Coefficient of Drag for Touring & Pure..... What does this mean?

[Babyrocko1908]

Fellas, I'm a newbie here and some of the terminology used yesterday doesn't make sense so hopefully you car guys can explain this to me. During yesterday's event, Derek talked about the improvement of Air's coefficient of drag to an industry leading 0.197cd around the 9:50 mark of the presentation. I assume this is for the Touring and Pure Models so I have a few questions:

1) What does coefficient of drag mean in layman's terms? Does is mean the car sits a bit lower and is sleeker?
2) How is it applied to Touring & Pure?
3) Does this mean there was a slight body/frame modification for the Touring and Pure as opposed to Grand Touring & Dream?

Thanks in advance!

 

[MHDave]

Fellas, I'm a newbie here and some of the terminology used yesterday doesn't make sense so hopefully you car guys can explain this to me. During yesterday's event, Derek talked about the improvement of Air's coefficient of drag to an industry leading 0.197cd around the 9:50 mark of the presentation. I assume this is for the Touring and Pure Models so I have a few questions:

1) What does coefficient of drag mean in layman's terms? Does is mean the car sits a bit lower and is sleeker?
2) How is it applied to Touring & Pure?
3) Does this mean there was a slight body/frame modification for the Touring and Pure as opposed to Grand Touring & Dream?

Thanks in advance!

"Drag" is how much the thing being measured is slowed down as it moves through air. Put the object in a wind tunnel and measure how much it is pushed back by the wind. If the wind flows smoothly over/under/around the object, it has less drag than if it is rough and catches wind everywhere. "Sleek" as you mention is a good word here.
As to why the differences, could be with slight tweaks to how air moves under the body, or the tightness of fit of trim, smoothness of paint and glass, etc. Probably many factors involved in changes made since the earlier measurements.

 

[larry]

As I understand it... As the drag measures how much the vehicle catches the wind (as MHDave said), the inverse means an implication on how much effort (i.e., power) is required to move the car, especially at higher speeds. If you have two cars of identical weight the one with a lower coefficient of drag uses less energy to go 70MPH. It can also go 0-60 faster.

So it's a bragging point, but also part of Lucid's general approach of "be as efficient as you can".

 

[Shuasha]

3) Does this mean there was a slight body/frame modification for the Touring and Pure as opposed to Grand Touring & Dream?

Very interested in this.

 

[Codyroo]

real world example. In my Acura Integra (1989), if I was coasting down the Sunol Grade (a short, steep hill in the Bay Area), I'd hit a top speed of 75 mph with the headlights down or 70 mph with the pop up headlights up. The pop up headlights were acting like mini parachutes (or in this case, mini bricks) that hindered air movement over the car and reduce the coefficient of drag to the point that i could go 5 mph faster if they were down.

When I drove a Prius down that same grade, I could hit 80 mph + because the shape of the Prius has an even lower coefficient of drag, thus the air movement slowed it down even less than the Integra.

And, likely, you (and we have all) done this. You roll down the window and stick your arm out. You rotate your hand and you can see the impact the wind has on it. Hold it palm facing the wind, the wind pushes your arm back (high drag). You rotate it 90 degrees so it looks like the wing of a plane and you hand now "slices" through the wind (low drag). And for fun, if you rotate it 45 degrees either direction, it goes up or down.....which is how an airplane wing works......

 

[maractwin]

The only exterior difference I'm aware of is the metal roof. Maybe that lowers the coefficent of drag? It's one piece rather than having a glass seam and then a metal bow tie like the glass has.

 

[Babyrocko1908]

real world example. In my Acura Integra (1989), if I was coasting down the Sunol Grade (a short, steep hill in the Bay Area), I'd hit a top speed of 75 mph with the headlights down or 70 mph with the pop up headlights up. The pop up headlights were acting like mini parachutes (or in this case, mini bricks) that hindered air movement over the car and reduce the coefficient of drag to the point that i could go 5 mph faster if they were down.

When I drove a Prius down that same grade, I could hit 80 mph + because the shape of the Prius has an even lower coefficient of drag, thus the air movement slowed it down even less than the Integra.

