Starting a BB Duster project

5.7 hemi said

The dyno doesn’t lie. It’s a tool for measurement, the fans tested were done after a baseline was had without any fan. The 30 hp loss was from the addition of that particular fan. Is there a loss, certainly, and that engine on that dyno showed it took, at peak, 30 hp loss.

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People make errors all the time when running tests, especially if they think they know what the answer should be. It is called confirmation bias and it happens a lot. Even highly experienced engineers fall victim to confirmation bias. My guess is that the engine master guys wanted to see a big drop in power since that would give them something exciting for their video. They found a big number and were happy. They didn't bother to think that it might not be correct.

The best way to test fans would be to use an electric motor to spin the fan and measure the current required. That will tell you the power consumed without having to use a dyno. An engine dyno isn't a very good tool for measuring small power differences, it is more of a gross measurement tool. Kind of like a yardstick. There are lots and lots of things that can change from pull to pull which is why an engine dyno can have problems measuring this kind of stuff.