What causes exaust blueing?

[Reecehk]

When I purchased my 1998 R1100RT last year it had done 55,000kms and the exhaust coming out of the cylinder head was perfect clean chrome.

Now less than 10,0000kms later they are so blue they are almost black!! I suppose there is no way to fix this but why did it go like that in the first place?

[Aussie Dave]

Heat!!! some blueing is quite normal on chrome, some systems virtually never blue and those are normally twin walled so the outer stays cooler. Stainless steel will normally get a golden tinge to it.

To clean off the blue you will need a polish such as smartwax, I can't recall if the old Autosol chrome polish does it or not but call into a Harley shop and I am certain they will have something.

If the engine gets too hot from idling too long etc you may want to consider turning off at lights you have just missed or other times you are stationary, the owners manual actually suggests this to avoid over heating.

Personally a bit of blueing just shows that the bike is used for riding not polishing.

[Reecehk]

Thanks for that, I must admit though that the chrome looks a lot better polished than blue/black!!!

I assume you mean smartwax Blue-B-Gone, rather expensive stuff.

BTW, I don't mind a bit of bluing but mine are basically black, you'd never know it was supposed to be chrome!!

 

Oh and welcome to the forum!

[AndyS]

 

Oh and welcome to the forum!

+1

[Will46r]

The bluing is heat coloring (I deal with it as a knifemaker) its a surface oxide. A fine polish like flitz or simichrome may remove it from the pipes but you'd have to polish it almost every ride because the engine exhaust temperature causes it.

[Eckhard Grohe]

Welcome to the forum and the charms of a BMW. It is the nature of the beast and you know that someone went to the trouble of optimizing the weight of the exhaust pipe taking into account all of the important parameters.

 

BTW the pipes are not chromed steel, they are stainless steel which is generally a more expensive and harder to work material than steel. If the pipes are darker than most maybe there is a mixture problem. If not and they still offend, get them ceramic coated.

[Reecehk]

Does the type of fuel matter, I have just been using standard unleaded, is it any better to use a higher octane/premium fue1?

I would imagine that would make the motor hotter.

[Mike Sawatske]

I do believe that Unleaded 95 and better is the fuel recommendation here in Oz for oilheads. I have no idea why they will NOT blue your exhaust though.

 

As a recent purchaser of a beemer I have myself been wondering why we can't use Unleaded 91 (I refuse to knowingly use ethanol fuels) as in the USA fuels generally are of lower octane ratings, and ethanol is sometimes difficult to avoid, and I don't think the bikes are much different. I have certainly been wondering whether an added benefit of what roger04 has been doing to his bike would allow use of 91?

 

Having said all that, 95 and 98 are better quality fuels and I can only surmise that their burning characteristics mean that the heat is used in the engine rather than disappearing out the exhaust as fanciful as that sounds?

 

Mike

[Tri750]

From a long time Brit bike rider, I say blue pipes (or black or gold) are a sign of life!

As maybe stated, most Japabese exhaust are twin walled, a pipe within a pipe. The BMW pipes are single and stainless to save weight, dissipate heat, and not rust like mild steel.

HD uses chrome shields over steel pipes that blue and turn all kinds of colors as well.

[Eckhard Grohe]

The compression ratio is 10.5 to 1 making this bike more sensitive to octane levels and ignition timing. The use of a lower octane fuel probably causes the exhaust to be over heated as it will encourage preignition resulting in a hotter exhaust. It can cause melted pistons as well.

 

My personal belief is that you run the bike as the manufacturer recommends or you assume all risk for whatever happens. The situation with BMW's is that they are a bike that is tuned to near it's maximum potential as it comes out of the showroom and any deviations from their recommendation generally negatively impact the performance, longevity and/or pollution products.

[Reecehk]

I will put it down to using standard instead of premium, I certainly don't want melted pistons either!!!

Thanks.