So I found the best deal on the Dinan X middle pipe for the M550i 2018 to 2020 https://www.dinancars.com/products/e...arts/D660-0080 From getbmwparts.com. Cost was $935, plus $3 shipping (really!) and your local tax, which they are obligated to collect.
Since the factory middle pipe is actually welded right up to the factory muffler, you have to cut it a few inches in front of the muffler. BMW accounts for this, and marks with a dimple in the pipe where the cut is made (if for example, the muffler needs to be replaced) and Dinan includes the additional clamps needed. So two quick cuts, then undo the clamps at the front of the exhaust at the down pipes and remove all the hangers and such (you can see the previous owner of my car had cut the resonators out, and then welded them back in before the sale). Dinan X pipe goes right back up...I little fiddling (rotating the pipes) to ensure none of the pipes are touching the underside of the car, then bolt it up. We did find the rear pipes end up about 1/2" off in separation (see middle photo) so took a little muscling to fit and clamp. Obviously Dinan's fixture is off, or something. At this time, I asked the tech to go ahead and adjust the muffler about 2cm further out, as I didn't like the stock flush look. Easy to do, now that the exhaust is cut, and just a little adjustment with the new clamps.
Overall, very happy with the final fit, welds and construction. Dinan uses 304 stainless steel, the BMW oem pipes appear to be a lower grade 409 stainless. Probably doesn't matter much from a practical sense.
From inside the car, (with active sound "off"), you can barely tell there is any change in Comfort or ECO modes. In Sport, there is obviously a rise in sound level, but not much, the car is too well insulated. From outside, in Sport, the car is significantly louder, and will spit and pop on overrun. Fun! Love the change, just wish it was even louder...I may need to find a used 2020 factory BMW muffler, as I know they are louder than the 2018/2019 and have a different part number, though they cosmetically appear the same.
Since the factory middle pipe is actually welded right up to the factory muffler, you have to cut it a few inches in front of the muffler. BMW accounts for this, and marks with a dimple in the pipe where the cut is made (if for example, the muffler needs to be replaced) and Dinan includes the additional clamps needed. So two quick cuts, then undo the clamps at the front of the exhaust at the down pipes and remove all the hangers and such (you can see the previous owner of my car had cut the resonators out, and then welded them back in before the sale). Dinan X pipe goes right back up...I little fiddling (rotating the pipes) to ensure none of the pipes are touching the underside of the car, then bolt it up. We did find the rear pipes end up about 1/2" off in separation (see middle photo) so took a little muscling to fit and clamp. Obviously Dinan's fixture is off, or something. At this time, I asked the tech to go ahead and adjust the muffler about 2cm further out, as I didn't like the stock flush look. Easy to do, now that the exhaust is cut, and just a little adjustment with the new clamps.
Overall, very happy with the final fit, welds and construction. Dinan uses 304 stainless steel, the BMW oem pipes appear to be a lower grade 409 stainless. Probably doesn't matter much from a practical sense.
From inside the car, (with active sound "off"), you can barely tell there is any change in Comfort or ECO modes. In Sport, there is obviously a rise in sound level, but not much, the car is too well insulated. From outside, in Sport, the car is significantly louder, and will spit and pop on overrun. Fun! Love the change, just wish it was even louder...I may need to find a used 2020 factory BMW muffler, as I know they are louder than the 2018/2019 and have a different part number, though they cosmetically appear the same.
