For many years now, OEMs have been downsizing engines to meet fuel economy and emissions standards without sacrificing power and torque by featuring turbochargers, direct injection and variable valve timing. While favorable to performance, these technologies heighten the possibility of low-speed pre-ignition (LSPI) events, which can destroy pistons, connecting rods and even the entire engine.
People think low-speed pre-ignition is from beating on the engine or high rpm, but that’s not what causes it. LSPI occurs under low speed, high-load conditions in turbocharged gasoline direct-injected (GDI) engines. Over time, oil vapors and gas vapors build up around the ring lands of the piston. When the oil and fuel mix, it can cause an ignition cycle prior to the actual ignition cycle and can be a very violent episode, commonly snapping the ring land of the piston (pictured).
Once the ring land breaks, you lose compression, you lose power, and ultimately, you can damage the cylinder walls and destroy the engine. In a high-performance engine, it’s a good idea to change the piston to a forged piston as one way to protect against LSPI. But, regardless of the performance of your GDI engine, using a motor oil specifically formulated to treat LSPI is what will help the most.
You want to use an API SP or direct-injection-specific motor oil. That API SP designation means the oil has been formulated specifically for direct-injected engines and it has passed an LSPI test(s). AMSOIL has been researching this issue for quite a while and has several oils specifically formulated to prevent LSPI, such as AMSOIL Signature Series, XL and OE Synthetic motor oils, which all meet or exceed these specifications.
The post How Can Oil Help Alleviate Low-Speed Pre-Ignition Issues? appeared first on Engine Builder Magazine.
