aFe Jeep XJ 4.0L Pro DRY S Intake

Intake for the specified Jeep 4.0L body and equipment

aFe 51-46209 Momentum ST intake pairs one Pro DRY S filter with a sealed auxiliary-scoop housing and a roto-molded tube for the specified Jeep Cherokee XJ 4.0L inline-six. The XJ uses three supplied housing grommets, its original mounting bolts/nut and a short silicone crankcase-hose replacement.

Key Features

• One eight-inch inverted-top Pro DRY S filter, service part 21-90099; three oil-free synthetic layers, never oil it.
• Sealed one-piece housing with auxiliary inlet and included urethane plug; closing the inlet changes noise and air-source behavior, not submersion capability.
• CAD-designed roto-molded plastic tube; no aluminum or specific XLPE material is borrowed from another kit.
• The current product text mentions T-bolt clamps, but the exact manual identifies two No. 048 worm clamps (03-50007) on the coupling and a separate worm clamp already supplied on the filter. Use the actual supplied hardware; a T-bolt conversion is not established.
• No cutting or drilling of factory parts per the current exact product page.
• Actual shared chart: dry 250 CFM versus stock 230 CFM at 7 inches H2O, about 8.7% by arithmetic. The page advertises up to 10%; those are not identical percentages.

Fitment

1991–2001 Jeep Cherokee XJ with the naturally aspirated 4.0L inline-six only, as specified by the current exact product page and shared manual. The older dry-kit title says 1997–2001, but the current dry page, manual and exact-part named table explicitly cover 1991–2001. Match the factory throttle body, crankcase hard-line and housing mounts. The named rows require the actual 4.0L engine; no 2.5L, diesel, Grand Cherokee or later Cherokee crossover approval is inferred. The missing 1994–2001 SE row is supported by each kit’s own retailer table; actual Base trim and the 1997 Classic/Limited gaps are retained.

Verify 51-46209 against the actual engine, sensor and vent connections, mounting locations and applicable emissions requirements before ordering.

Specifications

What's Included

The shared manual lists alternative dry, oiled and Pro GUARD media. This selected kit includes only its listed filter, not all three. The current product text mentions T-bolt clamps, but the exact manual identifies two No. 048 worm clamps (03-50007) on the coupling and a separate worm clamp already supplied on the filter. Use the actual supplied hardware; a T-bolt conversion is not established. The three housing grommets are newly supplied; the two original mounting bolts and one nut are reused.

About aFe Power

aFe Power develops application-specific intake, filtration, exhaust, cooling, tuning, suspension, drivetrain, and truck-performance components supported by product testing and documented installation requirements.

Related Parts

• Manufacturer product specifications for 51-46209
• Exact illustrated installation manual
• Manufacturer-linked dyno; read the test configuration and media qualification
• Manufacturer-linked selected-media bench-flow comparison
• Shop the complete aFe Power collection

Frequently Asked Questions

1991–2001 Jeep Cherokee XJ with the naturally aspirated 4.0L inline-six only, as specified by the current exact product page and shared manual. The older dry-kit title says 1997–2001, but the current dry page, manual and exact-part named table explicitly cover 1991–2001. Match the factory throttle body, crankcase hard-line and housing mounts. The named rows require the actual 4.0L engine; no 2.5L, diesel, Grand Cherokee or later Cherokee crossover approval is inferred. The missing 1994–2001 SE row is supported by each kit’s own retailer table; actual Base trim and the 1997 Classic/Limited gaps are retained.

No. The selected dry filter 21-90099 has three synthetic layers and must remain oil-free.

The current page specifies no cutting or drilling of factory parts. The exact manual mounts the housing with supplied grommets and original bolts/nut, and does not direct a sensor-hole operation.

Use all three supplied 03-50076 housing grommets with the two original bolts and one rear-stud nut. Retain the original crankcase hard-line while replacing its short valve-cover rubber section.

No. The five-inch, 1/2-inch-ID silicone hose replaces the short rubber crankcase-breather section between the valve cover and original hard-line; the other line end connects to the intake tube.

