Recommended exhaust size

[Wagon727]

I'll be doing an S62 swap, before long, in the ole wagon. I'm still utilizing my spare tire compartment, so I'll only be running a single muffler. What would be ideal for pipe and muffler size?

[BMW540san]

I've done extensive research on that subject when I did several custom complete exhaust setups on various E39's and 3" is plenty for stock S62.
2.5" if going dual.
This is information from several reputable technical articles where there is basicaly sort of a table stating optimal exhaust tubing ID in relation to engine size / output.
If going forced induction, than things are little different and you have to bigger at certain higher HP output.

[Wagon727]

Good to know. I was thinking maybe just going to 3" midway, for a single muffler. Or dual 2.5" if i could find the right dual in/out muffler.

I've done extensive research on that subject when I did several custom complete exhaust setups on various E39's and 3" is plenty for stock S62.
2.5" if going dual.
This is information from several reputable technical articles where there is basicaly sort of a table stating optimal exhaust tubing ID in relation to engine size / output.
If going forced induction, than things are little different and you have to bigger at certain higher HP output.