Direct Petrol Injection System with Bosch Motronic MED 7 - Volkspage

Test your knowledge
1. What are the advantages of the direct petrol injection system
In lean operating modes, the throttle valve is opened wider and air can be drawn in against
less resistance.
Heat is extracted from the intake air by directly injecting the fuel into the cylinders,
so allowing the compression ratio to be increased.
The direct petrol injection system allows the engine to be operated at an air/fuel ratio up to
lambda = 3.
2. When is fuel injected during stratified charge operation, in homogeneous lean operation
and homogeneous operation
In all three operating modes, fuel is injected during the intake stroke.
Fuel is injected during the intake stroke when the engine is operated in stratified charge mode
and during the compression stroke when the engine is operated in homogeneous lean charge
mode and homogeneous charge mode.
Fuel is injected during the compression stroke when the engine is operated in stratified charge
mode, and during the intake stroke when the engine is operated in homogeneous lean charge
mode and homogeneous charge mode.
3. What do the terms stratified charge, homogeneous lean and homogeneous mean
"Stratified charge" means that the mixture is located in the region of the spark plugs and is
enveloped by a layer of fresh air and recirculated exhaust gases.
"Homogeneous" means that the mixture forms shortly before ignition.
"Homogeneous lean" means that a lean mixture is evenly distributed throughout the
combustion chamber.
4. Why is the throttle valve not opened fully when the engine is operated in stratified charge
mode
Because the hydrocarbon and carbon monoxide emissions would otherwise be too high.
Because a certain vacuum must always be present for the activated charcoal canister and
exhaust gas recirculation systems.
Because the engine torque is controlled via the quantity of fresh air and the engine does not
require as much air at low loads and speeds.
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