The Pressure Sensor Glow Plug senses the combustion pressure in each cylinder of a production Diesel engine using a device already in the engine; no change in engine configuration is necessary. In effect this converts a production engine into a laboratory during the operation of the vehicle, allowing optimization of combustion by cylinder, under any conditions, over the lifetime of the engine. This capability has never been possible before.
The essence of PSG design is a movable heating rod in the glow plug that is sealed from a piezo-resistive sensor, ASIC, and flexible circuit by a metal bellows. Install the PSG plug and connect it to the engine control unit, and information about actual combustion conditions becomes available to the engine controller.
The most immediate benefit of the PSG plug is to enable engine manufacturers to address NOx emissions at the source - combustion - rather than remediate later. Improved combustion reduces NOx emissions by 50% or more while improving fuel economy. Engines under 3.0 liters should meet Tier 2, Bin 5 emission regulations with only a Diesel particle filter; urea-based systems should not be required. Smaller remediation systems can be used on larger engines, and on small engines when needed to meet even stiffer requirements. This saves fuel, weight, and vehicle expense, and is an environmental breakthrough.
But well beyond that, the PSG plug opens a new era in Diesel combustion technology. Closed-loop combustion control, as with Homogeneous Charge Compression Ignition (HCCI), is simplified by detecting combustion pressure. The promise of this is greatly improved lifetime fuel economy (possibly using a variety of alternate fuels), cleaner engines, and less maintenance expense.
The first appearance of this innovation (2008) was in the 2009 VW Jetta TDI.