Garret Gt 2260 V Variable Geometry Turbosupercharger; General; Operation At Low Engine Rpm; Operation At High Engine Rpm - Iveco daily euro 4 Repair Manual

D E 4
AILY URO
542410 GARRET GT 2260 V variable
geometry turbosupercharger

General

The variable geometry turbosupercharger consists of the
following:
- centrifugal supercharger (1);
- turbine (2);
- set of mobile blades (3);
- mobile blade control pneumatic actuator (4), vacuum
controlled by proportional solenoid valve controlled by
EDC 16 ECU.
Variable geometry enables:
- to increase the speed of the exhaust gases running into
the turbine at low engine rpm;
- to decrease the speed of the exhaust gases running into
the turbine at high engine rpm.
To obtain the max. engine volumetric efficiency also at low
rpm (with on-load engine).

Operation at low engine rpm

Figure 309
1. TURBINE - 2. MOBILE BLADES - 3. PNEUMATIC ACTUATOR - 4. REVOLVING RING
When engine is running at low speed, the exhaust gases
show weak kinetic energy; under these conditions a
traditional turbine shall rotate slowly, thus providing a limited
booster pressure.
In the variable geometry turbine (1), the mobile blades (2) are
set to max. closed position and the small through-sections
between the blades increase the inlet gas speed. Higher inlet
speeds involve higher tip speeds of the turbine and therefore
of the turbosupercharger.
Engine speed increase results in a gradual increase of exhaust
gas kinetic energy, and also in turbine (1) speed and booster
pressure increase.
Print 603.93.651
Figure 310

Operation at high engine rpm

Figure 311
62870
The ECU, through the actuator control solenoid valve,
modulates the vacuum acting on the diaphragm, so actuator
(3) controls through the tie rod, the gradual opening of the
mobile blades (2) until reaching the max. open position.
Blade through-sections results larger thus producing a speed
decrease in exhaust gas flow through the turbine (1) with
speeds equal to or lower than those of the low rpm
condition.
Turbine (1) speed is therefore adjusted to a proper value
enabling suitable engine operation at high speeds.
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F1C ENGINE
82871
62872
Base - March 2006