Subaru STi updates face new threat

THE escalating battle between Subaru and Mitsubishi for the hearts, minds and wallets of fast-four fanatics enters the next round in late September when the 2005 model year Impreza STi goes on sale.

Part of an MY05 update for the entire Impreza range, STi is by far the headline act, which considering its role as the flagship of the range is only appropriate.

STi’s combination of turbocharged performance, all-paw grip and rally heritage had been virtually unchallenged since it first appeared here as a limited edition in 1999 and then became a full-time member of the range in late 2001.

"Competitors come and competitors go, but WRX STi stays the course," was how Subaru Australia general manager Nick Senior summed it up at last week’s launch.

That’s an obvious reference to Mitsubishi, which dabbled in these waters in 2001 with the Lancer Ralliart Evolution VI Tommi Makinen Edition. Just 100 examples at a cool $79,990 barely caused a ripple for Subaru back then.

But Mitsubishi is back in 2004 with Evo VIII and starting to impinge on STi territory, even outpointing it in Motor magazine’s annual Bang for your Bucks performance comparison.

While currently a limited run import of 100, there are more Evo VIIIs on the way, with the promise it will become a full-time model from Evo IX time.

With pricing brought down from the stratosphere to $61,990 and a technical kit that includes an adjustable centre differential with snow, gravel and tarmac settings, Evo VIII is now a serious player in terms of price, performance and gadgetry.

So time for a response from Subaru, the cornerstone of which is a driver control centre differential (acronymed to DCCD), which allows the driver to dial up the preferred torque split in manual mode, or opt for auto mode and let the diff do the work for you.

In manual mode the DCCD can be adjusted from a locked 50:50 front/rear split up to a maximum of 35:65 torque split (front/rear). When in automatic mode, the DCCD uses input from a yaw rate sensor that ensures optimum torque split when cornering. A new front helical limited slip differential is added as well, with the aim of providing a more linear drive transfer.

"DCCD provides driver choice," said Subaru Australia technical manager Derek Ashby. "In open state it is more like a rear-wheel drive car. In 50:50 split it is more stable with a bit more understeer." Our brief sample on a wet slalom and then in the safe environs of Eastern Creek raceway in Sydney revealed that DCCD’s adjustability was very much noticeable.

Full rear bias produced tail-sliding fun, 50:50 lock a safe accuracy and auto meant on-the-run adjustability handled by the computer.

Our preference? Auto is the fast way around, a view shared by Australian rally champion Cody Crocker, who was on-hand on the day to demonstrate the system at its limit.

DCCD is not the only new STi weapon. There’s a smattering of other technical changes too:

• Wider eight-spoke 17x8-inch wheels.
  
  
• A ‘cannon mount’ steering rack.
  
  
• Rear track widens by 10mm thanks to new 225/45 Bridgestone Potenza tyres.
  
  
• Wheelbase lengthens by 15mm to 2540mm because of a revised rear suspension mount.
  
  
• An underfloor cover results in a 0.0006 drag cut.
  
  
• Damper valves added to reduce steering column kickback.
  
  
• Rear differential cushion spring rate is increased.
  
  
• Front suspension bracket housing strengthened.
  
  
• Front and rear suspension links are aluminium.
  
  
• Increased diameter front and rear sway bars.
  
  
• Unique wheel mounting and bearing design.
  
  

If you notice a theme emerging here that relates to handling, you’re dead right.

Chassis behaviour is an area where Evo VIII has been ranked ahead of the STi by independent testing and these moves are an obvious attempt to overcome that.

The proof Subaru supplies is a claimed maximum lateral g-force rating up from 9.4m/s2 to 9.7m/s2.

All that focus on chassis means life stays unchanged in the engine bay, where STi’s turbocharged 2.0-litre boxer engine continues to produce 195kW and 343Nm. That adds up to a 5.5 seconds claimed 0-100km/h dash and 13.8 seconds standing 400 metres.

Pricing for the STi will stay unchanged at $56,630, while the sales rate is also forecast not to alter much, staying around 40 per month.

STi versus Evo VIII

	STi	Evo VIII
Price	$56,630	$61,990
Power	195kW@6000rpm	195kW@6000rpm
Torque	343Nm@4000rpm	355Nm@3500rpm
Kerb weight	1470kg	1470kg
0-100km/h	5.5 sec	6.1 sec
0-400m	13.8 sec	14.5 sec