http://rob.com/lancair/2002.03/9side.jpg

Rob,

 

Your oil cooler appears to be in a direct blast of high speed air possibly forming pressure fronts on the vanes and closing off the air going thru.  Also, from my view, it looks too small for that engine - maybe 2 of them?.  Have you measured the pressure differential across the cooler?  From one of the charts it appears that the temps just kept rising, as though the cooling function was just short of that necessary to keep the temp constant.  More oil won't solve your problem.  Is the air backing up behind it.  What happens to the cyl head temps?  In other words, is it just that the oil cooling function is just short of fully cooling the oil?  Have you tried a diffuser in front of the cooler to slow donw the air but keep the pressure up?

 

Just a few questions.