37517-05500 Piston Suit for Mitsubishi S6R2 & S16R2 Diesel Engines
Structural Features and Advantages
The 37517-05500 piston suit is a premium top-end component set engineered for Mitsubishi’s next-generation S6R2 (6-cylinder) and S16R2 (16-cylinder) diesel engines. This suit typically includes the piston body, piston ring pack (three rings plus expander), piston pin (wrist pin), and two retaining circlips. Structurally, the piston is manufactured from a high-strength aluminum alloy with a fiber-reinforced combustion bowl – a composite insert at the rim of the omega-shaped bowl that increases thermal fatigue resistance by 35% compared to conventional aluminum pistons. The crown features an optimized re-entrant bowl geometry with a deep central depression and a pronounced lip, specifically tuned for the S6R2/S16R2’s high-pressure common-rail injection system (peak injection pressure up to 2000 bar). The skirt is coated with a low-friction MoS₂ (molybdenum disulfide) solid lubricant and includes an offset pin bore to reduce piston slap noise during cold starts. The piston ring pack consists of a physical vapor deposition (PVD) coated top compression ring (chrome nitride or CrN), a tapered second ring with a napier (hook) edge for improved oil scraping, and a three-piece oil control ring with a coil spring expander. Key advantages of the 37517-05500 piston suit include: significantly reduced blow-by (down to 15 L/min from 30 L/min on older designs), lower oil consumption (0.1–0.3% of fuel consumption), compatibility with extended oil change intervals (up to 500 hours on generator sets), and a faster break-in period (less than 10 hours under normal load).
Core Working Principle
The 37517-05500 piston suit functions as the moving boundary of the combustion chamber, converting the heat released from diesel fuel into mechanical work. During the intake stroke, the piston moves downward, drawing compressed air (from the S6R2/S16R2’s twin-turbo setup) through the intake valves. The air swirls into the re-entrant bowl, creating a high-tumble motion that promotes rapid mixing with injected fuel. As the piston rises on the compression stroke, the air is compressed to temperatures exceeding 550°C. Near top dead center, the common-rail injector sprays fuel in multiple pulses directly into the bowl. The fiber-reinforced bowl rim resists the intense local heat flux (as high as 3 MW/m²) and prevents micro-cracking. The expanding combustion gases force the piston downward with peak cylinder pressures reaching 190–210 bar (depending on S6R2 or S16R2 tuning). The offset pin bore reduces side thrust against the cylinder liner by about 15%, lowering frictional losses and improving fuel economy. The PVD-coated top ring provides a near-perfect seal against the liner even at high temperatures (up to 300°C at the ring face), while the napier second ring actively scrapes excess oil downward on the piston’s upstroke. The oil control ring meters the lubricating oil to less than 0.5 g per hour per cylinder, meeting Euro Stage V and EPA Tier 4 emission standards.
Main Application Equipment
The 37517-05500 piston suit is used in Mitsubishi S6R2 and S16R2 diesel engines, which power a wide range of demanding equipment:
High-efficiency generator sets (350–2500 kVA) for data centers, hospitals, and manufacturing plants requiring Tier 4 / Stage V compliance.
Marine propulsion for large tugboats, offshore service vessels (OSV), coastal freighters, and luxury yachts with S16R2 main engines.
Marine auxiliary generator sets onboard tankers, container ships, and passenger ferries.
Rail traction engines for heavy-haul locomotives in regions with strict emissions limits (e.g., Europe, North America).
Mining haul trucks (100–250 ton payload) and large hydraulic excavators powered by S16R2 diesels.
Industrial compressors and pumps used in oil & gas fields, water treatment plants, and pipeline booster stations.
Emergency power units for nuclear power plants and other critical infrastructure where S6R2 engines provide backup.
The S6R2 and S16R2 are Mitsubishi’s most advanced medium-speed diesel platforms, featuring electronic governing and common-rail fuel systems. The 37517-05500 piston suit is a critical component for maintaining OEM performance and emissions compliance.
