“Check out this fancar that set a new course record at Goodwood this year”
Fan car sets Goodwood hillclimb record with huge downforce.
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So, not exactly the ideas you're talking about, but the racing world is increasingly exploring outside of the aero that FIA/F1 et all have allowed. Check out this fancar that set a new course record at Goodwood this year: this video For anyone unfamiliar, a fan car uses motor driven fans to actively create a low pressure zone under the car, while also reducing the low pressure drag bubble behind the car. This particular one is all electric and quite compact. It's very fast, and yes footage of it looks weird, almost artificial, because its sustaining grip through corners that rivals F1 cars, with the torque of electric. Running full tilt the fan system creates about 2000 kg of downforce. But the neat thing is you can flip a switch and then the thing just becomes a Nissan Leaf with a really crazy body kit. So some future "track day" car based on this concept would be surprisingly practical. I think the future of auto racing in a pure electric era is going to be surprisingly bright. Anyhow, not really relevant to talking about making big trucks more efficient, but thought you'd find it interesting.