2.8 SuperTrapp Exhaust

Subject: Muffler system upgrade for a 2000 2.8 Z3 Roadster
Cost: $150 for the exhaust plus installation (approx $75), I just checked the website and the price increased to $160.
Good: Customizable sound & performance, low cost AND lightweight
Bad: Non-that I am aware of at this time.

Why do this: As the immortal Tim Allen said “MORE POWER”. One of the first things I did to get more power out of my 2.8 was to Fogg the cold air intake (CAI). Even though Shawn never did a 2000 2.8, I took his ideas and suggestions from both his instruction on the 1.9 and from communications with the immortal himself and I was able to modify my CAI to work similar to his.

Of course this was not enough. So the hunt was on for a more affordable power upgrades. So I started looking into exhaust system replacements. I looked at every type possible, even asking about replacing the exhaust manifold and/or catalytic converter, not without screwing up my emissions & computer. So I concentrated my search to muffler replacement only. I looked at Bola, Dinan, Supersprint, etc. I searched for all types of information (horsepower increase, cost, material type, etc.) that would help me decide what muffler to purchase. I read all the articles from the MZ3 website on exhaust/muffler systems.

To my surprise, I found that all the stainless steel mufflers’ costs were in excess of $300 to $600!!!! Not including installation. Plus I was not convinced that the performance versus cost ratio was worth the money spent. I then remembered about the SuperTrapp system. They were primary an aftermarket motorcycle muffler. But, I saw them on cars in the past, about the late 70s. Plus I knew that they made systems that were stainless steel and lightweight. So the hunt was on.

First: I found their limited website http://www.supertrapp.com/default/atv_splash.htm not a great site to see what was available. But it did explain on how their system works.

Second: I found a supplier (there were not many in my area): http://www.racesearch.com, Part number: 543-2519, http://www.racesearch.com/CGI/mhp?mode=sbpn&pn=543-2519

Third: I found the one I wanted Stainless steel 5″, now granted if you called SuperTrapp & view the Z3 Coupe message board, they recommend that I use a 4″ system for horsepower up to 250 Hp. The 5″ system is rated up to 400 Hp. The reasons for the 5″ is simple with the wider inner diameter, the exhaust gasses would flow easier, less noisy and the 5″ outer diameter fills the factory muffler exhaust cutout nicer.

Arrow points to the location where the stock exhaust tube was cutWhen I had my muffler installed I had the installer hack off the original muffler and it’s supply piping back to the rear axle. If you look at the picture, you will see that the bend to the muffler has been reduced. He then made some custom hangers to hang the muffler at the stock points. Due to the heat generated from the exhaust gasses and the many discussions on the message board on melted bumper fascias due to the muffler. I instructed the installer to have the muffler hang a little lower and poke out more than normal. Giving it less of a chance of the muffler from melting the bumper fascia.

What is with the metal disks and cover???? The SuperTrapp muffler is basically a “glass pack”, where you have an inner tube that has holes and an outer tube that has insulation between the two tubes. Since there is no bends or baffles within the muffler, the gasses are unrestricted to flow toward the end of the pipe. Now the glass pack system has been around for a long time, if you had a hotrod or muscle car, you will know what I mean. Now for the metal disks and cover. The disks that you see on the side of the muffler are really spacers that have been stamped to allow the exhaust gasses to pass between two spacers. The metal cap is to help tune the performance of the muffler and car. Now the easiest way to explain this is to imagine that you have a large bucket with some holes in it. Now fill the bucket up with water, you will see that the water takes a long time to empty out. Now add more holes to the bucket and add water, you will now see that the water will empty out quicker than before. So the more holes you add the faster the water exits. Now there is more to the SuperTrapp system, which deals with vanturies that help pull the exhaust gases from the car. View the SuperTrapp website for more information.

Basically this is how this works with the car: The less spacers you install on the muffler, will produce more backpressure on to the system. Thus, increasing your torque, decreasing overall horsepower and a more quiet sound. With (6) spacers, the noise was a similar to my stock system. The more spacers you install on the muffler, it will reduce backpressure. Thus, decreasing your torque, increasing overall horsepower and a more robust sound. I ran both (12), (18) & (24-max) spacers. I normally run (24) spacers as a daily driver. Which is has a nice growl during idle and a cool roar during hard acceleration plus, I have had no complaints from my neighbors. I did try the system with NO spacers and it was too loud for normal driving.

I have raced my new exhaust with only (12) and no spacers, only to find that no spacers worked best. I will try my (24) spacer setup to see how it fares. Since the installation, I have not conducted a horsepower comparison, my fault. It will be hard to see if my new muffler has done anything, because I have done a ton of things to get this car quicker than stock. Check out my website for details: http://www.z3power.net

Summery: I am happy with the purchase of this muffler and I would do it again. In addition, if I did not have any performance gains in torque or horsepower, I have reduced the overall weight of the car. Which is always a good thing for our heavy cars.

Dinan ///M Exhaust

1.9 Borla Exhaust

Pros: Performance, Exhaust Sound
Cons: Not a “Do It Yourself” Install
Cost: $400

BabyZ wanted to get her exhaust modified for two basic reasons. One for increased performance and two, so she would sound like the high performance sports car she is. Three things hindered performance of the OEM exhaust system. First of all the OEM unit is very heavy (approximately 30 lbs.). The reason it is so heavy is that there is a lot of baffle material in it to make the engine very quiet. This results in the second performance problem that this material creates a large backpressure that reduces engine horsepower. The third problem is an additional source of backpressure in the exhaust pipe. Where the pipe goes under the rear axle it has a large kink put in it to apparently increase the clearance from what look to be quite ample with a full diameter pipe to an even greater clearance.

The kink is not easily seen in this picture of the OEM system as it is right behind the massive hangar and in front of the shinny resonator (close-up of this kink follows in a bit). The second basic desire was to hear the engine. BabyZ didn’t like being a wolf in sheep’s clothing. She’s bad and doesn’t mind anyone knowing it!

Well we have a pretty good idea why BabyZ wants new pipes now, so the next problem is deciding what to put on instead. The first requirement was the system had to be all stainless like the OEM one. In some areas this may not be as important as it was to me but with the rain, humidity and chemicals present in Houston, this was a must. This eliminated the Remus as it is not stainless, a nice sounding unit for sure, but not stainless. The stainless units available were Supersprint, B&B and Borla. With Supersprint and B&B you can get a cat back bolt on system that uses the OEM hangars while the Borla is a weld up modular system. If you want to do this all yourself, and assuming you aren’t a stainless welder, you would not be able to do the Borla. This however may not be a total disadvantage if you don’t mind letting a muffler shop in on the fun. Two reasons balance out the ability to do it yourself are the cost of the system and the sound. Borla is cheaper even after the shop install and gives more sound with a deeper tone than either the Supersprint or B&B (IMHO). Based on the extremely detailed research done by theBaba, where he determined that the Borla did make a muffler (PN 40651) that fit the system and satisfied all BMW requirements (even though they did not list the Z3 on their application list) and testing out his fine ride, Hans, this was the system decided on for BabyZ. Another advantage for BabyZ is that she could keep the resonator which was felt desirable given her automatic tranny (of course you can drop the resonator for a manual if you like).

