my Staintune (with baffle) for 25,000 trouble free miles, so I don't think there's a problem with these exhausts.

As to Johnnys original question - I found low rev work was much better with the Staintune, the engine was quicker to 'go' off a closed throttle. With the stock exhaust there was always a slight delay (making puddle/log hopping more difficult). There was more 'feel' at low revs with the Staintune (more than just the noise I'd say). I couldn't really notice any difference at higher revs - certainly made more noise tho! So the exhaust helped off road (lighter weight aswell) but probably wouldn't be much different in performance terms on the road. (And we're only talking about 50hp anyway).
Swap them over one rainy Sunday Johnny - that's the only way to tell!
 

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Discussion Starter · #7 ·
Message for Trevor G.............(from a reply to my topic, from Chaingang site)

As far as we all can tell, the EFI does not have a way to sense manifold pressure. Therefore it cannot adjust mixture based on more air being available for combustion. Mine runs noticably lean on the Remus pipe. Not dangerously so. The Techlusion Fuel Nanny can fix some of this, but I have also been through two of these units in less than two years.

I thought as much...........
 
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quote from Jetdocs on the Chain Gang site at http://f650.com/forums/ShowPost.aspx?PostID=154759

"As far as (1) we all can tell, the EFI does not have a way to sense (2) manifold pressure. Therefore it cannot adjust mixture (3) based on more air being available for combustion. Mine runs (4) noticably lean on the Remus pipe. Not dangerously so. The Techlusion (5) Fuel Nanny can fix some of this, but I have also been through two of these units in less than two years."


(1) Who is "We" ? That is the opinion of one person.

(2) Agreed ... it doesn't sense manifold pressure. Sensing manifold "pressure" would be of no use anyway. BMW don't claim to do that.

(3) It senses oxygen levels in the exhaust, which gives precisely the same effect in telling the EFI module to enrichen or weaken the mix to give appropriate levels of O2 in the exhaust to give a correct fuel mix.

(4) He says it runs noticeably lean, but gives no explanation or evidence of it doing so, (plug colour, backfiring) and what does he mean by dangerously so?

(5) Jetdocs has run his with a "Fuel-Nanny", which when you use, you have to disconnect the wire to the exhaust sensor (lambda sensor). This may cause "his" lean problem. The USA bikes run even leaner than the UK ones as well, because of their stricter emissions laws. That's why they had worse "Suging & Stalling" on thier bikes (originally) than the European ones.

(6) The twins use a completely different form of EFI which "may" account for their problems.
 

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Hi,

I don't want to pour more oil on the fire here, but I thought I'd mention what my friend had to say about the issue, after all, she develops BMW Mini engine management. The Mini is a car not a bike, but my guess is she knows a thing or two about this.

It virtually doesn't matter these days what you do with an engine, 4 or 6 cylinder doesn't really matter. (The Jaguar X type is a Ford Mondeo is a Jaguar X type is a Ford.... only difference apart from styling is the managment!)

The only true master of your engine is you management computer, which knows all it needs to know about the state of your engine. (Unless you misplaced/buggered up/diconnected/damaged the wire of/ a sensor when fitting the new exhaust that is. As little a 1mm tolerance in sensor location will scew things up badly!)

Fitting a new exhaust system can change sensor readings as the sensor is tuned to work in stock environment and thereby change bike performance. As said, the tolerances are tiny, and unless you develop these systems, you will have little idea what effect a change will have. Even the staff on the factory floor need frequent training or they'll get things wrong. The amount of possibilities it too great to determine (sensor location/orientation/temperature/dirt/ etc, etc) in a forum, the BMW diagnostics tool at local dealer would be more appropriate tool to determine what causes your bike to behave different as normal.

hope this helps,
easy going,
:cheers:
logan
 
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logan said:
The only true master of your engine is you management computer, which knows all it needs to know about the state of your engine.
Agreed :-D

As little a 1mm tolerance in sensor location will scew things up badly!)
Hi Logan, but it depends what the sensor measures. If it's measuring the crankshaft rotation (as one sensor does) it will probably affect the way the engine runs. I say probably, because if a sensor goes 'kaput' on the BMS compact sytem, as used on the F650, a substituted value is used which will still allow the engine to run, but not as efficiently.

A sensor measuring O2 in the middle of the exhust won't matter as much in its positioning.

Fitting a new exhaust system can change sensor readings as the sensor is tuned to work in stock environment
The sensor isn't "tuned". It just measures oxygen content in the exhaust pipe. If there's too much it tells the electronics tp squirt a bit more fuel in on the next compression stroke to burn up that oygen for better efficiency. It reacts that quickly, hence the 'surging' on some of the early F650GS bikes, where it hadn't been 'smoothed out' correctly by the software.

