Volvo Turbocharger Technology: VGT vs. Fixed Geometry Systems.

Turbocharger Technical Summary

Volvo engines utilize two primary types of turbochargers to ensure performance and emissions compliance: Variable Geometry (VGT) and Fixed Geometry.

1. Variable Geometry Turbocharger (VGT)

The VGT is a highly versatile component designed to optimize engine behavior across all RPM ranges.

Primary Function: Provides boosted air to ensure peak performance and strictly adhere to emissions standards.

System Integration: It creates the necessary back pressure to drive the Exhaust Gas Recirculation (EGR) system and provides boost for engine braking.

DPF Support: During regeneration, the VGT restricts exhaust flow to increase temperatures for the Diesel Particulate Filter (DPF).

Smart Control: It features a magnetic speed sensor connected to the Engine Control Module (ECM) and uses an electronic actuator to adjust nozzle positions.

Cooling: Unlike fixed models, the VGT requires multiple oil and coolant lines to service the actuator and bearing housing.

2. Fixed Geometry Turbocharger

The fixed geometry model offers a streamlined design focused on reliability and efficiency.

Simplified Design: This version does not use an electronic actuator or coolant lines, relying solely on engine oil for lubrication and cooling.

MWE Technology: It utilizes Map Width Enhancement (MWE) design, splitting inlet air into two areas to maintain efficiency at both low and high RPM.

Advanced Bearings: Traditional journal bearings are replaced with a high-performance ball bearing cartridge.

Pneumatic Control: When equipped with a wastegate, the system uses a pneumatic actuator controlled by the Air Valve Unit (AVU) and the ECM.

3. The Wastegate Function

For engines with fixed geometry, the wastegate is critical for protecting the system during high output.

Load Limitation: The wastegate acts as a bypass valve, diverting a portion of exhaust gases directly to the exhaust pipe to reduce turbine load.

Boost Management: The ECM monitors boost pressure via the intake manifold sensor and commands the AVU to open the wastegate once a set pressure value is reached.

Operational Benefits: This regulation results in high torque across a large working area and prevents power loss when operating at high altitudes.