In the photo of the OEM and Borla mufflers on the ground the difference in size is apparent, but what you see is only part of the story. The weight difference is incredible with Borla weighing in at well under half of the OEM. The smaller size should also help with heat dissipation and reduce the heat exposure to the floor of the trunk and the battery. You can also see that the inlet and outlet to the muffler line up around the centerline of the muffler exactly at the same points as the OEM so the tips will line up with the bumper cut out without any modification.

This is a close up of the infamous “kink”. It actually is more of a smash. The pipe looses fully half of its diameter to go under the rear axle and meet the BMW engineers specified clearance. This smashed pipe is eliminated in BabyZ’s new pipe. In over 2 years of operation since installing the Borla with a full diameter pipe I do not see any indication on the pipe that it has ever been hit by the axle. This includes street, cross-country, track and autocross driving.

This shows the full diameter pipe going under the axle and you can hopefully see that there is plenty of clearance. Also, a new hanger was used on the pipe and attached to the original mounting point. (Note. The second OEM mounting point on the left of the muffler was also used but the third on the right rear of the muffler was not used.)

The shop foreman fabricated the stainless steel “Y” for the dual tips. It was quite a battle to see who would get to install the muffler on BabyZ, I guess this proves that “Rank Has It’s Privileges”. The tips are Borla Turbo Intercooled (PN 20102) and are also stainless steel.

The tips are staggered at the ends to follow the contour of the bumper. This is a personal preference as theBaba and others have theirs straight across and both ways look fine. Another thing to note is that the tips are not positioned on the centerline of the opening in the bumper cover but are moved toward the right side of the opening. This was done to give the maximum room for the tips to move left as the exhaust pipe warms up and expands. This will prevent the tips from touching and melting the surrounding bumper material. The tips are also positioned close together to further maximize the safe area for tip movement.

The finished product is and all stainless steel system with the resonator left in place to compensate for the low rpm preference of the automatic transmission. The Borla is the easiest available system to customize this way and can be installed with or without the resonator (true cat back) as per your preference.

Borla is also the loudest of the systems and depending on your desires this is either a positive or a negative. One drawback is that it is the loudest at 2300 to 2800 rpm’s. This equates to 50 to 60 mph and can resonate quite a bit with the top up. There are two other things wrong with that scenario in the first place; i.e. why is the top up and what are you doing going less than 60mph for any way, so it isn’t much of a consideration for me.

Installation of the Borla resulted in a nice performance boost that was most noticeable in the low rpm range especially in accelerating. The Borla was the first performance upgrade on BabyZ so there were no other mods that could have interfered with the effect of the exhaust upgrade. Since this time the chip has been upgraded with Dinan programming and the airbox has been “Fogged”. Each of these upgrades had an additional effect and I recommend that the full trifecta be done to get the maximum effect from all of the upgrades. One interesting side effect of the addition of the airbox upgrade is that the tone of the exhaust changed and a particular resonate tone was eliminated. I take this as an indication that a definite restriction in airflow was eliminated with this upgrade and that the exhaust was happy to accommodate the additional airflow.

One other benefit is that you won’t need “no stinkin stereo upgrades” when you are listening to the sweet Z3 engine music played through a Borla.

Cost of the muffler and tips is about $300. Installation, including all the needed pipe was $100 and it took about an hour and a half even with a substantial amount of discussion and picture taking. . The Borla is made of T-304 stainless and has a one million mile warranty. Borla’s website is at http://www.borla.com.

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Performance Exhausts for the BMW Z3

Exhaust Articles

  • 1.9 Remus
  • 1.9 Borla
  • 1.9 Supersprint
  • 2.8 Supersprint
  • 3.2 Tri-Flo
  • 3.2 Supersprint
  • 3.2 Remus
  • Exhaust Articles

    1.9 Remus

    1.9 Borla

    1.9 Supersprint

    2.8 Supersprint

    3.2 Tri-Flo

    3.2 Supersprint

    3.2 Remus

    Performance Exhausts for the BMW Z3

    May 31, 1999

    By: Robert Leidy

    Inside each cylinder, the BMW Z3’s electronic control module injects a calculated mixture of air and fuel. This mixture is then ignited which produces power. However a by-product is also produced from this process which is commonly referred to as exhaust. The burnt gas fumes (exhaust) exit the cylinder and travel through a pipe commonly referred to as a header. The header pipes from each cylinder are then combined and channel the exhaust fumes from the engine into a catalytic converter. The catalytic converter is a device filled with a metallic-mesh-like filter that removes some of the pollution from the exhaust fumes. Once the exhaust has passed through the catalytic converter, it is channeled through a single pipe to an exhaust resonator, which reduces some of the sound produced by the engine. Once the exhaust has passed through the resonator it is channeled to a muffler to “muffle” additional sound from the exhaust. Once the exhaust travels through the muffler it exists the Z3 via tail pipe(s) under the rear bumper.

    The theory behind performance exhausts is that each device that the exhaust fumes pass through cause resistance, which in turn increases the amount of air pressure inside the exhaust. The pressure built up also effects the cylinder because “back pressure” from the exhaust is putting additional effort on the cylinder as it is handling the next mixture of air and fuel. A performance exhaust is designed to reduce the amount of resistance in the exhaust making the exhaust flow more freely and reduce and amount of “back pressure”. In order to accomplish this, those devices within the stock exhaust that cause resistance can either be removed or redesigned to be less restrictive. However each component of the stock exhaust is there for a reason. The muffler is designed to remove sound at the cost of exhaust resistance. You can redesign a muffler to have less resistance but in general you will also be decreasing the mufflers ability to “muffle” sound. As with most things in life it is a give and take relationship. Finding the correct balance of give and take is a judgment call, so it can be different for different personal tastes.

    There are varying degrees an owner can take to reduce the pressure in the exhaust and increase performance of the engine. Perhaps the easiest way is to just replace the muffler. Or for a little more performance, replace the muffler and resonator. Professional racers like Mark Hughes remove all of these resistance-causing devices. However removing the catalytic converter would keep a Z3 from being street legal (which is not a problem for the Z3 Race Team). The most common after-market exhaust systems are called “cat-back exhausts”. With the design of the Z3 these “cat-back” systems bolt right onto the stock catalytic converter and replace everything “back” from there (keeping the Z3 street legal). The new pipes are larger, the resonator is removed and the muffler is less restrictive, so exhaust can exit the engine/exhaust with less resistance. This has two effects on the Z3, it increases the performance and it makes the Z3 louder (more sound from the exhaust).

