Servicing the Z3 Battery

The battery in the BMW Z3 is NOT a maintenance free battery; it needs occasional servicing. The leading cause of battery failure in the Z3 is from a lower water level. Fortunately it’s pretty easy to check the level and add more water.

The first step is getting access to the battery. For all but very early 1996 models the battery is in the trunk. You will have to raise the trunk liner and remove the plastic cover over the battery but then you will looking at the top of the battery.

Along the top of the battery are six plugs that unscrew from the battery. Remove the plugs but take care since you’ve just exposed corrosive liquid. You can look down into the battery, but don’t get to close (the water vapor can’t be very good for your eyes).

When you look down into the battery, you will see a little metal tab in each hole. The water level in the battery should be just over this metal tab. In the picture above, the battery needs water.

BMW Techs have a special water can that makes filling the battery easy and accurate, but there really isn’t anything fancy about this procedure. Richard Carlson suggested that the perfect substitute is a turkey baster. Just gradually add water and keep rechecking the water level until it covers the metal tabs. It’s best to use distilled water so no mineral deposits will be left from the evaporation of ordinary tap water.

When the battery is properly filled, the tab will still be visible, but obviously under water. Regular checking of the water level should greatly extended the life of the battery, especially during the hot summer months when the water will evaporate at a faster rate.

Update: Ron Styger reports that his 9-1-1999 build date M Coupe has a different battery. Not sure when BMW actually made the change but it is nice to see that they have a different battery now (maybe the new one will have a longer average life span).

Update: Tom Bilken sent me this note regarding the new battery (pictured above)…

I have a 1999 2.3 (build date of 3/99). I read a lot about the battery problems (low water) on the MB, and your article. When I looked at mine, it was the same as the added updated picture on the Mz3 site for Ron Stygers battery. But, under the decals on the top were the battery plugs. If you look in the picture that you posted of Rons battery, you can see the outline of one of the plugs. Mine has the “eye”, but after I peeled back the decals, and opened up the plugs, I had to add a lot of water. I just wanted you to know (and maybe you already do) that these batteries still have the plug caps, and my levels were still low.

Z3 Solution Cupholder

Pros: Very convenient location, holds 12oz cans and slim 20oz bottles, flexibly material so its easy to install and uninstall
Cons: Condensation can drip into door pocket
Cost: $24.95 (from Z3 Solution)

“Here I am driving one of the most fun automobiles in the world, yet I can’t find a good place to put this can of coke while I shift into 5th gear.” This has been a common statement ever since the introduction of the Z3. The BMW roadster is an amazing automobile, a near perfect balance of modern day technology and classic “retro” styling, but it doesn’t have a cup holder. This is where Z3 Solution enters into the story. Pictured below is a cupholder that Z3 Solution makes that snaps into the side door pocket.

This design is simple and functional, its a single piece of molded plastic/rubber material that was custom made for the Z3. The flexible material lets the unit snap into place in the door pocket. Once installed the cupholder holds standard 12oz cans and the newer styled slim 20oz plastic soda bottles. It sticks out from the door slightly more than the door pocket, so there is a slight loss of leg room. However the positioning doesn’t affect the driver, on long drives I even find myself resting the side of my knee on the soft rubber since its more comfortable than the door pocket.

I find myself using the cupholder to also hold my sunglasses and other items when I don’t have a drink in there. I needed to come up with some “cons” for this article, so I got really picky and found one. Condensation from the can ends up dripping down into the door pocket since there is no bottom to the cupholder. If you keep items other than the cup holder in the plastic door pocket they could get water dripped on them (so its not a good place to keep paper). I’ve learned to keep something like a napkin under the cupholder so this isn’t much of a problem.

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.


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.


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.


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.


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:


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


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.


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

Improving the Boot Cover Snaps

When I first got my Z3, I used the boot cover regularly, but then over time I slowly started using it less and less. I had always considered it a purely cosmetic piece of equipment and eventually grew tired of the hassle of installing it.

