In fact, it may sound as good as a V8.
Turbocharged engines offer lots of advantages, but we prefer the sweet sounding exhaust of a naturally aspirated car. BMW no longer produces a single naturally aspirated car, which we think has ruined their sound. Mercedes has found ways to make its turbo engines sound great, but so far BMW has kind of missed the mark. The latest F90 M5 is the best sounding turbocharged BMW to date, although we now have evidence that the base 530i is actually a great sounding car as well.
The 530i comes with a 248-hp four-cylinder that is really not meant to make the 5 Series a performance car. However, this aftermarket exhaust has made this tiny engine sound almost as good as a V8, especially at full throttle. We think that the 530i with this exhaust actually sounds better than the current M3 and M4, which use a twin-turbo inline-six engine. Perhaps BMW is starting to get the hang of making turbocharged engines with decent sound, which is good news for its future performance models.