    So now that we’ve covered the theory behind performance exhausts lets look at the type of decisions an owner would need to make in evaluating after-market performance exhaust systems:

    Stock Engine/Exhaust Design:

    The theory behind performance exhausts is that reducing the amount of pressure increases performance. So it only makes since that the amount of potential performance gain is directly related to the amount of resistance/air-pressure-buildup in the stock exhaust. In other words if the stock exhaust is very restrictive then there is a lot of potential performance gain.

    Assuming that between the different Z3 engine configurations the restrictiveness of the various BMW stock exhausts components is roughly the same, we can make some general observations looking at the different designs. The 1.9 Z3 is a 4-cylinder engine, the exhaust output from all four cylinders is combined before entering the single catalytic converter. So roughly 1.9 liters of exhaust output is sent through the stock exhaust each time the gas inside the cylinders is ignited.

    Compare that to the 6-cylinder 2.8 Z3, which has the exhaust output from all six cylinders combined before entering the single catalytic converter. So roughly 2.8 liters of exhaust output is sent through the same pipe. Comparing these two it would appear that the 2.8 would benefit more from a performance exhaust than the 1.9 would since 47% more exhaust is traveling through the exhaust.

    To continue the comparison, the 3.2 Z3 is also a 6-cylinder engine. However the exhaust output is split in half, the output from three cylinders is sent to the first catalytic converter, with the exhaust output from the other three cylinders is sent to a second catalytic converter. The exhaust output from each half is never mixed so in reality the each exhaust is only handling 1.6 liters of exhaust output. Comparing this output it would appear the 3.2 engine would benefit the least from an after-market exhaust.

    Metal Used:

    There are also differences in the type of metal used in exhaust systems, the big differentiation is it, or is it not stainless steel. The big advantage to stainless steel is its durability. If you live in an area where salt is used on roads then you know that rust can eat up car parts. For these areas stainless steel will last a lot longer so the increased price is easily justified. The other advantage to stainless steel is that it conducts 2/3 less heat than mild steel, which helps to keep temperatures in the exhaust to a minimum. However stainless steel also expands 40-45% more than mild steel when heated so fitting a stainless steel exhaust is slightly more difficult. (The stock exhaust system is not stainless steel).

    Exhaust Tips:

    Choosing exhaust tip style is usually a 90% cosmetic decision. However the type of exhaust tips also effect how the exhaust will sound. If the exhaust tip is angled up the sound will generally be louder, if the exhaust tip is angled down the sound will generally be quieter. Most exhaust tips point straight back just like the stock exhaust does.

    In the United States, five different engine configurations have been built in the Z3:

    M44: model year 1996-1998

    The M44 1.9 liter engine was the first Z3 sold in the United States. Several companies make performance exhausts for this Z3. However this engine configuration is no longer being made for the US market so it is doubtful that any additional aftermarket performance exhausts will be added to the list.

    Borla

    Remus

    Supersprint

    M52: model year 1997-1999

    The M52 2.8 liter engine was the second Z3 engine configuration to be sold in the United States. Several companies make performance exhausts for this Z3. However this engine configuration is no longer being made. BMW now has a new M52TU 2.8 liter engine that is different in design, so exhausts for the M52 Z3 will not work on the M52TU Z3 and via-versa.

    Borla

    Remus

    Supersprint

    S52: model year 1998-2000

    The S52 3.2 liter engine was the third Z3 engine configuration to be sold in the United States. Several companies make performance exhausts for this Z3 (officially called the M roadster and M coupe).

    Remus

    Supersprint

    Tri-Flo

    MXXTU: model year 1999-2000

    The MXXTU 2.3 liter engine is the forth engine configuration to be sold in the United States. MZ3.Net does not know of any M52TU Z3 “cat-back” performance exhaust systems at this time.

    M52TU: model year 1999-2000

    The M52TU 2.8 liter engine is the most recent engine configuration to be sold in the United States. Supersprint is the only company that MZ3.Net has heard that currently has a cat-back exhaust ready for the new 2.8 liter engine. Supersprint’s part numbers for the new exhausts are 78.67.06 or 78.67.66. I assume the two different numbers are for different exhaust tip options.

    Discuss this article and other Performance upgrades in the

    ///MZ3.Net discussion forum.

    B&B Triflo Exhaust

    B&B Triflo Exhaust

    April 28, 1999

    By: Robert Leidy

    Supersprint Exhaust for the 2.8 Z3

    Pros: Better Performance, Great Sound, Stainless Steel
    Cons: Expensive, Installation
    Cost: $614 (from BMP Design)
    $563 Straight Tips with free shipping (from HMS)
    $649 DTM Tips with free shipping (from HMS)

    In the never ending quest to find more power and otherwise tinker with my car, I decided to put a new Supersprint catalyst-back (cat-back) exhaust on my beloved BMW Z3. I have a ’97 model with the M52 2.8 liter engine.

    The upgrade had three desired goals/expectations

    I was looking to improve the sound of the exhaust. The stock exhaust didn’t sound “bad”, it was just too quiet for my taste. I had previously heard other 2.8 liter Z3s with the Supersprint exhaust so I was quite confident that I would be pleased with the sound.

    I was hoping to improve performance of the Z3 as well. This goal was questionable, several had speculated that there wouldn’t be an improvement in performance. However there were even more saying there would be. In order to satisfy my own curiosity I decided to do before and after dynamometer (dyno) runs on the car to measure before and after rear wheel horsepower and torque.

    The final expectation was purely cosmetic. I had already added chrome tips to the stock 2.8 exhaust (picture above) but after seeing the larger turned up DTM tips available on the Supersprint exhaust I decided I liked the looks of them much better (right picture).

    With these goals in mind I enlisted the help of Robert Leidy, who had already found a reputable dyno shop when he measured the power output from his M roadster. Since Robert and the dyno shop (Alamo Autosports) were both located in the greater Dallas/Fort Worth, Texas (DFW) area, and I was located in Houston, there was a bit of a logistical problem. Answer: Roadtrip!

    To ensure a proper installation, Larry Nissen from Moritz BMW in Arlington was invited. To ensure accurate dyno tests the following “recommended” process was used. We first backed the car onto Alamo’s dyno rack to get a baseline HP for the car. We then used the very same dyno lift to install the supersprint exhaust. Once the exhaust was installed the car was then re-dynoed to measure the change.

    Installation

    Prior to installing the Supersprint exhaust, three “before” or baseline dyno tests were preformed. The results of those test will be compared to the results from the “after” dyno tests in the next part of this article. But for now let me explain the installation process that took place between the before and after dyno tests.

