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JulianEdgar 06-21-2021 03:12 AM

My aerodynamic car for today
 
I am going to post some aero cars - not every day, as the thread name implies, but whenever I feel like it. (Unlike the Random Aero Cars thread, I will always try to provide some measured data.)

All the cars are covered in my book - A Century Of Car Aerodynamics (link below).

Today's car - the 1983 Fiat Uno.

https://i.postimg.cc/5tGxtB1J/1-3-941.jpg

The Uno was a low-cost car made in huge numbers over 8 million were built. Most interesting from an aerodynamics perspective, it was a small hatch. The smaller the car, the harder it is to achieve a low Cd. And since a hatch will always have a large wake, with that shape we have another aerodynamic negative. But Fiat took great care to optimise the aerodynamics especially drag at a time when few manufacturers were bothering much about the aerodynamics of their cheapest cars.

Cd was 0.34 (standard car), 0.33 (economy special) and 0.30 (Turbo). Lift figures were also good - and across the whole range of yaw angles.

https://i.postimg.cc/wMjFbmyt/Uno-graph.png

alexshock 06-21-2021 06:04 AM

Quote:

Originally Posted by JulianEdgar (Post 650844)
Cd was 0.34 (standard car), 0.33 (economy special) and 0.30 (Turbo). Lift figures were also good - and across the whole range of yaw angles.

May be it is more useful to post CdA instead of Cd?
The real fuel efficiency comes from the product of the drag coefficient (Cd) to the frontal area (S or A:confused:) = CdA - this is what really interesting (IMHO :rolleyes:).

JulianEdgar 06-21-2021 06:23 AM

Quote:

Originally Posted by alexshock (Post 650847)
May be it is more useful to post CdA instead of Cd?
The real fuel efficiency comes from the product of the drag coefficient (Cd) to the frontal area (S or A:confused:) = CdA - this is what really interesting (IMHO :rolleyes:).

Sure. It's a pretty small car, so you can do that research and post the figure. It's certain to be very good for the era.

alexshock 06-21-2021 06:45 AM

Quote:

Originally Posted by JulianEdgar (Post 650848)
Sure. It's a pretty small car, so you can do that research and post the figure. It's certain to be very good for the era.

I have found 2 good sources:
1. https://books.google.com.ua/books?id...20drag&f=false

2. Aerodynamics - Racing Cars

Both mention real area equal S=1.83 sq.m. and max drag area CdA=0.62 sq.m. (standard trim).

JulianEdgar 06-21-2021 05:56 PM

Quote:

Originally Posted by alexshock (Post 650849)

Both mention real area equal S=1.83 sq.m. and max drag area CdA=0.62 sq.m. (standard trim).

Close enough - the tech paper (and so my book) states 1.81m2 for the std car.

Gasoline Fumes 06-21-2021 09:09 PM

Quote:

Originally Posted by JulianEdgar (Post 650844)
Cd was 0.34 (standard car), 0.33 (economy special) and 0.30 (Turbo).

Great idea for a thread! What were the differences that reduced the drag? Not much jumps out at me when I look at photos of the Turbo Uno. Is all of the improvement from the air dam?

JulianEdgar 06-21-2021 10:09 PM

Quote:

Originally Posted by Gasoline Fumes (Post 650912)
Great idea for a thread! What were the differences that reduced the drag? Not much jumps out at me when I look at photos of the Turbo Uno. Is all of the improvement from the air dam?

Compared to the standard car, the Turbo had the following changes:

- Rear spoiler
- Different front bumper
- Flush glass on front doors
- Improved under-hood airflow
- Modified rocker panels

JulianEdgar 06-22-2021 03:53 AM

Another one from the Uno - front spoiler depth. (No smooth underfloor in a car of this age.)

https://i.postimg.cc/2ygXzTMZ/Uno-front-spoiler.png

freebeard 06-22-2021 12:24 PM

Quote:

Originally Posted by Gasoline Fumes
Great idea for a thread!

My aerodynamic car for this week.

JulianEdgar 06-22-2021 05:24 PM

Uno - Cd versus downward slope angle of the roof.

https://i.postimg.cc/cHYyM1C8/Uno-roof-angle.png


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