Targa Topping STi

 

Targa Tasmania is arguably one of the toughest motorsport events in Australia and has claimed countless exotic vehicles. It’s an achievement to merely cross the finish line on all four wheels but it’s quite another to score in the top five. And, even more incredible, do it in a Subaru STi that has relatively few mods!

Step aside race-prep’d Porsches and purpose-built race machines – this tweaked Subaru sedan is comin’ through!

Of course, it takes a pretty exceptional driver to wring so much speed from a mild-mannered STi. And that driver is none other than Tony Longhurst – two time Bathurst winner, winner of Sandown and long-time touring car/V8 supercar campaigner. So this isn’t your average helmsman...

Tony bought this MY05 Subaru Impreza STi brand new with the intent of entering Targa.

“I really wanted to get a STi Spec C which is lighter and better suited for Targa but, at the time, I wasn’t allowed,” Tony says.

“So I bought an Australian spec STi, ran it in - to about 5000 or 6000 kilometres - and gave it some little mods for its first year in the event. Working with Possum Bourne Motorsport and Subaru Docklands, it was remapped to suit Elf fuel, a bolt-in roll cage went in and some circuit tyres were fitted. That year, in 2005, we came ninth outright.”

That was a stunning result for a near-stock Subaru so, for ’06 Targa, Tony decided to up the ante...

Brisbane’s C-N-J Motorsport can be thanked for the subtle engine upgrade. An Autronic SM4 replacement board has gone into the ECU case and, in addition to providing fuel, ignition and boost control, it incorporates a launch control function. This helps Tony pick up valuable seconds of race time in the first few hundred metres of competition. The only other engine mod is a custom thin-wall exhaust with a metal cat, centre resonator and titanium rear muffler. Class regulations require that the standard dump pipe is retained.

Bill from C-N-J Motorsport says one of the difficulties tuning a CM22 class vehicle is that a post-intercooler intake air temperature sensor is not allowed – instead, intake air density calculations must be derived from the airflow meter which is oblivious to heat soak and the performance of the intercooler. Interestingly, the STi Spec C is factory fitted with an intake air temp sensor in the intake manifold – this alone would help extract more performance from the engine.

With Elf race fuel and boost pressure set to a steady 18 psi (as allowed by regulations), Tony’s STi puts out around 200kW at all fours wheels together with an excellent spread of torque. A 20 percent stiffer pressure plate, lightweight flywheel and a high quality full-face organic clutch eliminate driveline problems during those hard-fought stages.

According to Tony, the car could lose some weight as it currently tips the scales at around 1470-1480kg (including a full tank of fuel). Keep in mind the interior remains intact except for the removal of the rear seat. The interior is also competition prep’d with Racetech carbon fibre front seats, Sabelt harnesses, an Autotecnica wheel and Terratrip computer.

Targa Tasmania is an event that’s extremely unforgiving of vehicles which are set up for circuit work and have minimal suspension travel. With this in mind, Tony had a set of ProFlex adjustable struts (complete with external fluid reservoirs) fitted. The ProFlex struts give an incredible amount of adjustment and Tony often changes the settings for different stages – for example, on the bumpier stages he generally selects a slightly softer setting. Interestingly, the STi’s centre diff controller is best kept in its auto setting – playing around with it just messes things up.

“The car has ample suspension travel and I generally leave it fairly high – about the standard ride height. I’m really happy with it. It’s compliant, predictable and quick,” Tony says.

Tyre wear is kept manageable with some clever wheel alignment settings which also combine to achieve maximum cornering grip. Tyres are Bridgestone semi-slicks worn on 17 x 8.5 inch Enkei Racing alloys. Tony says there’s excellent grip over coarse bitumen though they are a bit slippery in the wet stages.

So what areas are there for improvement?

Well, the factory Brembo brakes are mightily powerful but, unfortunately, the discs and pads chew out over the course of the event. Targa ’06 consumed two sets of AP grooved discs and three sets of pads. And don’t ask what type of pads are used – that’s a secret.

“Coming fourth outright and first in the class, we [Tony and his co-driver Michael de Vere] finished behind two Porsches and a Lambo,” Tony says.

“It’s only really the uphill stages where the car falls behind – downhill and in the twisty sections it’s very competitive.”

With this in mind, Tony says the next logical step for the car is to remove about 100kg and/or give it more power. The chassis can certainly handle it. But rather than pursue the Number One spot in this particular car, Tony is now preparing a STi Spec C – the car he wanted all along.

Time to go Lambo bashing!

Contact/Thanks:

C-N-J Motorsport +617 3290 3966

www.cnjmotorsport.com.au

Tony would like to thank C-N-J Motorsport, Exide batteries, Budget Car and Truck Rentals and Murray Coote.