August 4, 1999
By: Doug Morgan

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.