Overview#
The Cat G3516H is a high-efficiency natural gas engine designed for continuous-duty power generation and combined heat and power (CHP) applications. Producing 1982 ekW at 1500 rpm, the G3516H is the current-production variant of Cat's proven G3500 gas engine platform -- a V-16, turbocharged-aftercooled lean-burn engine with ADEM4 electronic controls and separate-circuit aftercooling (SCAC).
At 43.5% electrical efficiency and 85.9% total CHP efficiency, the G3516H is engineered for baseload and distributed generation rather than emergency standby. The lean-burn combustion system achieves 0.5 g/bhp-hr NOx engine-out, often eliminating the need for exhaust aftertreatment in many jurisdictions.
Engine platform#
The G3516H shares the G3500 block architecture used across Cat's gas engine lineup:
- V-16 configuration with 12.1:1 compression ratio
- SCAC (separate circuit aftercooling) -- two-stage system with independent low-temperature and high-temperature water circuits to precisely control manifold air temperature
- ADEM4 control system with integrated air-fuel ratio management and ignition timing optimization
- Dry exhaust manifold design for heat recovery efficiency
The engine is rated without fan at ISO 3046/1 standard reference conditions (25C, 100 kPa barometric). Altitude capability is 1400 meters at 25C inlet air temperature before derating.
Efficiency and heat recovery#
The G3516H is designed for total energy utilization. At full load:
- Electrical output: 1982 ekW (43.5% efficiency)
- Jacket water heat: 485 kW recoverable
- Lube oil heat: 184 kW recoverable
- Stage 1 aftercooler heat: 407 kW recoverable
- Exhaust heat to 120C: 919 kW recoverable
- Total CHP efficiency: 85.9%
These heat recovery values make the G3516H a strong candidate for district heating, industrial process heat, and greenhouse heating applications where both electrical and thermal output are valuable.
Emissions profile#
The G3516H achieves low NOx through lean-burn combustion without exhaust aftertreatment:
- NOx: 272 mg/Nm3 (corrected to 5% O2) at full load
- CO: 975 mg/Nm3 -- an oxidation catalyst may be required for CO/HC compliance depending on local regulations
- Formaldehyde: 117 mg/Nm3
Our service experience#
The G3500 gas engine platform is well-established in continuous-duty applications. Key maintenance considerations include spark plug replacement intervals (typically every 4,000 hours), SCAC water quality management, and the ADEM4 control system that requires Cat Electronic Technician (Cat ET) software for diagnostics and tuning. The two-stage aftercooling system demands careful attention to coolant temperature stability -- inlet water temperature must be maintained within +/-1C to prevent detonation risk.
