I know this may strike at the heart of some but I just wanted to ask if anyone has ever installed a cat converter on an e9 with any success? I ask because my '74 has a very "70's" smell to the exhaust that sometimes flows through the interior and I find myself a little embarrassed from the smoke coming out of my car so it made me think about putting a cat on just to see. Thoughts?
Catalytic Converter Conversion
- Thread starter royal3po
- Start date
Mario L.
Well-Known Member
We build a few systems using cats for the S38 M88 and the S14 engined BMWs.
A cat will hide oil consumption and to some extent a rich running car. But before you add a cat, I suggest you put some one inside your trunk, close the lid and go around the edges with a flashlight to find where the exhaust leaks into the car. Just light up the trunk joint and the person inside can see the leak . .
Then let the person out !!!!
Adjust trunk lid and replace gasket as needed.
Note that a smelly engine can also vent in through the cowl. Replace the seal between the cowl and the engine at the top of the firewall and the snorkel hoses that drain the cowl.
Should you still choose to add a cat, a metallic cat will leave you with less power loss than a ceramic cat . . add an additional metal heat shield under the car to protect your floor boards and not overheat the asphalt based interior factory sound insulation.
Mario L.
A cat will hide oil consumption and to some extent a rich running car. But before you add a cat, I suggest you put some one inside your trunk, close the lid and go around the edges with a flashlight to find where the exhaust leaks into the car. Just light up the trunk joint and the person inside can see the leak . .
Then let the person out !!!!
Adjust trunk lid and replace gasket as needed.
Note that a smelly engine can also vent in through the cowl. Replace the seal between the cowl and the engine at the top of the firewall and the snorkel hoses that drain the cowl.
Should you still choose to add a cat, a metallic cat will leave you with less power loss than a ceramic cat . . add an additional metal heat shield under the car to protect your floor boards and not overheat the asphalt based interior factory sound insulation.
Mario L.
Mike Goble
Well-Known Member
So that's where you keep it...
I installed a Magnaflow ceramic cat. with a shield. Not sure about any power loss. It does eliminate the 70' smell you describe. See photos.
http://www.larsenarchitect.com/BMW/Sections/Exhaust/BMW Exhaust Frameset.html
http://www.larsenarchitect.com/BMW/Sections/Exhaust/BMW Exhaust Frameset.html
Tierfreund
Well-Known Member
I had a cat on my otherwise stock carbed 3.0S for a while. Removed much of the smoking and smell, did not hinder performance one bit. Even kept the rear clean (it´s a white car and the exhaust did tend to stain the side with the exhaust pipe). It was positioned directly behind the downpipes beside/under the gearbox. Single, decent sized cat.
But, as the engine wore and started to burn oil I one day ran into quite a problem. I was driving home about 400mls (from Berlin to Düsseldorf) and had a nice clear, empty autobahn so I let it rip (VMax for as long as I could). I´d done that often enough before and with the cat and no problems. But this day and at that level of engine wear and oil burn rate I ran into a problem where obiously the ehaust gas temp and the oil fumes burning off in the cat sent the cat over its melting temp and into a viscous circle. At first I just had a slight power loss, but even after going back to cruising speed the car lost more and more power. In the end I had a hard time getting it over 70-80mp/h. I did make it home and the car ran fine at idle but It wouldn´t pull properly. After much head scratching I took the exhaust of the car and took a look indise the cat. The front third of the cat had molten away and it´s remains had severely restricted the rest of the cat. Exhaust back pressure must have been riddiculous, it´s a miracle the car ran at all.
Had to bang the cat out and later removed it completely to get the car running properly again.
Long story, short info: A cat will work fine, not restrict performance, make your car smell a lot better and keep it´s butt cleaner.
But if your engine is very worn the oil fumes may iginite in the cat and melt it, at least at high speed/load. So maybe not the best idea for track or autobahn.
But, as the engine wore and started to burn oil I one day ran into quite a problem. I was driving home about 400mls (from Berlin to Düsseldorf) and had a nice clear, empty autobahn so I let it rip (VMax for as long as I could). I´d done that often enough before and with the cat and no problems. But this day and at that level of engine wear and oil burn rate I ran into a problem where obiously the ehaust gas temp and the oil fumes burning off in the cat sent the cat over its melting temp and into a viscous circle. At first I just had a slight power loss, but even after going back to cruising speed the car lost more and more power. In the end I had a hard time getting it over 70-80mp/h. I did make it home and the car ran fine at idle but It wouldn´t pull properly. After much head scratching I took the exhaust of the car and took a look indise the cat. The front third of the cat had molten away and it´s remains had severely restricted the rest of the cat. Exhaust back pressure must have been riddiculous, it´s a miracle the car ran at all.
Had to bang the cat out and later removed it completely to get the car running properly again.
Long story, short info: A cat will work fine, not restrict performance, make your car smell a lot better and keep it´s butt cleaner.
But if your engine is very worn the oil fumes may iginite in the cat and melt it, at least at high speed/load. So maybe not the best idea for track or autobahn.
I'm going to add one.
I am increasingly concerned about all the crap I put into the atmosphere with the coupe. It may not be bad, but it can't possibly be good.
I am increasingly concerned about all the crap I put into the atmosphere with the coupe. It may not be bad, but it can't possibly be good.