TDI-PD = Pumpe Düse
What is Pumpe Düse?
Pumpe Düse is a new fuel management and delivery system that places a pump injector at each individual cylinder producing a finer spray for better and more efficient combustion. Instead of a pre-combustion chamber found in most diesels, fuel is injected directly into each individual combustion chamber under terrific pressure at precisely the right moment.
The PD works like an overhead cam system, using cam lobes to determine the timing and amount of the spray into each cylinder. The new system reduces heat loss, results in a quieter, cleaner engine, faster cold weather starts and improved low-end torque
A diesel engine with the PD pump injection system has the following advantages over an engine with a distributor injection pump such as found on the original 1.9L TDI engine.
- Lower combustion noise
- Better fuel economy
- Cleaner emissions
- Higher performance and efficiency
In the Golf, Jetta and New Beetle, the 1.9L TDI-PD generates 100 HP and 177 lbs-ft of torque.
In the Passat models, the 2.0L TDI-PD generates 134 HP and 247 lbs-ft of torque.
Pump Injector Unit
To ensure efficient combustion, fuel must be injected in the correct quantity at the right time and at high pressure. Pumpe düse technology accomplishes this very effectively.
Let's focus on high pressure. In this pump injector drawing, the injection cam activates the injector pump piston with a roller-type rocker arm for high pressure injection.
By injecting the fuel at extremely high pressures (in the upper range of 2050 bar or 29 750 PSI) the highly atomised fuel will permit higer fuel burning efficiency resulting in lower emissions and cooler operation due to less wasted heat, thus resulting in lower fuel consumption increased performance.
In this animation, you can see the fuel being released by the pump injector. A cross section of the pump injector also shows the pump piston (in green) push downward at high velocity, ensuring a high injection pressure that is attained quickly.
The injection lobe, which is attached to the camshaft serves two purposes:
For the first phase, a small amout of fuel is injected into the cylinder through the first nozzle at lower pressure. This begins the burning process and also reduces the shock of the main injection cycle, thus resulting in quieter engine operation, especially when the engine is cold.
For the second, main injection phase the rest of the fuel quantity is injected at extremely high pressure, which is regulated by an electro-mechainical solenoid (or valve) which governs the exact timing and duration of the injection pulse. This time period is goverend by many factors through the main engine control unit (or ECU), which include engine speed and load, exhaust gas levels (obtained through the O2 sensor), EGR operation as well as both engine and ambient air tempratures.
This precise metering of fuel and the timing of the injection pulse gives the TDI-PD engine its tremendous efficiency and fuel economy as well as an almost imperceptible amount of visible exhaust emissions.