Engine Piston 8941528920 8-94152892-0 For ISUZU D-MAX 8DH TFR TFS 4JA1T 4JA1-T 2.5 TD — Reinforced Ring Land, Alfin Insert + Invar Strut, 93mm STD, 31mm Pin

The Engine Piston with OEM reference 8941528920 / 8-94152892-0 is a verified direct-fit replacement for ISUZU 4JA1T / 4JA1-T (2.5L turbo diesel) engines, used in D-MAX (8DH), TFR, and TFS pickups. This piston is the reciprocating component that converts combustion pressure into crankshaft rotation, and on the turbocharged 4JA1T it must withstand higher cylinder pressures and thermal loads than its naturally aspirated counterpart.

This piston is specifically designated as a reinforced / strengthened version ("PISTON (STRENGTHEN)" in factory listings), featuring an Alfin insert at the ring-land area for ring-groove reinforcement and an Invar strut for controlled thermal expansion. The turbocharged 4JA1T application demands these features to maintain ring sealing and piston-to-wall clearance under boost. It is supplied in standard (STD) 93.00 mm bore with a 31 mm full-floating piston pin.

• Bore & Pin Verified: 93.00 mm bore, 31 mm pin diameter, 76 mm pin length — consistently confirmed across multiple technical sources.
• Compression Height Split Verified: 47.9 mm KH (KOLBENSCHMIDT 99340600) vs. 51.84 mm KH (NÜRAL 87-246200-00) — both listed for 4JA1T applications, confirming the need for physical verification.
• Construction Features Verified: Alfin insert and Invar strut — confirmed by autoparts007 specification for the 4JA1 platform. NÜRAL listing adds "con porta fascia elastica" (with ring carrier) and oil jet cut-out.
• Factory Cross-Reference Verified: 8-94152892-0 and 8-94152892-HY are factory / tooling references for 8941528920. Additional related references include 8-97942985-0 and 8-97942986-0.
• Vehicle Coverage Verified: Confirmed for ISUZU D-MAX 8DH 2.5 4x4 79 KS 4JA1T and TFR / TFS pickup applications.
• Quality Certification Reference: Manufacturer listings reference TS16949 / QS9000 certification for the 4JA1 piston platform. Supplier warranty reference is 6 months.

• Loss of compression / hard starting under boost: Worn or stuck rings in a turbocharged 4JA1T reduce cranking pressure and boost response — often the first sign of piston ring land wear.
• Excessive blue/white exhaust smoke: Oil passing the rings or incomplete combustion — piston and ring replacement is the standard correction when cylinder bores are within specification.
• Increased oil consumption: Glazed bores or tired ring packs allow oil into the combustion chamber, raising operating costs on D-MAX/TFR fleet vehicles.
• Piston scoring or scuffing: Visible skirt wear or liner scoring caused by thermal expansion, insufficient lubrication, or turbo-related heat load — requires immediate replacement.
• Ring land cracking: The reinforced ring land design addresses a known weakness; on high-mileage or overheated 4JA1T engines, the original ring land can crack, leading to compression loss and potential piston break-up.
• Knocking or tapping noise: Piston slap from excessive skirt-to-bore clearance or a worn 31 mm pin bushing requires inspection before further operation.

1. Confirm KH and ring groove spec first: Measure the removed piston's compression height and ring groove widths. Match the replacement to these dimensions, not just the OEM number.
2. Check cylinder liner wear: Measure liner bore for taper and out-of-roundness. If wear exceeds specification, replace the liner rather than fitting a new piston into a worn bore.
3. Verify ring end gap: Fit the new rings into the bore and check end gap against the workshop manual before assembly.
4. Install pin and circlips: Lubricate the 31 mm pin and bore, slide the pin through the piston and connecting rod small end, and seat new circlips fully.
5. Stagger ring gaps: Position ring end gaps at 120° intervals.
6. Lubricate and install: Coat the piston skirt and rings with clean engine oil; use a ring compressor for insertion.
7. Connecting rod torque: Follow the workshop manual specification and sequence for the 4JA1T.
8. Weight matching: If replacing fewer than four pistons, verify weight compatibility with the existing assemblies.

• Oil changes: Use the correct diesel engine oil and adhere to ISUZU recommended intervals. Degraded oil accelerates ring and skirt wear, especially on turbo engines.
• Compression / blow-by check: At every 50,000 km or if hard starting, smoke, or oil consumption develops.
• Cooling system: The 4JA1T is sensitive to overheating; maintain coolant condition and thermostat function to protect piston-to-liner clearance.
• Air filter integrity: Dust ingress is a leading cause of piston ring and skirt wear on turbo diesel pickups in dusty environments.

• Standard packing: Neutral carton with protective wrapping; package size 88 × 93 × 93 mm (reference); wooden pallet available for bulk export orders.
• Package contents: 1 × Piston (with pin & circlips). Piston rings and cylinder liner are NOT included unless explicitly stated.
• Set options: Single piston / matched set of 4 for one 4JA1T engine — specify at inquiry.
• Suitable for: ISUZU D-MAX / TFR / TFS pickup repair shops, 4JA1T engine rebuilders, spare parts distributors, and export wholesalers serving Southeast Asia, the Middle East, Africa, and Latin America.
• Related parts available: Piston ring set (confirm groove widths), cylinder liner, piston pin (31 × 76 mm), pin bushings, and complete 4JA1T overhaul kits.