Magnaflow & X-pipe removed today

[TowX]

Went back to my fab shop and had them remove the X-pipe and Magnaflow resonators. He fabbed up straight 2-1/4" pipes and made a 2" balance tube between them in the same location that the stock muffler has holes inside so that the effective crossover is in about the same location.

Fired it up and it's much throatier as one would expect. Nice rumble but not at all loud, and hardly noticable inside with the windows up and a/c on. So how does it run? Way better than the other setup. In fact the low end torque and throttle response is back to the way it was stock. From 3000 on up it flows better than stock with a nice bark to the exhaust note. Only drove 10 miles home but I'm happy with the performance again. Fuel economy is up from 12.5 to 13 in just that short distance without even resetting the mpg. So obviously running more efficiently too.

So what was the problem? Not sure I'll know for sure. But it had to be the x-pipe or at least the location of it. My guess and that of a well know long-time Porsche guru is that the x was in the wrong location relative to the exhaust pulses in the pipes and was just causing turbulence. Maybe moving it back 2" or some nominal distance would have made a big change but it was definitely interfering with the exhaust flow in the 2000-3000 rpm range. Above 3000 it pulled very strong, stronger even than the straight pipes on there now, but I don't drive everyday over 3000, and I need the pulling torque in the 2500-3000 range for the trailer.

So back to making power again and lesson learned. The German car makers are doing a pretty good job of designing exhaust systems these days. There's been many a late model 996 or Cayman Porsche owner who's installed a well known aftermarket exhaust only to find that while they may make an extra 5 or 6 hp near redline, they actually loose torque in the normal driving ranges, backed up with dyno numbers. And the software has to match the changes in exhaust too. Just changing the headers on my 911 from 1-1/2" primaries to 1-5/8" requires a lot of software remapping to make it work. That 1/8" difference will cause the engine to go very rich from 3500-4500 rpm and cause a flat spot on acceleration unless remapped. I'm betting the same thing happened here as well. But for warranty purposes, my software had to stay stock.

So I have this beautifully made stainless Magnaflow x-pipe and resonators that is now expensive yard art, unless someone wants to try their luck with it on their X5, but with all my warnings.