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BMW 3-Series (E90 E92) Forum > E90 / E92 / E93 3-series Powertrain and Drivetrain Discussions > NA Engine (non-turbo) / Drivetrain / Exhaust Modifications > Smell with Headers



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      11-09-2017, 02:05 PM   #1
anotherchengman
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Smell with Headers

Hey guys,

How does the n52 smell with open headers and stock exhaust with the secondary cats? I am thinking about trying some eBay headers but hate the smell of open cats. Also has anyone tried the team-2-fast headers? Thanks
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      11-09-2017, 02:46 PM   #2
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With secondaries in place, you'll be fine.

Removing those too is what causes it to constantly stink.
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      11-09-2017, 03:13 PM   #3
rick100
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No smell inside the cabin with windows up.

once windows come down it ll smell specially on a hot day. Cars behind are going to smell it , people outside the car are going to smell it, if you dont care about that then it should be fine
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      11-09-2017, 09:15 PM   #4
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Quote:
Originally Posted by rick100 View Post
No smell inside the cabin with windows up.

once windows come down it ll smell specially on a hot day. Cars behind are going to smell it , people outside the car are going to smell it, if you dont care about that then it should be fine
Ok I need some help with this.

I've read numerous articles that claim exhaust catalytic converters are useless on a modern well running motor. The claim being that a modern well maintained motor has few unburned hydrocarbons emitted from the exhaust. The argument being these are another government boondoggle like ethanol.

It that's true, how can the removal effect the smell?
Fact being that since humans stopped hunting for dinner our sense of smell has gone down hill.

Are we talking about a smell during warm up when a normal car is running rich in an attempt to heat up the cats? We know that a good Catless tune should disable the rich warm up.
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      11-09-2017, 10:12 PM   #5
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Quote:
Originally Posted by rjahl View Post
Ok I need some help with this.

I've read numerous articles that claim exhaust catalytic converters are useless on a modern well running motor. The claim being that a modern well maintained motor has few unburned hydrocarbons emitted from the exhaust. The argument being these are another government boondoggle like ethanol.

It that's true, how can the removal effect the smell?
Fact being that since humans stopped hunting for dinner our sense of smell has gone down hill.

Are we talking about a smell during warm up when a normal car is running rich in an attempt to heat up the cats? We know that a good Catless tune should disable the rich warm up.

all cars that I have been around with catless headers smelled , during warm up and while running it.

The secondaries cats help a little bit , and that is probably the reason the smell is not inside the cabin

I may have a more sensitive smell than others , my wife in the other hand did not smell anything , then again , she can t even smell my farts so her sense of smell is very poor

However , while running catless headers I had co workers tell me I had an exhaust leak , I had friends driving behind me tell me how horrible smell of the exhaust when I accelerated . If it was a hot day and I was with the windows down stopped in traffic I was able to smell the exhaust

I got bored of it , I liked the power and all , but I was driving a 4 door BMW , not a hot rod , so for me , it was either get rid of the headers or do something about it.

I call a few performance shop , email AA , spoke to my mechanic , called shops that specialized on custom exhaust set ups. I even considered getting superstrpint headers or AFE headers. We came up with 2 possible solutions , first one was to remove the headers and install to high flow cats somewhere , however this was costly and very hard to do. So the second solution was to add a set of high flow cats behind the secondaries.

I went ahead and add it a second set of cats behind the secondaries for 400$.. Money well spent ! , smell is almost gone , unless I m ripping the car over 5k , there is barely any smelled. I did not loose any power, car still pulls hard, dyno sheets still show my gains , headers sound is identical.

Heck I even raced my brothers A4 after adding the set of cats and I still beat him , just like I did when I did not have the extra cats. All the shops I spoke too said the loss would be minimal if anything , even if I lost a 2-3hp , it was well worth it.

Again , that is my personal preference , some people are totally cool driving a car that smells bad , to each its own . If this was my weekend car I would've left it alone .
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      11-11-2017, 12:20 PM   #6
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I was really close to going to catless headers ... but after smelling a few catless cars (including another 328) I ditched the idea. I don't have the most sensitive sense of smell, but I could easily smell them.

