Audi TT (2007 year). Manual — part 223

25

Fuel supply

The fuel system is basically adopted from the A3 `04.
The fuel tanks differ from one another in terms of their shape, which is dependent on the vehicle's drive
concept.
They are made of HPPE (high-pressure polyethylene). To safeguard the fuel tank against destruction in the
event of an accident, it is mounted in front of the rear axle. Here it is fixed to the underbody by means of
ratchet straps. It is not necessary to disassemble the rear axle to remove the fuel tank. The front tank has
a capacity of 55 litres, the quattro tank 60 litres.The US spec quattro tank has a capacity of 55 litres, because
a different breather system is used due to the different statutory requirements which apply.

Fuel tank
breather pipe

Breather pipe

Fuel delivery unit

Fuel filter

Breather pipe

to tank

Front tank

Fuel tank
breather pipe

Breather pipe

Fuel delivery
unit

Fuel filter

Breather pipe

to tank

quattro tank

Suction jet pump
(entrainment pump)
+ 2nd fuel tank sender

380_020

380_001

26

Engine

Pressure regulation

The fuel filter is bolted to the exterior of the fuel tank. The pressure regulator is integrated in the fuel filter.
In case of excess pressure, the governed fuel is returned to the tank. The pressure regulator in the FSI engine
cuts off fuel delivery at 6.4 bar (relative). In the case of the MPI engine, fuel cut-off is at 4 bar (relative). Both
systems are returnless, with the distinction being that the pressure in the MPI engine is maintained at
a constant 4 bar, while the FSI engine utilises a supply-on-demand fuel system.

380_021

For the MPI and FSI engines, a fuel delivery unit with
integrated fuel gauge potentiometer and a suction
jet pump are arranged inside the fuel tank.

Fuel gauge sender

Fuel pump

Suction jet pump

In the case of the quattro tank, a second fuel gauge
potentiometer is arranged inside the second half of
the fuel tank.The second half of the fuel tank also
houses the suction jet pump, which pumps the fuel
into the fuel delivery unit reservoir. The suction jet
pump is attached securely to the sender flange by
means of clips. The thin line is the propulsion jet
line. It is driven by the suction jet pump. The thicker
line is the mixing tube, in which the intake fuel is
pumped to the fuel delivery unit.
The fuel gauge senders are configured as slider
potentiometers.

380_023

Suction jet pump

Fuel gauge sender

Reference

Pressure regulation in the 3.2l and
2.0l engines is described in Self-
Study Programme 290 and Self-Study
Programme 332 respectively.

27

Fuel tank breather system, ROW spec (2.0l and 3.2l engines)

Fuel tank breather system, US spec (2.0l and 3.2l engines)

Activated charcoal canister

Engine connection, fuel

Tank connection, breather

Tank connection, fuel

Activated charcoal canister

Engine connection, fuel

on 3.2l engine only

Tank connection, breather

Fuel system diagnostic pump

380_034

on 3.2l engine only

380_033

Tank connection, fuel

28

Engine

Soundpipe

A soundpipe is used on the 3.2l V6 engine to give the engine a sportier sound. The intake noise is transmitted
to the vehicle body via a connecting line from the intake manifold to the plenum chamber and via a resonator.

The soundpipe has been developed to accentuate the dynamism and sportiness of the 3.2l engine
The soundpipe produces a sporty sound in the vehicle interior without impairing comfort. The pressure
pulsations are amplified by the gas exchange cycle via the soundpipe without exceeding the exterior noise
limits. Unwanted noise emission from ancillary units and tire noise are to a large extent avoided by the fact
that the occupant cell is well-insulated. As a result, comfortable travelling is still possible.

Secondary pipe

Sound generator

Primary pipe

380_014

Air filter