catted midpipes with cattless downpipe

[sdmodified]

so I am planning on getting an n55 1er pretty soon and very quickly will be opening up the exhaust system, jb4, intake, etc... On my cars I have always gone the high flow cat route to avoid any inspection issues, smell, and volume.

My thoughts are to use a cattless downpipe (VRSF or low cost option) and maybe pick up a used n54 midpipe and weld in some high flow (magnaflow or other) cats. The idea here is to use two cats at no more than maybe 200 cells to really open up the exhaust flow and move them further down the line away from increased heat that my future tuning plans (pure stg 2) will create.

I have been searching but I am just not finding any options other than the very costly milltek system that actually does it this same way. I know most go cattless but I am very curios in this alternative.. A catted downpipe just seems to be way too costly and then when I get to upgrading the turbo I would be risking it getting ruined pretty quick.

Hopefully I can run cats at a higher boost level (pure) without them breaking up from heat if they are in midpipe? Would 2 high flow cats in midpipe be much less restrictive therfore only slightly impacting HP loss over full cattless? Anyone have thoughts on this?

[mike@x-ph.com]

Glad to see you already have big plans for the car

You are correct, catless downpipes + catted mid pipes is a good options.

You can also get catted DP, they are not all pricey. Wagner catted DP is very reasonably priced and is a quality product

[sdmodified]

Originally Posted by mike@x-ph.com

Glad to see you already have big plans for the car

You are correct, catless downpipes + catted mid pipes is a good options.

You can also get catted DP, they are not all pricey. Wagner catted DP is very reasonably priced and is a quality product

Thanks for reply!! Also, you website is very helpful and I have spent a lot of time already looking through your products!

My concern with a catted downpipe is that when I upgrade turbo (ps2), I will either have too much backpressure and/or the higher boost will destroy the cat quite quickly. My thoughts are that by only having high flow cats in midpipe, I can move them further away from the heat and with 2 (2.5 or 3 inch) cats, I would significantly increase the amount of flow volume over 1, 4 inch cat. especially with 200 cell count cats.

[mike@x-ph.com]

Originally Posted by sdmodified

Thanks for reply!! Also, you website is very helpful and I have spent a lot of time already looking through your products!

My concern with a catted downpipe is that when I upgrade turbo (ps2), I will either have too much backpressure and/or the higher boost will destroy the cat quite quickly. My thoughts are that by only having high flow cats in midpipe, I can move them further away from the heat and with 2 (2.5 or 3 inch) cats, I would significantly increase the amount of flow volume over 1, 4 inch cat. especially with 200 cell count cats.

Thank you, im glad you found our website helpful .
catted midpipes + catless downpipes is the best choice in my opinion

[loesch]

Originally Posted by sdmodified

so I am planning on getting an n55 1er pretty soon and very quickly will be opening up the exhaust system, jb4, intake, etc... On my cars I have always gone the high flow cat route to avoid any inspection issues, smell, and volume.

My thoughts are to use a cattless downpipe (VRSF or low cost option) and maybe pick up a used n54 midpipe and weld in some high flow (magnaflow or other) cats. The idea here is to use two cats at no more than maybe 200 cells to really open up the exhaust flow and move them further down the line away from increased heat that my future tuning plans (pure stg 2) will create.

I have been searching but I am just not finding any options other than the very costly milltek system that actually does it this same way. I know most go cattless but I am very curios in this alternative.. A catted downpipe just seems to be way too costly and then when I get to upgrading the turbo I would be risking it getting ruined pretty quick.

Hopefully I can run cats at a higher boost level (pure) without them breaking up from heat if they are in midpipe? Would 2 high flow cats in midpipe be much less restrictive therfore only slightly impacting HP loss over full cattless? Anyone have thoughts on this?

