Originally Posted by The HACK
$1,000 for a good high capacity radiator with aluminum neck (I assume) is CHEAP. I have "connections" and it still cost me $800 for a radiator for my E30 318is, and I am almost certain there were no mark-up on that and I got "jobber" price.
And an upgraded radiator will go a very VERY long way to solving some limp issues but not all. The issue is inherent with the long engine block. The last 2 cylinder just isn't getting the proper cooling air and water flow and forcing the oil to do more work to keep the engine cool. To "solve" limp problem on the N54 you need an entire OVERHAUL of the cooling system and even then there's no guarantee it'll work.
Additional aux. pull fan
2ndary oil cooler in addition to the OEM one
Reprogrammed water pump to flow at higher capacity (ala Dinan)
Air duct altering underbody air flow to redirect ambient air to the last two cylinder
Automatics need not apply. There's just no way to build enough heat exchanger to allow the system to evacuate heat fast enough because the radiator needs to cool down transmission fluid too. If it's an automatic I wouldn't even bother tracking it.
$1000 for a radiator is not expensive at all.
I'll tell you what cost the most, to draw up the inlet and outlet, program the CNC machine and the run-time to make it. If you really want to know how much a prototype one cost us, you better be sitting down.
It would be easier if BMW just kept the old E30/36 style hose clamp hose ends, then maybe the radiator can sell for $800.
With the prototype all aluminum radiator, we had zero issues with our Time Attack 335i, even in the heat of Buttonwillow and Las Vegas. When ER and Berk had coolant temp issues on the long straights with extended time under full bost, we were nice and cool. What is amazing is the recovering time of the all aluminum radiator, it wook no time to come back down to the 190s F.