LE MANS-HONED FSI TECHNOLOGY REACHES AUDI A4
The FSI petrol engine technology which enabled the Le Mans conquering Audi R8
sports cars to race harder and longer between fuel stops becomes available for
the road-going Audi A4 from this week. The new combustion system brings lower
exhaust emissions, improved fuel economy and increased power and torque compared
with an equivalent, conventionally injected
engine.
The new Audi A4 2.0 FSI can be ordered now for £19,565 OTR in saloon
form or £20,695 OTR as an Avant. Positioned between the continuing 130bhp
2.0 model, over which it carries a price premium of £925, and the revised
163bhp 1.8 T,
the newcomer strikes an even finer balance between performance, fuel economy
and emissions than both of the above. The traditional rules dictating that an
increase in power must go hand-in-hand with a downturn in economy, or vice versa,
do not apply here.
With 150bhp and 200Nm of torque, the FSI saloon can reach 62mph from rest in
9.6 seconds and continue to a 135mph maximum speed, yet at the same time is
capable of covering just under 40 miles per gallon of petrol (combined
cycle).
In the interest of the environment, and UK company car drivers, the control
of emissions has been considered just as carefully in the design of this engine
as the optimisation of power and fuel consumption. An under-bonnet three-way
converter behind the manifold and a NOx storage-type converter under the floor
pan help to achieve an impressively low CO2 output of
170g/km (A4 2.0 190g/km)
This exceptional trade-off between power and economy, which is currently unrivalled
in the compact executive class, is achieved by an advanced lightweight aluminium
four-cylinder petrol engine which, unlike the majority
of its rivals, is directly fuel injected to maximise efficiency. Fuel is delivered
straight to the cylinders by a high-pressure common rail injection system supplied
by a single-piston injection pump - rather than into the
intake manifold, as is the case with most petrol engines.
This common rail technology, which has traditionally been confined to diesel
units, is combined with other special features to enable the engine to operate
in two ‘modes’. When a high power output is required, the electronics
select the homogeneous mode, which is the normal operating state for conventional
indirect injection engines. Even in this mode, the FSI
engine holds an advantage over less advanced petrol units in that it leaves
no fuel unburned - the mixture is completely vaporised in the combustion chamber
for greater efficiency.
At normal cruising speeds, under part load, the engine switches to ‘stratified
charge’ operation. In this state, the air, or ‘charge’, is
directed extremely accurately towards the spark plug using the ‘tumble’
principle, created by a tumble flap within the intake manifold and a specially
shaped bowl in the piston crown.
Fuel is injected only in the piston’s compression phase, rather than during
induction as is the norm, and is placed in the tightly controlled stream of
intake air moving towards the spark plug. The combustible mixture is therefore
only present in a restricted area of the combustion chamber, surrounding the
spark plug, and injection takes place at a very shallow
angle, minimising the potential for losses.
For the best possible engine efficiency, and therefore lowest fuel consumption,
ultra- low sulphur or sulphur-free fuel is recommended for use in FSI-powered
models. However, the new engines are also designed to run on 98RON super unleaded
or 95RON unleaded with virtually no losses in performance or economy.
The new A4 2.0 FSI saloon and Avant are the latest models to be rolled out
as part of the ongoing Audi FSI programme, which began with the 110bhp, 1.6
FSI version of the A2 variable compact. First UK deliveries of all three
models will begin in early September.
The power outputs of the 1.8 T petrol and 2.5 TDI engines in the A4 saloon and
Avant range have been increased to 163bhp in both cases, up from 150bhp in the
original 1.8 T and 155bhp in the outgoing 2.5 TDI. Performance
figures have increased accordingly
These power upgrades are effective immediately, and both revised models are available to order now.