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.
Last edited by BMW540san; 11-01-2022 at 07:34 PM.
2010 BMW M6 SMG Coupe * Black Saphire Metallic * Full Leather Merino Black
2019 BMW X3 M40i * Alpine White * Mocha Leather
Former:
1997 BMW 532M (528i with 3.2 S52 engine from E36 M3 / 5 speed manual)
1998 BMW 540i 6 Speed
2003 BMW M5
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