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Old 06-21-2021, 04:12 AM   #1 (permalink)
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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.



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.


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Old 06-21-2021, 07:04 AM   #2 (permalink)
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Originally Posted by JulianEdgar View Post
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) = CdA - this is what really interesting (IMHO ).
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Old 06-21-2021, 07:23 AM   #3 (permalink)
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Quote:
Originally Posted by alexshock View Post
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) = CdA - this is what really interesting (IMHO ).
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.
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Old 06-21-2021, 07:45 AM   #4 (permalink)
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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).
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Old 06-21-2021, 06:56 PM   #5 (permalink)
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Quote:
Originally Posted by alexshock View Post

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.
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Old 06-21-2021, 10:09 PM   #6 (permalink)
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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?
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Old 06-21-2021, 11:09 PM   #7 (permalink)
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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
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Old 06-22-2021, 04:53 AM   #8 (permalink)
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Another one from the Uno - front spoiler depth. (No smooth underfloor in a car of this age.)

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Old 06-22-2021, 01:24 PM   #9 (permalink)
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Quote:
Originally Posted by Gasoline Fumes
Great idea for a thread!
My aerodynamic car for this week.
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Old 06-22-2021, 06:24 PM   #10 (permalink)
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Uno - Cd versus downward slope angle of the roof.


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