aFe Magnum FORCE Stage-2 Cold Air Intake 51-12912-B – BMW 340i / 440i / M240i (B58)

OVERVIEW

The aFe Power Magnum FORCE Stage-2 cold air intake replaces the restrictive factory airbox on the B58-powered BMW 340i, 440i and M240i with a fully engineered induction system. A CAD-designed, dyno-tuned roto-molded intake tube feeds a large 7" conical filter, and the system flows 400 CFM at 7" H₂O for dyno-tested gains of up to +9 horsepower and +10 lbs. x ft. of torque.

This version uses the oil-free Pro DRY S filter, built from three layers of progressively finer synthetic media for excellent filtration efficiency with no re-oiling required at service time. A lightweight vacuum-formed black plastic cover shields the filter for a stealthy under-hood look and tames intake noise without sacrificing power; an auxiliary air inlet in the cover feeds additional cool air, and a urethane plug is supplied if you prefer to block it off.

Every clamp, coupling and fastener needed is in the box. The kit is a direct bolt-on that requires no cutting or drilling of factory parts.

SPECS

• Dyno-tested gains: +9 HP and +10 lbs. x ft. of torque (peak)
• Measured airflow: 400 CFM @ 7" H₂O
• Outflows the factory intake
• Filter media: aFe Pro DRY S oil-free, 3-layer progressively finer synthetic media (aFe P/N 21-90096)
• Filter: 7" tall conical, 360-degree radial-flow element
• Intake tube: CAD-designed, dyno-tuned roto-molded plastic (aFe P/N 05-76309B4)
• Cover: lightweight vacuum-formed black ABS plastic (aFe P/N 05-12912B2)
• Auxiliary air inlet in the cover, with a urethane block-off plug included
• Installation: direct bolt-on — no cutting or drilling of factory parts
• Fitment note: does not fit Convertible models
• Emissions status: not CARB exempt at this time — not legal for sale in California or for use on any vehicle registered with the California Department of Motor Vehicles.

PARTS INCLUDED

• Pro DRY S air filter (21-90096) — 1
• Black vacuum-formed intake cover (05-12912B2) — 1
• Roto-molded intake tube (05-76309B4) — 1
• Silicone plug (05-01387) — 1
• Silicone double-hump coupling (05-01417) — 1
• Hose clamp, #060 (03-50002) — 2
• M4 Torx screw (03-50490) — 2

TECH RESOURCES

Additional Parts Required

• None. aFe Power specifies no additional hardware, tune or fluids for this intake — it is a direct bolt-on kit that requires no cutting or drilling of factory parts.
• Installer-supplied: basic hand tools, including a T-handle or driver for M4 Torx screws and a nut driver for the hose clamps.
• Optional service item: the Pro DRY S filter is washed and air-dried only — no filter oil is required.

Installation

• aFe Power 51-12912-B installation instructions (PDF)

Notes

• Does NOT fit Convertible models. Chassis codes and year ranges above follow aFe Power’s current installation instructions, which are broader than the 2016–2018 range shown in the product title. Confirm fitment with Speed Logic before ordering.

PART NUMBER

• 51-12912-B — Magnum FORCE Stage-2 intake, Pro DRY S filter, black cover (this listing)
• 51-12912-C — same kit with Pro DRY S filter and carbon fiber look cover
• 54-12912-C — same kit with Pro 5R oiled filter and carbon fiber look cover

VEHICLE APPLICATIONS