Advanced science.  Applied technology.


Engine Rebuild Impact on LSPI, 03-R8796

Principal Investigators
Aaron Buster
Inclusive Dates 
09/01/17 to 01/05/18


Low Speed Pre-ignition (LSPI) is a potentially destructive form of abnormal combustion present in turbocharged, direct injection, spark-ignition engines. Although LSPI is stochastic in nature, SwRI has developed a test methodology for quantifying the impact of engine conditions, fuels and oils on LSPI activity using an engine on a test stand. Suppliers of engine parts – specifically pistons and rings – may occasionally make changes to improve fuel economy or durability or may introduce designs to specifically mitigate LSPI. To evaluate the efficacy of these changes, these components needs to be installed and evaluated in an actual engine. The objective of this project was to study the impact of engine disassembly, cleaning and reassembly on LSPI activity of a baseline engine to determine if the engine rebuild affects LSPI activity and if such a test engine can be used to evaluate hardware changes without otherwise influencing the LSPI activity.


To achieve this objective, two evaluations were performed. The first evaluation entailed disassembly and reassembly of a test engine with the original parts, simulating an engine inspection. A previously-stabilized LSPI test engine was disassembled by removing the head, pistons and rings and then rebuilding it using the same, uncleaned parts. The three tests that followed the rebuild did not show any downward trend in LSPI activity, usually encountered with new engines, confirming that a rebuilt engine does not require stabilization of LSPI activity. For the second evaluation, all disassembled parts were cleaned before reassembly. LSPI activity was comparable to before the second rebuild and was again stable following the rebuild. A final bracketing LPSI evaluation confirmed that LSPI activity was not affected by engine rebuilds.


Results confirmed that the engines used for LSPI can be disassembled, cleaned and reassembled without the need to re-stabilize and without affecting the LSPI activity, making it a suitable platform for engine hardware evaluations.