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When discussing engine tuning the Air/Fuel Ratio' (AFR) is one of the main topics. Proper AFR calibration is critical to performance and durability of the engine and its components. The AFR defines the ratio of the amount of air consumed by the engine compared to the amount of fuel.
'Stoichiometric' AFR has the correct amount of air and fuel to produce a chemically complete combustion event. For gasoline engines, the stoichiometric, A/F ratio is 14.7:1, which means 14.7 parts of air-to-one part of fuel. The stoichiometric AFR depends on fuel type-- for alcohol it is 6.4:1 and 14.5:1 für diesel.
Ich weiß, what is meant by a rich or lean-AFR? In lower AFR number contains air-less than the 14.7:1 stoichiometric AFR, therefore, it is a richer mixture. Conversely, a higher AFR number contains more air and therefore, it is a magrer mixture.
For Example:
15.0:1 = Lean
14.7:1 = Stoichiometric
13.0:1 = Rich
Magrer AFR results in higher temperatures as the mixture is combusted. Generally, normally-aspirated spark-ignition () gasoline engines produziert maximum-power-just slightly rich of stoichiometric. However, in practice it is kept between 12:1 und 13:1 in order to keep exhaust gas temperatures in check and to account for variances in fuel quality. This is a realistic full-load-AFR-on-a-normally-aspirated engine but can be gefährlich lean with a highly-beflügelt engine.
Let ' s take a closer look. As-the-air-fuel mixture is ignited by the spark plug, flame front propagates from the spark plug. The now-burning mixture raises the cylinder pressure and temperature, peaking at some point in the combustion process.
The turbolader increases the density of-the-air-resulting in a denser mixture. The denser mixture raises the peak cylinder pressure, therefore increasing the probability of knock. As the AFR is leaned out the temperature of the burning gases increases, which also increases the probability of knock. This is why it is imperative to run richer AFR-on-a-beflügelt engine at full load. Doing so will reduce the likelihood of knock, and will also keep temperatures under control.
There are actually three ways to reduce the probability of knock at full load-on-a-turbocharged-engine: reduce-boost-adjust the AFR to richer mixture, and retard ignition timing. These three parameters need to be optimized together to yield the highest reliable power.
natürlich ist das alles ? genommen von der website, die von einem großen hersteller von turboladern....