Suggestions, which exhaust combo

[matacuero]

Living in Northern VA, trying to mod my exhaust but I am unsure of 2 things:

Which combination will bump up my power and how will it affect my Virginia emissions test.

I bought an active autowerke axle back that I've heard on a neighbor's car and loved it but I want to combine it with either the midpipes or downpipes.

Will I get more power with the downpipe replacement? I am aware that the axleback is more for sound although the Active autowerke provides a little bit of weight reduction.

Another option is to leave the stock DPs but replace the midpipes when I install the axle back.

So again, which would yield a little more power? My guess would be that the DPs being closer to the turbos would provide a little more flow. Am I correct?
I don't want to do all 3 (DPs, MPs and axle back as I think it will get too loud).

Lastly, I want to know if this will drastically affect my Virginia emission's test? Anyone know.

Thanks for your suggestions.

[135Pats]

1. Axle-back will add volume/tone, negligible power gains.
2.downpipes are the most restrictive part of the OE setup, you can gain solid whp by replacing the catted units. They WILL make your vehicle fail emission testing if VA uses obd+visual, as MD does. They will also add noise, and rasp.
3.midpipes will open things up a bit, and add a bit more noise. Not to the same deg. Downpipes will though.

If you have an N54, the entire OE exhaust is restrictive. I replaced the stock axle back and midpipes, the DPs need to stay for warranty work and emissions testing. If you dont care about those two/ are willing to remove the dps every time, gthaus+berk+AR would be beastly...

[matacuero]

Thanks for the info. So if I understand correctly then I would need to do midpipes and the axleback I already have and I won't have any emission issues.

I would love to do the DPs but won't yet until I run a couple of times at the track and get bored of whatever power I am able to generate with this set up. Will be installing the exhaust and an injen intake next week. I have a Dinan Stage 2 tune and I see an aftermarket intercooler in the near future. Thanks

[135Pats]

Originally Posted by matacuero

Thanks for the info. So if I understand correctly then I would need to do midpipes and the axleback I already have and I won't have any emission issues.

I would love to do the DPs but won't yet until I run a couple of times at the track and get bored of whatever power I am able to generate with this set up. Will be installing the exhaust and an injen intake next week. I have a Dinan Stage 2 tune and I see an aftermarket intercooler in the near future. Thanks

As long as you don't touch the factory downpipes, you shouldn't have any issues with run of the mill emissions testing or CELs. There are tons of tunes available for the N54, if you haven't already check them out.

[gmair]

I have a 2008 135i convertible with a Dinan Stage 2 software upgrade. I'm also contemplating an exhaust and intake upgrade. Looking at the OEM schematic it looks like there are secodnary catalytic converters in the mid pipe. If I install a cat back system like Berk Technology will I have problems passing emission tests?

http://www.realoem.com/bmw/showparts...70&hg=18&fg=10

[135Pats]

Yes the midpipes do indeed have secondary cats, but no you will have no emissions issues if you remove them. As long as the primary (DP) cats stay in place, you will pass standard emissions testing. If the stock cats are staying in place Berk race is a great exhaust, alot of members here have it. Well priced too.

[gmair]

Thanks,
I was also considering the Meisterschaft midpipe and axleback, but very $$$$$,
I think about $2,500 for both compared to $900 for Berk Technology BT1801-MMP

[135Pats]

I understand your hesitance, the gthaus midpipe is criminally expensive, so i went with the berk mids for about half what the other midpipes cost. They should be here on friday, im not sure when ill install them but when i do ill give you my impressions. The gthaus axleback is one of the loudest available, so the midpipe is more for tone than outright noise. I think theyll pair quite nicely.

[gmair]

Thanks, I'm curious to know what you think of it.