Making the Ioniq slippier

[Vekke]

Originally Posted by Phase

Can anyone explain why the new Mercedes EV that gets 1000km of range is 2 points lower in drag than the xl1? Heck the xl1 has a longer boat tail, is narrower, rear wheel spats, and deleted the side mirrors

The Mercedes keeps the side mirrors and doesn’t use rear wheel spats!!

EQXX has air curtains in front wheels, I think XL1 has none
its fully electric so less cooling flow needed through the engine bay area

Those are the biggest differences

[Vman455]

Originally Posted by Phase

Can anyone explain why the new Mercedes EV that gets 1000km of range is 2 points lower in drag than the xl1? Heck the xl1 has a longer boat tail, is narrower, rear wheel spats, and deleted the side mirrors

The Mercedes keeps the side mirrors and doesn’t use rear wheel spats!!

It could be any number of reasons. Even small changes in body shape can have significant effects on airflow, as I've constantly found in testing (and you--and everyone else here--could too). A good example of this is the last section in this article:

To answer that, let’s compare my truck to a friend’s 2011 Toyota Tacoma. Not only is this a truck of similar shape and size, it’s built by the same company, is the successor to my older truck (one generation removed and fattened up for the US market), and may have even been tested in the same wind tunnel when it was designed. How similar are the flows over the side windows of each truck?



Answer: not very. Less disruption from the mirror, less separation at the A-pillar, and less turbulence in general can be seen on the newer truck, tested at the same speed, on the same road, and in similar conditions.

Seemingly inconsequential differences in the shape of each truck’s hood, wheel arches, windshield, A-pillar, roof, door, mirror, and window add up to a substantial difference in the character of the airflow over them. The flow over the side window of the 2011 Tacoma is cleaner with a mirror than the 1991 Hilux without one. Only twenty years separate these two trucks, and to many people they look pretty much the same!

You're welcome to believe the people who will post definitive answers to your question here (as above), but the reality is none of us can say.

[Phase]

Originally Posted by Vman455

It could be any number of reasons. Even small changes in body shape can have significant effects on airflow, as I've constantly found in testing (and you--and everyone else here--could too). A good example of this is the last section in this article:



You're welcome to believe the people who will post definitive answers to your question here (as above), but the reality is none of us can say.

There’s no flow separation with my Ioniq side mirrors. Only reason I’m taking them off is because of the frontal area drag and wake behind them. Tuft testing and Rainx with rain show attached air flow in my 2020 Ioniq.

[Phase]

Originally Posted by freebeard

Your search term is 'Bonneville spoiler'. Here are some examples:

Starting off with Bombshell Betty


Bonneville has lots of 1953 Starliners



customrodder.forumactif.org/t1872-bonneville-co

So long story short, extending the spoiler works?

[freebeard]

....at Bonneville; elsewhere YMMV.

[Phase]

Removed side mirrors and did a b testing last night. 2mpg gain give or take

Will be putting mirrors back on till I can fabricate my little mini side mirrors over the next few weeks. Def seems like some free mpg. That’s about a 24 extra miles of range per tank. Almost a gallon of gas saved every 2 full ups, which is over 5 dollars here in Portland

Now I’m just busy trying to trace out a good rear wheel skirt with cardboard and need to go to a craft store to get some type of bendable support frames to test those!

[aerohead]

Originally Posted by Piotrsko

Irv Culver was a disciple of 1.5 times the height equals the horizontal spacing distance for maximum drag reduction. I couldn't argue with him, gave me headaches keeping up with his grasp of the math involved

Could you please expand on Culver's ratio for drag minimum?
'The horizontal spacing distance' has me scratching my head.
Are we discussing topographic structures attached to the same surface, in train with one another, or individual bodies, at least one 'drafting' behind the lead body?
None of my tabulated data for empirical measurements indicate minimums for either 3D, or 2D structures at ratios this 'small.'
Thanks in advance.

[aerohead]

1) The thickness/ chord ratio for a symmetrical section of minimum drag is 3.92:1.
2) The data is from the drag table for the above-named, appearing on page-244, of AERO-HYDRODYNAMICS OF SAILING, by Marchaj.
3) I published a dedicated graphic for this table in 2012 here at the Forum.
4) Just as with streamline bodies of revolution, there is one ratio at which both surface friction drag and pressure drag are at minimums, at the 'bottom of the drag bucket.'
5) Extending the length increases overall drag due to increased friction drag.
6) Reducing length increases overall drag due to increased pressure drag.
7) Peering upwards, through a 'transparent' road, a wheel fairing package for either front, or rear wheels, one might expect a minimum drag, as a first principle, when the fairing constituted the 3.92:1 ratio.
8) The 'aft-body' portion behind the axle centerline would be 2.378 X the fairings width.

[aerohead]

Originally Posted by Phase

Can anyone explain why the new Mercedes EV that gets 1000km of range is 2 points lower in drag than the xl1? Heck the xl1 has a longer boat tail, is narrower, rear wheel spats, and deleted the side mirrors

The Mercedes keeps the side mirrors and doesn’t use rear wheel spats!!

1) There were dozens of subtle aero optimizations performed on the M-B EQXX.
2) And the EQXX is actually 12% 'longer' than the XL1, where it counts.
3) At a difference of 14.4-counts, each little 'cut' for the Mercedes made up the difference.
4) And as others have already mentioned, the EV's 'engine' is up to 350% more efficient than the VW's Diesel. That makes for less heat flux, less cooling load, more time the active radiator shutters are 100% closed.
5) For it's drag coefficient, the XL1 has the worst shape compared to 1937 Schl'o'rwagen, 1987 GM Impact, or 1987 Renault VESTA-2.
6) Too much 'nose', not enough 'tail'.

[aerohead]

Originally Posted by freebeard

Agreed. You left out pantaloons, or pants.

What you're calling spats, I'd call a cycle fender. And some of those new OEM deflectors are nothing more than strakes, or wickerbills.

No idea on the Mercedes EV. Generative AI?

1) 'pants' works! The literature is littered with this term, in lieu of 'skirts.'
2) Dr. Wolf H. Hucho's use of 'spat' described a fully-encapsulating inner fender, as FoMoCo used on their Probe-IV and V concepts. Perhaps GM's Aero 2002A follow-on to the Aero 2002 ) The car is never shown with the wheels off center ).
3) 'Strakes' were used by AeroVironment/General Motors, to describe the yaw-control devices attached to the underside trailing edge of the 1987 GM Sunraycer, World Solar Challenge winner solar racer. It's the first time this adjective appeared in print, to my knowledge.
3) In 'spirit', I can see your reasoning for 'wickerbill', as associated with wheel deflectors. The 2012 SolarWorld GT I saw had nothing more than aluminum angle extrusion attached ahead of the front wheels to 'jump' the flow 'over' the sand-dial/ hour-glass wheel-house, wheel-flop openings.
4) I do believe that 'deflector' is the proper term.
5) 'Wickerbill' is associated with the Dan Gurney, 'Gurney flap', as could be ordered on the 2015, Chevy Camaro Z-28 ( $395, plus $ 117 installation ). It provided 150-lbs downforce @ 150-mph, generating downforce all the way down to 40-mph.