Protruding A-pillar for better aero

[RedDevil]

When I saw an article about the 2015 Honda Fit I couldn't help but notice how far the A-pillars protrude forward compared to the glass. As if the front windshield is lowered, so the edges stick out forward.

At first I thought it to be strange. It could not be very aerodynamic?
But it claims stunning FE in hybrid form.
No doubt they put it in a windtunnel and deliberately designed it this way.

Then I saw other cars with the exact same feature, the Mercedes-Benz CLA sedan and their A- and B class, and in fact many other.
The Seat Leon even hides the windshield wipers in the A pillar!
Even my own Insight has this feature, though very shallow except on the base of the pillar.

So why does this work?
I think it does 2 things: it helps push the air over the car rather than curl sharply over the A-pillar, and when it does the latter it will not begin as laminar flow, so it should go smoother.
People have experimented with vortex generators over the A-pillar; I believe protruding the edge has the exact same effect.

I would be interested in retrofitting/augmenting this feature.
I'm not the first though; at least
Aeromodder has mentioned a plan to add rails.

Any thoughts?

[Frank Lee]

Aerohead has mentioned in the distant past about a device to aid boxy things- like semi-trailers- that consists of a quarter round length mounted such that it stands proud of the front surface and flush with the sides/top. It traps a "stagnant" bubble in front while promoting ordered flow past it to the sides/top.

All indications are that these types of "A" pillars are basically doing the same. Of course since they are angled back on the cars it's not so much a stagnant bubble as the bulk of the air mass is going up and over, but I suspect there are "stagnant" or probably more like sliding zones along the fronts inner to the pillars and the flow to the sides is orderly.

That posit makes sense to me as evidenced by the A-pillar wiper parking, which would be aero disaster with A-pillars that are flush to the windshield.

[JasonG]

While for slightly current reasons, this reminds me of the roof rails that Nascar uses.
Wonder it I could use some landscape edging.......

[RedDevil]

Originally Posted by Frank Lee

Aerohead has mentioned in the distant past about a device to aid boxy things- like semi-trailers- that consists of a quarter round length mounted such that it stands proud of the front surface and flush with the sides/top. It traps a "stagnant" bubble in front while promoting ordered flow past it to the sides/top.

All indications are that these types of "A" pillars are basically doing the same. Of course since they are angled back on the cars it's not so much a stagnant bubble as the bulk of the air mass is going up and over, but I suspect there are "stagnant" or probably more like sliding zones along the fronts inner to the pillars and the flow to the sides is orderly.

Exactly. The trapped, or slightly thicker than usual layer of 'slow' air if you will, also makes the hood to windshield transition more smooth, and maybe that's why you see this feature more and more pronounced with the boxier new cars, as their windshield is steeper.
When the edges are wider at the bottom that would have the same effect as if the windshield were tilted slightly more horizontally.

Another plus is that the A pillar can be thicker and stronger this way without impairing vision.

[freebeard]

My 1958 VW convertible was like that. The main thing I noticed is snow couldn't slide off, so it built up and tried to strangle the windshield wiper.

[Frank Lee]

That's because the windshield was so cold due to the famous VW defrosters.