325i dual exhaust to single conversion: How are people doing this?

[phenryiv1]

If I were to do it all over again, I would just put it on my press and press the outlet from 1.75" to 2.5" instead.

btw, I also put two vbands right before the Y to make things easier when we have to drop the exhaust for whatever reason.

I am considering a combination of the press idea, heat, and one of these to make the collected OEM pipe into a 2.5" almost-circle.

http://www.harborfreight.com/automotive-motorcycle/exhaust/large-tail-pipe-expander-69549.html

Thoughts?

[DetailAddict]

I am considering a combination of the press idea, heat, and one of these to make the collected OEM pipe into a 2.5" almost-circle.

http://www.harborfreight.com/automotive-motorcycle/exhaust/large-tail-pipe-expander-69549.html

Thoughts?

[Gary Horneck]

Worth trying. They are not very tough though. The only way I have found to make those HF pipe expanders work is to dismantle them first and polish the parts that make contact with the expanding cone. Then thin film of 90w gear oil. They should sell them in a 3 pack...

[Gary Horneck]

Rallycross update

Are you concerned that the 2-to-1 muffler hangs so low? How does it compare to the height of the OEM system?

First Rallycross of the season this past Sunday, and the exhaust had no problems. I moved the tail section up a few inches, and used a heavy duty universal rubber, reinforced hanger. Never felt the muffler take a hit, and I was coming down on the bump stops hard. Muffler really is not lower than the lowest point on the headers, the pic I took sucked. Skid plate is the lowest point on the car, then the headers.

[TheTacoMan]

Y pipe into a full 3in.

[Gary Horneck]

I was going to use the same method TacoMan, but use oval 3" pipe for the subframe clearance. Crossing under using one of these http://www.spintechmufflers.com/oval...es/cat_51.html Then our Autocross venue instituted a 96db max with a 95db warning, so plans had to change.

[TheTacoMan]

I was going to use the same method TacoMan, but use oval 3" pipe for the subframe clearance. Crossing under using one of these http://www.spintechmufflers.com/oval...es/cat_51.html Then our Autocross venue instituted a 96db max with a 95db warning, so plans had to change.

Yea, even with a muffler this setup is extremely loud. Well over 96db at WOT

[phenryiv1]

They should sell them in a 3 pack...

Hahaha!

[phenryiv1]

I thought that I'd follow up to post how I got the 2-to-1 conversion completed. After running short on time, we took the pipe that had the oval-shaped end and went to an exhaust shop who basically flattened a 3" pipe and welded it to the oval-shaped outlet on the stock pipe. From there, I had them weld in a 3" to 2.5" reducer to make it easier to source parts and to route the exhaust.

Pictures:

[efficient]

thats real cool. welding is something id like to learn.