Explain rear diffuser function

[blown motor]

Can someone explain the science of the rear diffuser? How does it effect performance?

[Mr Cuda]

Just checked google.
 Lots of well written engineering articles about function.
 However,  an E body (108w.b.)  seldom will get driven at speeds to feel the effects,  as it will swap ends before that. Maybe challenger is more stable.

 A chin spoiler will increase the vacuum under the car to keep the front down, and prevent e body liftoff, at 100-120.
 That's why god made 71 b bodies.

[dodj]

Air dam, front spoiler etc to prevent air going under the car. The rear diffuser is get the air under the car...out from under it as fast as possible. Both help keep the car from being 'lifted' by air and help keep the car planted to the pavement.

e-bodies do not have a diffuser..they have a rear scoop under the bumper to make air flow worse....

[blown motor]

I don't understand how the diffuser gets the air out from under the car unless there's more to it than what I'm seeing. In my small mind I think that the diffuser is putting slender objects, the fins, into the path of the airflow and each fin will create drag on the airflow as the air brushes along the each side of each fin.

[Brads70]

I don't understand how the diffuser gets the air out from under the car unless there's more to it than what I'm seeing. In my small mind I think that the diffuser is putting slender objects, the fins, into the path of the airflow and each fin will create drag on the airflow as the air brushes along the each side of each fin.

I think its best effective then the entire bottom of the car is flat and straight. If there was no diffuser the air under the car would have no direction and would exit from under the car at various areas. Adding the diffuser directs the air out the back taking best advantage of aerodynamics allowing better speed, stability, and fuel economy. Think of it this way, stick your cupped hand out the window going 60 MPH , now imagine air under your car hitting various panels, suspension, exhaust etc... acts like a big parachute forcing the air to even exit out the side of the car in theory making the car unstable at high speeds. Don't worry about our old Mopars as they were not stable above 100 MPH  unless you start adding spoilers etc... ( wing cars would be the exemption) I had my first Challenger ( a 73 Challenger in about 1987) up to about 125 on the Don Valley and took all 3 lanes to make the turn as the car would not steer very well as the front of these cars lift at high speeds.
I never did that again !  I have had my current Challenger up to about 120 and it was much better than my old 1973, but it sits lower, better tires and has that big old snow plow up front to direct some of the air. 

[Racer57]

Buddy Baker said that while testing a Plymouth Superbird or Daytona Charger(don't remember which) at Talladega the spotters told him the front tires were lifting at the end of the straight. They added a front air dam and it kept the tires on the ground.

[dodj]

Venturies speed up the air to evacuate it faster

[jimynick]

Venturies speed up the air to evacuate it faster

Yep, Mr. Bernouli   at work. Think of the air as you would a regular fluid.

[mopar jack]

I'm sure we have seen this when a rice rocket passes by.