An SI owner wanting exhaust options

[Jaydon Fabulous]

Am i alone here? Nothing is really meant to fit our car. I just want an affordable axle back exhaust. I wish RPI would step up and help us SI owners out. I'm always seeing pics of their exhaust on the ///m and i keep getting jealous:

[Incompatible]

Originally Posted by Jaydon Fabulous

Am i alone here? Nothing is really meant to fit our car. I just want an affordable axle back exhaust. I wish RPI would step up and help us SI owners out. I'm always seeing pics of their exhaust on the ///m and i keep getting jealous:

There are options out there from specialty manufacturers such as supersprint, stebro, ..... but they come with a price. If you go that route, be sure to verify that the muffler configuration is for the post facelift Si as the prefacelift cars are different. There are also several threads for custom installations using a magnaflow muffler. See http://www.zpost.com/forums/showthre...sonator+delete.

I'm in the same situation as you are and hope to have something in about a month or so if I can get away from work long enough.

A few things to remember:
1. The oe exhaust does sound good, no drone, good tone.... I would like just a little more volume, with no drone.
2. One option would be to remove only the resonators and replace with straight pipes, keeping the oe muffler. Forum responses on this have been mixed as to the results. I don't remember anyone who has actually did this on our cars and posted the results.
3. It's impossible to compare sound/videos for sound quality due to the many differences in recording conditions, equipment, environmental aspects... You're best bet is to be patient, find cars with these types of exhausts, and listen for yourself. A number of posters have gone with a particular setup and then changed back to oe or another mfg due to the sound not being the same as the video they listened to.
4. Don't count on any type of serious performance gains with only an axle back or even cat back system on our cars. BMW did a good job and you can expect somewhere between 0-5 hp generally in the top range without additional mods. In essence, you're spending your money for sound only.
5. Depending on what you're looking for in sound quality, you also have the option of removing one or two of the foam plugs from the sound generator tube on your car. This will increase the volume of the intake sound in the passenger compartment of the car without any change in the exhaust.

[BossE86]

As a fellow SI owner I feel your pain in the search for an exhaust.

A very well written post Incompatible, thank you. Do you have anymore information on the removal of the aforementioned foam plugs?

After seeing the prices of some of the exhaust systems for the Z's I've been debating bypassing the cats with a straight pipe, I am looking for the same sound... just louder!

[Incompatible]

Originally Posted by BossE86

As a fellow SI owner I feel your pain in the search for an exhaust.

A very well written post Incompatible, thank you. Do you have anymore information on the removal of the aforementioned foam plugs?

After seeing the prices of some of the exhaust systems for the Z's I've been debating bypassing the cats with a straight pipe, I am looking for the same sound... just louder!

By "bypassing the cats" I assume you're talking about the two resonators in the tunnel, they look somewhat like small cats but on our cars they are simply resonators. The cats are part of the exhaust manifold. If you don't mind some trial & error work, see #2 in my post which replaces the resonators only. Another option which might be to loud (?) is to remove the muffler at the axle and run pipes out from there while retaining the resonators.

Something I've been thinking of and haven't had a chance to get the car up in the air to check clearance is a magnaflow 12761, 12280, or 11385 located in the tunnel. I've had several suggestions to use a 2.25" dia single inlet size to keep the volume down but I'm concerned about flow restriction at the higher rpm range so have considered a 2.5" dia pipe for single applications. My understanding is that the aftermarket mfg systems use single pipe diameters in the range of 3". Our cars run twin 1.88" dia pipes and although I realize that when going to a single pipe you can go smaller while still retaining good flow characteristics, a single 2.25" seems to small. I haven't been able to talk to someone who has a good understanding of the physics involved.

Sound generator: easy mod, do a search and you'll come up with a number of posts/diy.

[Twisted Six]

Guys...going from a twin set thats 1.88" diam........means combined a somewhat 3.75' single pipe max.

