View Full Version : Spoiler vs Splitter, what's the difference ??

10-07-2010, 12:28 PM
Until about 5 years ago , I had never heard the term " splitter" used to describe the aerodynamic device at the front of a car .
( don't laugh ) . Or the term "diffuser" at the rear of the car .
We had always called them "spoilers" or "airdams".
Either a front spoiler , rear spoiler , front air dam or a rear wing was the common term used in the 80's.
So what is the big difference between a spoiler and a splitter ??

10-07-2010, 12:36 PM
Don't quote me, but I beleive a chin spoiler is an air-dam that does not extend past the front of the bumper; and a splitter is an air-dam that extends past the front of the bumper (thus being the item that "splits the over/under air apart).

The big advantage to the "splitter" is you control where the air is split to go over and under the car, with the split being so close to the ground, the amount of air introduced under the car is reduced.

John Wright
10-07-2010, 12:41 PM
A Front Wind Splitter is a protruding flat surface in the front of a car that is designed to decrease front end lift and exert downforce. By creating a high pressure area on top of the wind splitter, high pressure air flow is restricted to flow underneath a car. With low pressure below the car, the effect of lift is reduced and a driver can gain from the extra traction and control.

The APR Performance Front Wind Splitter (hereinafter referred to as "Splitter") is an aerodynamic tuning component that plays an important role in helping a vehicle achieve aerodynamic balance. Just as there are significant forces acting upon the rear-end of a rear wing-equipped vehicle, there are also significant forces acting upon the front-end of a Splitter-equipped vehicle.

It is common to see new sports cars designed with items such as factory undertrays and other advanced aerodynamic components to produce "zero-lift". Although these components are great at reducing lift, they may not bring the added stability and traction road racers are looking for when taking fast turns. APR Performance utilizes these components and integrates them with a Front Air Dam.

The APR Front Air Dam goes beyond reducing lift and increases stability & downforce at high speeds. Aside from the performance benefits, the Front Air Dam also adds an aggressive yet functional appearance to a sports car.


APR Front Bumper Canards are the perfect answer to aerodynamically tune the handling for the front of a car. Made of lightweight and durable carbon graphite composites, APR Front Bumper Canards help increase front downforce at high speeds. The added downforce stabilizes the cars chassis during hard cornering and increases traction for faster lap times.

APR Vortex Generators help to guide the air flow on cars with very steep drop-off angles between the roof and the rear window. Air flow has a tendency to become turbulent as it separates from the surface of the car in this region. This turbulent air causes drag and reduces the effectiveness of a rear wing. The APR Vortex Generator helps to reduce drag and improve the effectiveness of the rear wing by delaying the air flow separation and reducing turbulence.


10-07-2010, 12:48 PM
Air Dams and Front spoilers are the same as they have always been, They are relatively vertical to push the air around the car or at a 45 degree (or so) angle to try and create down force. Splitters on the other hand are essentially horizontal. The air flow is brought to a standstill above the splitter by the air dam or spoiler, creating high pressure. Under the splitter, the air is redirected away from the standstill and is accelerated, causing the pressure to drop. So the combination of high pressure above and the accelerated low pressure below creates the down force.

Diffusers on the other hand are at the rear under body of the car and aren't really related to the rear wings or spoilers at all, although they do work in conjunction to create rear down force.

10-07-2010, 12:59 PM
A high presure area develops on the front end of the moving car. Some of the pressure bleeds under the car and some over. A splitter will allow the high pressure to be concentrated to act downwards on the splitters upward facing surface and create a downforce, F=PressurexArea. There will generally be a drop in aerodynamic efficiency(i.e. reduced acceleration and top speed) in return for added traction in corners.

A "spoiler" does just that. It disrupts air flow that would normally cause lift. A spoiler is like that used in the older Nascar cars. It also causes excess drag.

A wing has air flowing over the top and bottom to create the pressure differential that causes lift/downforce. A wing also adds drag.
You are converting forward energy into downward force.

Regardless, you will hear the terms "spoiler", "wing", etc used interchangably even though they are different animals.

10-07-2010, 01:04 PM
A real diffuser is most useful when the car has a smooth flat bottom. The smooth bottom maintains undercar air speed relative to over-car air speed thus reducing the air speed differential. Lift is created by the air speed differential over the car(which acts like a wing). Keeping the undercar airflow high will affectively add downforce(by reducing natural lift). The advantage of the smooth belly pan is it makes the car more aerodynamic(i.e. higher topspeed, acceleration, gas mileage) AND creates effective downforce(higher cornering speeds) at the same time.

10-07-2010, 01:13 PM
This is good , keep 'em coming ..

I got this off of wikipedia:

Splitter -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.
Spoiler-A spoiler is an automotive aerodynamic device whose intended design function is to 'spoil' unfavorable air movement across a body of a vehicle in motion. Spoilers on the front of a vehicle are often called air dams, because in addition to directing air flow they also reduce the amount of air flowing underneath the vehicle which reduces aerodynamic lift.
Wings- Automotive wings are devices whose intended design is to generate downforce as air passes around them, not simply disrupt existing airflow patterns.

10-07-2010, 03:13 PM
I almost feel as though I need a masters to read this info. Great stuff. I might make sense of all this someday. Thanks for starting this Jeff.

10-27-2010, 05:31 PM
I'm thinking of doing a splitter against the bottom of the front bumper on my '57 Chevy. It isn't going to be a track car, so I won't make an effort to get it down against the ground or anything that radical. With those big, cow-catcher front bumpers that curve under, what are the odds that such a splitter would keep enough air from flowing under the car to reduce lift at speed?

10-31-2010, 04:50 PM
I'm thinking of doing a splitter against the bottom of the front bumper on my '57 Chevy. It isn't going to be a track car, so I won't make an effort to get it down against the ground or anything that radical. With those big, cow-catcher front bumpers that curve under, what are the odds that such a splitter would keep enough air from flowing under the car to reduce lift at speed?

Splitters loose effectiveness the furhter from the ground they get. So if your 57 is low enough, and the splitter tray is long (forward) enough, it should work.