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BMW 3-Series (E90 E92) Forum > E90 / E92 / E93 3-series Powertrain and Drivetrain Discussions > N54 Turbo Engine / Drivetrain / Exhaust Modifications - 335i > Can some one explain to me about exhausts, downpipes, etc?



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      03-11-2010, 11:54 PM   #1
sourphish
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Can some one explain to me about exhausts, downpipes, etc?

So I've been reading up on this stuff over the past few months through my searches but now I just have tons of tidbits of information regarding the exhaust system. I would greatly appreciate if y'all could clarify/explain a few things out to me.

I'm looking to upgrade to a full catback system like HKS or Vanguard (because I'm confused about all the mixing and matching that many people seem to do), but I wanted to know how everything plays in together with regards to downpipes, O2 sims, catted, catless, the section 1, 2, and 3 (I know what these are visually, but why do people mix and match these?), and what not -- especially with passing California's strict emissions tests.

Everyone seems to do some sort of combination and it just confuses me. Would I just be able to install a system like HKS or Vanguard and be done with it? Or will I need to worry about O2 sims or DPs etc? And I want to be able to pass my emissions tests =p. Thanks in advance!!
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      03-12-2010, 12:04 AM   #2
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Seeing that your goal is to pass emissions test, you'll need:
1. Catted downpipes: this may or may not trigger the CEL but if it does, you'll need the BMS o2 sensor fix that's wired IN the ECU.
2. Downpipe-back exhaust with high-flow cats like AE. I'm not so sure on Vanguard so ask the vendor.

So in essence, you'll have two sets of high-flow cats. One in the downpipes and one after the downpipes. This should pass in California but I can't verify it.

Here's another option that I've verified with someone who passed smog in Cali:
1. Catless downpipes
2. Keep the stock exhaust system, including the secondary cats

Here's another option but it may not pass in California:
1. Catless downpipes
2. Downpipe-back exhaust with high-flow cats

Some people like to keep the stock exhaust or do their own custom piping at a shop. They usually get catless or catted downpipes then cut off the secondary cats by buying Riss Racing or Borla mid-pipes. If they go full catless, they realize it becomes too raspy so they either buy an axel-back exhaust to tone it down. What is left from this is section 2, which is not restricted by anything so they leave it stock.

In the end, it's all up to you and what you want. Happy modding. Post videos when you get your setup!
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      03-12-2010, 11:52 AM   #3
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Ah, thanks a lot for the info! I'm definitely not going to do custom piping or cutting/welding that comes with mixing and matching. Can anyone else verify the combinations above that can pass the emissions test??
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      03-12-2010, 11:57 AM   #4
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If you are confused, don't do anything until you clear everything up
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      03-12-2010, 12:03 PM   #5
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You can do what I do, makes it easy for CA smog every 2 years.

AR catted DP's.
AE catless exhaust.

Every 2 years for the emissions check I throw a stock exhaust back on and passes with ease. Putting the stock back on takes around 1 hour with a lift, so not too much work required every 2 years.
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      03-12-2010, 12:11 PM   #6
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Quote:
Originally Posted by Syndicategt View Post
You can do what I do, makes it easy for CA smog every 2 years.

AR catted DP's.
AE catless exhaust.

Every 2 years for the emissions check I throw a stock exhaust back on and passes with ease. Putting the stock back on takes around 1 hour with a lift, so not too much work required every 2 years.
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      03-12-2010, 12:28 PM   #7
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Quote:
Originally Posted by cstavaru View Post
If you are confused, don't do anything until you clear everything up
Yeah, that's why I haven't bought anything yet :P
I'm still green when it comes to dealing with cars so for every mod I purchased and installed, I tried my best to learn as much as I could about it, its effects, and how it could benefit (or be a detriment) to me and my car. Now, I've moved on to researching about these exhaust systems!

Quote:
Originally Posted by Syndicategt
You can do what I do, makes it easy for CA smog every 2 years.

AR catted DP's.
AE catless exhaust.

