I was curious as to why no one here is running a Borla exhaust on their E60? I have had very good experiences with them on past cars. Everyone is telling me to get an RPI but I am having a hard time pulling the trigger on a relatively new company over a very well established one such as Borla or Magnaflow. Opinions?

 

I've got borla, but it came on the car when I bought it so I can't compare it to stock. It has a nice subtle purr and isn't very overwhelming noise-wise. I don't think it has any performance enhancement...

 

I am your dream response!

I just sold my Borla and bought a used RPI (only 3 mos. used). Didn't notice if you a have a 6 or an 8 but I have an 8. When I bought the Borla, the RPI didn't exist. Borla does not make an axle-back system for the 545, not sure about other E60 models. So I purchased a universal Borla muffler and had a custom exhaust pipe created. This was much cheaper than buying an Eisenmann or Supersprint axle-back system. There were few, if any other choices for bolt-on axle-back systems for E60 545.

That being said, I was very happy with the Borla and it was a lot of fun to drive. I noticed no loss or gain of power, but it was never dyno'd so I don't have any objective data for you.

The difference with the RPI is quite noticeable.

First, the RPI will cost twice as much as a custom Borla system.

Second, the RPI is specifically designed for the car... not a universal muffler with a pipe. As others have noticed, the exhaust pipe attached to the RPI muffler is smaller in diameter than stock pipe, then expands to 3" where it attaches to existing stock pipe. I am not a physicist but my intuition tells me that this was done to maintain some back pressure, thus increasing HP without losing too much torque. I'm just guessing here! RPI has a good reputation here and they may not be willing to divulge all their engineering secrets.

Third, the sound is FANTASTIC! The Borla sounds MEAN..., the RPI sounds MEAN AND TUNED. The RPI sound is cleaner... more European, super-car sound. Borla is more raspy, American, muscle-car sound.

Fourth, there is a noticeable acceleration improvement with the RPI. Again, this a subjective assessment from the driver's seat. As I said before, with the Borla, I noticed no loss or gain. With the RPI, there is a noticeable gain.

Fifth, for $500 the Borla sounds good and is a lot of fun. Got lot's of compliments at redlights, parking lots, etc. If you are willing to pay $1000, the RPI is worth every dime and then some!

I have a shitty camera so the recordings aren't great, but here's a comparison on my car:

Borla:

RPI:

 

magnaflow is another option, but not as popular as the RPI. but yes it is cheaper, mostly we do magnaflow setups for those who want a custom quad setup, but also there has been a couple for just the dual as well. then again, there is no proven guaranteed power with magnaflow.