Quote:
Originally Posted by joeo
I didn't have an IR temperature probe, just my trusty hand. At those temperatures, hoses to both coolers were hot to the touch. Take that for whatever it's worth.
You are correct that the coolers should be the same size and have the same restriction to have even flow to each, however, if one is larger it should have more flow. It's very similar to two resistors in parallel. I humbly disagree with plumbing them in series being best practice.
In Carroll Smith's book 'Tune to Win':
"When using multiple heat exchangers remember that the greater the difference in temperature between the liquid to be cooled and the air that is doing the cooling, the greater will be the temperature drop across the cooler. That has two ramifications of interest to us. First, plumb multiple coolers in parallel rather than in series. Second, do not mount your oil cooler directly ahead of or behind your radiator."
If you plumb them in series, your second heat exchanger will have low efficiency since the inlet fluid temp will already be lowered. Heat exchanger efficiency is Tin-Tout/Tin-Tamb where
Tin = inlet temperature
Tout = outlet temperature
Tamb = ambient temperature
-Joe
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Yes, of course the larger the delta T between the oil temp and the ambient temp the more heat transfer you will have, but that doesn't change the fact that you're primarily only using one cooler right now.
I understand the parallel resistance analogy (I have a degree in both Electrical and Mechanical Engineering.) Flow works in the exact same way, everything has to obey the same laws of physics. You just don't know what the effective resistance of both coolers is so you have no way to quantify that how much flow each is getting. The one thing I do know is that the OEM cooler is extremely restrictive so I wouldn't count on it doing anything when paired with a nice, large, aftermarket cooler.
For what's it's worth I run identical dual coolers in series, for simplicity, and the oil comes back way cooler than it ever did running a single cooler. My car spends 90% of its time on track and this has eliminated my oil temperature issues. I don't think the oil cools as much as you think, so I don't think the second cooler loses much efficiency.