Jean & Ben both have valid points about the appearance of the cat. You have a high probability of passing the visual BAR inspection with the BMW logo on the cat.
I would be more concerned about the actual tail pipe emissions (sniff test) not passing. Think about it, the M3 is 2500cc 4 cyl, vs. your transplant at 3500cc 6 cyl. That's a 29% bigger (& all the combustion gas volumn etc.) motor (yea!!) - but you trying to put all the combusted volume through a cat that is made to function correctly (convert NOX) at @ 30% less volume. I'm sure the manufacturer overbuilt the cat somewhat - but the exotic materials inside it are very expensive so I question if they put 30% more than it needed. Said another way - if you have a 100,000 gal pool & put a filter on it that is for a 70,000 gal pool, it's not going to get out all the gunk.
The following is an excerpt from a discussion on "cats" on the e30M3sig. While it does not apply totally to Andrews swap, it does make some valid points on their operation.
"Group,
I have watched this thread for a few days and felt the need to address it.
I am a BMW Technician,repair shop owner, a BMW owner for over 30 years, and many of you know me through racing and club activities esp in CA.
As far as the smog issue , Yes clean oil will help, fresh spark plugs and filters a plus. A well functioning oxygen sensor is necessary BUT if the cat isn't working well enough then it won't pass . End of story.
Some of you have stated ideas, and theories and while all have merit(most of you are VERY intelligent well schooled people). Practically speaking as the car ages, the cat ages, and becomes contaminated with fuel, and oil.
There are some ways to minimize their effect(intake cleaners, etc) but unless you replace the cat, the only way you can get the cats to "light" and work properly is to get them hot, and Darrens suggestion to run the hell out of them, high RPM runs for 10 minutes or so ,maybe more, then run it ASAP to the smog station is really the best way to deal with an older catalytic converter.
Here in CA. we have a very strict smog test, and we have to smog the cars every 2 years, (some every year) and I probably take at least 5 cars a month to be smogged and we have to do this procedure to most if they won't pass on the first attempt, after we take it for a good run almost all pass on the next attempt.
All said it works, and unless you can afford a new cat then this is the only viable answer. Sometimes it doesn't work as the internals of the cat are just not functioning and your only recourse it to replace the cat.
Thanks for reading, I HTH...
Billy Maher"
excerpt #2
"Group,
Billy that was a very good explanation of the problem and its resolution.
Now the technical reason....
FYI: The Cat is made with two active materials:
Platinum or Palladium for the CO and HC reduction.
Rhodium for the NOx reduction. Both are usually mixed together in a one cat system. But many times they are in separated sections. The rhodium needs a higher temp to work and the platinum/paladium and HC and CO oxidation creates the higher temperature (exothermic) for the Rhodium to work which is a non heat production process (endothermic). So if the cat is dirty with oil or fuel deposits on the Platinum/Paladium, then the Rhodium does not work well/ So in a nutshell the hotter the cat the better the rhodium works (NOx reduction).
John Siemak
MS in Chemistry...
Work with the Catalyst Production departments at GM and Toyota..."
Before I buy an M3 muffler & run up the bill at Mesa Muffler, I would pick the brains of a capable smog tech or engineer & see if the cat from a @30% smaller engine is going to effect the tail pipe emissions.
I think it was Jean who prepared a binder with all the swap specifics (part #'s etc) to show to the referee - that is an excellent idea !!
I would be more concerned about the actual tail pipe emissions (sniff test) not passing. Think about it, the M3 is 2500cc 4 cyl, vs. your transplant at 3500cc 6 cyl. That's a 29% bigger (& all the combustion gas volumn etc.) motor (yea!!) - but you trying to put all the combusted volume through a cat that is made to function correctly (convert NOX) at @ 30% less volume. I'm sure the manufacturer overbuilt the cat somewhat - but the exotic materials inside it are very expensive so I question if they put 30% more than it needed. Said another way - if you have a 100,000 gal pool & put a filter on it that is for a 70,000 gal pool, it's not going to get out all the gunk.
The following is an excerpt from a discussion on "cats" on the e30M3sig. While it does not apply totally to Andrews swap, it does make some valid points on their operation.
"Group,
I have watched this thread for a few days and felt the need to address it.
I am a BMW Technician,repair shop owner, a BMW owner for over 30 years, and many of you know me through racing and club activities esp in CA.
As far as the smog issue , Yes clean oil will help, fresh spark plugs and filters a plus. A well functioning oxygen sensor is necessary BUT if the cat isn't working well enough then it won't pass . End of story.
Some of you have stated ideas, and theories and while all have merit(most of you are VERY intelligent well schooled people). Practically speaking as the car ages, the cat ages, and becomes contaminated with fuel, and oil.
There are some ways to minimize their effect(intake cleaners, etc) but unless you replace the cat, the only way you can get the cats to "light" and work properly is to get them hot, and Darrens suggestion to run the hell out of them, high RPM runs for 10 minutes or so ,maybe more, then run it ASAP to the smog station is really the best way to deal with an older catalytic converter.
Here in CA. we have a very strict smog test, and we have to smog the cars every 2 years, (some every year) and I probably take at least 5 cars a month to be smogged and we have to do this procedure to most if they won't pass on the first attempt, after we take it for a good run almost all pass on the next attempt.
All said it works, and unless you can afford a new cat then this is the only viable answer. Sometimes it doesn't work as the internals of the cat are just not functioning and your only recourse it to replace the cat.
Thanks for reading, I HTH...
Billy Maher"
excerpt #2
"Group,
Billy that was a very good explanation of the problem and its resolution.
Now the technical reason....
FYI: The Cat is made with two active materials:
Platinum or Palladium for the CO and HC reduction.
Rhodium for the NOx reduction. Both are usually mixed together in a one cat system. But many times they are in separated sections. The rhodium needs a higher temp to work and the platinum/paladium and HC and CO oxidation creates the higher temperature (exothermic) for the Rhodium to work which is a non heat production process (endothermic). So if the cat is dirty with oil or fuel deposits on the Platinum/Paladium, then the Rhodium does not work well/ So in a nutshell the hotter the cat the better the rhodium works (NOx reduction).
John Siemak
MS in Chemistry...
Work with the Catalyst Production departments at GM and Toyota..."
Before I buy an M3 muffler & run up the bill at Mesa Muffler, I would pick the brains of a capable smog tech or engineer & see if the cat from a @30% smaller engine is going to effect the tail pipe emissions.
I think it was Jean who prepared a binder with all the swap specifics (part #'s etc) to show to the referee - that is an excellent idea !!
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