Fuelling...does this make sense?

[Dave T]

Hi all,
been out for a few beers , so forgive my ramblings, but this has been on my mind while I've been out (is this the beginnings of true Tosserdom ????)...

As you know, I've just ordered a new R1200GS, but I'm contemplating a full fat, cat free 'open' exhaust - maybe BOS (as per the demo bike I rode), maybe Akrapovic (if my numbers come up).

Using the 'search', there seem to be some concerns that the bike may run a touch lean (and I know I should get it on a dyno to make sure and put my mind to rest), but I'm assuming that since they are designed to run on 95 ron fuel (standard unleaded), if it is a touch lean, a change to Shell Optimax (98ron), BP ultimate (97 ron) or similar 'super' unleaded would move things back towards 'optimal' without the need for a 'gadget' (power commander type thingy). Does it really work that way, or am I barking up the wrong tree...

Cheers,
Dave

 

[Deleted account 211025001]

Mmmmmmm...........I'm not sure but I don't think the octane rating of a fuel will compensate for an altered fuel air mix.

The octane rating is a measure of how much a fuel can be compressed before it spontaniously combusts, hence the need for higher octane fuels in high compresion engines.

If you alter your fuel air ratio, i.e. make an engine run weaker by allowing more air in (high flow filter) or draw more air out (high flow exhaust) then the only cure, I would have thought, is to put more fuel back into the system in order to compensate. A higer octane fuel is not going to achieve the same result.

FWIW I have a full BOS system and have kept meaning to have it dyno'd just to put my mind at ease. However, it's now been on the bike for over 10,000 miles and the longer it stays on there without any problems (far from it as it has transformed the bike) the less inclined I feel to get it dyno'd.

HTH
Andres

PS You may be better posting this on the Technical section rather than the 1200 section?

 

[Dave T]

Cheers Outtomunch.

Mods, if you think this thread would be better elsewhere, please feel free to move it.
Thanks,
Dave T.

 

[Dave T]

Re-posted in 'Technical'.

Mods, please delete this thread if you like!!! (Ta!)

 

[Fanum]

Re-posted in 'Technical'.

Mods, please delete this thread if you like!!! (Ta!)

Dave, I suspect there's a bit of confusion here

If you look at the section that the 1200GS forum comes under, it's already in 'Technical'....the idea was to have 1200 specific tech stuff in here, and more general oilhead stuff in the vaniulla 'technical' section that's non-bike specific .


We don't have a seperate 'general' forum for 1200's because after the initial launch fuss was over with, we didn't want the social side of things dividing into different groups........so the 1200 section is meant only for technical or 1200 specific stuff .


In other words, this is the correct section for the thread

Hope that makes sense
Bill

 

[Dave T]

Ah well,
It's in both bits now...
Suppose it just means that I have to check both bits for any replies...

My only defence is too much and not enough

Dave.

 

[birdseye]

Octane rating isnt related to mixture - its basically a measure of the explodability of the petrol. If you are squashing the mixture more in a high compression engine, you want petrol that is less inclined to explode under pressure and that means a higher octane rating.

The 1200 GS has sensors that detect the weakness / strength of the air /petrol mixture and adjust automatically. Short of a massive air leak or some other change beyond the range of the adjustment system, the engine can neither run weaker nor stronger mixtures that BMW designed it to do.

Question is whether messing around with the exhaust (why, for heavens sake, since its not a sportsbike?) will put the system outside its control range. I guess the best thing is to ask the exhaust maker since he should know and since he will be stuck with a claim if his system causes you to burn through a piston with weak mixture. If he doesnt know, I would avoid his system like the plague - he's a chancer not an engineer.

 

[Wizard]

why, for heavens sake, since its not a sportsbike?

To allow the use of leaded fuel in other countries, to improve low and mid-range power, to make the bike look better, or to (allegedly) make it more noticible by having a loud exhaust.

Great things motorbikes, no matter how many leave the factory, you'd be pushed to find two the same after that.

 

[NorthernBoy]

Question is whether messing around with the exhaust (why, for heavens sake, since its not a sportsbike?) QUOTE]

That is a strange question, as BMW themselves realised that the bike needed more power when they took it up to 100 from the 86 (or whatever it was) on the 1150. How much is the right amount for this bike? Cleary 85 was not. Is it 90, 95, 100, 110?..

Just because it is not a sports bike, that does not mean that it could not benefit from a chunk more power and torque.

Many of us bought the bike for use at least 99% of the time on-road. For us (especially those of us used to fast cars annd bikes), the GS can sometimes feel underpowered.

If there is any way to get an extra 20bhp, and 10lb-ft, without losing out anywhere (vie decatting, blueprinting, turbo, or something similar), I will be happy to pay up for it.

 

[Ken H.]

>> If there is any way to get an extra 20bhp, and 10lb-ft, without losing out anywhere (vie decatting, blueprinting, turbo, or something similar),

There isn't.

At least not by decatting, or blueprinting, or any similar technique. Now turbocharging it, maybe, if you can engineer it.

 

[WindyChuffer]

Excuse my ignorance - but how much more power / torque does de-catting make. Does it make a nicer noise with the standard can?

Presumably thats technically illegal in the UK, but who gives a shi*e about that. Are cats a legal requirement on bikes now? If so and you are unfortunate to get caught without one, whats the penalty? £20 fine? How would you get caught? (ignore MOT). And what about warranty implications?

Ta.