Oil cooler operation???


I like all of this. Minus the extra heat pushed onto you. Here in Houston any extra heat on you, and you won't even want to ride.


I went for a ride today of nearly 100 miles. It was a nice day in high 70s. I did the same route as before that included a really good "torture test" of the effectiveness of my latest fan mod. This test was while riding continuously up hill on a mountain road for about 7 miles. On several prior occasions, up this same road, my EOT increased to at least 270F without the benefit of a fan. On one such ride, a few months ago, I saw the oil temp get up to nearly 290F!!!

I was expecting a much lower peak this time with my new fan running to supplement and improve oil cooling of the engine. Amazingly, the EOT only got up to 226F by the end of the up hill ride; a whooping reduction of almost 65F!

My overall ride lasted for about three hours over a variety of roads and at speeds averaging around 40 mph in the Santa Cruz Mountains South of San Francisco. The highest EOT got all day was 230F while heading for home riding on the freeway about 30 minutes straight at an average speed of ~60mph. As soon as I got off the Interstate and resumed a slower rate of speed, the EOT immediately began to drop to a lower level.

This is because the fan is much more effective at slower speeds since as the bike slows down, and engine revs drop, the oil pressure drops and the oil takes longer to flow thru the cooler. This results in a higher delta T across the cooler and thus more heat is transferred to the moving air flow thru the cooler (aided by the fan) and away from inside the engine. The heat load on the cooler is also reduced due to the engine producing less friction at lower speeds, so the oil cooler (heat extractor) becomes more effective as well.

P.S. I did not experience ANY discomfort from heat exposure to my legs as a result of additional moving air thru the cooler while the fan was operating.
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Since my last post, I measured the RPM of all these fans. The highest speed fan is the SPAL 5.2"D at over 5800 RPM. Second best is the other 5.5"D SPAL at just over 5400 RPM. The slowest is the Chinese made, all metal fan which is also 5.2" in diameter. All these fans have the same 5 paddles blade design and it appears both SPALs use the same motor; far more powerful than the slower speed, all metal fan.

To make the speed measurement, I had to remove the 5.5"D fan, so I decided to swap fans. Now, the SPAL 5.2"D fan is installed. This fan allowed me to use all 100% of the circular blade area behind the cooler without any overlap at the bottom. This arrangement means that I will have every last bit of the fan's air flow going through the core of oil cooler for optimum heat transfer from the oil.

The weather here has taken a turn for the worse, so I'll have to wait a few days to road test any improvement in EOT. My expectation, however, is that should be as good as gets and well worth the cost to do this relatively simple mod.