And, likely, you (and we have all) done this. You roll down the window and stick your arm out. You rotate your hand and you can see the impact the wind has on it. Hold it palm facing the wind, the wind pushes your arm back (high drag). You rotate it 90 degrees so it looks like the wing of a plane and you hand now "slices" through the wind (low drag). And for fun, if you rotate it 45 degrees either direction, it goes up or down.....which is how an airplane wing works......

This is awesome and I'm going to totally do this tonight after work. Freezing temps be damned!

 

[Codyroo]

This is awesome and I'm going to totally do this tonight after work. Freezing temps be damned!

And I also found that my cars lost or gained another 5 mph or more depending if it was winter (cold weather = denser air) or summer (warmer weather = less dense air), with summer coasting being faster than winter coasting. The joys of hypermiling, I tell you.....

 

[borski]

Very interested in this.

It’s the new 20” wheels and aero covers. I confirmed this last night.

 

[Team Geezer]

I'm thinking that we need to dimple the surface of the Lucid like a golf ball.

Not really, but its an interesting phenomena.

 

[Codyroo]

I'm thinking that we need to dimple the surface of the Lucid like a golf ball.

Not really, but its an interesting phenomena.

Leave it parked outside in Texas during a hailstorm......that'll fix that aero issue

 

[Babyrocko1908]

It’s the new 20” wheels and aero covers. I confirmed this last night.

Thanks.

 

[Sid432]

It’s the new 20” wheels and aero covers. I confirmed this last night.

Is it still summer tires ?

 

[Slam08]

I'm thinking that we need to dimple the surface of the Lucid like a golf ball.

Not really, but its an interesting phenomena.

Interesting possibility.

Apparently the dimples create lower drag and more lift. Would this work on EV? Imagine if Tesla came out with a dimpled paint. Immediately it would be the coolest thing ever!

 

[Shuasha]

Interesting possibility.

Apparently the dimples create lower drag and more lift. Would this work on EV? Imagine if Tesla came out with a dimpled paint. Immediately it would be the coolest thing ever!

They tested this on Myrhbusters. IIRC, it worked pretty well.

 

[Slam08]

They tested this on Myrhbusters. IIRC, it worked pretty well.

Thanks for sending me down that internet rabbit hole…

 

[GearHead]

real world example. In my Acura Integra (1989), if I was coasting down the Sunol Grade (a short, steep hill in the Bay Area), I'd hit a top speed of 75 mph with the headlights down or 70 mph with the pop up headlights up. The pop up headlights were acting like mini parachutes (or in this case, mini bricks) that hindered air movement over the car and reduce the coefficient of drag to the point that i could go 5 mph faster if they were down.

When I drove a Prius down that same grade, I could hit 80 mph + because the shape of the Prius has an even lower coefficient of drag, thus the air movement slowed it down even less than the Integra.

And, likely, you (and we have all) done this. You roll down the window and stick your arm out. You rotate your hand and you can see the impact the wind has on it. Hold it palm facing the wind, the wind pushes your arm back (high drag). You rotate it 90 degrees so it looks like the wing of a plane and you hand now "slices" through the wind (low drag). And for fun, if you rotate it 45 degrees either direction, it goes up or down.....which is how an airplane wing works......

Bear in mind that in determining the total drag of an object the coefficient of drag (CD) is only part of the formula. Total drag requires, among other factors, accounting for the frontal area as well. A Formula 1 car has a CD around .7 but will have much less total drag than a Lucid Air! In your example, the Prius's smaller frontal area was probably a bigger factor than its coefficient of drag. Within similar vehicle types of similar sizes (i.e. mid-size sedans, full-size trucks, etc.) comparisons of CD are reasonably valid as they will be rather close in frontal area. Regardless, Lucid's .197 rating is impressive!

Pete

 

[Codyroo]

Please go to the 5:20 minute mark of this video....... (Throttlehouse video on the Lucid) James discusses drag coefficient (and for those not getting the joke, he probably botched this part of the video dozens of times before he got it right).

 

[Slam08]

If it’s total drag that matters in the end. Why does everybody talk about mainly coefficient of drag?

 

[GearHead]

If it’s total drag that matters in the end. Why does everybody talk about mainly coefficient of drag?

It's still an indicator of aerodynamic efficiency and one of the few factors an engineer can control. My only point was to be careful in saying the Lucid has less drag than Brand X. Unless they both have the same frontal area, that may or may not be true.

Pete