Hyundai KIA Smartstream G3.5 MPi/GDi G6DU/G6DT Engine Specs, Problems, Reliability, Info

Hyundai/Kia Smartstream G 3.5 V6 Engine Info

The Smartstream G3.5 (G6DU/G6DT) is a naturally aspirated 3.5-liter V6 gasoline engine produced by Hyundai Motor Group since 2020. This engines replaces the previous second-generation Hyundai Lambda V6s (3.3L MPi G6DB/G6DF or 3.8L GDi G6DN), focusing on improved fuel efficiency and lower emissions while providing robust power. It is available in GDI and MPI variants and delivers up to 300 hp and 265 lb-ft (359 Nm) of torque. The Smartstream G3.5 V6 engine uses an 8-speed automatic transmission, powering vehicles like the Hyundai Palisade, Kia Carnival, and Hyundai Santa Fe.

Smartstream G3.5 Engine Overview

The Hyundai-Kia Smartstream 3.5L V6 engine features aluminum construction: it has an aluminum cylinder block with cast iron sleeves, and aluminum DOHC heads with four valves per cylinder. The camshafts are chain-driven. The Smartstream 3.5L engine is equipped with Continuous Variable Valve Timing technology for both intake and exhaust valves (Dual CVVT).

The G3.5 MPi G6DU variant comes with a conventional multi-port fuel injection system, while the G3.5 GDi G6DT engine utilizes a combined fueling system (direct and port fuel injection). The G6DT also features a higher compression ratio (12.3 instead 10.6) and it comes with high-pressure pump (in addition to regular fuel pump inside a fuel tank) providing ultra-high pressure to the direct injectors, which spray fuel directly into the combustion chamber. Direct injection is great for efficiency, while conventional port injection is for longevity and reliability (it helps to minimize low-load carbon buildup). The G3.5 GDi G6DT uses both modes depending on the load and driving conditions.

Both 3.5-liter Smartstream V6 engines are equipped with an Integrated Thermal Management System (ITMS). This electronically operated 3-way valve system monitors and regulates the coolant flow to the radiator, transmission oil warmer and heater. They also come with the Hyundai Variable Intake System (VIS). It adjusts the intake manifold's volume to improve air intake efficiency at low, medium, and high speeds. This results in better power output and throttle response. All Smartstream's engines feature high-energy exhaust gas recirculation (EGR) with water cooling, high-energy individual ignition coils, iridium spark plugs, and friction-optimized moving parts (FOMS).

The Smartstream G3.5 MPi (G6DU) makes 269-272 hp at 6,400 rpm and 244 lb-ft (331 Nm) of torque at 5,000 rpm. The GDi version (G6DT) provides more power: 294-300 hp and 262-265 lb-ft (355-359 Nm). The Smartstream family (Lambda III) also includes a 3.5-liter twin-turbo V6 engine, featuring a 380 hp (279 kW) output at 5,800 rpm and 391 lb-ft (530 Nm) of torque, called the Smartstream FR G3.5 T-GDi (G6DS). This power unit is designed for premium all- and rear-wheel-drive models like the Genesis G80, GV70 and G90.

Engine Specs

Hyundai/Kia Smartstream G 3.5L V6 Problems and Reliability

The Hyundai/Kia Smartstream 3.5L V6, both MPi and GDi variants (G6DT/G6DU), are considered more durable than the older Hyundai Lambda II V6 engines. So far, no major flaws or any frequent problems have been reported. However, nothing is perfect, and this V6 series has some weak spots as well.

ITMS Reliability Issues

The Smartstream 3.5 L V6 comes with an ITM module, which is essentially a set of electronically controlled valves that manage coolant flow, rather than a mechanical thermostat. It is a complex and expensive unit known for some reliability issues.

Carbon Buildup

The G6DT engine with gasoline direct injection (GDI) systems is prone to carbon buildup in the intake system. This engine also has an additional port fuel injection (MPI), which helps to prevent this issue, but it doesn't provide 100% protection.

Direct Injector Failures

GDI injectors operate under high pressure, which can lead to accelerated wear and tear. A faulty injector may cause rough idling, stalling, and hesitation when accelerating. To protect the fuel system, it's important to use high-quality fuel and change the oil frequently.

Smartstream G3.5 V6 Longevity

The Hyundai/Kia 3.5-liter V6 Smartstream engines (G6DT and G6DU versions) are generally considered to be good, reliable power units designed for high longevity with an expected lifespan of over 200,000 miles with proper maintenance.