[Zer0Cool92]

I got m5 RPI mufflers installed as well as a resonator delete. Sounds badass.

I told the guy if he can do 3" piping from after cats up to resonator delete but he said it wouldn't really make a difference in performance or sound and he didn't want to waste my money.

But what do you guys think? Can performance / sound be improved with the 3" piping?

He said It would run $120

[FenixMike]

Originally Posted by Zer0Cool92

I got m5 RPI mufflers installed as well as a resonator delete. Sounds badass.

I told the guy if he can do 3" piping from after cats up to resonator delete but he said it wouldn't really make a difference in performance or sound and he didn't want to waste my money.

But what do you guys think? Can performance / sound be improved with the 3" piping?

He said It would run $120

Bigger is always better, however there is a point of diminishing returns to where money is wasted. Ive been building custom exhaust for about 12 years now and while I love dual 3 inch exhaust, and most of the time install it on my own vehicles, its really a waste unless money is no object and you want every last possible horsepower out of your combination. Flow wise, about 600 rear wheel horsepower is where dual 2.75 inch (factory 550i) becomes a "restriction", but we are really talking minimal gains going to dual 3 inch where it wont be noticeable and you might see 5 rwhp gain on a dyno at higher rpms only. FWIW, my 03 Cobra made 800 rear wheel horsepower on dual 2.5 inch and trapped over 140 mph consistently in the 1/4 mile, 3 inch was too much of a pain on that car and 2.5 didn't seem to hurt it I actually stepped down to dual 2.5 on my 550i because this car wont ever see enough horsepower to make big exhaust worth it and the cost of 2.5 inch components is far less than 3 inch.

[550Reasons]

you might get some drone as well, not sure tho

[Zer0Cool92]

Originally Posted by FenixMike

Bigger is always better, however there is a point of diminishing returns to where money is wasted. Ive been building custom exhaust for about 12 years now and while I love dual 3 inch exhaust, and most of the time install it on my own vehicles, its really a waste unless money is no object and you want every last possible horsepower out of your combination. Flow wise, about 600 rear wheel horsepower is where dual 2.75 inch (factory 550i) becomes a "restriction", but we are really talking minimal gains going to dual 3 inch where it wont be noticeable and you might see 5 rwhp gain on a dyno at higher rpms only. FWIW, my 03 Cobra made 800 rear wheel horsepower on dual 2.5 inch and trapped over 140 mph consistently in the 1/4 mile, 3 inch was too much of a pain on that car and 2.5 didn't seem to hurt it I actually stepped down to dual 2.5 on my 550i because this car wont ever see enough horsepower to make big exhaust worth it and the cost of 2.5 inch components is far less than 3 inch.

Thanks for the input! I'm not too worried about a performance increase as this car is pretty quick the way it is. With a tune it will be more than enough. But do you think there will be a drastic sound increase from the 3" piping?

[FenixMike]

Originally Posted by Zer0Cool92

Thanks for the input! I'm not too worried about a performance increase as this car is pretty quick the way it is. With a tune it will be more than enough. But do you think there will be a drastic sound increase from the 3" piping?

It varies, 3 inch typically has a deeper sound with more resonance, but my experience is limited to going dual 2.5 to dual 3 inch... never worked on a car with dual 2.75. That being said, there are so many restriction points in the factory exhaust that removing all mine and doing 2.5 with zero restrictions seemed to make it quieter (on top of removing all resonators) inside while giving a noticeable difference in performance. I imagine the stock piping has some severe restrictions especially behind the second resonator where it pinches down to almost 1 inch and has some severe angles to go through. I wish I did a good before and after picture, but I can say just removing restrictions helped out a ton. Im going to *try* to install my new mufflers tomorrow but 60 hour weeks on top of 100-110 degree weather here just have me really not that interested.