[seank]

Originally Posted by gmd2003

I have spoken with several vendors and the Zionsville is the best option for direct fitment and they have avery good reputation. It is very interesting that the stock Z4M radiator is from the non M E46 , thus E46 M3 radiator upgrades are a total no go. Zionsville takes a custom aluminum core that is slightly larger than stock with better fin design and welds it to aluminum expansion tanks, also larger than stock(and not plastic) but is in the same vertical and horizontal dimensions. They say it has approximately 10% more cooling capacity than the stock radiator. My hope is by installing it, a fresh OEM water pump (I'm at 70k miles), BMW motorsport thermostat, and using pure distilled water/Mocool I can get to a stable 210 water temp on track.
I went ahead and ordered from them because I am a very impatient man, and want to do some track days without issues! I will be the guinea pig for everyone else

Thank you.

It definitely does not have enough cooling capacity for SC applications especially the radiator system. To confound the issue those running an intercooler now have it disrupting flow to part of the radiator and a large oil cooler in front of it as well. The stock coolant system just can't handle that on track (water temps in the red within 3 hot laps on a 90 degree day.
Stock it really is variable , but depends on the track and most importantly the drivers skill level. I had no problems NA at Roebling Road (Momentum track with a long straight), but did run hot at CMP (lots of braking/ turns and acceleration).
The bottom line is to truly track a car hard in hot conditions cooling modifications are always useful . The Z4M for an OEM car is set up well for occasional track use but once you reach an advanced skill level it is not enough on many tracks.

Agreed.