This article was first published in 2006.
Fitzgerald’s Audi S4 is one of the best modified street cars we’re ever
talking about huge, inaccessible power figures. The tweaked Audi bi-turbo is on
boost the moment you breathe on the throttle; its real-world performance is
scorching. Don't bother watching the tacho - just nail it and go!
The re-valved suspension gives a refreshingly comfortable ride –
completely in keeping with the luxury feel of the car. The
free-flow exhaust system is quiet and free of annoying drones. The quattro
all-paw drive and electronic stability control add to the feeling of comfort and
only dislike was the heavy action of the short-shift mechanism. Mr Fitzgerald
answers this by pointing out you can easily reduce the number of gear shifts. He
suggests shifting from first to third to fifth gear - and the engine sure as hell has
enough torque to do it...
Rewind to 1999 for a moment. The Audi S4 was
released in Australia featuring quattro four-wheel-drive and a new
five-valves-per-cylinder 2.7-litre V6 with twin turbochargers. With its 195kW and
400Nm from 1850 to 3600 rpm, the ’99 S4 was hailed one of the most rapid saloons
in the world – claimed 0 – 100 km/h was 5.6 seconds.
The only problem was the AUD$113,800 price of
Today, the Audi S4 bi-turbo is still regarded as a
genuine performance saloon – the biggest difference is you can pick up a
second-hand model from around AUD$60,000. And now that it’s out of factory
warranty, there’s nothing to stop you tweaking it for even more speed; that
bi-turbo engine is waiting to be unleashed!
Peter Fitzgerald, one of Australia’s most awarded
drivers of the last 25 years, is one of the few people to recognise the
potential of the twin-blown Audi.
“I bought the S4 as a road car because I had owned
a Merc CLK430 and BMW 540i and I was used to having a bit of punch.
“I researched the S4 and, after taking some for
test drives, I was quite impressed.
“The Audi also had the Euro heritage and feel to
it. It was a little bit unique,” Mr Fitzgerald says.
But, after purchasing a discounted example with a
few cosmetic scratches, the standard performance of the S4 soon dulled.
“I know that Audi claim 5.6 seconds 0 to 100, but
with 195kW and 1600kg I think that’s a bit optimistic. To me, it didn’t feel
that quick – it wasn’t super outstanding - but it did have the torque to make it
really nice to drive in the city.”
At this point, Mr Fitzgerald turned his attention
to modification - and the first step was to obtain a baseline power figure. In
stock form, power at the wheels was 117kW (measured on a Dyno Dynamics AWD
The first upgrade was the fitment of a Remus
cat-back stainless exhaust. According to Mr Fitzgerald, the Remus system gave a
good power gain (about 13kW at the wheels) but failed to deliver the note he was
chasing. He later added a Miltec front section of exhaust which bolts to the
back of the turbos and includes a 100 cell stainless cat converter. Mr
Fitzgerald fabricated a joiner section to mate the Miltec and Remus systems.
Meanwhile, the air intake had also been upgraded.
Mr Fitzgerald fitted an Evo Motorsport cold air kit and revised the plumbing to
deliver the most consistent intake temperatures possible. Using a digital temperature
probe, Mr Fitzgerald has measured intake
temperatures that rarely rise 5 degrees Celsius above ambient. A conical air filter
was also installed as part of the upgrade.
After being treated to its free-flow exhaust and
cold air intake, the V6 engine spat a water pump – according to
Mr Fitzgerald, a common problem. So, while repairs were being carried out, the opportunity was
taken to replace the standard crank-driven cooling fan with an electric thermo
fan. This might help achieve slightly more power.
An ECU tune was next on the agenda but dyno
testing at this time showed there was something amiss in the Audi’s engine bay.
Fault-finding revealed some deteriorated boost/vacuum hoses and a broken airflow
meter. Once these were replaced, PowerChip retuned the factory ECU to deliver a
fat torque increase across the rev range.
This graph shows the current output (plotted in
dark blue) reaching 174kW at the wheels. The pink plots show the output when
there were problems with the airflow meter and under-bonnet hoses. In total, the
changes to Mr Fitzgerald’s S4 have achieved around 40 percent more power.
Flywheel output is estimated at around 260 – 270kW.
But this car isn’t all about power.
Handling is improved with the fitment of
aftermarket suspension and wheels. A set of H&R replacement struts were
fitted but these have since been re-valved to deliver a more comfortable ride.
Mr Fitzgerald says the suspension is around 10 – 20 percent stiffer than the
factory-tweaked Audi RS4. The standard wheels have also stepped aside for 18
inch BSA alloys wearing Falken tyres. These are left-over wet weather race
In standard form, the S4 has plenty of visual
bling – just look at its high-fashion aluminium mirrors – but Mr Fitzgerald’s
example has some extra eye-catching appeal. The big wheels, lowered stance,
Remus exhaust tips and tinted windows are all that’s needed. A respray has also
eliminated the scratches caused by the previous owner.
Inside, the S4 comes with leather Recaro seats,
full instrumentation and equipment. Mr Fitzgerald’s example is fitted with black
trim - other examples he drove had a light colour trim which showed more signs
of wear. The only interior change is an Evo Motorsport short-shift.
At present, Peter is considering fitting a RS4
body kit (which will mean hacking off part of the rear bumper), RS4-type
turbochargers, improved intercoolers and bigger injectors. There’s
immense potential - 300kW seems like a pretty achievable goal... And all in a car that one of the sweetest we've ever driven!
Fitzgerald Racing Services
+61 3 9897 1555