What is Nissan’s VC Turbo Engine?

The standard formula for an internal combustion engine has remained relatively unchanged in the modern era of automobiles. While there have been countless small changes in technology that improve performance, efficiency, and reliability, not to mention the widespread adoption of turbocharging, the true guts of an engine (pistons, connecting rods, bearings, valves, and camshafts) have remained the same. 

What is Compression Ratio? 

An engine’s compression ratio is the difference in the volume of the cylinder when it’s at the bottom of a stroke and top dead center. Compression is an essential part of the combustion process, forcing the air and fuel molecules closer together before combustion, allowing for a cleaner and more efficient burn. Compression ratios are impacted by bore, stroke, head gasket thickness, piston shape, and the size of the combustion chamber in the cylinder head. Higher compression engines make more power, burn hotter, and more efficiently, while lower compression engines make less power and run cooler, but are less efficient.

Compression Ratio and Forced Induction

Forced induction (turbocharging and supercharging) forces air into the combustion chamber at a pressure higher than that of the atmosphere. Since the air entering the cylinder is already pressurized, the compression ratio on forced induction engines is typically lower than on naturally aspirated motors, helping reduce the risk of pre-detonation(pre-detonation is when the air and fuel mixture ignites before the spark plug touches it off, which can cause a host of issues).

The trade-off is when the engine is not making boost (pressurizing the intake air), it makes lower power and runs less efficiently. A variable compression engine solves this problem, optimizing power and performance regardless of whether the turbocharger is spooled up or not. 

Nissan’s Variable Compression Engine

One big issue with compression ratios is that they are fixed, meaning no matter what conditions the engine operates under, the compression ratio stays the same. Nissan brought the first variable compression engine to the market in 2019, introducing it on the Infiniti QX50, calling it the VC-Turbo Engine. The engine is now available in two configurations; a 1.5-liter 3-cylinder, and a 2-liter 4-cylinder. 

How Does the Nissan VC-Turbo Engine Work?

To achieve variable compression, Nissan had to rework the entire bottom end of the engine. The VC Turbo engine utilizes a multi-link system rather than a traditional crankshaft, which connects to a control shaft and actuator. The actuator adjusts the angle of the multi-link system depending on driving conditions. This allows the compression ratio to change between 8:1 and 14:1.

When off throttle or cruising, the compression ratio will go up to 14:1, allowing for optimal efficiency. When power is needed and the turbo starts to spool up, the compression ratio drops to 8:1 to accommodate the pressurized air and maximize power output. 

What Vehicles Use the VC-Turbo Engine?

Nissan originally introduced the 2-liter VC-Turbo engine in the Infiniti QX50 in 2019 and has since offered it in the QX55 and QX60. Nissan brought the 1.5-liter version to the Nissan Rogue, and the 2-liter to the Altima. 

Is the VC-Turbo Engine Reliable?

Being such a new engine, it will be a little while before any issues are fully identified. With that being said, there have been reports of engine knocking, power loss, metal in the oil pan, and even total engine failures with these motors. Given these problems, the NHTSA has launched an investigation into the VC-Turbo engine. Time will tell if this technology is as reliable as a traditional engine. 

Nissan Service at Micro Import Service

While most VC-Turbo powered vehicles are still under factory warranty, if you are looking for a trusted Nissan or Infinity expert in Tucson, look no further than Micro Import Service. Our team of skilled and experienced technicians will keep your Nissan running like it should, whether you drive a VC-Turbo Altima or a 350Z. Give us a call or schedule an appointment online today!