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      03-05-2014, 05:12 PM   #1
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Drives: 2010 328i, 2014 Z4
Join Date: Jan 2010
Location: NJ, USA

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2014 28i Full Turbo Back Exhaust - Evolution Racewerks - Supersprint - Magnaflow

Since I’ve received a number of questions about the exhaust setup on my Z4, I figured it would be good to post a thread on it. First, the overall goal for the exhaust system was to have as little back pressure as possible post turbo and to maintain good flow. The second consideration was sound, specifically how loud the exhaust would be, as several of the tracks I take the Z4 on have sound restrictions that need to be met to avoid a black flag. This is a long post, you may want to scroll to the end if you just want my impressions on the final result

Prior to installing the full exhaust system, I decided to do a rear muffler delete to get a bit more of an aggressive exhaust tone. This was simple enough, I left the front resonator and all of the stock pipes in place up to where the stock rear muffler was, welded in a custom Y pipe and a simple black-chrome exhaust tip. This worked well enough, but was never intended to be a long term solution. Once I had the 3D-Design rear diffuser in place it was time to upgrade the exhaust to quads and finally get some performance gains from an improved system.

The first component I looked into was a catless downpipe. Several vendors have products available for the N20, but I decided on the Evolution Racewerks Competition Series 4” Catless Downpipe ( All of the products available seemed to have good reviews on the various forums, but ER also offer an optional ceramic thermal coating along with extra bungs for an additional O2 sensor and EGT sensor. Having the extra bungs from the manufacturer is a great plus and would avoid any issues with drilling and welding in additional bungs later. I placed the order through **********s right around Christmas time (December 26th to be exact) with the knowledge that ER was to be closed till after New Years so I fully expected having to wait a bit for the order to be processed. I was almost immediately contacted by Alyssa at **********s who wanted to make sure I knew that ER was closed for the holidays and wouldn’t be back until after the New Year. Although I could have ordered directly from ER, **********s had slightly better pricing. As soon as Evolution Racewerks returned from the holiday I was contacted by Christine who informed me that due to variations in length between vehicles they actually had two different variations of the N20 downpipe. She asked if I could send some pics of the OEM downpipe so they could ensure they built and shipped the correct one. This is a nice bit of extra customer service which I think is great for them to be doing. Pictures were sent to Alyssa at **********s and Christine at ER on January 3rd and I was told the lead time would be about 3 weeks for them to manufacture the downpipe and maybe a bit more for the thermal coating. I received no less than 4 status updates during the wait (about one a week) from Alyssa at **********s and my downpipe was finally shipped on February 19th. Assuming they didn’t start the build until the Monday following when I sent the pics, the 4 weeks it took to build, thermal coat and ship was pretty much inline with the expectation I was originally given and the status updates along the way kept me from guessing on when the part would arrive.

The ER downpipe is very well built and the ceramic thermal coating was flawless. Having said that, despite the extra measures taken to ensure that I received the correct downpipe, the fitment on the pipe mounting was pretty a bit off. The downpipe reuses the factory bracket that mounts to the engine and once connected to the turbo this bracket was misaligned by about 1/2”. Annoying, yes, but not the end of the world. A small tweak to the factory bracket and everything was mounted securely. A little additional research post-install shows that there is actually 3 different variants of the catalytic converter on the N20, one variant for the F3x 328, one for the F25 X3 and yet another for the E89 Z4. In addition, as I have a 2014 (LCI) Z4 its quite possible BMW decided to make a change to this bracket. This isn’t reflected in the BMW ETK and actually the part number for the bracket isn’t even listed for any model year E89 despite the fact that it is most definitely on the car. What it looks like to me is that for the E89 the bracket can only be ordered with the OEM catalytic converter which went through 3 revisions of its own on the E89. Interestingly the part number for this bracket is listed for the F25 X3 and F3x 328. Based on the parts listing in the ETK I would say that if you have an E89 that was built before January 2013 the Evolution Racewerks downpipe will be a direct bolt on; if it is built from January 2013 onward you will have the same issue with this bracket until ER comes up with a fix.

I have passed this information on to both Alyssa at **********s and Christine at Evolution Racewerks. Additionally, ER will be having one of their lead engineers get in touch with me in the next few days to discuss and review the changes in the mounting bracket for the downpipe on the 2014 models.

