aFe 51-31912 is the Magnum FORCE Stage-2 oil-free intake for qualified E-series BMW N55 3.0L turbo applications. One Pro DRY S filter and molded tube retain the original lower airbox and downstream coupling. The optional black cover is separate; a new enclosed lower housing is not supplied.
Current exact dry primary identifies 135i E82/E88 and 335i E90/E92/E93 2011-2013, plus X1 E84 2013-2015 with N55 3.0L turbo. The exact shared manual lists X1 2011-2015, while original xDrive35i 2013-2015 remains and earlier-market evidence is held. Original 335i and 335i xDrive Base model rows require actual E-series N55 chassis rather than F-series inference. All original four application rows, year bounds and native memberships remain. Additional exact selected-dry named/chassis proof was unavailable from current secondary research; no 135i package-to-trim conversion, N54, 335is, M-model or F-series mapping is invented.
| Years | Make | Model | Named trim; actual engine and hood requirements apply |
|---|---|---|---|
| 2011-2013 | BMW | 135i | Base |
| 2011-2013 | BMW | 335i | Base |
| 2011-2013 | BMW | 335i xDrive | Base |
| 2013-2015 | BMW | X1 | xDrive35i |
Verify 51-31912 against the actual engine, sensor and vent connections, mounting locations and applicable emissions requirements before ordering.
| Brand | aFe POWER |
| Manufacturer Part Number | 51-31912 |
| Product line | Magnum FORCE Stage-2 |
| Selected filter | One 21-90083 Pro DRY S; three oil-free synthetic layers |
| Filter dimensions | Oval 7 x 3-inch flange; 5-inch height; replacement listing |
| Tube | 05-31912B1; molded intake tube |
| Sensor hardware | Two 03-50490 M4 screws; length not stated in own bill |
| Original interface | Lower airbox, downstream coupling and original MAF sensor retained |
| Optional cover | 54-31918-B; separate accessory, not included |
| Original clips | Keep four original metal clips when fitting optional cover |
| Airflow evidence | No current linked flowchart establishes baseline, pressure or numeric increase |
| Dyno qualification | Linked chart explicitly oiled 54-series no-cover run: point +15.67 hp / +25.70 lb-ft versus maxima +3.58 hp / +34.01 lb-ft; not dry certification |
| Emissions | Current manufacturer/manual: not CARB exempt; California restriction |
| UPC | 802959514788 |
| WARNING | This product can expose you to chemicals including lead and phthalates, which are known to the State of California to cause cancer and reproductive harm. For more information go to www.P65Warnings.ca.gov. |
| Quantity | Manufacturer service part | Component |
|---|---|---|
| 1 | 21-90083 | Selected Pro DRY S oil-free filter |
| 1 | 05-31912B1 | Molded intake tube |
| 2 | 03-50490 | M4 sensor screws; length not specified |
The alternate oiled filter in the shared bill is not a second selected filter. No new lower airbox, cover, downstream coupling, MAF sensor or separate gasket is itemized, despite generic coupler flags and sealed-system overview wording. Original lower airbox and coupling remain. The filter clamp shown in the procedure is supplied with the filter. Black foam tape is mentioned as an optional fit/protection measure but is not itemized in the selected bill; do not promise it as supplied. Shared manual includes the 52-series family number as well as both selected media versions.
aFe Power develops application-specific intake, filtration, exhaust, cooling, tuning, suspension, drivetrain, and truck-performance components supported by product testing and documented installation requirements.
One 21-90083 Pro DRY S oil-free filter with three synthetic layers, oval 7 x 3-inch flange and 5-inch height.
Is a new airbox or coupling included?No new lower airbox or downstream coupling is itemized; both original components remain.
Which sensor transfers?The original MAF transfers using two supplied M4 screws. The own bill does not specify screw length.
When should MAF be reconnected?Reconnect its harness first, before inserting the new tube end into the original coupling.
Should the four original metal clips remain?Keep them for the optional cover. The exact procedure permits removing them when running the intake without a cover.
Is black foam tape guaranteed in the box?No. The procedure mentions optional fit/protection use but does not itemize it in the selected bill.
Does the linked dyno independently test this dry intake or optional cover?It explicitly names the oiled 54-series intake and No Cover. Results remain qualified historical evidence, not selected dry or cover certification.
What torque and follow-up apply?The exact intake manual specifies no numeric torque or mileage interval. Verify MAF connection, tube support and clamp engagement.
Verify aFe 51-31912. Read all twelve pages and figures A-E. Work cool and observe the negative-battery disconnection warning. Unclip original airbox in four places and loosen the first hose clamp after MAF. Lift original tube enough to disconnect MAF harness, then remove original tube and filter while leaving lower airbox in place. Keep all four metal clips if installing the optional cover; when running without cover, the manual permits removing clips by closing fully and pushing down firmly. Remove original MAF using T25 and pull sensor straight out. Install it in supplied tube using both supplied M4 screws. Fit selected dry filter onto tube as one assembly. Reconnect MAF harness FIRST, then insert tube end into original coupling. Press tube into position over original airbox edge and secure clamps. Optional black foam tape may protect original box surface or improve tube-to-box fit, but is not itemized as supplied. Verify sensor, tube support and clamp engagement and restore battery connection. No numeric torque or mileage recheck interval is specified in this intake manual; do not borrow the separate cover 100-mile instruction as this intake own interval.
Current dry primary advertises 32-percent more flow without a linked flowchart; no unseen baseline or pressure is reconstructed. Its actual linked 2011 335i N55 dyno explicitly identifies the oiled 54-series intake and No Cover configuration, not an independent selected dry-media test. Marked differences are 192.93 minus 177.26 equals 15.67 hp near 3100 rpm, and 316.64 minus 290.94 equals 25.70 lb-ft near 3300 rpm. Run maxima differ by 3.58 hp and 34.01 lb-ft. Both July 7, 2014 runs use SAE 1.05, original tune, downpipe and exhaust, 275/30-19 tires and fourth gear; times and weather differ. Neither point differences nor separate maxima certify all chassis or optional cover performance. Current manufacturer says not CARB exempt and unavailable for purchase in California or use on California-registered vehicles. Older manual race wording is not a waiver of that current restriction.
California Proposition 65 warning: this product can expose you to chemicals known to the State of California to cause cancer and reproductive harm.
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