When I traded in my Z3 to get an M roadster, I took the new boot cover out of the trunk and put it on the shelf where it pretty much stayed. The few times I used it left me frustrated at how hard it was to install. I’m not sure why the new one was harder to install than the old one. I kept trying to convince myself, “maybe if I use it more, the boot cover will get broken in and be easier to install.”

Despite my repeated attempts, the boot cover would eventually find its way back onto the shelf for another extended stay. I had become spoiled with the power top, and found the boot to only lesson its usefulness. I had also become lazy and just plain fed up with the hassle of installing the boot cover.

The boot cover made a comeback when I started using the roadster tonneau cover. The tonneau cover required the boot cover be installed to function, but it also enabled me to keep the boot cover on for extended periods of time. The two products proved to be a great combination when the weather allowed for extended top-down periods. But the tonneau isn’t a year-round product, and eventually the boot cover found its way back onto the shelf for another extended stay.

Then I installed a light gray interior liner to the convertible top. It didn’t take me long to realize that light gray doesn’t look very good dirty. Without the boot cover, the liner was picking up a lot of dirt and dust when the top was down. So now I’ve got two accessories somewhat dependent on the BMW boot cover. So I find myself once again saying, “maybe if I use it more, the boot cover will get broken in and be easier to install.” I still hold some hope in that theory, however this time I’m going to make things a little easier on myself.

I remembered an additional paragraph tacked onto the end of the original BMW windscreen instructions that said to install some washers to make the boot easier to use with that windscreen. BMW doesn’t even make that windscreen anymore, but I managed to find my old copy of those instructions and figured I would share an old idea (slightly modified) to those that were not Z3 owners back in 1996 when the first windscreen was introduced. The official name for this “knob thingy” is a Tenax fastener. There are two of them screwed into the back of the storage area that the boot cover snaps onto. The theory behind the fix is that if these fasteners were sticking out a little farther, the boot cover would be easier to install since you were not having to stretch it as much.

Once you locate these two Tenax fasteners, you can unscrew them with a standard 11/32 open ended wrench. The screws are longer than you would think they should be, but this extra length is about to work to our advantage.

The original BMW instructions had you using standard everyday washers. However, on the suggestion of an MZ3.Net reader I went to the hardware store and found some black rubber faucet washers. Looking at the different sizes I determined that the “00 Flat Washers” appeared to be just what I was looking for. I used one of them on each side rather than a stack of regular washers.

With the rubber washers installed behind the Tenax screws, the fastener portion of the snap now sticks out an extra 1/8 inch. That small difference makes the boot cover a little easier to install. However, even with this addition, I still consider the boot cover a pain to put on. But this upgrade cost me under a dollar, so I’ll take any help I can get and I’ll keep telling myself, “maybe if I use it more, the boot cover will get broken in and be easier to install.”

Discuss this article and other Convenience upgrades in the

///MZ3.Net discussion forum.

Cell Phone and Radar Detector Power, Another Way

I was getting tired of plugging my cell phone charger into my cigar lighter, so I decided to permanently wire it into my car. I was thinking that I would use power from one of the various unused connectors or perhaps from the radio. But then I came across Vince’s article and it gave me the idea that I could use the BMW cell-phone connector.

What’s more important to note here is that I could use this connector for more than just a cell phone. I could use it for anything I wanted. Vince’s article details a way that you can order the connector and pins for the cell phone connector. In addition, both switched and unswitched power are available, and they are both regulated by individual fuses in the fuse box, so you can play around without the danger of seriously hurting the car. But best of all using this connector means no permanent wiring changes to the car. I would not have to cut a single wire that was part of the car, which sounded pretty good to me!

First thing I did was prepare the charger. I opened it up, and replaced the metal contacts on the circuit board that ran to the tip and the sides of the cigar lighter with wires about 1 foot long. Then I closed the charger back up, running those wires out the hole in the tip of the charger.

Next I prepared the radar detector by cutting the cord right before the cigar lighter plug. I placed the radar detector where it was supposed to be on the windshield, then ran the wire along the inside of the window and down the seam of the door, and under the steering column. From there, if you lift the cover on the shifter and the handbrake, you should be able to fish the wires through to where the cell phone connector is. NOTE: Those that are truly anal-retentive will probably want to run the wire INSIDE the plastic pieces along the inside of the windshield. Other articles here can tell you how to remove it.