The current product text mentions T-bolt clamps, but the exact manual identifies two No. 048 worm clamps (03-50007) on the coupling and a separate worm clamp already supplied on the filter. Use the actual supplied hardware; a T-bolt conversion is not established. Neither exact manual supplies a numeric clamp torque.

Both selected-media pages link the same actual Momentum ST dyno, which does not identify the filter media or exact vehicle year on the sheet. Its intake-run notes say stock exhaust, bladed fan and third gear; baseline notes say stock configuration, blade fan and hood open. Marked differences near 4,363 rpm are 16.19 HP and 19.48 lb-ft; peak-to-peak differences are 12.43 HP and 10.83 lb-ft. These figures do not independently certify a separate dry or oiled result on an individually identified XJ. The chart’s test configuration and differing ambient conditions must remain attached to the claim. Actual shared chart: dry 250 CFM versus stock 230 CFM at 7 inches H2O, about 8.7% by arithmetic. The page advertises up to 10%; those are not identical percentages.

The current exact manufacturer page says only some or all listed applications are exempt and refers to CARB D-550-50. The official indexed table specifically names this kit family for 1991–2001 Cherokee 4.0L naturally aspirated applications; full-document conditions were not independently reviewed because official direct access was previously blocked. Match the actual vehicle/engine and EO label, retain required equipment and apply the supplied identification label as directed; do not extend the exemption to other engines or modifications. Secure every connection and recheck after 100–200 miles. Verify the housing mounting nut/bolts and all three main intake connections.

Installation Instructions

Verify aFe 51-46209. Read the entire manual on a cool engine, disconnect the negative battery terminal and retain original parts. Disconnect the stock crankcase line, release the factory tube clamps, remove the tube and airbox lid/filter, then save the two bolts and nut securing the lower airbox. Install all three supplied grommets into the new housing, align the housing with the fender, start the saved rear-stud nut by hand and secure the remaining original mounting hardware. Seat the selected filter. Fit the silicone elbow reducer to the tube with the two supplied worm clamps loose; loosen the clamp already on the filter, insert the tube into the filter flange and position the elbow over the throttle body. Tighten the throttle-body coupling clamp, tube-side coupling clamp and filter clamp after alignment. Remove the original short rubber hose at the valve-cover crankcase hard-line and replace it with the supplied five-inch, 1/2-inch-ID silicone hose; reconnect the other end of the original hard-line at the intake-tube fitting. The current product text mentions T-bolt clamps, but the exact manual identifies two No. 048 worm clamps (03-50007) on the coupling and a separate worm clamp already supplied on the filter. Use the actual supplied hardware; a T-bolt conversion is not established. No numeric torque is specified, and this exact procedure does not instruct transferring a mass-airflow or temperature sensor. Check all connections and recheck bolts, clamps and hoses after 100–200 miles. Apply the supplied EO label on or near the device as directed.

Important Disclosures

The current exact manufacturer page says only some or all listed applications are exempt and refers to CARB D-550-50. The official indexed table specifically names this kit family for 1991–2001 Cherokee 4.0L naturally aspirated applications; full-document conditions were not independently reviewed because official direct access was previously blocked. Match the actual vehicle/engine and EO label, retain required equipment and apply the supplied identification label as directed; do not extend the exemption to other engines or modifications. Both selected-media pages link the same actual Momentum ST dyno, which does not identify the filter media or exact vehicle year on the sheet. Its intake-run notes say stock exhaust, bladed fan and third gear; baseline notes say stock configuration, blade fan and hood open. Marked differences near 4,363 rpm are 16.19 HP and 19.48 lb-ft; peak-to-peak differences are 12.43 HP and 10.83 lb-ft. These figures do not independently certify a separate dry or oiled result on an individually identified XJ. The chart’s test configuration and differing ambient conditions must remain attached to the claim. Match the actual 4.0L engine and documented sensor/vent/mounting configuration; trim names alone do not identify the engine. The auxiliary plug and sealed housing do not establish greater water-fording capability.

California Proposition 65 warning: this product can expose you to chemicals known to the State of California to cause cancer and reproductive harm.