Cool-X LLC recently conducted a transmission dyno test of its Cool-X® ATF Nanofluid Coolant at SuperFlow Technologies in Iowa. The testing showed a 20oF decrease in oil temperatures under a modest load under normal conditions. A more detailed analysis of the test and its findings follows.

While Cool-X LLC and our partners have conducted numerous dyno tests, many are subject to NDAs and confidentiality agreements. Cool-X LLC conducted one test recently, at SuperFlow Technologies, that is both illustrative and representative of our previous results.

SuperFlow connected a GM 4T65E Final Drive Unit to one of their Axiline Transmission Dynos. The gearbox was filled with Dextron III/Merc ATF, in this case from Valvoline. SuperFlow designed a test, whereby the gears would be shifted through a series of shift sequences, from first to fourth gear, and then back, while under a modest load, and then allowed to pause for a minute, and then the cycle would repeat. The entire test was designed to last a little over an hour.

It was agreed that the test would commence when the oil was heated to 200oF. When the oil reached 240o F, considered its maximum safe temperature, the fans would be switched on, which it was expected would cool the transmission. The remainder of the test would be run with the fan turned on.

The first thing we noted was that it took almost 3x longer for the oil in the gearbox with Cool-X to warm up to 200oF. Then the test was begun, and both oils slowly increased in temperature, with only minimal differences, until 232oF was reached. It took one cycle longer, roughly 4 minutes, for Cool-X to heat up. At this point, the fan was turned on in both tests. At this point, the discrepancies showed up. Within 30 minutes, the Cool-X treated oil was 20oF+ degrees cooler. It appeared to reach an equilibrium temperature of 204oF. By contrast, the plain ATF reached an equilibrium temperature of approximately 215oF, maybe higher, and it took 20 minutes longer to reach this temperature. At first, we were a little bit confused by these results, but on further contemplation they made perfect sense and, indeed, explain the effects and limitations of Cool-X on a cooling system.

First, why did it take 3x longer for the Cool-X treated transmission to warm up? We believe that is because the Cool-X heated the metal in the gearbox quicker, and the metal acted like a heat sink, keeping the oil cooler longer.

Second, why did the Cool-X treated oil then heat up almost exactly the same as the standard ATF? This is because the fan wasn’t turned on, and there was no air movement in the enclosed dyno room to dissipate the heat from the gearbox. In designing the test, we had underestimated how important a factor air movement truly was. Air is a 4x better insulator than oil. Basically, all the heat was bottled up in the transmission case, and with no air cooling available, it made no difference how fast the heat passed from the oil to the transmission case, because it had no place to go when it got there.

Finally, once the fan was turned on, and the transmission case cooled by the flow of air, then the effect of the Cool-X became apparent. Heat was transferred more efficiently from the oil to the case, and from there to the atmosphere, and within a short time the gearbox with the Cool-X was substantially cooler (by 20o-25oF) than the one without. That is the essence of how Cool-X works. It improves heat transfer between oil and metal surfaces, and if those metal surfaces are cooled by air or by water (using a transmission cooler), it will make that cooling much more efficient and reduce overall oil temperatures. The amount of the temperature reduction is going to depend on a series of factors, including ambient conditions (how hot or cold is the outside air), how much airflow is going by the heat, and what the load (and heat generation) is on the gearbox itself.

Now the next time we repeat this test, which we hope to do shortly, we intend to have SuperFlow leave the fan on the entire time, so we can have exactly comparable ambient conditions for both throughout the test. In this case, the fan was turned on 4 minutes earlier for the plain ATF, which distorts the results for a short period, until the systems reach equilibrium temperature again. The second thing we plan to do is to operate the test at much higher loads. The GM Final Drive Unit we tested here was a mule used by SuperFlow, and they (understandably) did not want us to test the limits of its performance.

We have seen similar results in testing in engine oil, and in testing on an Indy Car gearbox using a full synthetic oil and CVD coated parts. Many engines ran 10o-15oF cooler with Cool-X in their motor oil than without. While reduced friction may play a role, again we believe the primary reason for the lower temperatures observed is the increased heat transfer between the engine oil and the engine block, which results in lower oil temperatures.

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