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Apprentice: understanding the MPPSK map
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==== Vanos settings ==== '''Ref''': [[DME_table_reference#Vanos_settings|Vanos settings]] The VANOS tables are lookups of load and RPM to VANOS ''setpoint'' (a value which modifies the valve opening time relative to the combustion cycle). To understand the VANOS changes, it helps to look first at the differences to stock. Stock values for the intake side are reduced by 1-5 degrees and there are no changes to the exhaust side. Reducing the intake values opens and closes the intake valve ''earlier''. The effect of this reduction is to increase valve overlap. There are no changes to the valve lift so the intake duration remains unchanged. In the graph below, the effect of valve lift would be to move the bell curve up or down. This does not change in MPPSK, which simplifies matters. [[File:vanos-1.png|Vanos overlap vs setpoint]] Vanos maps have a characteristic ''fisherman's chair'' shape. There are saddles in both the load and RPM axes with the minimums at about 70% load and 3500 RPM. As the car accelerates, load and RPM increase, so the setpoint will track diagonally across the map (and there is a saddle in that direction too). [[File:Mppsk-vanos-w2-wf.png|MPPSK intake setpoint]] Some properties of this are: # Typically the B58 idles at <20% load and 650 RPM. Here, the vanos setpoint is high. This ensures low valve overlap and thus a good idle. The MPPSK has a touch more overlap than stock, perhaps to make the idle sound more lumpy? # As soon as any load is put on the engine, setpoints drop, which increases overlap to improve the engine's efficiency and introduce the EGR required to reduce lethal NOx emissions to targets. # As RPM (and load) increase, the timing of the intake valve is retarded (i.e. the setpoints increase). The values are choosen (presuably correctly) to optimize cylinder charging and thus maximise power.
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