Low-speed pre-ignition (LSPI)

Down-speeding has become synonymous with GDI development, taking further advantage of the high torque at low engine speed characteristics. Small capacity, turbocharged/supercharged (or twin-charged) engines have become popular but have introduced the practical issue of low-speed pre-ignition (LSPI), which tends to occur during heavy loads at low engine speeds – ie, the conditions in which GDIS are intended to excel. As LSPI is caused predominately by calcium deposits in the oil being present within the engine cylinder and igniting the air/fuel mixture at the wrong moment, retarding the ignition will not make any difference. In the long term, the result will be mechanical damage, such as broken spark plugs or broken piston ring lands.

LSPI sounds different to the traditional ‘pinking’ that experienced Diyers can detect. We suggest that you listen for any distinctive ‘banging’ sounds from the engine at low revs, or heavy throttle applications. Adapt your driving style, such as allowing the engine to rev at higher speeds when accelerating. Aside from regular oil changes, be aware that oil specifications are becoming almost bespoke for newer cars, so consult the handbook and check that any lubricant complies with the unique manufacturer specifications listed. This is in addition to the usual viscosity and SAE specifications. CM understands, however, that no official anti-lspi oil formulation has been developed by the American Petroleum Institute (API) or the European ACEA, as yet, but we understand that research is ongoing.