Originally Posted By: bulwnkl
It _is_ LSPI according to the Oronite explanation linked to earlier in the thread. That page and explanation says:
Quote:
Shedding Light on Low Speed Pre-Ignition (LSPI)
...
LSPI is an abnormal combustion event in which the fuel-air mixture ignites before intended, causing excessive pressures inside the engine's cylinders. In mild cases this can cause engine noise, but when severe enough, LSPI can cause engine damage.
That phenomenon is not specific in any way to DI or TDI engines.
Perhaps you intend to describe something else? Something specific to DI or TDI engines? For my own part, I'd be happy to read of the difference(s) you intend to illuminate.
https://en.wikipedia.org/wiki/Low-speed_pre-ignition
Quote:
Low-speed pre-ignition (LSPI), also known as stochastic pre-ignition (SPI),[1] is a pre-ignition event that occurs in gasoline vehicle engines when there is a premature ignition of the main fuel charge.[2]
LSPI is most common in certain turbocharged direct-injection vehicles operating in low-speed and high-load driving conditions.[3]
LSPI events are random and infrequent, and their effects on impacted vehicles can include very high-pressure spikes, loud knocking noises and sometimes catastrophic engine damage.
And from the SAE:
https://www.sae.org/publications/technical-papers/content/2013-01-2569/
Quote:
As one of spark ignition (SI) engine solutions to improve fuel economy while maintaining drivability, concept of combing turbocharging and direct injection (DI) fuel injection system with engine down-sizing has increased its application in the market. Abnormal combustion phenomena referred to as Low Speed Pre-Ignition (LSPI) has been recognized as potential restriction to improve low speed engine torque that contributes fuel economy improvement.
And the Chevron link you appear to be alluding to:
https://www.oronite.com/products/lspi.asp
States:
Quote:
Turbocharged, direct-injected (DI) gasoline engines are rapidly growing in use because of their design to provide improved fuel efficiency when compared with other gasoline engine designs. In particular, there can be significant efficiency benefits achieved when a smaller, turbocharged DI engine is used to replace a larger, conventional engine of the same power. However, the higher power density of these engines makes them prone to a phenomenon called low speed pre-ignition (LSPI). LSPI is an abnormal combustion event in which the fuel-air mixture ignites before intended, causing excessive pressures inside the engine's cylinders. In mild cases this can cause engine noise, but when severe enough, LSPI can cause engine damage.
They SPECIFICALLY refer to Turbocharged, Direct-Injected gasoline engines when referencing the phenomena.
I wouldn't necessarily claim that it is exclusive to the realm of turbo DI, however its recognition as an issue that needed to be dealt with was a direct result of that technology and the efforts taken to deal with it are all relative to it as well.
