Cost: ~$399 (incl. parts, install, tax, beer bribe) Pros: Much better sound. Added HP (according to butt dyno) – particularly with intake and ECU mods Cons: Volume (doesn’t bother me, but the neighbors might have a different opinion) Body work damage possible but can be avoided. Installation Time: ~3 hours
Shortly after installing the Dinan chip and Air intake, I decided it was time to replace the exhaust in Dieter Z (the last of the intake/chip/exhaust upgrade trilogy). Having heard a couple other Z3s with various exhaust systems, I opted for a Borla muffler with complete cat back modifications.
The Borla exhaust is not for the feint of heart. At an idle, you can hardly notice a difference from the stock exhaust. Revving the engine at a standstill, there is a definite growl. At full load, running through the gears, the Borla will bring most pro wrestlers to their knees and a tear to a hard core biker’s eye.
BMW Z3 2.8 with Borla exhaust at idle and revving
BMW Z3 2.8 with Borla exhaust running thru the gears
With Dieter Z up on the rack, the work began. (I really hated to see cutting torches that close to Dieter).
We first looked over the stock exhaust and went over what we were going to do.
and ending in a big bulky muffler (the thing must weigh some 20 pounds)...this definitely had to go.
The stock system is quiet, but the exhaust tone lacks much, and with the air intake and chip, the back pressure sounds as if it would blow the stock muffler right off.
It took them 3 tries to form the 2.25 inch pipe just right. They wanted just the right fit with as little bending as possible. Dieter Z lost about .5 inch in clearance so they could bend it around the same area where the stock exhaust was crimped.
Once it was all staged, they welded the pieces together.
They then fabricated a Y and applied the BORLA inter-cooler tips.
They attached the tips in a staggered fashion that allowed the tips to follow the curve of the rear-end better than if they were attached even.
With Dieter Z's setup, the tips were set even in the cutout area, but melted a bit of the left side of the tip cutout as the exhaust got hot and shifted to the left. This melting only occurred to a small extend until the exhaust had traveled its full extent, and was easily cleaned up later.
In another Borla install, tips were constructed closer together and angled a bit to the right. This allowed more room for the tips to move to the left when the engine was running and the exhaust system got hot.
Because the BORLA was so much smaller, they had to custom build new hangers.
They replaced the BMW rubber mounts with Honda mounts. The Honda mounts are about the same size, but have more rubber to them making them more rigid.
They then bent and welded J hooks from the mounts to the muffler. Note the right angle and braced hanger on the right rear of the muffler.
This setup made the muffler setup very rigid, but allowed vibrations to be dampened by the mounting rather than traveling back to the engine or body.