Behind the downpipe I was torn for awhile on exactly what I wanted to do. Initially, I was thinking of just replacing the front resonator with a Magnaflow muffler and having the rest of the system custom built with no rear mufflers to the quad tips. After seeing that Supersprint had a full exhaust for the N20 Z4 that had an optional X pipe to support dual exit and each part could be ordered individually. As I had already decided to run the Cyba carbon fiber angle-cut quad tips, the Supersprint rear mufflers would not really be an option without cutting off the tips they come with. The Supersprint mufflers are also extremely expensive. I’m sure they are top-quality, but just not worth the cost IMHO. In the end I settled on the non-resonated Supersprint front pipe (#987102) and Supersprint X pipe (#987213) to get the exhaust to the back of the subframe. I placed my order with Turner Motorsport as they are now the official distributor and importer for all Supersprint products in North America. From order to delivery the process was painless and took about 3 weeks total. Here is a link to the Supersprint exhaust components for the N20 E89 Z4:

The Supersprint parts are built from high quality stainless steel and is listed as 70mm where the stock front pipe is roughly 63.5mm OD and the rear pipes are 55mm OD. The one thing Supersprint does not make clear is if 70mm is the outside diameter or inside diameter… Exhaust pipe SHOULD be measured by I.D. (at least it is in the US). Now 70mm is roughly 2.75” which is actually a little big IMO for the N20 if we are measuring by I.D. but of course the Italians must do it differently… The front pipe has an outside diameter of approximately 2.75” and the X pipe has an O.D. of about 2.5”. Although, not exactly as described, this is a reasonable increase over the stock 2.5” front pipe and 2.25” rear pipes. All the welds are extremely clean and its mandrel bent to keep the diameter the same throughout the entire length of the pipe.

Fitment was a bit of a different story… The hanger on the front pipe was about 2” off from the factory mount, it actually looked like it was welded on backwards. This hanger was cut off and re-welded to face towards the front where the OEM rubber mount was located. The front pipe fit perfectly to the ER downpipe and the fit between the front pipe and X pipe was also spot on and very tight. Similar alignment issues were found with the X pipe however where the brackets that attach to the factory rubber mounts being off by about 1”, but this time in the other direction from the front pipe issue. So assuming the front hangar wasn’t backwards, that would have put the mounts in the X pipe 3” off where they should have been and the bends in the X pipe would not have cleared the subframe. Again, not a show stopper; cut off the mounts and re-welded them in the correct position and the problem is solved.

At this point, I basically have nice stainless steel mandrel bent straight pipes running to the rear ending just behind the output shafts. To help keep the noise level somewhat acceptable some sort of muffler would be needed in the back. Also, since I was converting from a single exit to dual exit exhaust, I ordered the OEM heat shielding from the 35i for the right side:

Heat insulation, rear silencer, right - 51487191044
Body nut (x3) - 07146949380

While the space available for a muffler on the left side is quite large, the space on the right is very limited due to the evap canister placement. Due to the limited space available and to keep the restriction in the system at a minimum I chose the Magnaflow MPE-14148 Race Series Mufflers ( These things are tiny! Overall dimensions for the case is 6” long x 8” wide x 5” thick with a 2.5” inlet and outlet and come with a nice polished stainless steel finish.

From the muffler outlets to the exhaust tips just needed a simple 2.5” to 2.25” stainless steel reducer. The challenging bit was getting from the Supersprint X pipe outlets to each mufflers inlet. The Supersprint pipes have an outside diameter of 2.5” and the Magnaflow’s have a inside diameter of 2.5” and a pipe with a double bend was needed to allow the muffler to be placed properly. This is the only real bit of custom fabrication that was required (other than dealing with the earlier alignment issues). The pipes were mocked up using some standard pre-bent galvanized steel piping and tested for fit by Northeast Motorsports in Mahwah, NJ. Once everything was placed properly and lined up the galvanized mock-ups (which went through a few revisions) will be used as templates to fabricate the final stainless steel pieces from 2.5” I.D. mandrel bent pipe. A small expansion on one side and reduction on the other before welding the new pipes in place.

Overall impression is that this is a really solid setup despite any of the issues encountered during the install. Even with the tweaks required to get everything to fit the Supersprint parts were less expensive than having a full custom mandrel bent exhaust made and the quality is excellent. I would suggest if you are thinking of ordering the downpipe and have an E89 built after January 2013 to contact Evolution Raceweks directly first. The people at ER are extremely helpful and great to work with.

Any codes after removing the cat? Not with the JB4 installed I don’t - auto clear takes care of that.

So, what about sound and performance??

The sound from this setup is awesome! With no front resonator, no cats and just the two small Magnaflows in the rear the N20 has a very deep growling sound. It is louder than just the OEM rear muffler delete, but not obnoxiously loud either. With just the rear muffler delete the sound was a bit higher pitch and metallic sounding vs the deep bass sound it has now. It does drone on the highway but that was always expected and doesn’t bother me at all. The sound of the turbo spooling up is also much more noticeable now as well.

Performance wise there is a noticeable improvement simply because of now being able to increase the MAP on my JB4 to MAP2 (peak boost 21psi). I will be scheduling a dyno day in the near future at Rogue Engineering and will post the results once complete.

Attached Images
Driver, Ratchet Head Racing #93 BMW Z4
Club Organizer, Garden State Euros Motorsport Division
2014 Glacier Silver Z4 28i M Sport - See the build thread:

Last edited by wmandra; 03-06-2014 at 11:56 AM.
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      03-06-2014, 02:28 AM   #2
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Drives: BMW Z4 E89 2.0i
Join Date: Jun 2012
Location: Italy (Pisa)

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Wow, fantastic post wmandra, can't wait for the video of this awesome configuration.
Thank you for sharing.
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