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