Ferrari SF90 Stradale Diffuser Rear Diffuser

the Rear Diffuser for the Ferrari SF90 Stradale is one of the car’s most complex aerodynamic components. It isn’t just a styling piece; it’s a massive, multi-part assembly that manages air extraction from the underbody and houses the car’s active aerodynamic elements.

1. Technical Identification & Options

There are two distinct versions of the SF90 diffuser based on the car’s specification:

• Standard Diffuser: Made of a high-strength, heat-resistant thermoplastic composite, usually finished in matte or satin black.

• Carbon Fiber Diffuser (Assetto Fiorano): Included in the Assetto Fiorano package or as a standalone carbon option. This version significantly reduces weight and features a high-gloss visible weave.

• Key Feature (Shut-off Gurney): The diffuser works in tandem with the “Shut-off Gurney” at the rear. While the Gurney is on the upper body, the diffuser’s shape is optimized to create a massive low-pressure zone that complements the active rear wing’s downforce.

2. 2026 Market Pricing (Estimated USD)

Replacing a full diffuser is one of the most expensive cosmetic repairs on an SF90 due to the sheer size of the part and the shipping logistics involved.

3. Components & Sub-Parts

The diffuser is rarely sold as a single “one-piece” unit. It usually consists of:

• The Main Tray: The large horizontal section.

• Vertical Fins (Strakes): These are often replaceable individually if you scuff one on a curb.

• Exhaust Surround: The SF90’s high-exit exhaust exits above the diffuser, but the heat shielding integrated into the top of the diffuser assembly is critical.

• Active Aero Flaps: Depending on the configuration, some SF90 variants have moving flaps within the diffuser channels to stall airflow at high speeds and reduce drag.

4. Common 2026 Damage: Ground Strikes

By 2026, the #1 cause for replacement of part number 844415 (and its variants) is road impact.

• The “Scrape”: Because the SF90 is extremely low and the diffuser extends far back, it is prone to bottoming out on steep inclines.

• Heat Damage: If an aftermarket exhaust is installed without proper heat shielding, the resin in the carbon diffuser can “haze” or even begin to melt near the center section.

5. Installation & Calibration

• Active Aero Handshake: If your SF90 has active flaps in the diffuser, replacing the unit requires a “Proxy Alignment” with the Ferrari DEIS tool. If the computer doesn’t see the correct resistance from the flap actuators, it will throw a “Manettino Failure” or “Aero System Failure” light.

• Sensor Transfer: You must transfer the rear parking sensors and the proximity sensors for the “hands-free” trunk (if equipped) from the old unit to the new one.