BMW G80 M3 & G82/G83 M4 Rear Diffuser with F1 Style Brake Light – Prepreg Dry Carbon Fiber (Unitexclusives)

We designed this rear diffuser to give the BMW G80 M3 and G82/G83 M4 a race-car signature under the bumper: prepreg dry carbon with an F1-style LED brake light at its center, wired to come on with your brake lights.

The look

The light catches the eye first. It sits low in the middle in a square housing, behind a gridded lens that shows as small red dots on the white M3 in our photos. A carbon arch rises over it like a bridge, so it looks built in, not added on.

Two upright fins stand on each side of the arch, with a pair of quad tips between them. At the outer ends the carbon swells into thick shoulders that tuck up under the bumper corners.

Under its gloss finish, the twill weave draws a crisp dark line below the white M3’s paint and catches the daylight on every fin of the blue one.

Made for the M3 and M4

BMW gives every M3 sedan, M4 coupe and M4 convertible of this generation a plain black diffuser around twin pairs of 100 mm tips. Its own carbon diffuser is one part for all three bodies, and so is ours.

All of them run the 3.0-liter S58 twin-turbo six, with 473 hp, or 503 hp as a Competition at launch. The M3 CS and M4 CS get a carbon diffuser from the factory; the M4 CSL’s is built into its rear apron.

Why this one

BMW’s genuine carbon diffuser for the factory exhaust, part 51128075031, is the one sellers list with the M Carbon exterior package, and ours comes in well under its price. BMW’s M Performance part 51195A198B5 is another carbon diffuser, but it is made only for the M Performance exhaust.

Ours adds the F1-style light, in a shape we drew ourselves.

Highlights

• F1-style LED brake light. Built into the center and wired to your brake lights.
• Prepreg dry carbon. Made in prepreg dry carbon fiber, finished in gloss.
• Arch and fins. A carbon arch frames the light; four upright fins frame the quad tips.
• Our own design. Drawn for these cars in-house at UNIT 17 Auto Styling.

Living with it

Each time you brake, the LED adds a light low in the middle for the driver behind. The diffuser hangs at the bottom edge of the bumper, so leave room at tall parking blocks when backing in and take steep driveway exits slowly.

Check before you buy

• The cut-outs suit the factory quad tips, a pair at each side. The M Performance exhaust has center tips and its own diffuser: check with us if your car has it or another aftermarket exhaust.
• Rules on extra rear lights differ from state to state. Check yours before the light is wired in.
• The M3 CS, M4 CS and M4 CSL come with a carbon rear diffuser. Check with us before ordering for one of those.

Installation

• Mounting. In the factory diffuser’s place, with OEM-style fitting
• Bumper. The rear bumper comes off, both to wire the LED to the brake lights and to remove the factory diffuser properly
• Factory clips. Each has a lock that is pressed down from inside the bumper. Don’t pull it off the way F80 M3 owners may be used to; that takes great force.
• In the box. Rear diffuser with F1-style LED brake light (1)
• Difficulty. Straightforward, and the bumper comes off easily (from the listing)

Good to know

• Both M3s in our photos also wear a carbon trunk spoiler and carbon corner trim on the bumper; those are separate parts.