What is the effect of engine management systems?
Engine management systems are now an important part of the strategy to
reduce automotive pollution. The good news for the consumer is their
ability to maintain the efficiency of gasoline combustion, thus
improving fuel economy. The bad news is their tendency to hinder tuning
fog power. A very basic modern engine system could monitor and control:-
mass air flow, fuel flow, ignition timing, exhaust oxygen ( lambda
oxygen sensor ), knock ( vibration sensor ), EGR, exhaust gas
temperature, coolant temperature, and intake air temperature. The knock
sensor can be either a non-resonant type
installed in the engine block and capable of measuring a wide range of
knock vibrations ( 5-15 kHz ) with minimal change in frequency, or a
resonant type that has excellent signal-to-noise ratio between 1000 and
5000 rpm.
A modern engine management system can compensate for altitude, ambient
air temperature, and fuel octane. The management system will also
control cold start settings, and other operational parameters. There is
a new requirement that the engine management system also contain an
on-board diagnostic function that warns of malfunctions such as engine
misfire, exhaust catalyst failure, and evaporative emissions failure.
The use of fuels with alcohols such as methanol can confuse the engine
management system as they generate more hydrogen which can fool the
oxygen sensor.
The use of fuel of too low octane can actually result in both a loss of
fuel economy and power, as the management system may have to move the
engine settings to a less efficient part of the performance map. The
system retards the ignition timing until only trace knock is detected,
as engine damage from knock is of more consequence than power and fuel
economy.
This article is from theGasoline
FAQ,
by Bruce Hamilton with numerous contributions by others.
Read more:http://stason.org/TULARC/vehicles/gasoline-faq/7-5-What-is-the-effect-of-engine-management-systems.html#ixzz1hkgY0qdP
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