SO....going single with a 3' pipe with our HP levels would work fine...even if turbo charged.

A single 1.25" would become a restriction and hiss under high rpm's. No good.

[Incompatible]

Originally Posted by Dark Schnitzer

Guys...going from a twin set thats 1.88" diam........means combined a somewhat 3.75' single pipe max.

SO....going single with a 3' pipe with our HP levels would work fine...even if turbo charged.

A single 1.25" would become a restriction and hiss under high rpm's. No good.

Vinny,
Valid if comparing cross-sectional area. My limited understanding is that due to flow characteristics you can actually go smaller on a single pipe (effect of laminar flow at the walls) and achieve equal if not better flow rates for same area twins. My problem is I don't know how to calculate what the equivalent size is. There is also an sound quality component between the two. Again if I understand correctly, the twin pipes will produce slightly lower tone/quieter/less drone sound for our cars. I don't know and have resorted to a let me hear it - see it method.

I do agree that a single 2.25 seems to small, but I could be wrong.....

[BossE86]

I appreciate this help, I'm afraid though that I've yet to take any classes in regards to this material and can't contribute to the conversation.

I am however looking into the Posts / DIYs on the sound generators.

[3002 tii]

si owners have 2 choices:

supersprint
http://www.supersprintna.com/categor...tegory_id/139/

or

bastuck
http://bastuckusa.com/ (search for z4 -> post facelift)

i went with bastuck b/c at the time supersprint had not yet come out with si-specifc parts. they were selling their pre-facelift z4 exhaust as one size fits all, but clearly was not the case. if you compare on supersprint's site, they now have diff part numbers for pre and post-facelift.

i'm very happy with my bastuck. i opted for the midpipe w/ silencer since i didn't want any drown. never got a chance to dyno but butt dyno showed improvement as i was able to get through the revs quicker. also, i liked the option of the slash cut design that follows the lines of the bumper.

[midn12ght]

Originally Posted by Dubbedown

si owners have 2 choices:

i went with bastuck b/c at the time supersprint had not yet come out with si-specifc parts. they were selling their pre-facelift z4 exhaust as one size fits all, but clearly was not the case. if you compare on supersprint's site, they now have diff part numbers for pre and post-facelift.

i'm very happy with my bastuck. i opted for the midpipe w/ silencer since i didn't want any drown. never got a chance to dyno but butt dyno showed improvement as i was able to get through the revs quicker. also, i liked the option of the slash cut design that follows the lines of the bumper.

at some point you were sporting the stebro though, yes? i've been silently monitoring mod development for the SI and fell in like with the sound. wanted something close to the magnaflow S4 or labree/fast intentions tones from my [past] audi experiences of course limited by a single (not dual) exhaust system :/.

-lisa

[3002 tii]

Originally Posted by midn12ght

at some point you were sporting the stebro though, yes? i've been silently monitoring mod development for the SI and fell in like with the sound. wanted something close to the magnaflow S4 or labree/fast intentions tones from my [past] audi experiences of course limited by a single (not dual) exhaust system :/.

-lisa

yup, but it grew to be too loud for my taste overtime. if you are buying new, i'd say don't bother with the stebro b/c the fitment isn't meant for the Si. my exhaust shop had to play around with the hangers which turned out to be a pain. oh yea, their customer service BLOWS and they'll continuously make up excuses as to why your muffler hasn't arrived (originally quoted me 1 week shipping but tracking shows that it never left their shop till 3 weeks later).

i also came from the audi/vw scene so i know what you're talking about. my bastuck with silencer is pretty tame but i like it b/c it retains the luxury/comfortable cabin feel. however if you went with the straight pipe option i'm almost certain you'd get that aggressive tone you're looking for.

[BossE86]

I had yet to check out the Bastuck exhaust. I must say I like the sound a lot. An acquaintance on YouTube with a Z4 w/ Bastuck exhaust is planning to upload a video for me of the exhaust. I'll make sure to share that here B]