F800GS straight thru downpipes

[Bury_Dave]

I've seen straight thru downpipes advertised where the CAT is removed. Is this a weight or power or sound thing ?

Is it a big deal ? I've seen them from £170 to £290. Why the price range for something that can only be identical products doing exactly the same thing. i.e. going from A to B in the shortest distance with stainless tubing

I'm presuming if you do have them fitted that you need to change back to the CAT ones before the MoT ?

Cheers,
Dave

 

[chas820]

They don`t check emissions on bikes.

 

[Bury_Dave]

Thanks Chas I assumed that if a bike was a modern one and therefore would have a CAT that they would at least look to see if one was in place. You live and learn

So there's no real point in removing the cat anyways ?

Dave

 

[Schtum]

So there's no real point in removing the cat anyways ?

There is but it comes with the caveat that you should dyno the bike to check the fuelling and that you'll probably only reap the full benefit if you remap it to obtain the optimum fuelling for full performance. Removing the cat will let it exhale more easily and spin up more readily. You should gain a few horsepower at the top end but you might also lose a bit of tractability at the bottom end.

 

[Bury_Dave]

Ah, now I see. Thanks for explaining a little of the dark art .

So, as I'm not looking for more power or increased anything (I was thinking about surplus weight more than anything ), I think I'll leave it well alone ad I'm sure BMW know what they've done.

Cheers
Dave

 

[Miikka]

Just installed Arrow headers to my 800.

Results so far:
- 1,5kg diet (+/- 0,1kg)
- bike sounds like a proper motorbike.
- have to mod bashplate (adv-spec) attachment points and drop plate1-2cm's. Bummer.

As far as I know, there's no need for remapping/dyno business. These downpipes
have a spot for the original o2-sensor, so bike is able to adjust itself to it's new and
unforeseen asthma free situation..

-m

 

[Schtum]

As far as I know, there's no need for remapping/dyno business. These downpipes
have a spot for the original o2-sensor, so bike is able to adjust itself to it's new and
unforeseen asthma free situation..

It'll only "adjust itself" when the engine is running in closed-loop mode, ie at relatively low revs and small throttle opening and then only if the fuelling requirements are within the parameters of the ECU map + trims. It won't adjust itself when running in open-loop mode, ie large throttle openings and high revs and that's where an overly lean mixture presents the greatest risk to engine life.

To achieve what you think will happen, would require a wideband lambda sensor and an adaptive ECU. So that'll be a Power Commander V with Autotune module....

 

[mark71]

Ahh at last someone who understands how things work........

These pipes are great if done on a dyno and set up correctly but if not they have a tendency to run lean at higher revs, I previously did a mod on my 1200 which was to keep the down pipes and just cut out the CAT. It was quite liberating as it freed up the engine and kept the original configuration of the downpipes thus not running lean at higher reves, and of course it only cost me about 1 hour of my time.

My advice would be to get someone who can weld to cut out the CAT of your original pipe and save a fortune as if you haven't already realised anything made for an BMW cost a fortune.

And yes I will do it for a small fee if your local and want it done..

Happy riding

Mark

 

[Miikka]

Ahh at last someone who understands how things work........

Mark

Mark, Thanks for your

But maybe you should stick to IVY league discussion forums if it bothers you that we poor peasants don't know what we're talking about?

Arrow customer support says their headers for F800 doesn't require fuel remapping. I don't know if it does or not, but that's what I got as a response.

In your opinion 300 euros for brand new Arrow headers is a fortune; I think it's a really reasonable price. If not a bargain.
Furthermore, if I had a shop to remove the CAT from the original pipe...that would cost me minimum 100e. Propably way more. Labour over here tends to be pretty expensive around these days. By having Arrow headers I still get to keep my original as a spare.



Schtum, thank you for the info on open/closed loop!

Diameter (outer) of the original header is 38mm and Arrow is 41mm.
I have a booster plug installed which is supposed to make the mixture richer on open loop operation.
I realise that this setup is a poor man's solution compared to a Power Commander.

In your opinion, is this setup going to burn my valves over the years?

-m

 

[mark71]

Well that's me told so I better keep quiet in the future...........or not.

Happy riding and I hope that you enjoy your pipes but keep and eye on the plugs and look out for the early signs of it running lean.

All the best and welcome to the site.

Mark.

 

[Miikka]

Cheers, Mark!

And moving on.

Slightly off topic, but related. What do you guys think about Booster Plug and similar gadgets?
Any solid reason why one should be doubtfull about it's performance/function? The device is supposed to provide 6% richer mixture.

I guess I'm looking for some piece of mind with my new shiny pipes..?