Before we start unbolting things and having fun with our new toys, we first needed to strap the M5 down to our Super Flow dyno to get our baseline power data. You can see just how far the stock chrome tips stick out in this pic…eew. In order to dyno the E39 M5 the ABS and traction control systems must first be disabled in any of the following three ways. The best way to do it is to use a BMW specific scan tool that allows you to disable the systems with a simple touch of a few buttons. You can also pull the DSC and ABS fuses or you can simply unplug the ABS/DSC control unit which is on the passenger side of the engine bay. We don't have a cool BMW scan tool, so we just unplugged the control unit in the engine bay.
Here are the grand majority of our baseline pulls, minus the first one. The green and blue lines represent pulls 4 and 5, you can clearly see how the computer is hard at work keeping things safe as it detects the car's temperature rising. The red line is our final pull which was done after letting the car roll on the dyno for quite a while (about 15-20 minutes) to let its temperature stabilize. The sixth and final pull yielded the highest power numbers and it will be what we use as our baseline = 282 whp & 265 lbs ft of torque.
Were you expecting larger numbers? Well, so were we. The S62 is rated at nearly 400 flywheel horsepower, so take into consideration a 20%-25% drivetrain loss and the power numbers should be closer to 300whp. Considering our E39 M5 has a little over 120k miles on the clock and it's running 10w/70 Penrite oil (the BMW recommendation is 10w/60), we feel it's putting down some pretty respectable numbers.
With our baseline power numbers documented, it is now time to remove the stock exhaust system. The process is pretty straight forward and a relatively easy bolt-on affair. If you plan to tackle this on your own, we highly suggest having an extra set of hands with you. The stock exhaust will make you wish you did not skip chest day at the gym. It's large, bulky, heavy and it's all one piece from the catalytic converters back!
What the deuce?! The bottom of the pic is the front of the car and after the O2 sensors there is supposed to be a clamp…where the F is it?! Word on the street is that certain E39s came with a welded exhaust rather than a clamped one. Whether this is true or not we have not confirmed, but this was definitely an unexpected hurdle we were going to have to overcome. Turns out our couple hour install was quickly turning into an all day affair.