re: You need an oil cooler
Oil operates best between 100C and 120C. At 150C the combustion by-products start causing significant chemical reactions that start to break-down the oil (kind of catalized oxidation). As the temperature rises from 150C both the viscosity and the oil itself start to deteriorate quickly. At some point the oil film strength will no longer support the crank bearings and they will fail i.e. your engine blows up. Above numbers are more representative of good synthetic oil. for regular oil all of this happens much faster at ower temperatures.
Oil temperature is not so dependent on mods. Oil picks up heat from its surroundings i.e. comes up to engine (water) temperature quickly. (Here power adders that generate more heat will have marginal effect on oil temps). Most of the temperature rise comes from internal friction. Hence, high-revving low-clearance 4-cylinder motors heat up oil more then slow-spinning American V8's.
On the track, you should be running the car between 6500 and redline. This will heat up the oil very quickly, especially since the motor does not hold all that much (not like dry sump). Heat will go into the oil and it has no place to escape (you cannot get theoil colder than the oil pan temperature.)
On the street or canyon running there is enough time for oil to cool down to engine temperature in the pan between sprints... maybe...
Once the oil starts approaching its critical temperature the wear increases rapidly and complete break-down happens very fast. Oil viscosity vs. temperature is plotted on a log*log paper (the slope is VI). This means it is a double exponential onset i.e. very quick once it starts.
The only way to run on the track is maybe run 5 mins hot and 5 to 7 mins slow... maybe.
Run good synthetic for more protection i.e. Redline (commercial stuff is not what is used in jet engines it is a cheaper base-stock for cars).
None of the above will provide you with protection.
How much $$ did you spend for track time? to enjoy only half of it? at most? What ois the cost of increased wear on the motor? or possibility to blow it up? vs. cost of an oil cooler?
If you want to save $$. Buy a used cooler on e-bay. Make sure it is NOT from a blown motor (can never get all the junk out before it goes through your motor and blow it too!). Plumb and instal lit. The heat in the oil needs to escape somewhere and the oil pan in a Lotus is all covered up (yeah.. there are small NACA ducts on the bottom, but not enough). It is very little heat but it needs to go or the temperature will continue to rise.
Anton
If some data supports that it's ok running without a cooler i'm not going to mess with a rear mounted unit. I'm concerned about a 20 minute HPDE session now.
FYI: I have already removed the front cooler and all the lines. I'm not running any engine mods or forced induction.
