HEAVY DEPOSITS AND WEAR CAN LEAD TO COMPRESSION LOSS
Matt Erickson | DIRECTOR, TECHNICAL PRODUCT MANAGEMENT
It took engineers at Infinity* 20 years to move 1.2 millimeters. Let me explain.
Maybe you’ve heard of Infinity’s new VC-Turbo* 2.0L engine, the world’s first production engine capable of varying its compression ratio. It uses a multi-link system that ties the connecting rods to the crankshaft and varies piston stroke 88.9 to 90.1 mm, a difference of just 1.2 mm. This effectively allows the engine to achieve any compression ratio between 8.0 (for increased performance) and 14.0 (for increased efficiency). Engineers spent 20 years developing the system.
The engine, available in the 2019 Infinity QX50* and Nissan* Altima*, marks a monumental leap in technology. Engineers have spent more than 100 years chasing the variable-compression dream. While research dates to the 1920s, the technology never gained ground. That is until now as automakers search for ways to meet tightening fuel-economy and emissions requirements.
Why all the fuss? Because operating at the optimum compression ratio for different driving conditions leads to higher performance while using less fuel. Think of it like transmission gears. A transmission with one gear isn’t nearly as efficient as one with several.
As with any internal-combustion engine, however, Infinity’s VC-Turbo can only reach its full potential if owners use a quality motor oil. To understand why, we need a primer on engine compression.
At the risk of oversimplifying, engine compression equals engine power. Compression refers to the pressure your engine generates inside its cylinders while running. How much pressure the engine produces and how well it converts that pressure into usable work influence your engine’s efficiency and power.
During combustion, pressurized gases drive the piston down the cylinder to turn the crankshaft. Ideally, all the pressure generated during combustion works to move the pistons and none of it is wasted as it escapes the combustion chamber. A good analogy is a hydraulic floor jack. Pumping the handle will raise the vehicle as long as the release valve is tightly seated and doesn’t leak. A poorly sealed release valve, however, allows pressure to escape, causing the vehicle to sink to the ground no matter how much you pump the jack handle.
The same principle applies inside your engine. If pressure created during the compression and combustion strokes escapes past stuck piston rings or through worn seals, the engine will create less power.
So, what might cause the rings to stick or valves not to seal properly? Wear and deposits. Now you can see how motor oil affects engine compression and, in turn, power and efficiency.
Let’s start with the piston rings. Most pistons contain three rings, the top two of which are responsible for pressing tightly against the cylinder wall and forming a good seal. Deposits in the ring lands can cause the rings to stick in their grooves rather than press against the cylinder wall, creating a tiny clearance through which pressurized gases can escape the engine,
taking power and efficiency with them. Ring wear can have the same effect.
The same holds with the valves and valve seals. Worn seals reduce compression, as do heavy valve deposits that don’t allow the valve to seal properly. The result is an engine that slowly loses compression over time and, with it, horsepower.
The antidote to wear and deposits robbing your engine of compression is to use a high-quality motor oil that fights wear and keeps engines clean. An oil like AMSOIL Signature Series Synthetic Motor Oil. We installed Signature Series 5W-30 (ASL) in a Ford* F-150* with a new 3.5L Ecoboost* engine to test its ability to protect turbocharged direct- injection (TDGI) engines from torque and horsepower loss during extended drain intervals up to 25,000 miles. Power sweeps were done at the beginning and end of the test to evaluate horsepower and torque retention. As the graph shows, Signature Series helped maintain engine performance throughout the 100,000-mile test. That translates into an engine that delivers like-new performance for years.
Today’s engines may be more sophisticated, but what good are they if the oil can’t keep pace?
This Article From the May 2019 Edition of AMSOIL Magazine, Dealer Edition