I have tried just about every option. Stock exhaust; catless dp w/ straight through axle back; catless dp w/ N54 mids w/ straight through axle back; catless dp w/ N54 mids w/ muffler; also catless dp w/ gutted N54 mids w/ muffler (my current setup). When I had a catless dp w/ N54 mids and AA Gen II exhaust it was too quiet. Sounded stock. Even now with the secondary cats gutted there is no drone at all and it's a tad quiet at times. On the flip side, when I had a completely open straight through exhaust with no cats it got super raspy. Hated it. It's hard to get a good sense of the sound level but here's what mine sounds like now. Inside you can hold a conversation without raising your voice at all.

Based on what people are saying, the Pure Stage 2 is other worldly. I'm in the middle of installing one myself. Can't wait.

[Tiago@VRSF]

A catless downpipe is a great solution. Our proto 135i exhaust is currently catless and sounds awesome.

[rhodesman]

my $0.02, you are right to go catless DPs. I have catted DPs and they are pretty much burnt through. I'm probably going to just get catless in the near future because I wanted ceramic coated DPs. Maybe I can just have the cats gutted on my current DPs and coat them that way LOL.

[2PUTT]

if you need a nice set of used BMW PE, i have a set. i am local too. =)

[litebulb]

Last month, I went catless DP and MP on my N54 and it is paired to a BMW PE w/o the resonator delete. I hated it! The sound was too much like a old diesel truck, there was an awful drone at 1-2000 RPM, the smell was considerably worse than I thought it would be and there was excessive smoking, which was embarrassing. I mainly drive city so you could understand how annoyed I got. I threw back on my N54 MP which completely changed it somewhat for the better. I might do the resonator delete to get back some of the aggressiveness. Can anyone elaborate on how much better aftermarket cats compare to the ones on the stock N54 MP (I thought I read somewhere that they are high flow)? Thank you

[sdmodified]

Thanks for all replays. Good videos lose His! All Good info... Rhodesman, your point is my main concern. Especially if going pure stage 2. On my gti I removed the catted down pipe and replaced with catless but I have a high flow cat in my exhaust further down(135i mid pipe region). New Jersey does visual inspection and obdii only plus I hate smell and raspy ricer sound so I really want a cat. The maddad mid pipe should pas visual but since it is a fake cat I will still have sound and smell. I know guys will say cats reduce horsepower but I think with two 200 cell high flow cats from magnaflow welded into mid pipe I will suffer very minimal hp loss And get the Catts moved downstream in the exhaust away from the engine and heat to hopefully improve longevity.
Another question is that in this situation the O2 sensor will need to be in the doe pipe and with jb4 though the check engine light will turn off, it is my understanding that in a dmv obdii scan it will come up as not ready? How are people doing with spacers in this regard in n55s? I assume a flash will fix this but only in pre 2012 build dates? Would a pro tune fix this in a 2013? If I still need to swap the stock down pipe back to pass emissions I might as well go catless...

[ShocknAwe]

Originally Posted by sdmodified

Thanks for all replays. Good videos lose His! All Good info... Rhodesman, your point is my main concern. Especially if going pure stage 2. On my gti I removed the catted down pipe and replaced with catless but I have a high flow cat in my exhaust further down(135i mid pipe region). New Jersey does visual inspection and obdii only plus I hate smell and raspy ricer sound so I really want a cat. The maddad mid pipe should pas visual but since it is a fake cat I will still have sound and smell. I know guys will say cats reduce horsepower but I think with two 200 cell high flow cats from magnaflow welded into mid pipe I will suffer very minimal hp loss And get the Catts moved downstream in the exhaust away from the engine and heat to hopefully improve longevity.
Another question is that in this situation the O2 sensor will need to be in the doe pipe and with jb4 though the check engine light will turn off, it is my understanding that in a dmv obdii scan it will come up as not ready? How are people doing with spacers in this regard in n55s? I assume a flash will fix this but only in pre 2012 build dates? Would a pro tune fix this in a 2013? If I still need to swap the stock down pipe back to pass emissions I might as well go catless...