And as rick100 mentioned ... I have a 4-door sedan, not a hot rod ... so having a bit of a smell with the car isn't a trade off I'm willing to deal with. Plus with it being a mostly-daily driver I decided to ditch the idea ... and decided to put the funds towards a used X5.

If AFE's catted headers were a bit closer to AA's catless cost wise ... I'd likely go that route at some point but ~ $2k (figuring $1,600 headers, header install cost, plus BPC update cost) isn't quite worth it for an extra 16 hp or so ... IMHO.
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      11-11-2017, 04:44 PM   #7
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Originally Posted by N52UNED View Post
I was really close to going to catless headers ... but after smelling a few catless cars (including another 328) I ditched the idea. I don't have the most sensitive sense of smell, but I could easily smell them.

And as rick100 mentioned ... I have a 4-door sedan, not a hot rod ... so having a bit of a smell with the car isn't a trade off I'm willing to deal with. Plus with it being a mostly-daily driver I decided to ditch the idea ... and decided to put the funds towards a used X5.

If AFE's catted headers were a bit closer to AA's catless cost wise ... I'd likely go that route at some point but ~ $2k (figuring $1,600 headers, header install cost, plus BPC update cost) isn't quite worth it for an extra 16 hp or so ... IMHO.
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      11-11-2017, 09:18 PM   #8
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The problem with aftermarket catted headers is that the cats are often poor quality.

Since they are "high flow" they typically just pass the OBDII ready tests for the first year or two. Then as they age, they can no longer pass the ready check and fail emissions.

Your mileage may vary but I've seen this on many aftermarket high flow cats.
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      11-11-2017, 11:52 PM   #9
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Quote:
Originally Posted by N52UNED View Post
I was really close to going to catless headers ... but after smelling a few catless cars (including another 328) I ditched the idea. I don't have the most sensitive sense of smell, but I could easily smell them.

And as rick100 mentioned ... I have a 4-door sedan, not a hot rod ... so having a bit of a smell with the car isn't a trade off I'm willing to deal with. Plus with it being a mostly-daily driver I decided to ditch the idea ... and decided to put the funds towards a used X5.

If AFE's catted headers were a bit closer to AA's catless cost wise ... I'd likely go that route at some point but ~ $2k (figuring $1,600 headers, header install cost, plus BPC update cost) isn't quite worth it for an extra 16 hp or so ... IMHO.
Adding a set of high flow cats behind the secondary really gets rid of the smell. Not 100% but its day and night difference. Really no difference in performance and still cheaper than buying catted headers and probably better performance wise as the cats are located further back

Still does not solve the problem of emissions for some people
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      11-12-2017, 08:25 AM   #10
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IMO the stink isn't too bad, and it isn't constant. Some days I smell it and sometimes I don't. No secondaries, just res and muffler.
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      11-13-2017, 11:26 AM   #11
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Quote:
Originally Posted by rick100 View Post
Adding a set of high flow cats behind the secondary really gets rid of the smell. Not 100% but its day and night difference. Really no difference in performance and still cheaper than buying catted headers and probably better performance wise as the cats are located further back

Still does not solve the problem of emissions for some people

I'll definitely have to check that out. Thanks for the tip ... I live in Florida so emissions aren't an issue.
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      11-13-2017, 11:36 AM   #12
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Quote:
Originally Posted by matteblue3er View Post
The problem with aftermarket catted headers is that the cats are often poor quality.

Since they are "high flow" they typically just pass the OBDII ready tests for the first year or two. Then as they age, they can no longer pass the ready check and fail emissions.

Your mileage may vary but I've seen this on many aftermarket high flow cats.
I can see that. I've read a post where a set of AFE's cats internals disintegrated after a short time. AFE replaced the set for the person, but it's still a concern.
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      11-14-2017, 05:18 PM   #13
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No one has mention anything on the ebay headers. Im interested as well.
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