    The keen eye will notice that the pictures on this page are from two different vehicles. Prior to my installation, another Z3 owner had installed a Supersprint exhaust on his Z3 and Robert was there to take pictures of that installation as well. The only difference between the two Supersprint exhausts were the type of exhaust tips. Chris got the straight tips and I got the turned up or DTM style tips. Since the type of tips on the end of the exhaust have very little impact on installation the two sets of pictures could be used together.

    The first step was to remove the stock exhaust, problem was we had just completed the first set of dyno tests so the stock exhaust was hot. After the stock exhaust cooled down to a point where we were able to hold it (15 minutes) we were able to remove it.

    The exhaust is held in place in four places (pictures below). The first (front most) connection is where the exhaust bolts onto the flange of the catalytic converter via two 2 13mm nuts and bolts. The middle connection is actually just a safety/backup connection, but it uses a rubber belt (attached to the vehicle) around an additional bracket (attached to the exhaust) to catch the exhaust if the rear mounts fail.

    Towards the rear bumper, two additional rubber rings support and attach the rear of the exhaust to the vehicle. In order to remove them we sprayed the rubber muffler hangers with lubricant and then popped them loose using a pry-bar. The actual order we used in removing the exhaust was to loosen the front bolts, unbolt/remove the middle bracket. Then with someone holding the front of the exhaust, the rear connections were worked loose. With a person holding either end the removal was easily accomplished, however it would have been rather difficult with only one person. trying to juggle both ends.

    After removing the stock exhaust it was time to unpack the Supersprint exhaust. I purchased this exhaust from BMP, it came very well packaged, the entire exhaust was wrapped in thick shrink wrap with additional padding covering the exhaust tips. Not sure if this is something BMP does or if all Supersprint exhausts come this way. The packaging provided a very effective protective layer over the exhaust, however the shrink-wrap was so tight one of the support brackets was bent. We didn’t realize this at the time, but later it was easy to fix by just bending the support back to its normal position, the catch of course being that you won’t know what the “normal” position is until you’ve got the exhaust installed and you’re trying to put the rubber hangers on.

    There is one important part I should point out, you better get a friend to carry the new and old exhaust for you. The exhaust is rather large and does not fit in the trunk (not even close). You could carry the new exhaust up front with you but the used/stock exhaust will be very dirty. For this installation Nancy carried my exhaust along with Alan’s two exhausts in her SUV. Once the stock exhausts were removed we wrapped them in trash bags and duct tape for the drive home.

    Comparing the stock and Supersprint exhaust side by side was interesting. The Supersprint exhaust looked quite handsome with its black-crackle finish and polished stainless steel tips. It also looked much more svelte and linear than the stock exhaust. The stock exhaust had 4 diameter changes in just the piping alone. The resonator and the garbage-can-sized muffler looked like something off of a truck when compared with the Supersprint. There was a brief moment where I thought BMP had shipped me the wrong exhaust. The muffler part of the exhaust was smaller so the rear support arms were longer (to make up the difference). But what concerned me was how much different the connection from the catalytic converter to the muffler was. The Supersprint still had the crimp in the exhaust but the path seemed much straighter. However my concerns of receiving the wrong exhaust were removed when we stacked the two exhausts on top of each other and noticed the mounting locations were the same.

    Mounting the new exhaust was a definite two-man job. The “safety hanger” was reinserted into the rubber hanger/bracket, and the flange-end of the exhaust was fitted to the catalytic converter, loosely fitting the nuts. We then re-popped the muffler hangers on to the Supersprint, and VOILA!, it didn’t fit. We stepped back to analyze the situation and found immediately that the hanger brackets on the Supersprint had been bent somewhere along its route from Italy to Texas. Using the biggest pair of channel-locks we could find, we adjusted the brackets to proper alignment, and VOILA!, it still didn’t fit.

    We has been warned by other Z3 exhaust upgraders that the tight fit of the exhaust tail pipes had previously led to some bumper trim scarring/melting. Because of this warning we were paying very close attention to how the tips fit in the cutout. Ahead of time we were warned that the exhaust tips will move towards the drivers side of the cutout when the exhaust gets hot and back towards the passenger side when it cools back down. So our goal was to get the exhaust tips to hang towards the passenger side of the cutout as much as possible (exhaust was cold as we were mounting it).

    The problem we ran into was after installing the exhaust we noticed the tips were already off center towards the drivers side. We knew that this was going to be a problem because once the exhaust got hot it would push even further towards the drivers side and probably scar/melt the bumper trim. Further analysis indicated that the “safety hanger” on the Supersprint was too far to the passenger side of the car. After inspecting how the bracket worked we determined that the sides of the bracket serve very little purpose because the support loop uses the top of the bracket. We were also told that this bracket is just a backup bracket in case the rear ones fail.

    For a brief moment we considered removing it all together, but then we thought of a better plan. We decided to modify the safety bracket, since it appeared cheaper to replace than the exhaust if we screwed it up (Supersprint has been informed of the problem and is investigating a solution). The bracket pictured to the left is after the modification (compare it to one of the pictures at the top of this page and you will noticed the removed metal). The fine folks at Alamo ground off one side of the bracket, and after we re-installed everything the exhaust was no longer being pushed against the drivers side of the rear bumper apron.

    All that remained was to fine-tune placement of the tips within the rear bumper apron. This was accomplished using the aforementioned massive channel-lock pliers to tweak the muffler hanger brackets. We aligned the exhaust to “dress to the right” when cold, as 2.8 Supersprint exhausts are known to shift left about one-half inch at operating temperatures. It looked fantastic.

    Update: Supersprint is modifying all current and future 2.8 Z3 exhaust systems to correct for the safety bracket misalignment. Supersprint is also adding side-to-side adjustable hangers to allow for precise fitting of the exhaust tips in the cutout.

    Performance

    Now that the Supersprint exhaust was installed, it was time to dyno again. When we first ran the car on the dyno, (pre-exhaust) I was nervous to say the least. My car already had the Dinan High Flow Cold Air Intake System and Dinan ECU upgrade (not really a “chip” anymore) and I had heard ad-nauseum about how the adaptive nature of the OBD II ECU software would show no power gains no matter what.

    Running your car on a dyno is one of those surreal experiences you have to do once in your life. On a lift dyno, your car is roughly four feet in the air strapped to the lift, going 70+ mph The image of the car shooting off the lift keeps popping up in one’s mind. Anyway, we do three baseline runs. They are all pretty consistent, with the best being 167.6 hp and 175.5 ft lbs of torque. Remember that this it rear-wheel horsepower and torque, not the crankshaft horsepower and torque as quoted by the factory.

