The roller bearings reduce mechanical friction
within the turbocharger to a minimum. The
charger therefore responds more readily and
reaches its maximum speed of up to 169,000
rpm more rapidly.
How electronic charge pressure control
optimises responsiveness
With a maximum charge pressure of 2.1 bar
(1.9 bar in the basic version), the 2.0-litre turbo
engine is also the top performer in this respect.
The electronically controlled wastegate (exhaust
relief valve) allows the charge pressure to be
controlled even more precisely and flexibly
while optimising responsiveness, especially
when accelerating from partial load. Numerous
parameters are taken into account in this
process.
The main input signals for the wastegate
control unit are the charge pressure, throttle
flap position and the knocking tendency.
The modifying signals include the intake air
temperature, engine temperature, engine speed
and atmospheric pressure.
This also makes temporary boosting of the
charge pressure (overboost) possible under
acceleration. Fresh air is used in addition to oil
and water to cool the turbocharger.
This is directed specifically to the charger from
the radiator grille, via the engine cover designed
as an air deflector and ducts beneath the
bonnet.
The concept is based on the principles and
experience gained with the cooling for the
internally mounted turbochargers of the current
AMG 4.0-litre V8 engines, starting with the AMG
GT in 2014. In addition the turbine housing has
integral insulation.
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PECM Issue 41