Audi S4 - Rear Diffuser - Aero Tuning
Click here for tips for buying from sellers in the USA
Product Type: Aero
If you are looking for a Audi S4 Rear Diffuser primarily for looks, the main thing is it looks good to you!
For a functional Audi S4 Rear Diffuser look for:
A shallow angle less than 7 degrees
Ideally the profile of the Audi S4 Rear Diffuser will curve upwards, rather than just be flat. A curved profile might also allow more vertical angle
Vertical strakes to keep turbulence from around the wheel away from centre of car
The further the Rear Diffuser goes under the car the better
If the Rear Diffuser covers the exhaust that is a big plus (assuming it can withstand the heat)
If the strakes also curve outwards that will also be better than straight strakes, again, the angle of max 7 degree of deflection could be the sweet spot.
Benefits of a Audi S4 Rear Diffuser
Primarily looks for a road car
Reduced aerodynamic drag giving:
The range of Audi S4 Rear Diffusers on ebay seems to be growing weekly. Most of the parts seem to be made from plastic rather then fibreglass which is a definite plus.
Another trend with Audi S4 Rear Diffusers is that there are more and more direct fit products available, whereas before the majority were universal items
This is not to say that universal Rear Diffusers are bad, its just they should be much easier to install because they use existing mounting points on the Audi S4
Having said that, the bigger Rear Diffusers will probably be of the universal type
About Rear Diffusers
Rear Diffusers are designed to reduce drag and increase downforce at the rear of the Audi S4
A Rear Diffuser achieves this by seperating the turbulent air created by the tyre from the relatively smooth air passing under the car
Keep a smooth flow of air exiting the rear of the car maintains air speed and correctly designed Rear Diffusers open the rear of the car increasing the speed of the air passing under a Audi S4 , this reduces air pressure reducing lift or creating downforce
The most effective Rear Diffusers for the Audi S4 will have vertical strakes seperating the air into channels helping the efficiency of the Rear Diffuser
On a road going Audi S4 the effect of a diffuser will probably be minimal, on a race car Audi S4 , a Rear Diffuser can have a huge effect on lap/stage time
Kyle Engineers - CFD analysis of Rear Diffusers
Kyle Engineers Again - How does cutting the bumper compare?
And on the benefits of a flat floor