New Generation N62 Engine
Chapter 3 P.5
Course Contents/Background Material
© BMW AG,
Service Training
The volumetric efficiency of the engine cylinders is determined
by physical processes which occur in the intake pipe while the
engine is running.
For optimum filling in every speed range, the engine needs an
intake manifold with different intake path lengths.
Long intake paths for low engine speeds, and short intake paths
for high engine speeds. Until now, the intake pipe length was
determined by the torque curve or output requirements.
Previously, if a good torque was needed at low engine speeds,
the engine was fitted with a long intake pipe. The consequence
was a poorly-running engine with insufficient end output.
If the emphasis is on a lively, high-capacity engine, a short intake
pipe is needed.
A fixed length intake pipe, therefore, is a compromise.
The introduction of the diversified intake manifold (DISA) has
made it possible to adjust the intake pipe to form a long or short
intake path, using a flap in the intake manifold.This variable
facilitates good torque curves as well as very good engine
output in the higher speed ranges.
With the N62, a variable intake manifold is used for the first time.
It ensures that the intake path is always the optimum length for
the engine speed, thus ensuring the best possible volumetric
efficiency.