I then found the cell phone connector as detailed in Vince’s article. I took the wires from the charger and the radar detector and started soldering the pins on them. One wire from the radar detector (the positive lead) goes to a pin. One wire from the charger goes to a pin (once again, the positive lead). The remaining wires (which should both be ground [negative lead]) should go together into one pin.

Now put the charger inside the center console, with the piece that connects to the cell phone (and the coiled cord with it) coming out from under the bottom of the console on the passenger side behind the seats. I used a piece of Velcro (the non-fuzzy side) to hold the cell phone connector against the back wall.

Time to start the final piece. Put the pin for the radar detector into the hole in the connector for switched power, and put the pin for the cell phone charger into the unswitched power hole. Put the shared pin into the hole for the ground connection. Plug the connector into the cell phone connector in the car and you’re ready to go!

NOTE: I also replaced the fuses in the fuse box that related to the cell phone power with 5 amp fuses (smaller than the standard fuses). This just gives me an extra degree of protection that I like. I would have used smaller fuses (like 1 or 2 amps), but I couldn’t find any in that form-factor that had such a small rating.

Finding Power in your Center Console

Note: This article is for the 1996 and 1997 model year BMW Z3, I’ve had vague reports that on 99 models (and perhaps some 98 models) the connector has changed.

Do you need power in your center console?

There are several reasons why you might need access to a switched or unswitched power in the Z3 center console. I needed to install a hands-free kit for my Nokia phone. As luck would have it, BMW prewired the Z3 for their cell phone kit. Part of this prewiring is a connector providing switched and unswitched power (as well as radio mute).

To find the connector, lift up the shifter boot. There are 4 tabs (two on each side) that snap it down. Squeeze the side on either side and then lift once it’s loose. Once you’ve lifted the boot, you’ll see several bundles of cables:

1 bundle for each window switch

1 bundle for the hazard light switch

1 bundle terminating in a 2-pin female connector (purpose unknown)

1 bundle terminating in an 8-pin female connector (circled in red and seen in the close up picture below)

The bundle terminating in the 8-pin connector has what you’re looking for. It is a little hard to find! The connector is buried underneath a layer of carpet just to the left of the hazard switch. Just look for a bundle of 5 wires and follow it. I assume this was done so that while floating about it didn’t touch anything and short out the battery (it has fairly exposed 12V and ground connections). It may also be hidden under the emergency break boot (look for a square cut-out in the carpet).

Using the numbering in the picture to the right, Here’s the pinout:

Pin 1 – 12 volts, unswitched

Pin 2 – Ground

Pin 3 – Unknown — if anyone can identify it, let me know.

Pin 4 – Not connected

Pin 5 – 12 volts, switched

Pin 6 – Radio Mute

Pin 7 – Not connected

Pin 8 – Not connected

Now the bad news. The pins required for the connector are odd-sized. They’re 0.098 inch pins. The common 0.093 inch pins won’t stay in. The good news. You can get the correct size pins and even the mating connector free from AMP. Call (800) 522-6752 ask for some engineering samples. Ask for part numbers 1-828737-1 (the mating connector) and 927797-2 (the pin). I asked for 5 connectors and 20 pins, and they didn’t bat an eye.

Interestingly enough, you’re not allowed to buy the connector unless you are a BMW contractor. But ask for free ones, and there’s no problem. I love the way the world works!

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.


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?”


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.


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


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.

Chrome Lighted Shift Knob

Since you can never have enough chrome in an M Roadster (open to debate, perhaps) I decided to add the BMW chrome gearshift knob. However, if I did that I would loose that cool lighting effect from the stock gearshift knob. I decided to try and make a chrome lighted gearshift knob.

You will need to remove the standard shift knob. Lift the cover up around it (it’s just held in place by small tabs on the side), and find the connectors for the wires leading to the knob. Disconnect these and simply pull straight up on the knob. It’s tight, but it should come off. Be careful not to hit yourself while pulling it up.