    After we installed the Supersprint we fired up the engine to warm it up, and it sounded fantastic, too. Stock, the car just didn’t have a sporty-enough sound. With the addition of the Dinan Intake and ECU upgrade, it had a very feral howl, but only on wide-open throttle. The Supersprint exhaust added a “bass track” to the sound, sounding it out nicely. Now, full throttle applications combine the howl with a deep growl, making for a formidable sounding beast.

    Below is an amusing animated picture Robert created from a couple still pictures his camcorder recorded. The first frame is from the “before” dyno test with the stock exhaust. The second frame is hours later from the “after” dyno test with the Supersprint exhaust (with turned up DTM style exhaust tips). I’m sure the angle of the exhaust tips had more to do with it than the amount of exhaust, but notice the Dynojet banner in the background. Now that’s what I call a free flowing exhaust 🙂

    Once we warmed up the car, it was time to dyno. The sound of the car running up to over 70 mph in what was essentially a one-car garage was a sound not easily forgotten. One alarming note, though, was the plumes of smoke emanating from the rear of the car. Turns out that it was the exhaust burning off coatings, grease, and other contaminants. It had a mighty stench as well, which I was told would linger for about 500 miles. I was glad I had a long roadtrip home.

    Once again, we do three runs, and they are again very consistent. This time the best one is 171.7 hp and 181.1 ft lbs of torque. Click on the small portion of the graph to the right to see the full size before and after comparison of the torque curve. At the peak torque values, the Supersprint exhaust gained 5.6 ft/lbs of torque. Looking at the entire RPM torque curve and measuring the differences every 50 RPM the Supersprint exhaust averages a gain of 4.3 ft/lbs of torque between 2000 and 6200 RPM.

    It would appear that this is an apples and oranges comparison, and it is somewhat. However, there are correction factors, and the one we’ll use here has been ascribed to a well known Utah-based chip tuner, but I can’t confirm that origin. This correction factor to convert rear wheel HP to crank HP is 1.21, or about a 17.2% loss. Given that, my numbers would work out as follows using the equation RW * CF = C, where RW is rear wheel HP or Torque, CF is the above correction factor, and C is the crank HP or Torque.

    Stock 1997 2.8 – factory specs

    189 HP

    156.2 HP – converted to rear wheel

    203 ft-lbs Torque

    167.8 ft-lbs Torque – converted to rear wheel

    With Chip & Intake:

    167.6 * 1.21 = 202.8 HP

    175.5 * 1.21 = 212.4 ft-lbs Torque

    Chip & Intake gain over stock:

    13.8 HP – estimated @ crank

    11.4 HP – estimated @ rear wheel

    9.4 ft-lbs Torque – estimated @ crank

    7.7 ft-lbs Torque – estimated @ rear wheel

    With Chip, Intake & Exhaust:

    172.6 * 1.21 = 208.9 HP – estimated @ crank

    181.1 * 1.21 = 219.1 ft-lbs Torque – estimated @ crank

    Chip, Intake & Exhaust gain over stock:

    19.9 HP – estimated @ crank

    16.4 HP – estimated @ rear wheel

    16.1 ft-lbs Torque – estimated @ crank

    13.2 ft-lbs Torque – estimated @ rear wheel

    Chip, Intake & Exhaust gain over Chip & Intake:

    6.1 HP – estimated @ crank

    5.0 HP – measured @ rear wheel

    6.8 ft-lbs Torque – estimated @ crank

    5.6 ft-lbs Torque – measured @ rear wheel

    So what does this tell us? Well, if we believe in rear wheel measurements only, I got a 5 HP, 5.9 ft-lbs, increase in overall power. Examining the dyno curves, this really makes itself known over the 3000 – 5500 rpm range. I am happy, and I can feel a difference.

    Sound

    Bryan: One month after install

    Living with the exhaust has been a pleasant experience. I had to first get over the feeling that someone was following me, as I wasn’t used to the subtle tone of the exhaust coming from the rear at all RMPs. Next, I was worried about the much larger exhaust melting the rear bumper fascia. I’ve seen some exhaust applications that have eaten holes in the fascia, but that hasn’t been a real problem. There has been a little scorching on the inside lips of both sides of the fascia, but nothing to be concerned about. One very unexpected benefit is that my gas mileage has increased by 1-2 miles per gallon. Bottom line: would I do it again? Yes. What would I change? the safety bracket

    Chris: 1 month after install

    Chris Bull checked the rear apron around his Supersprint exhaust installation with straight tips and reports that no melting or scarring has taken place. He is VERY pleased with the upgrade and highly recommends the Supersprint exhaust to other 2.8 Z3 owners.

    Spence: 1 month after install

    Chuck Spensor checked the rear apron around his Supersprint exhaust installation with DTM style tips and reports that there is some melting on the drivers side. However the scarred area is not very noticeable and the exhaust tip hides most of the damage. He is VERY pleased with the upgrade and highly recommends the Supersprint exhaust to other 2.8 Z3 owners.

    Update from Supersprint:

    There are two different 2.8 Z3 exhausts, one for the ’99 on Z3 2.8 coupe and roadster, and one for the ’98 and before Z3 2.8 roadster. The part number for the 99 is 78.67.06 or 78.67.66 (I guess one is straight tips and the other is dtm–don’t know which is which). Supersprint experimented with a ’99 Z3 2.8 coupe and moved the center bracket approximately 6-8 mm towards the driver’s side of the car to give it a perfect fit. They did many runs to get the exhaust up to temperature and verified that it did not come into contact with the apron even under hard cornering. One point to note is that the ’99 models apparently have a bigger cutout in the rear apron than the ones before that. For the ’98 and before 2.8 roadster, Supersprint is modifying all current and future stock to have a side-to-side adjustable hanger to allow for precise fitting.

    Supersprint Exhaust for the M Roadster

    Pros: Great Sound, Increased Performance, Visually Striking, 100% Stainless Steel
    Cons: Cost, Installation
    Cost: $1,402 (from BMP Design)
    $1,339 with free shipping (from HMS Motorsport)

    The M roadster has a fairly impressive stock exhaust–quad polished tips exit from dual mufflers and emit a mellow note. However, like anything in life, even something good can be improved. Supersprint has made aftermarket exhaust systems for BMWs for years, has been making high-quality exhaust systems since 1955, and is highly regarded. In fact, the quality of the exhaust meets TUV standards for construction and is treated as if it were an OEM exhaust in Germany, which typically is very picky about aftermarket modifications to cars.

    Supersprint is based in Italy, and their official U.S. Importer is BMP Design, based in Texas. BMP carries the full Supersprint line, including the 100% stainless steel dual M roadster exhaust with quad DTM tips. The exhausts arrived in perfect condition (a feat in itself given that the shipment consisted of two 6-foot-long boxes that had to travel from Italy to BMP in Texas, and then from there to the reviewer). The packaging is first-rate, with the exhausts themselves being sealed in plastic, with special packing around the tips to preserve them, and with plenty of paper padding protecting the exhausts inside the boxes.

