The aFe Magnum FORCE Stage-2 intake replaces the factory upper airbox, tube and filter on the N55 3.0L turbo six with an aFe intake tube and a Pro DRY S filter that sits in the reused lower airbox. The filter uses three-layer oil-free synthetic media that is cleaned and reused without oiling. The factory mass air flow sensor moves to the aFe tube with two M4 screws.
Specifications
| Type | Cold Air Intake System |
| Series | Magnum FORCE Stage-2 |
| Filter Media | Pro DRY S, three-layer oil-free synthetic, washable and reusable |
| Engine | 3.0L turbo inline 6-cylinder (N55) |
| What's in the Box |
|
| Fitment Notes | N55 engine only: 135i and 335i / 335i xDrive 2011-2013, X1 xDrive35i 2013-2015. The factory lower airbox is reused |
| Install | Bolt-on with 6mm and 8mm nut drivers and a T25 Torx |
| Replacement Filter | 21-90083 (Pro DRY S) |
| Filter Color | Gray |
| Hardware Included | Yes |
| Air Flow Gain | 32 Percent |
| Pre-Filter | 28-10153 |
| Air Box Type | Open |
| Heat Shield Included | Yes |
| Tune Required | No |
| Gains | Up to +16 Horsepower hp and +26 Ft-Lbs lb-ft (aFe dyno) |
| Quantity | 1 kit |
| Warranty | 2 years on components (original owner) |
| Part Number | 51-31912 |
This part fits:
| Year | Make | Model | Submodel |
|---|---|---|---|
| 2011-2013 | BMW | 135i | Base |
| 2011-2013 | BMW | 335i | Base |
| 2011-2013 | BMW | 335i xDrive | Base |
| 2013-2015 | BMW | X1 | xDrive35i |
Documents: Installation Instructions (PDF)
Which BMW models does it fit?
- The 2011-2013 BMW 135i, 335i and 335i xDrive and the 2013-2015 X1 xDrive35i with the N55 3.0L turbo.
Does it replace the whole airbox?
- No. The upper airbox, tube and filter are replaced; the factory lower airbox is reused.
What is the replacement filter?
- Part number 21-90083, a Pro DRY S filter that can be cleaned and reused.
Shipping
- Orders placed before 3 PM EST typically ship the same business day. Larger items ship within 1 to 3 business days.
- Standard, expedited, and overnight options at checkout.
- Oversized items ship by freight and take longer.
- Special order items follow a lead time we confirm with you individually before the order is committed.
- Backordered items ship as soon as stock lands. Lead times are manufacturer estimates and can change. Contact us for current ETAs.
- Need to cancel? Email us right away. Cancellations are not guaranteed once an order is in process. In-stock orders cancel free before they ship; a 6% fee applies only to confirmed backorders and special orders.
- International orders: prices do not include VAT, duties, or import fees. Your country charges these at import and they are the buyer’s responsibility.
Returns
- 30 days from delivery to request and ship back a return on new, uninstalled items in original packaging with all hardware.
- Standard returns: 8% restocking fee on the item price before tax and shipping. Shipping is not refunded in either direction. All waived if the item is defective or we made the error.
- Fitment guaranteed: select your vehicle above, or confirm fitment with us in writing before you order. If the part shows as a fit and it is wrong, the return is on us, even after installation. Otherwise, installed or used parts cannot be returned.
- Final sale: special orders, coilovers, electronics, engine internals, turbochargers, superchargers and turbo kits, unless defective or we sent the wrong item.
- Product images may be representative. The SKU and specifications in the listing are what ships.
- Email us for return authorization before shipping anything back.
Full details: Shipping Policy · Returns & Refunds · Warranty
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