I've been in the market for a downpipe back exhaust and was leaning toward the AWE because of the sound. However, the 2.5" diameter tubing seems too small.
I noticed many aftermarket exhausts for 2.0L engines have 3" mandrel bent tubing. I was wondering why most manufacturers of F56 aftermarket exhausts are using 2.75" rather than 3". And AWE is using 2.5".
I understand most of the gains are due to the removal of the secondary cat. I think the larger diameter piping would also result in additional power.
To my understanding. Smaller tubing increases the velocity of the gasses and keeping turbo response. Removing cats are the important part. 3inch is over kill.
Even on my Stage 3 R56 with a 45mm turbo, I had a 2.5in exhaust.
I ran a 3.5 on my high hp evo x there really wasn't much difference besides sound and better increase in top end at high rpm but I never put it on the synopsis after upgrading. I agree with the above its overkill and will probably even make it feel sluggish in certain areas of the power band unless it's a pretty high hp mini. This was the 3.5..
Think of the exhaust diameter as the final step in dialing in your power band. Assuming no significant change in the volume of air though your engine, a larger diameter pipe slides the power band range higher in your rpm's.
Using a totally HYPOTHETICAL example,
say your power band with stock exhaust is 2500 to 5500 with redline at 6000.
1) increase exhaust diameter stock+0.5 inch
result: power band is 3500 to 6500rpm (redline still at 6000)
2) decrease your exhaust diameter stock-0.5 inch
result: power band is 1500 to 4000 rpm
3) increase exhaust diameter stock+1 inch
result: power band is 4200-7000 rpm (again redline still 6000)
To be clear, this is with no significant change to the volume of air though the engine.
Obviously if you change the volume of air through the engine with +boost, bigger turbo, whatever. THEN increasing exhaust diameter is required IF you want to keep the same rpm power band range.