    The pictures above exhibit the external differences between the Supersprint exhaust (left) and the stock exhaust (right). The tips are larger and upturned, the muffler itself is smaller, and the whole system is bead-polished to a high shine. As the arrow shows, the Supersprint exhaust also features straighter pipe between the fitting (which will be attached just behind the catalytic converter) and the muffler.

    A side note: When arranging for a place to install the Supersprint exhaust, it may be best to also arrange for a friend with either a sports utility vehicle or a pickup truck to be available to help you transport the new exhaust to the installation location, and to help you transport the old exhaust home.

    Installation

    The exhaust is held in place with bolts just aft of the catalytic converters (red arrows), and a set of brackets/rubber attachment points (second picture) at the rear of the car. The the middle there is a safety/backup hanger (blue arrow) which has a rubber belt around the middle of the exhaust.

    Some spray silicone lubricant on the middle bracket may make it easier to slide the belt holding the exhaust off the support. Once this middle connection is free you can remove the front bolts to break the connection to the catalytic converter. Lastly remove the bolts attaching the rubber hangers at the rear of the car.

    After removing the stock exhausts, it is time to mount the new Supersprint exhausts. The best way to do this is to first guide the main support into the rubber hanger (blue arrow above) and then to loosely fasten the remaining brackets and bolts. Then, with a couple of people helping, you can align the exhaust and tighten the bolts. (Note that in most cases, we do not recommend hanging from the new exhaust as an alignment method.)

    Take your time while adjusting the new exhausts. Even when everything looks fine from under the car, you may still want to tweak the alignment. You want to make sure that the tips are not in contact with the plastic of the rear bumper. Maintain about a finger’s width clearance between the tips and the lower lip of the bumper. Also, stand behind the car and check that each side is symmetrical. As you can see from the picture above, the right tips are slightly rotated clockwise, and need to be adjusted for a better match with the left side.

    There were only two negatives to the installation. The first is just due to the inexperience of the reviewer–alignment took a long time. If you have an exhaust shop install your exhaust, this is a non-issue. The second negative is that the new exhausts did not come with 4 necessary nuts and washers. The stock exhaust has nuts integrated into its brackets which bolts go into, while the Supersprint exhaust just has holes in its brackets which bolts go through. This necessitated a quick trip to a hardware store, and cost about $1.00. It is not clear if the missing nuts were an oversight or if they must always be purchased separately, but Supersprint has been notified of this slight glitch and is looking into the issue.

    Overall, the installation was uneventful, and took about 2 hours–not bad for a do-it-yourself job. A muffler shop would probably knock out the job in less than half the time. The final result is a set of 4 gleaming tips which emit a healthy growl.

    Ok, so it looks and sounds great. Now you want to know about the performance:

    Performance

    Note: Alamo Autosports is recommended to those in the North Texas area for dyno testing. $60 buys you 3 runs on a Dynojet Dynamometer, worth it just for the experience of seeing and hearing your car dynoed. Contact Brice, Steve Pak, or Steve Webb at

    Alamo Autosports

    1218 Colorado Ln.

    Arlington, TX 76015

    817-860-4300

    There is a lot of discussion over whether you can improve a car’s performance by replacing the stock exhaust with a “free-flow” aftermarket exhaust. How best to come up with a quantitative answer? With before and after dyno runs, of course.

    A day on the dyno at Alamo Autosports in Arlington, TX was scheduled.

    Three stock dyno runs were done. They were all close, but the best and worst were thrown out for the purposes of this article. The M roadster, with stock exhaust and no performance modifications, reached a peak rear-wheel horsepower of 217 between 6150 and 6250 RPM. Peak rear-wheel torque was measured at 217 ft./lbs. between 4000 and 4150 RPM. At the bottom of this section of the article is a chart with the full numbers, and the full-size graph of the stock HP and torque curves may be seen by clicking on the small graph at right.

    How might an aftermarket exhaust improve performance? By freeing the exhaust flow. This picture shows one way the Supersprint exhaust improves over the stock exhaust. The pipes shown go between the connection at the rear of the catalytic converter and the muffler. The Supersprint exhaust is on top, and the stock exhaust is on bottom. Notice how the Supersprint exhaust pipe takes a straighter path. Also notice how the stock exhaust is somewhat crimped in the middle (to clear a chassis cross-member, which the Supersprint avoids by routing the pipe slightly lower).

    After the three “before” runs were completed, the car was driven off of the dyno and allowed to cool. After cooldown, the car was put back on the dyno (used as a lift), and the Supersprint exhaust was installed. After installation was complete, three “after” dyno runs were conducted. Peak torque gain was 6 ft./lbs., and peak HP gain was 5 HP. Since the dyno runs were conducted immediately after the exhaust installation, the numbers reported are for a non-broken-in exhaust. A follow-up set of dyno runs is planned to acquire HP and torque curves for the exhaust after break-in.

    Click on the left picture below to hear and see one of the dyno runs after the Supersprint exhaust was installed. The video is of the Supersprint run that produced the highest HP value. Please note that the numbers below are from the middle stock dyno and the middle Supersprint dyno, so the peak HP below is 1 less than the peak HP mentioned in the video.

    Click on the right graph below to see the full-size comparison of before and after torque curves. As you can see from the graph, there is a definite increase in torque (important for acceleration) in the entire midrange.

    Sound

    The Supersprint exhaust produces a deeper and slightly louder sound than the stock exhaust. Do not take this to mean that it is overwhelmingly loud. The Supersprint exhaust meets tough European TUV standards for sound levels. The second-best way to describe the sound is that it makes the M roadster sound like it should sound. The best way to describe the sound, of course, is to let you hear it for yourself. You will need the RealPlayer to hear the audio, if you don’t have the RealPlayer the good news is it is free!.

    The sound recordings were made during dyno runs of the stock exhaust and the Supersprint exhaust. A Hi8 camcorder was used to capture the audio, and was placed about 6 feet to the side of the car and slightly behind the car. RealAudio is by no means a crystal clear audio media, but comparing the sound files (Stock vs Supersprint) is a really good comparison of the real life difference. Once the Supersprint exhaust is fully broken in, a “run through the gears” sound sample will be added to this page.

    Stock M roadster

    Supersprint M roadster

    Remus Exhaust for the M Roadster

    Pros: Better Performance, Improved (Lower) Sound, Easy Installation
    Cons: Expensive, Not Stainless Steel
    Cost: $801 (includes shipping) from MG Racing

    The stock exhaust on the M roadster is pretty good, however I was always wanting a little more rumble and sound. Previously I owned a 1.9 Z3 and had upgraded its exhaust using the Remus brand. I was very pleased with the results and when the itch to upgrade the M roadster exhaust hit me I decided to try the Remus M exhaust.