Common Failure Symptoms & Repair/Replacement Guidelines
Failure symptoms indicating a worn or damaged 37517-05500 piston suit in an S6R2 or S16R2 engine:
High oil consumption with blue smoke – Exceeds 0.5% of fuel consumption; often caused by worn napier rings or damaged oil control ring expander.
Blow-by exceeding 60 L/min – Measured with a manometer; indicates top ring sealing failure or ring sticking due to carbon deposits.
Piston crown erosion or melting – Usually a result of injector nozzle failure or overfueling; visible with borescope as irregular depressions on the bowl rim.
Cylinder pressure imbalance (detected via electronic engine monitoring) – More than 5% variation between cylinders points to ring sealing differences or piston damage.
Metallic knocking that worsens with load – Piston slap after skirt coating wear or excessive pin clearance.
Oil dilution with fuel – Fuel percentage in oil > 5% indicates blow-by past rings, requiring immediate overhaul.
Repair and replacement points:
Always replace the full piston suit (37517-05500) for any failed cylinder. Do not reuse old rings or pins even if they appear serviceable – the coating and fatigue life are consumed.
Inspect the cylinder liner bore for scoring, glazing, or out-of-roundness. For S16R2 engines, replace liner if wear exceeds 0.10 mm; hone to 0.3–0.5 µm Ra for ring re-seating.
Check the connecting rod small-end bushing wear. Replace bushing if pin clearance > 0.08 mm. Required bushing ID after reaming: 60.025–60.045 mm for the 37517-05500 pin (pin OD = 60.00 mm).
Ring gap verification (cold, installed in liner):
Top compression ring: 0.45 – 0.65 mm
Second ring: 0.50 – 0.70 mm
Oil ring rails: 0.30 – 0.55 mm
Lubricate cylinder bore and piston with clean engine oil. Use a quality ring compressor; do not use a screw-style compressor that can damage the PVD coating.
Torque connecting rod bolts to factory spec: typically 110–120 Nm + 90° (torque-to-yield – replace bolts every time).
After reassembly, perform an initial break-in on a dynamometer or under controlled load: run at 60% load for 2 hours, then 80% load for 4 hours, then full load. Avoid prolonged low-load idling (causes ring glazing).
For S16R2 engines with 16 cylinders, replace all pistons on one bank if a single failure occurs – unbalanced blow-by can affect engine control logic. Alternatively, weight-match new piston to within 5 grams of the adjacent cylinder’s piston.
Why Choose Rsolid Engine Parts for the 37517-05500 Piston Suit
Rsolid Engine Parts (www.rinjector.com) supplies OE-grade 37517-05500 piston suits for Mitsubishi S6R2 and S16R2 engines, meeting the highest quality standards for aftermarket and rebuild applications. Advantages of sourcing from Rsolid include:
Full OEM specification – Each piston is cast or forged (depending on production batch) to match S6R2/S16R2 bowl volume, compression height, and cooling gallery design (if applicable).
High-performance ring sets – Rings are supplied by ISO-certified manufacturers with PVD top ring, napier second ring, and stainless steel oil ring for extended service life.
100% dimensional inspection – Every piston is checked for skirt profile, pin bore roundness, ring groove parallelism, and critical radial runout.
Weight-matched sets – For S16R2 engines, all 16 pistons are supplied within ±2 grams to minimize engine vibration and bearing loads.
Fast global shipping – Large inventory of 37517-05500 suits ready to ship same day from regional warehouses.
Installation support – Free downloadable torque sheets, ring gap tables, and break-in procedures. WhatsApp technical support for complex rebuilds.
Competitive pricing – Up to 40% lower than Mitsubishi genuine prices without compromising quality. Volume discounts for fleet operators and rebuild shops.
Order the 37517-05500 piston suit for your Mitsubishi S6R2 or S16R2 engine overhaul today. Contact WhatsApp: +8615975376778 or visit www.rinjector.com to get a quote and check stock.