The first thing I did was to take apart the stock knob to see how it worked. It’s really just 3 tiny LEDS and a resistor under a knob emblem that let’s light shine through. Since BMW does not sell this emblem as a separate piece, you will need the one from the stock knob. Put your fingernail under the edge and simply pry up. It’s held on by double-sticky tape and should come off easily. Be careful not to scratch either side. Also important, the “silver” look of the numbers is not really paint. It’s some sort of dust that very easily wipes off. Do not get your finger anywhere near it, or you’ve just ruined the emblem.

The next thing you will need is the wire connector off the standard gearshift knob. Cut the wires (but leave some space to work with). I choose to get some nylon connectors from a local electronics store and solder it on the end of the BMW connector. That way I can still take my knob off without dealing with the BMW connector (which is a little big and won’t come off though the hole in the cover that easily).

Now it’s time to work on the chrome knob (which you need to purchase, of course). You need to get the emblem off without scratching the knob itself. The knob itself is covered in some sort of thin film that protects the metal (which is very soft). If you scratch the knob, it will look BAD. So don’t do that *smile*. The emblem is held on by the same double-sticky tape, but lots more or it. The best way I found is to use a dremel and drill directly into the center of the emblem with the dremel screw-like attachment, then yank the emblem off. Remove the remaining double-sticky tape, but save it – you will need it later.

Under the emblem you will find a little hole which is almost the right size. If you were to put the M emblem over this hole, the “R” and the “5” would not light up, because the hole isn’t big enough. Carefully grind the edges away where those two spaces would be (i.e. instead of a round hole, you would create a hole that looked like it had mickey-mouse ears). You don’t need to go very deep, long enough so that light can shine through. Now look at the underside of the knob. Inside you will see a couple horizontal plastic bars that hold the knob in place and keep it from spinning around. Through the center of the knob (in the hole on the top) drill out a vertical line that intersects the horizontal bar. Go all the way through till it’s completely open. You are almost done at this point.

Go back to your car. Figure out where that horizontal bar would go (it’s plainly obvious). Now cut (grind, actually) a small groove down one side of the stick. It doesn’t need to be very big, but you need something to run the wires in. On the stock knob, the wires actually run along the outside of the knob, but with the chrome knob we can’t do that so we need this grove. It won’t affect the functionality at all, there’s still PLENTY of metal left. When I did this, I took a vacuum and left it up close to where I was grinding to keep all the particles from spraying through the inside of my car.

Back to the chrome knob. Take some very small gauge wire (I used the individual strands of a telephone wire) cut two 18″ pieces. One one side, solder an LED to it. I used a jumbo orange LED from radio shack, their part number is 276-206 and the color matches the rest of the car pretty well. On the other end of one of the wires solder a 470 ohm resistor. Then solder on the mating end of the connector that you soldered on the BMW connector.

Go back to the car. Thread the connector attached to the knob through the leather shifter cover, and place the cover back on the car. Now carefully place the chrome knob on the car. Line up the wires in the groove you cut and on the top have the wires come out next to the horizontal bar (i.e. the LED [attached to the wires] still isn’t in it’s final position, it’s sticking out further). If you did everything right, the knob should be in position and on tightly, but if you hold both ends of the wires you can gently slide the LED back and forth. Pull on the wires until the LED is flush in the hole.

Lastly, you need to put a diffuser and the emblem back on. For a diffuser, you can use the white plastic one from the stock shifter, or simply cut a piece of white paper in the appropriate size. Use that double sticky tape you saved earlier to put the emblem back on. Re-connect the wires and put the leather cover back in place, and you are all set!

Another thing to watch out for is to test-fit the emblem into the chrome knob. I’ve had two different knobs, in one the M emblem fit just fine, but in the other I had to slightly grind the emblem down to get it to fit. Also, be careful not to push too hard getting the emblem in place, it CAN crack internally and have ugly white lines running through it. In direct sunlight, the knob can get VERY hot – so you may want a pair of driving gloves. And the wires you use to connect the LED can get damaged very easy, so if you take the knob off again you may want to plan to replace those wires.

All in all, I’m happy with my unique shift knob!