"Raspy ricer sound" is from improperly muffled and/or un(under)resonated exhaust piping, not a lack of cats.

Get a downpipe fix and set jb4 to map 0 or flash to a stock bin, do your drive cycle for readiness. Unless they use a sniffer you should be ok.

[loesch]

Originally Posted by ShocknAwe

"Raspy ricer sound" is from improperly muffled and/or un(under)resonated exhaust piping, not a lack of cats.

Get a downpipe fix and set jb4 to map 0 or flash to a stock bin, do your drive cycle for readiness. Unless they use a sniffer you should be ok.

Agreed. I was very surprised to have 0 rasp with just a muffler in the axle back being the only restriction. No cats.

[sdmodified]

Originally Posted by ShocknAwe

"Raspy ricer sound" is from improperly muffled and/or un(under)resonated exhaust piping, not a lack of cats.

Get a downpipe fix and set jb4 to map 0 or flash to a stock bin, do your drive cycle for readiness. Unless they use a sniffer you should be ok.

Good to know. Thanks again for feedback. Does the built in JB4 downpipe fix allow a pass or do you need an O2 spacer or other means to keep o2 sensor in ready state? This would be for N55 engine and later model so no flash tuning.

[mike@x-ph.com]

Originally Posted by sdmodified

Good to know. Thanks again for feedback. Does the built in JB4 downpipe fix allow a pass or do you need an O2 spacer or other means to keep o2 sensor in ready state? This would be for N55 engine and later model so no flash tuning.

Jb4 will only auto clear the code, it will not allow you to pass emission

[RVAN]

Originally Posted by sdmodified

Thanks for all replays. Good videos lose His! All Good info... Rhodesman, your point is my main concern. Especially if going pure stage 2. On my gti I removed the catted down pipe and replaced with catless but I have a high flow cat in my exhaust further down(135i mid pipe region). New Jersey does visual inspection and obdii only plus I hate smell and raspy ricer sound so I really want a cat. The maddad mid pipe should pas visual but since it is a fake cat I will still have sound and smell. I know guys will say cats reduce horsepower but I think with two 200 cell high flow cats from magnaflow welded into mid pipe I will suffer very minimal hp loss And get the Catts moved downstream in the exhaust away from the engine and heat to hopefully improve longevity.
Another question is that in this situation the O2 sensor will need to be in the doe pipe and with jb4 though the check engine light will turn off, it is my understanding that in a dmv obdii scan it will come up as not ready? How are people doing with spacers in this regard in n55s? I assume a flash will fix this but only in pre 2012 build dates? Would a pro tune fix this in a 2013? If I still need to swap the stock down pipe back to pass emissions I might as well go catless...

I installed catless downpipes and found someone who wanted to swap mids straightup. So I have catted mids and catless dp's. No smell, and now with E50 blend really no smell.

I believe if they do an ODB check you can't pass unless the DP fixes have gotten better.

[sdmodified]

This group of folks are still trying to finish developing a true downpipe fix for the n55 engine. Seems that they are very close but not 100% yet. Thought some of you may be interested in checking this thread out over at e90post.

http://www.e90post.com/forums/showthread.php?t=1122568

[CharsadehBEAST]

Originally Posted by RVAN

I installed catless downpipes and found someone who wanted to swap mids straightup. So I have catted mids and catless dp's. No smell, and now with E50 blend really no smell.

I believe if they do an ODB check you can't pass unless the DP fixes have gotten better.

What axle back do you have? I'm thinking about doing something similar as the smell from the catless dp is too much for me. I have a 2012 (n55) and am looking into a custom midpipe with resonators and high flow cats. The n54 mids will probably work fine with the PE axle back I have but I'm thinking about going with the Berk street and concerned with drone. in other words, I would have catless dp + custom resonated catted mids + Berk stree axle back.

[ShocknAwe]

Running a single 3.5" cat in my midpipe. Works great.

N53 ported head, Hydra HP800 turbos.