Operation
8135−1/A1
Winterthur Gas & Diesel Ltd.
1/ 5
Exhaust Waste Gate (Low-load Tuning)
1. General
The Low-load Tuning (LLT) gives the lowest possible Brake Specific Fuel
Consumption (BSFC) in the range of 40% to 70% engine load (see Fig. 1 for the
schematic diagram of the LLT function).
With LLT, engines can operate continuously at all loads in the range of 30% to 100%.
The LLT uses a specially designed turbocharger system and specified engine
parameters. These parameters are related to fuel injection and exhaust valve control
and get the best decreased part-load BSFC in LLT.
Engines with LLT have an exhaust waste gate installed (i.e. a pneumatically operated
valve on the exhaust gas manifold upstream of the turbocharger turbine). Exhaust
gas blown through the waste gate flows to the exhaust uptake.
The LLT uses a turbocharger for part-load operation. The combustion pressure is
increased at less than 75% load through an increased scavenge air pressure (waste
gate closed). The waste gate opens at engine loads of more than 85% to prevent
damage to the turbocharger and the engine from overload.
The higher scavenge air pressure at part-load causes a decrease in the thermal load
and thus, better combustion for the full part-load range.
The engine parameters that control the fuel injection and exhaust valve operation are
selected to make sure that the applicable NOx limit is obeyed.
The specified parameters make sure that the waste gate opens and closes smoothly
throughout the full range. But, higher scavenge air pressure increases NOx
emissions. Thus, to get the correct value for the test cycle, it is necessary to adjust
the parameters for the scavenger air pressure increase.
WASTE
GATE
AIR
EXHAUST
EXHAUST GAS MANIFOLD
SCAVENGE AIR RECEIVER
ENGINE
TURBOCHARGER
Fig. 1: Schematic Diagram Exhaust Waste Gate
2014
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