Every 2 years for the emissions check I throw a stock exhaust back on and passes with ease. Putting the stock back on takes around 1 hour with a lift, so not too much work required every 2 years.

Interesting, thanks for that suggestion! An hr or two of my time per 2 years isn't much at all haha.
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      03-12-2010, 02:28 PM   #8
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Quote:
Originally Posted by sourphish View Post
Yeah, that's why I haven't bought anything yet :P
I'm still green when it comes to dealing with cars so for every mod I purchased and installed, I tried my best to learn as much as I could about it, its effects, and how it could benefit (or be a detriment) to me and my car. Now, I've moved on to researching about these exhaust systems!




Interesting, thanks for that suggestion! An hr or two of my time per 2 years isn't much at all haha.
When it comes to emissions these guys ^^ up there have pretty much figured it out. Most of our customers with emissions got rid of the secondary cats with our exhaust. Not sure what they were doing with the DPs but haven't heard about anybody failing.

The exhaust is an easy an easy removal in comparison to the DPs if your going to replace anything every time you have emissions it should be the exhaust not the DPs.
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      03-12-2010, 02:37 PM   #9
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Quote:
Originally Posted by sourphish View Post
So I've been reading up on this stuff over the past few months through my searches but now I just have tons of tidbits of information regarding the exhaust system. I would greatly appreciate if y'all could clarify/explain a few things out to me.

I'm looking to upgrade to a full catback system like HKS or Vanguard (because I'm confused about all the mixing and matching that many people seem to do), but I wanted to know how everything plays in together with regards to downpipes, O2 sims, catted, catless, the section 1, 2, and 3 (I know what these are visually, but why do people mix and match these?), and what not -- especially with passing California's strict emissions tests.

Everyone seems to do some sort of combination and it just confuses me. Would I just be able to install a system like HKS or Vanguard and be done with it? Or will I need to worry about O2 sims or DPs etc? And I want to be able to pass my emissions tests =p. Thanks in advance!!
I just received my Vanguard exhaust this week. It looks sweet and is really high quality. I am installing it in the morning. It eliminates your secondary cats but you do get two resonators. I'll post some pics afterwards.
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      03-12-2010, 02:54 PM   #10
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Quote:
Originally Posted by Got_da_booze View Post
I just received my Vanguard exhaust this week. It looks sweet and is really high quality. I am installing it in the morning. It eliminates your secondary cats but you do get two resonators. I'll post some pics afterwards.
when u r ready to sell your jb+ just pm me if ididnt get already ill take it off ur hands
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      03-12-2010, 09:57 PM   #11
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Quote:
Originally Posted by Got_da_booze View Post
I just received my Vanguard exhaust this week. It looks sweet and is really high quality. I am installing it in the morning. It eliminates your secondary cats but you do get two resonators. I'll post some pics afterwards.
Yeah definitely post up some quality pics afterward! I'd love to see it =].

Quote:
Originally Posted by Nick.CBR
So are you going to be running a tune or no? The Procede does the O2 "sims" a little different in that it's built into the box instead of an actual harness. You can use the O2 modifier user adj. to eliminate the cat. codes.

Something to think about as well. If you're going go with the stock DME programming and just exhaust, then you'll need the O2 sim gear for sure.

Nick
I've been running with JB3 for the past 3k miles or so. I guess getting the O2 sims / sensor fix will probably be a necessity. Simple fix to do anyway.

Thanks for all the info guys!
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      03-13-2010, 12:44 AM   #12
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So, what would you guys do? Get high-flow catted downpipes and stock exhaust, or stock downpipes and aftermarket exhaust...? Which would have the most gains...?
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      03-13-2010, 07:30 AM   #13
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dp's

Get catless DP's and stock exhaust with golf-tee(like) mod
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      03-13-2010, 04:14 PM   #14
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Well, I'm in Cali so I want to pass emissions. I don't have the ability to swap exhausts or downpipes frequently, so I want a hassle free solution.
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