ANORAK ALERT!!! - Excess exhaust welding.

[sandbar]

I found an old BMW anorak a week or so ago and amazingly found that I could still just about get into it. Therefore I felt that I should do something appropriate, and what could be more suitable than removing the excess weld inside the exhaust headers.

So I did - and it took most of the day. It also took 3 or 4 grinding stones, only one of which is still usable for any other job!! I can well understand why, if BMW let them get away ith it, the manufacturers can't be bothered to do it. There is quite a lot of work involved.

I decided that I would make good use of the anorak, and try to measure the restrictions and then calculate the amount that the cross sectional area of the pipe was restricted by the excess. At the rear of the header where it goes into the Y-pipe (or Cat.) the restriction was about 12%. At the front I calculated that the the restriction was just over 25% of the X-sectional area - but it is probably not as important at the front because the exhaust gases have all kinds of things to deal with at that junction. Two circular exhaust ports going into a sort of rectangular chamber, then into the header's ovalloid shape, past the weld restriction and then into the circular exhaust pipe. If there wasn't another combustion cycle following on I think the exhaust gases would just give up at that point and stay there!!

But what really p*ssed me off was to find that there is also excess weld inside the Laser Y-pipe. I would have thought that a 'performance' product that retails for about £650 or so should have had a bit more work put into it!

This was brought into perspective a couple of days later when the bike went to be dyno'ed. (More snippets about that in another post!!) The dyno guys were dealing with a customer who was buying a 3.5" complete exhaust system (for an Impreza WRX) that had been especially brought in all the way from Australia. Apparently that was the only place they could get a 3.5" exhaust from. That included a s*dding great casting that joined the exhaust to some vast turbocharger, all the mountings and the enormous silencer (cars have silencers - not cans) and there was not a sign of any excess weld at any of the flanges (and there were quite a few) and the whole thing was beautifully polished. Retail price was still only £635!!! That might have been plus VAT, but you get the point.

Anyhow I have no idea whether or not the removal of those 25% and 12% restrictions made any difference to the figures on the dyno - but I would like to think that my work was not in vain.

As this forum suggests, maybe I found the suggested 0.02 bhp!!!

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[bernsmartco]

Have to ask why bother?

Before I fitted my mid pipe i used two grind stones just aroung the joints then thought about the other joints i could not get at where the pipes join and around the sensor hole and gave up.
Could easily have used at least another two stones to get a nice smooth flat surface - SS not being the softest thing to remove.

The mid pipe made such a difference that I did not notice the extra .001bhp I obtained for an evenings work.

[sandbar]

I totally agree.

In hindsight, the phrase "I've started - so I will finish" springs to mind.

The fact that the excess is even there is the irritating bit. Not just not removed but unnecessary in the first place!

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