Making the Ioniq slippier

[Phase]

Originally Posted by aerohead

When you do the rear skirts, the rear bottoms should be spaced out enough to allow for full-depth clearance to the wheels.
If you add a short tail, it will integrate directly to the trailing edge of the new skirts.
If you do a short box cavity, it's trailing edge will have to address a phantom aerodynamic integration to the back of the skirts.

I’m aiming for about an inch clearance around the wheels. Bottoms will have to curve and flare out a bit. Is an inch enough or should I add even more space?

[WD40]

Originally Posted by Phase

I’m aiming for about an inch clearance around the wheels. Bottoms will have to curve and flare out a bit. Is an inch enough or should I add even more space?

From my own experiences with the law, the lowest point of the car can be no lower than the bottom of the wheel (rim)

[aerohead]

Originally Posted by Phase

I’m aiming for about an inch clearance around the wheels. Bottoms will have to curve and flare out a bit. Is an inch enough or should I add even more space?

Unless you do snow chains, one inch should be ample.

[Phase]

Originally Posted by aerohead

Unless you do snow chains, one inch should be ample.

My car is front wheel drive so chains go on the front anyways so I should be fine

[Phase]

In case anyone wants to know what the Ioniq looks like without the spoiler…

[Phase]

Okay so I finally found a farm road during my Idaho road trip to do coast down testing

There was one stretch of flat road that was perfect but not very long

Found 2 marker signs and did a base line test with windows up

Test started around 73 mph and when I reached the second marker, the speed was 68 mph

Did the windows down test, and it was 66 mph at the second marker

So 2 mph drop thanks to drag

Did my cardboard wheel skirts, speed dropped from 73 down to 69 mph

Only a 1 mph change. But it clearly worked. The results show that all 4 windows rolled down causes more drag than the gain you get from wheel skirts ( obviously!) also- with the wheel skirts, acceleration out of the parking lot felt more stable and actually faster. Hard to explain.


So what I’m asking is- how many cd points does the windows down add to your average vehicle, or how much drag percent is added based on the 2 mph slower test I just mentioned. Once we find that out, we could half that and say that’s how many cd points I’d be lowering with rear fender spats?

Math anyone?

[freebeard]

Did my cardboard wheel skirts, speed dropped from 73 down to 69 mph

Only a 1 mph change.

I'm squinting at that and scratching my head.

Math? You've got 2 data points. Get a number with skirts and windows down and you have a third data point.

[Phase]

Originally Posted by freebeard

I'm squinting at that and scratching my head.

Math? You've got 2 data points. Get a number with skirts and windows down and you have a third data point.

Didn’t have enough time. Still lots of tourists driving the roads since it’s summer travel season, and girlfriend was in the car getting annoyed on our vacation road trip with me circling around doing the same route several times lol.

[Joggernot]

Originally Posted by freebeard

I'm squinting at that and scratching my head.

Math? You've got 2 data points. Get a number with skirts and windows down and you have a third data point.

From 68 mph to 69 mph...I think.

[aerohead]

Originally Posted by Phase

Okay so I finally found a farm road during my Idaho road trip to do coast down testing

There was one stretch of flat road that was perfect but not very long

Found 2 marker signs and did a base line test with windows up

Test started around 73 mph and when I reached the second marker, the speed was 68 mph

Did the windows down test, and it was 66 mph at the second marker

So 2 mph drop thanks to drag

Did my cardboard wheel skirts, speed dropped from 73 down to 69 mph

Only a 1 mph change. But it clearly worked. The results show that all 4 windows rolled down causes more drag than the gain you get from wheel skirts ( obviously!) also- with the wheel skirts, acceleration out of the parking lot felt more stable and actually faster. Hard to explain.


So what I’m asking is- how many cd points does the windows down add to your average vehicle, or how much drag percent is added based on the 2 mph slower test I just mentioned. Once we find that out, we could half that and say that’s how many cd points I’d be lowering with rear fender spats?

Math anyone?

1) While you're experiencing a 'trend' in the data, the test methodology isn't rigorous enough, nor data points of sufficient extent to enable the use of the mathematics.
2) Coastdowns must be conducted just as proscribed in the SAE Handbook.
3) Every rotating component in the car must be quantified for moment of inertia, or estimated according to SAE instructions.
4) You need your own weather station, or, perhaps timely AWOS ( automated weather observation service ) updates from a local airport, adjusted to raw barometer. ( I paid CAR and DRIVER road warriors to test my CRX at the Chrysler Proving grounds for top speed, and coastdowns. They threw in skidpad testing for free ). Chrysler has a sheltered straightaway, designated specifically for coastdown testing. Cost was equivalent to 1-hour in a wind tunnel, in 2014-2017 dollars ( DARKO or A2 ).
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5) We don't know what happens to the IONIQ's engine BSFC when the cars' drag is reduced at a constant test speed.
6) We don't know anything about it's actual rolling resistance.
7) We don't actually know if it's published Cd was @ radiator shutters fully-closed, zero-yaw, crosswind-averaged, etc.. We do know that the wheels were rotating in the wind tunnel.
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8) MPG data would only help, fully-warmed, at a constant speed, without any hybrid function, in both directions, just the engine operating at a constant speed, with weather monitoring. And at an accuracy you're comfortable with.