36
Engine management
The Bosch MED 9.1.2 measures load by means of the intake mani-
fold pressure sender G71 and the engine speed sender G28.
The target for emission classification was compliance with exhaust
emission limits EU 5. This was achieved by using the following
subassemblies in combination with special injection and catalyst
heating strategies:
• Intake manifold with intake manifold flaps
• Multi-port injectors in combination with flat pistons
• Close-coupled pre-catalyst
A secondary air injection system was not needed.
451_053
Combustion process
The basis for the development of the combustion process was the
Audi 2.0 litre TFSI engine. Like this engine, the 2.5 litre TFSI unit
benefits from the acknowledged advantages of multiport valve
technology, as shown in diagram 451_053.
Optimised tumble intake port
Spray-optimised six-port high-
pressure injector
Flat-crown piston
Operating modes
The following operating modes are possible:
• High-pressure stratified starting down to an ambient tempera-
ture of -26 °C
• Catalyst heating and engine warm-up with twin injection
• When the engine is warm and running at low rpm, the amount
of residual gas in the cylinders is minimised by high scavenging
rates, achieved by adjustment of the intake and exhaust cam-
shaft phasings and by adaptation of the valve timings and event
duration*.
In the upper rpm band, the entire system is optimised for high
flow rates. In this regard, it is essential that the intake, pressure
and exhaust lines be carefully matched and optimised for pres-
sure losses.
By optimising the spray parameters in combination with a flat pis-
ton crown shape, it was possible to improve carburetion compared
to the 2.0 litre TFSI engine, despite the approx. 25 % increase in
the flow rate of the high-pressure injectors.