    After placing my order and waiting a week the doorbell finally rang. It was the UPS delivery man with two very large boxes for me. Just like the 1.9 exhaust the new Remus exhaust was packaged without any padding inside the cardboard box, one of the boxes was fairly chewed up the other one only had slight damage. I didn’t notice it at the time, but one of the supports on the passenger side exhaust had been slightly bent. Let me just get this complaint out of the way, would it kill them to package these things in Styrofoam or something. Just like the 1.9 exhaust this one had become damaged (support rod bent) in shipping, the damage is easily repairable but it sure would be nice if I didn’t have too.

    The good news was that the chrome tips on each exhaust arrived unharmed. Measuring the exhaust tips I found that the inside diameter was the same as the stock exhaust, but the thickness of the exhaust tip was 5mm bigger making the overall outside diameter of the Remus exhaust 10mm bigger than the stock exhaust. On the top of each chrome tip is an engraved Remus name logo. Once the exhaust is installed both the name and the logo can be seen. The shipping weight on the Remus exhaust was 70lbs total (35 per side), while I have not weighed the stock exhaust myself I remember BMW saying it weighed roughly 100lbs.

    Installation

    The hardest and longest part of the installation was the first step, getting both the Z3 and the new exhausts to the installation location was more difficult than I thought it was going to be. There was no way these big things were going to fix in the Z3. They also did not fit in the trunk of my wife’s 318i, luckily I found a way to fit one in the back seat and another in the passenger seat. I ended up having to drive the 318i (carrying the exhausts), then drop off the exhaust, then return home, then drive the M roadster to the shop, install the exhausts, drive the M roadster home, return with the 318i, load up the stock exhausts and them drive them home. I probably spent more time driving cars around than it took to actually install the exhaust.

    The actual installation process was very easy, but before I could start I needed to let the exhaust cool off. During the installation process you will be holding some parts of the car (like the muffler) that get quite hot while the car is running.

    Once it had cooled down the first step was to remove the stock exhaust. There where 10 bolts in total (5 per side) holding the stock exhausts in place. On each side there are two bolts mounting the exhaust to the catalytic converter (top right), two bolts holding the rear of the exhaust in place (bottom right), and one bolt in the middle (middle right).

    I should point out that the exhaust is actually held in place via some rubber hangers that allow the exhaust to slight move and adjust in normal operation. The bolts I’m referring to attach the rubber hangers to the car.

    Instead of removing the rubber ring that was holding the middle of the exhaust in place, I decided to remove the bolt that holds the bracket that the rubber ring is mounted on. This made lowering the exhaust a little easier. I started by removing the rear bolts first, then the middle, and then the front. But I had someone holding the rear (muffler) exhaust while I was doing this.

    The only part I replaced (at the advice of Larry Nissen – BMW tech) was the ring seal that fit between the cat-back exhaust and the catalytic converter. Larry didn’t think this was “necessary”, but it was possible that a exhaust leak might occur using the old rings, so we decided to replace them just in case.

    After one last side by side comparison it was time to install the Remus exhaust. I was quite impressed at how easily and precisely the Remus exhaust fit into place. Starting with the rear bolts first (while someone held the front of the exhaust) the new exhaust was put into position. The first pass the bolts were left loose, a second pass tightened them all down. The only part of the installation that wasn’t smooth was the support that had become bent in shipping. But after a few whacks with a hammer it was bent back into position and the installation was complete.

    Once the Remus exhausts were installed I took a look at the exhaust tips to see how centered they were in the cutouts of the rear bumper. I was concerned that an off center exhaust tip might melt some of the rear bumper because I have seen that happen with some aftermarket exhaust. But I was relieved to see that the exhaust tips were perfectly centered in the cutouts. The Remus exhausts really were a direct replacement, practically plug-and-play. They fit precisely in place of the stock exhaust without any modification. But now that they were installed the next question was, “what will this do to the M roadster’s performance?”

    Performance

    I always liked the Remus exhaust I put on my previous 1.9 Z3, but I regretted not doing “before” and “after” dynos on the car to see how much of a performance gain the aftermarket Remus exhaust gave me. I didn’t make that mistake this time, a “before” dyno was recorded with the M roadster in stock condition after it was broken it (click on the graph for a larger view).

    After the installation the car felt quicker and it seemed to run through the upper RPM range faster. In fact I even bounced it off the rev-limiter a few times on accident until I got use to the new tach speed. But all this was just non-scientific (what some people call the “butt-dyno”) data. I knew the car felt quicker but what I needed was a real dyno to prove it. I returned to the same place where I had my M roadster dynoed before to see just how much of a gain the Remus exhaust gave me (click on the graph portion to the right for a full screen view).

    What the dyno did was prove what I was feeling, the Remus exhaust boosted the torque across nearly the entire RPM range. The biggest gains were found in the range between 3500 and 5100 with a peak gain of 13 ft/lbs of torque at 3800 RPM. The only exception was the RPM range between 2300 and 2500 which showed no gain. A few skeptics said that an aftermarket exhaust might gain power in one area but then loose it in another. What the dyno showed me was that the Remus exhaust never hurt performance, improved the performance across most of the RPM range, and even smoothed out some of the torque curve where dips in power occurred on the stock dyno.

    I was hoping to back up the dyno data with performance timing, so I purchased a GTechPro which measures 0 to 60 and quarter miles times. I took several measurements before the exhaust upgrade and several measurements afterwards. However I don’t think that data can be trusted because what the GTechPro really did was teach me how to drive the car faster. In between the before and after testing I had improved my driving skills enough to make those tests invalid. I also didn’t pay much attention to the temperature variations which might also explain the gains I was seeing. So really the only thing I got out of the timing tests for this article is this fairly cool real video.

    Sound

    The Remus makes the exhaust note lower and slightly louder, but rather than have me try to describe the sound in words check out the sound files below. You will need the RealPlayer to hear the audio, if you don’t have the RealPlayer the good news is it is free!.

    For the following sound recordings two ’98 M roadsters were put side by side. A Hi8 camcorder was used to capture the audio, I was standing about 10 feet behind the two roadsters and did not move between recordings. RealAudio is by no means a crystal clear audio media, but comparing the sound files (Stock vs Remus) is a really good comparison of the real life difference.

    Stock M roadster

    Remus M roadster

    Long Term Update

    4/30/99:

    I think my initial figures are incorrect, especially after looking at the other exhausts articles and comparing the results. When I initially posted the article I used before and after dynos taken on different days. I think the ODBII adaptation caught me, because if you look at the numbers it would appear that I had a peak gain of 7 ft/lbs, average gain of 5.8 ft/lbs across the entire RPM range, 7.8 ft/lbs gain in the 3k to 5k range (driving range). The 7.8 ft/lbs of additional torque is roughly a 4% gain in power in the highly used 3k to 5k RPM range.

