I have the largest (ECD54-329) plumbed between two 400 ci water radiators. I can tell you it is very effective. With my cowling off, extended full power ground runs I see oil temp trailing water temps by 40-50 degrees.

Where are you taking the temp measurements for the oil and water? Under these conditions, the water is heating the oil. If heat is being transferred from oil to water, the water at the exit of the first rad would need to be 60-70 degrees lower than the inlet; which would suggest a very low coolant flow rate; much oversized rad; or something suspect. Either it has not come to steady-state, or perhaps the temp measurements are suspect. Or; there is something suspect about my understanding of setup.

 

With lower cowl only, same conditions, the oil tracks the water a little closer. 20-40 degrees. With full cowl the temps come up together and stay together after about 170 degrees.

What accounts for the big change with and without the cowl?

 

Al G

 

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