page_title: Diffuser (automotive)
section_title: Splitters
hierarchical_section_title: Diffuser (automotive) / Splitters
caption_attribution_description: English: Porsche RS Spyder front splitter, headlamp, nose and flaps.
context_page_description: A diffuser, in an automotive context, is a shaped section of the car underbody which improves the car's aerodynamic properties by enhancing the transition between the high-velocity airflow underneath the car and the much slower freestream airflow of the ambient atmosphere. It works by providing a space for the underbody airflow to decelerate and expand so that it does not cause excessive flow separation and drag, by providing a degree of "wake infill" or more accurately, pressure recovery. The diffuser itself accelerates the flow in front of it, which helps generate downforce. This is achieved by creating a change in velocity of the air flowing under the diffuser by giving it a rake angle which in turn generates a change in pressure and hence increases downforce.
context_section_description: As the front of the car slows down the air without a diffuser, this is the ideal place for an inlet. A splitter is commonly used here, serving to increase the amount of downforce at the front of the car. The airstream is brought to stagnation above the splitter by an air dam, causing an area of high pressure. Below the splitter, the air is redirected away from the stagnation zone and is accelerated, causing the pressure to drop. This, combined with the high pressure over the splitter, creates downforce. The larger the area of the splitter, the more downforce is generated. In most closed-wheel race cars, the underside of the splitter smoothly integrates with the undertray, creating one large flat plane that is driven by the rear diffuser. Some race cars, such as the Toyota GT-One, actually use an additional diffuser immediately behind the splitter to help create more downforce. The air extracted by this diffuser is exhausted through vents in the sidepods or above the car around the cockpit.
caption: The Porsche RS Spyder Evo uses a front splitter combined with dive planes
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