Editing Stratified charge engine (section)

==Combustion management==
Combustion can be problematic if a lean mixture is present at the spark plug. However, fueling a petrol engine directly allows more fuel to be directed towards the spark-plug than elsewhere in the combustion-chamber.<ref>{{cite web |url=http://www.renault.com/en/Innovation/eco-technologies/Documents_Without_Moderation/PDF%20ENV%20GB/Stratified-charge%20engine.pdf |title=32 (17) strat |access-date=2014-05-10 |url-status=dead |archive-url=https://web.archive.org/web/20130927033559/http://www.renault.com/en/Innovation/eco-technologies/Documents_Without_Moderation/PDF%20ENV%20GB/Stratified-charge%20engine.pdf |archive-date=2013-09-27 }}</ref> This results in a stratified charge: one in which the air/fuel ratio is not homogeneous throughout the combustion-chamber, but varies in a controlled (and potentially quite complex) way across the volume of the cylinder.

Charge stratification can also be achieved where there is no 'in cylinder' stratification: the inlet mixture can be so lean that it is unable to be ignited by the limited energy provided by a conventional spark plug. This exceptionally lean mixture can, however, be ignited by the use of a conventional mixture strength of 12-15:1, in the case of a petrol fuelled engine, being fed into a small combustion chamber adjacent to and connected to the main lean-mixture chamber. The large flame front from this burning mixture is sufficient to combust the charge. It can be seen from this method of charge stratification that the lean charge is 'burnt' and the engine utilising this form of stratification is no longer subject to ' knock' or uncontrolled combustion. The fuel being burnt in the lean charge is therefore not 'knock' or octane restricted. This type of stratification therefore can utilise a wide variety of fuels; the specific energy output being dependent only on the [[calorific value]] of the fuel.

A relatively rich air/fuel mixture is directed to the spark-plug using multi-hole injectors. This mixture is sparked, giving a strong, even and predictable flame-front. This in turn results in a high-quality combustion of the much weaker mixture elsewhere in the cylinder.