January 10

1991 BMW 750i – Catalytic Converter Replacement for AirCare

Auto Repair, BMW


Today’s featured service is Catalytic Converter Replacement to rectify AirCare Test Failure on a 1991 BNW 750i and brought to us by a client in Marpole, Vancouver

BMW 750iL
1991 BMW 750i, Top of the line in it’s day and still a beautiful car.

This beautiful flagship BMW 750i features a 5 liter V12 engine. While the V12 engine is fabulously smooth, at a 5 liter displacement I would say it’s really overly complex. When many manufacturers make a much larger, more powerful and just as smooth V8 engine who really needs the extra 4 cylinders. It’s just a lot of extra stuff to go wrong.

Our clients 750i failed AirCare from bad catalytic converters. I use the term bad, as opposed to worn out, because the converters in this vehicle were only 4 months old! They were very poor quality and did little to reduce the emissions of the engine.

Some important lessons can be learned here and that is to be careful where you buy your parts. In the case of these cats, the owner purchased the pair for $500.00 from an internet part supplier. While they bolted in very nicely, clearly the catalyst inside was very poor quality. With catalytic converters you really get what you pay for. The reason being is that the catalyst materials are precious metals: platinum, palladium and rhodium. These are very expensive materials so reducing their quantity saves cost.

While I did not price out original BMW converters I would guess that for this car they would cost between $1000.00 and $2000.00 each. While you will get a very high quality converter, at that price it can be prohibitively expensive.

BMW 750iL
Poor quality catalytic converter removed from BMW 750i. From the outside it looks perfectly good. It’s what’s inside that counts!

What we did for our client is custom install Walker Calcat catalytic converters. These units meet California emission standards and as can be seen by the fabulous results on the AirCare retest, they really work. Cost for these converters installed was about $1100.00. Lots more than the internet garbage but a far cry cheaper than OEM.

For more about the BMW 750i click here http://en.wikipedia.org/wiki/BMW_750i

For more about Walker Calcat Converters click here http://www.walkerexhaust.com/products/catalytic-converters/carb-compliant

BMW 750i
AirCare test results: the poor catalytic converters are on top and the new cats results on the bottom. Big difference!

About the author 

Bernie Pawlik

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