Mine's a 2003 540i/6 m sport and here's what I did for my track day (she handled it way better than my stock 99 540/6):
- M Performance 6 piston BBK (similar or the same as 135i brakes)
- ECS Tuning floating rotors
- Stainless lines
- Always fresh DOT4 fluid before the track day
- Removed dust shields and keeping the factory brake ducts and openings (anyone know why the 540i M got these, but not the M5? That makes no sense to me, but I'm not complaining)
- Thermostat spacers to cut out the electric thermostat and put a conventional 80C one in (the M62tu in the 540 runs at an outrageous 110C). I got the spacers from this guy on ebay and shipped me extra gaskets later for free. Pretty rad dude: sebastian_workshop_2011 on eBay
-Just using standard coolant for now, but will consider a higher water content mix next time
- Electric fan conversion using the thickest, highest static pressure SPAL fan I could buy. I fiberglassed the fan into the shroud and am running a variable speed PWM fan controller that soft starts the fan at 60 percent and then ramps up to 100 if needed or if my manual bypass switch is on)
- Gulf oil filter housing and AN10 braided lines and fittings
- Setrab 16 row series 6 oil cooler behind the kidney grills
- Had no idea what oil temps would get to, so I opted to run Mobil 1 15w50 for my track day anticipating oil temps would get much higher than they really did.
- BC Racing coilovers (just the stock setup, I didn't do any special spring rates)
- Rogue Engineering Thrust arm bushings with the black street urethane instead of the blue. They are still MUCH stiffer than a brand new stock thrust arm.
- Ball joints, tie rod ends, sway bar pushings and endlinks, and center track rod were shot, so replaced all of those and went urethane on the sway bar bushings.
- Eibach 18mm rear sway bar and replaced all the bushings and endlinks back there
- I forgot my exact alignment settings, but kept it street friendly with a little more camber all around, and less toe in the front than stock.
- Doesn't really matter that much to me for a fun track day, but I did do the M60 manifold swap.