    What’s interesting is if you compare Alan and my “after” dynos you see that they are practically identical. How can the Remus give me a 4% gain and the Supersprint give Alan a 2% gain, but we end up at the same numbers? I think the answer is that my original “before” dyno is questionable. What I did to try and “fix” this error was take the two different “before” dynos and combine them by using the high points from each graph. I then used this new line and compared it back to Robert’s original “after” dyno.

    Looking at the “fixed” comparison, I think these figures are more correct. Peak gain of 4 ft/lbs, average gain of 2.9 ft/lbs across the entire RPM range, 3.7 ft/lbs gain in the 3k to 5k range (driving range). The 3.7 ft/lbs of additional torque is roughly a 2% gain in power in the highly used 3k to 5k RPM range.

    K&N Cone Filter

    Pros: Easy To Install, Improves Intake Sound
    Cons: Possibly hurts performance especially in hot weather
    Cost: $149

    In January of 1997, I purchased the K&N Filter Charger from Bavarian Autosport for $149. Once installed, it made a noticeable change in sound. I think I can tell a performance difference but, it is hard to judge what this upgrade alone would produce. Previously I upgraded the exhaust and I think I’m dealing with a “the sum is greater than the parts” issue here. The installation instructions were pretty well written but didn’t contain any pictures. You might want to take a look at my on-line instructions before installing yourself.

    7/1/97 Update:

    Since the installation (02/28/97) it has gotten quite hot here in Texas. This exposed a flaw in the K&N cone filter design. Since the filter is not vented with outside “cooler” air I think this upgrade is actually loosing power. So the K&N cone filter has come off and is currently sitting on the shelf.

    10/1/97 Update:

    I tried building a heat shield to protect the filter from the engine heat (a tip that was recommend on the message board). However I wasn’t pleased enough with the results to allow it as a permanent solution (filter remains on the shelf). At this point I’m not very happy with this product, especially in hot weather.

    11/29/97 Update:

    Someone e-mailed me and offered to buy the filter charger from me. They own a 318ti and live in Alaska (I’m not making this up), given the Alaska climate the shortcomings of this upgrade are probably negated for him.

    12/29/97 Update:

    Received an e-mail from the purchaser, he loves the cone filter. So if you live in a cool climate the cone filter is a good investment (especial if you can buy one of a Texan that can’t use it).

    Installation of K&N Cone Filter

    This is an OCR/Scan of the original instructions.

    1. DIRECTIONS: Be sure your engine is cool and ignition is OFF. We recommend you lay a fender cover or a blanket on your fender to protect it before beginning the project. Locate the factory air box on the driver’s side inner fender.
    Get familiar with the layout, and figure out exactly what it is that you will be replacing. The area surrounded in red will be replaced.

    2. In the front of the air box is a sensor. Depress the clip so the wire plug will pull out. Then remove the actual sensor from the box.
    Remove the entire air sensor from the stock air filter box. Press the silver wire thing in and the plug comes right off. Make sure you pull out the sensor.

    3. Depress the two clips that hold the top of the factory air box to the air flow meter.
    Depress all you want, it’s going too take a screw driver to pop these brackets off. Let me also point out that the instructions assume I knew what the air flow meter was, I didn’t. It took several cycles of reading this sentence and staring at this contraption before I understood.

    4. Next, unclip the top portion of the air box from the bottom half of the air box.
    Pretty straight forward, I unclipped the top portion from the bottom portion. However I think they also intended for me to remove the top of the air box, it was a couple steps later when I actually did. The four arrows in the graphic point to the clips but the top and left clip can’t be seen in this picture. You will have to look around and under to find them.

    5. Undo the two studs attaching the base portion of your factory air box to the inner driver’s fender. On some models the cruise control may also be attached to these studs. If the cruise control is connected to these studs you must reconnect the cruise control after you install the new filter system. You will need to remove both studs from the factory air box.
    The nut heads easily came off, let me also say that if you drop one it will fall all the way through and roll back to your rear tire. The crap about the cruise control you can ignore, it’s not attached here on the Z3.

    6. After you undo the nuts on the studs you need to wiggle the base of the air box as it has an air duct attached to the housing near the radiator. Once it has come free of this duct you can take out the base of the air box.
    During this step is when I figured out the top should have been removed back in step 4. Because I still had the top on this step was more difficult for me. Once I removed the top I could see the part that was catching and I wiggled her right out of there.

    7. Put the small black hose on the air flow meter.
    Okay, this step got me a little angry. First of all, I think I know what the air flow meter is. But where the hell is this small black hose? When someone uses the word hose I think of a tube, like a drinking straw or fuel line. I’m also not sure if this small black hose is something that’s already in the car or is it a piece that came with the kit. Well after several minutes I noticed the same phrase “small rubber hose” on the “Kit includes” list, and deduced that they must be talking about this rubber ring.

    8. Then install the new air filter and position the filter so the small hole in the neck of the filter faces the driver’s inner fender.
    My silver bracket was shipped already installed on the filter. The instructions later tell you about installing this, so unscrew and remove it now, then just push on the filter over the rubber ring thing.

    9. Position the metal bracket so the end with the cup on it will seat around the rubber bushing at the top of your frame rail. The other long end goes to the inner fender and is secured by the one stud that was attached to your original air box.
    What metal bracket? Oh, this thing that came with the kit. The Cup end? two of the ends are “cupped” but one is cupped more than the other. Rubber bushing at the top of you frame rail? What the hell is a frame rail? Well after trying several different interpretations here’s what I came up with, a picture is worth a thousand words, above is what they were trying to explain.

    10. Before securing this stud you need to position this bracket on the new air filter with the clamp. The clamp is designed to hold the bracket to the filter assembly and the filter to the air flow meter. remember you must not cover the small hole in the filter and the hole must be pointed toward the inside driver’s fender.
    Good thing I’ve got this thing figured out in my head because the instructions are getting worse. I think the K&N people recognized this, because the ONE picture that is included in the instructions is useful in this step.

    11. Carefully push in the sensor you took out of your original air box. It should sit snug in the small hole in the side of the new filter.
    When your doing this push the sensor in until you can’t see the green rubber ring on the sensor. Also position it so the fatter end doesn’t rub against the filter rim.

    12. Carefully tie strap the wire to the one metal bracket so it is away from the fan belt on the car.

    13. Tighten the clamp holding the filter in place against the bracket assembly.

    The instructions warn you to make sure the filter is not touching the radiator. However when I attach the bracket with this rubber screw thing it pushes the filter into the radiator. The instructions are unclear but originally the rubber side was on the left but this pushed the filter to far, I got around this by moving the rubber side of the attachment bolt to the right. This kept the filter out of the radiator but it was not tight so I pulled one of the gold spacer clips off the original box and it worked great.