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.

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.