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Car Aerodynamics Questions

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  Car Aerodynamics Questions Christopher Howard <christopher@librehacker.com> - 2026-06-17 08:49 -0800
    Re: Car Aerodynamics Questions ram@zedat.fu-berlin.de (Stefan Ram) - 2026-06-17 18:23 +0000
      Re: Car Aerodynamics Questions Jeremiah Jones <jj@j.j> - 2026-06-19 22:39 -0700

#896117 — Car Aerodynamics Questions

Hi, I am wondering about two things in regards to car aerodynamics:

(1) In pictures of sportcars (I can't afford one) the wheels are thin
and the body is very low to the ground. What is the reason for this? Is
there some inherent aerodynamic advantage to having the body of the
vehicle very low to the ground? Or are we just trying to keep the wheels
inside the body, so that we don't get additional air drag on the wheels?

(2) Why is it that, in all the vehicles I've seen, there is an intake
for cooling air — pulled or pushed through by the radiator — but not
really an exhaust for it? I assume most of the incoming cooling air goes
through the radiator and then is bludgeoned down underneath the car. I've
read articles on careful management of cooling airflow in aircraft, but
this doesn't seem to be a concern for cars...?

-- 
Christopher Howard

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#896118

Christopher Howard <christopher@librehacker.com> wrote or quoted:
>(1) In pictures of sportcars (I can't afford one) the wheels are thin
>and the body is very low to the ground. What is the reason for this? Is
>there some inherent aerodynamic advantage to having the body of the
>vehicle very low to the ground? Or are we just trying to keep the wheels
>inside the body, so that we don't get additional air drag on the wheels?

  A low-slung chassis chokes off the air flowing underneath.
  Forcing that air through such a tight squeeze makes it speed up
  and drop in pressure as it dumps out the back. That generates a
  vacuum via the Bernoulli principle that literally glues the car
  to the tarmac, giving you insane grip without adding dead weight.

  Regular cars sit high, letting a ton of air underneath. At speed,
  that air acts like a wing, lifting the chassis and making the
  steering feel sketchy and washed out.

  Slamming the car shrinks the frontal area, which is the total surface
  cutting through the wind. Less frontal area directly cuts aerodynamic
  drag, letting you hit higher speeds with less effort from the motor.

  Keeping the heavy bits like the engine, transmission, and chassis
  right on the deck keeps body roll to a minimum.

  When a high-riding SUV takes a hard turn, weight transfers
  violently to the outside tires, making the truck lean and
  lose its bite. A low-profile sports car spreads those cornering
  loads evenly across all four patches of rubber.

  Those thin low-profile tires have stiff sidewalls. When you
  turn the wheel, the rubber does not deflect or roll over,
  giving you instant turn-in.

  Mind you,

  Speed bumps, steep driveways, and potholes will easily tear off
  pricy front splitters and carbon underbody trays.

  Since the sidewalls have no meat on them, they cannot soak up bumps.

  Low-profile tires give zero cushion to the alloy wheels, leaving
  them wide open to bending or cracking if you nail a pothole.

>(2) Why is it that, in all the vehicles I've seen, there is an intake
>for cooling air — pulled or pushed through by the radiator — but not
>really an exhaust for it? I assume most of the incoming cooling air goes
>through the radiator and then is bludgeoned down underneath the car. I've
>read articles on careful management of cooling airflow in aircraft, but
>this doesn't seem to be a concern for cars...?

  Managing cooling airflow actually tops the agenda for automotive
  engineers, though the hardware stays out of sight. You rarely spot
  dedicated exit vents on daily drivers due to a blend of packaging
  bottlenecks, design cues, and budget limits. 

  Hood vents or fender louvers let moisture, road grime,
  and engine noise migrate to where passengers catch wind of
  them. Plus, routing clean, ducted exhaust pathways eats up
  prime real estate inside a packed engine bay.

  To handle this air without glaring vents, modern rides count
  on undertrays and active grille shutters. Active shutters seal
  off the front inlets when the engine runs cool, forcing air to
  sweep over the hood rather than crowd the high-drag engine bay.

  When they snap open, the oncoming air hits the radiator and gets
  channeled along the underbody by contoured panels. These trays
  keep the air from pooling and generating lift, turning the
  underside into a low-pressure zone that sucks the hot air out.

  On high-performance builds and track cars, this aerospace-grade
  thermal management breaks the surface. Race cars and track-focused
  supercars regularly sport deep hood vents right behind the radiator.

  This setup lets air pass through the front grille, exit straight
  through the top of the hood, and wash cleanly over the roof. 
  By ducting the air upward, engineers wipe out front-end lift
  and drop the drag coefficient, hitting the exact sort of
  fluid dynamics you see in aviation.

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#896132

ram@zedat.fu-berlin.de (Stefan Ram) wrote:
> Christopher Howard <christopher@librehacker.com> wrote or quoted:
>
> >(2) Why is it that, in all the vehicles I've seen, there is an intake
> >for cooling air — pulled or pushed through by the radiator — but not
> >really an exhaust for it? I assume most of the incoming cooling air goes
> >through the radiator and then is bludgeoned down underneath the car. I've
> >read articles on careful management of cooling airflow in aircraft, but
> >this doesn't seem to be a concern for cars...?
> 
>   Managing cooling airflow actually tops the agenda for automotive
>   engineers, though the hardware stays out of sight. You rarely spot
>   dedicated exit vents on daily drivers due to a blend of packaging
>   bottlenecks, design cues, and budget limits. 
> 
>   Hood vents or fender louvers let moisture, road grime,
>   and engine noise migrate to where passengers catch wind of
>   them. Plus, routing clean, ducted exhaust pathways eats up
>   prime real estate inside a packed engine bay.
> 
>   To handle this air without glaring vents, modern rides count
>   on undertrays and active grille shutters. Active shutters seal
>   off the front inlets when the engine runs cool, forcing air to
>   sweep over the hood rather than crowd the high-drag engine bay.
> 
>   When they snap open, the oncoming air hits the radiator and gets
>   channeled along the underbody by contoured panels. These trays
>   keep the air from pooling and generating lift, turning the
>   underside into a low-pressure zone that sucks the hot air out.
> 
>   On high-performance builds and track cars, this aerospace-grade
>   thermal management breaks the surface. Race cars and track-focused
>   supercars regularly sport deep hood vents right behind the radiator.
> 
>   This setup lets air pass through the front grille, exit straight
>   through the top of the hood, and wash cleanly over the roof. 
>   By ducting the air upward, engineers wipe out front-end lift
>   and drop the drag coefficient, hitting the exact sort of
>   fluid dynamics you see in aviation.

Come on... the scoops and vents are really all about
appearance, aren't they?  Like the flashy airplane fins that
cars had in the early 60s.

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