SAE International, 2022-28-0509 ( Aer0 vs Range)

[aerohead]

Delta-10% drag = Delta 5% range on BEVs.
https://www.sae.org/publications/tec.../2022-28-0509/
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If you just do the 'Preview Document', you get the 'meat and potatoes' of the Paper, without spending the $37.00.

[MetroMPG]

Too bad we don't learn what vehicle they optimized.

But based on them playing with rear spoiler addition/angles, I'm guessing it's a sedan.

[ennored]

"The car chosen for this study is an urban electric hatchback car, designed for Indian conditions." "Length(mm) 3280....."

The dimensions given match a Mahindra e2o:

https://autocatalogarchive.com/wp-co...2o-2016-IN.pdf

Their best rear spoiler lowered the drag by 5.6%. They say it extended the range by 3.5km, but don't give a base range. The range in the brochure (above link) is listed as 120km, so a 2.9% improvement. They did not say what drive cycle that would be though, nor does the brochure. Brochure does say it has a top speed of 81 kph though, so not fast.

(Their airdam did nothing at best, and hurt in some configurations.)

[aerohead]

Originally Posted by ennored

"The car chosen for this study is an urban electric hatchback car, designed for Indian conditions." "Length(mm) 3280....."

The dimensions given match a Mahindra e2o:

https://autocatalogarchive.com/wp-co...2o-2016-IN.pdf

Their best rear spoiler lowered the drag by 5.6%. They say it extended the range by 3.5km, but don't give a base range. The range in the brochure (above link) is listed as 120km, so a 2.9% improvement. They did not say what drive cycle that would be though, nor does the brochure. Brochure does say it has a top speed of 81 kph though, so not fast.

(Their airdam did nothing at best, and hurt in some configurations.)

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1) If delta- CdA 10% = delta- range 5%
2) and, if delta CdA 5.6% = delta 3.5 km
3) then delta CdA 10% = delta 6.25 km
4) and if 6.25 km = 5% range
5) then 6.25 / 0.05 = 125 km range ( close to the Mahindra! )
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6) The car is extremely 'bluff'.
7) Dividing it's length by the average of it's height, body height, and width produces only 2.215, compared to 2.619 for my BOLT, of Cd 0.312 ( the Tesla Model 3 is 3.136, @ Cd 0.225 for the outgoing, 2023 year model ).
8) In mirror image ground reflection, it's 'free-air' fineness-ratio would only be 1.051, not any better than a 'sphere', compared to 1.305 for the BOLT, and 1.626 for the Model 3 ).
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9) To experience a 'highway' road load, where aero power is 48% of the total road load with the BOLT requires driving at 38-mph ( 61.15-km/h ).
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10) The 'honeycomb' inlet of the airdam would be saturated in choked, vena-contracta entry losses, perhaps the worst possible choice in design.
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11) Choosing a 6-degree diffuser over all other candidates would beg an explanation.