You will have little idea what effect a change will have.
Loads of folks around the world have used all sorts of pipes on the FI models with no ill-effects. I have even been assured by the BMW experts that the sensor will cope with the changes in an "open" pipe. ie NO silencer at all, (but not recommended) so it's got a good range in its ability to compensate.

Keep those comments coming :dance:
 
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Returning to the stock pipe

Message for Johnnyboxer:

Before you purchased the Staintune system did you consider Remus? I know that the former is considerably more expensive especially if you buy the dummy matching can for a twin can look. I refer here to the latest Staintune oval stainless steel design.

I still cant decide what make to choose. What was your initial re-action when first riding the Staintune system. I know that when I fitted Remus cans to a Cagiva Gran Canyon (900 Ducati engine) my initial impression was that the engine could at last breathe properly!

Did the Staintune fit OK without any 'local' mods? Any information will be of assistance.

Kind regards,

Peter Buckingham
 

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Discussion Starter · #12 ·
Hi Pete,
Firstly fitted a 500 mile old Arrow Titanium can to the Dakar, bought at a reasonable price and looked gorgeous.
Fitted easily, about 2 minutes, after stock cans removed
Result very noisy and bike was lumpier.........but went well......sold it to Komitas

Borrowed a very used Staintune from a friend who had it lying around in the garage.
It had a removable baffle and was still noisy and lumpy, although better.

Went back to stock cans and bike was smoother, less lumpy and more importantly quieter
Top speed was about 5mph faster on stock cans and speedo showed about 109mph (which equates to about just over the ton)

Both cans I tried were single cans, so I have no experience of dual aftermarket pipes

Having followed around behind a young lady on a 650 Dakar with a single - sided Staintune, for the last 3 days, whilst on my 1150 Adv - I can confirm the exhaust is still too loud for my ears

So I'll stick to the standard set-up until somebody proves to me there's a need for an aftermarket exhaust which makes a performance benefit, because I'm yet to be convinced and believe the only benefit is WEIGHT-SAVING
 
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Stock Pipes - Stay with or Staintune?

Hi JB,

Thanks for the info re your experiences with both. I understand the latest Staintune oval stainless model for the f650 is an improvement on the original and comes with (at added expense) a dummy can for the right hand side. Reports trickling back seem to be favourable and I am erring on their side at the moment. It will be an expensive suck it and see but perhaps I will do a little more research with our friends in the States to get their views.

By the way, how did you explain to the young lady you were following that her exhaust was too loud?

Thanks once again,

Peter
 

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Discussion Starter · #14 ·
Re: Stock Pipes - Stay with or Staintune?

Peter Buckingham said:
By the way, how did you explain to the young lady you were following that her exhaust was too loud?
Asking her for some aspirins at a coffee stop (or was it the previous night's beer)

Also fuel consumption was better with stock pipes and the power delivery less lumpy...........
 
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Reply to original post

"Does the 650GS run leaner with an aftermarket pipe...........any evidence?"

The air filter/carb/cylinder head flow/exhuast are all one system. The reporting on performance from the Chain Gang is the mid range is increased with the top end decreased and no low end range below 3k for almost any 3rd party better flow exhaust.

From exhaust changes in my Norton riding days (blast to ride, bummer to constantly work on), it is a delicate balance. By having better exhaust flow, the midrange is immediately effected. But there seems to be a 'void' by the time the top end or main jet range is reached. This would give a leaner mixture that would seem to me to require larger carbs, or at the very least carb components adjusting/experimenting. The larger carbs would be a more robust solution in tuning, where as carb component replacement alone would be 'iffy' in a completely 'smooth' throttle range. If you are just bolting something on, then you will just be getting a different flow combination (not necessarilly better) and not a 'tuned' combination. i.e. rich in mid/lower range and lean in high range.

Most posters have mediocre results at best (that I've read) due to not balancing the carb/exhaust flows out. Gas mileage will not suffer significantly with a properly tuned larger carb because of power/weight factors effect mileage the most (if not gassing it, ha-ha).
 
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forgot about fuel injection on newer F650's

That's why no one with a later bike talks about carb changes with new exhaust, doah!

Ron Woods reports 32% increase with carbs/filter/exhuast changes, so I am holding on to my 97 Sachs/carb edition. I got one of the first ones in US in Jan/97. It is almost the same bike in Europe since 1992: not many bikes (if any) have gone virtually unchanged for 5 to 7 years in a row.

I do not know how the fuel injection models could increase hp 32%, in fact many (if not most) users (that I've read) switch back to stock exhaust due to noise, lean fuel mixtures, and not significantly better performance if not worse. Evidently there must be no way to change mixture on fuel injection, so I'd save your hard earned money and make no changes at all with fuel injection. Its probably as good as it going to get: an engineered carb/exhaust flow.
 
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