Thursday, November 7, 2013

Car restoration Part 9 (Exhaust and catalytic converter) in Juny 2012

Although the exhaust system is a full stainless steel exhaust from factory, after many years the air rust mixed with dirt started to settle down on the surface.
Removing the rust and polishing the exhaust at the same time was possible with a rotary wire brush. It was a mad task, because of the flying debris consisting of broken brush wires and rust particles. Wearing a protective mask and glasses was essential but the effort paid off.

Left: Dirty muffler                                   Right: Cleaned and polished muffler

The exhaust tip has a fine smooth metal surface, therefore for the cleaning purposes I have used a polishing compound.
Left: Unpolished muffler tip                  Right: Polished muffler tip

After running a few kilometers the polished exhaust pipes developed a slight gold tint in the heating and cooling process. Looks pretty cool though.

Polished exhaust pipes after running a few kilometers.

After the restoration work had been almost completed I drove to the MOT station to undergo a technical exam. Unfortunately the car failed on emission test. This meant that a new catalytic converter was due. Well I wasn't happy with that. Of course without emission testing machine I couldn't have a slight idea that something was wrong with it. There was no previous indication that it has not been working correctly. The O2 sensor was replaced in 2010 and was working in good condition.
After spending many hours researching what type of catalytic converter would be ideal for my application I discovered the Magnaflow brand converters. The cat I bought was almost a half shorter than the OEM and 1.5 kg lighter.

Old OEM catalytic converter.

New Magnaflow catalytic converter.

I decided to replace the cat by myself although I am not a welder by training. I put lot of effort to correctly align the pipes and get rid off any sharp edges that could disrupt the exhaust flow. On this occasion I also got rid off the B pipe bottleneck by welding an extension pipe with constant diameter.

B pipe bottleneck removed.
My ultra sophisticated welding rig.
Finished repair.
Goldish tint after running the engine.
New cat from another view.

I did not have an appropriate welding machine such as TIG, only a plain simple Arc welding machine with stainless steel electrodes. As stated before I am not welder by training, that is the reason why the welds look like shit :). But the exhaust is tight without any leaks and most importantly the new cat passed the emission test.


  1. Hey man, did you just use a normal wire brush attached to a drill on the muffler? I have been wet sanding mine but it takes forever

    1. Yep, everything including the rear muffler was cleaned using the wire brush, higher drill rpm made it shine again.