Killer GTS Coupe

The HSV GTS Coupe is king of the LS1-powered monsters in Australia. Its sexy profile combines with Calloway C4B grunt (all 300kW of it!) to create a package that has car enthusiasts tripping over their tongues.

You just want one?

Sure. Come and join us near the back of the queue!

One of the first people on that queue for a new GTS Coupe was Doug X of Queensland. Since first laying eyes on the mighty Coupe, Doug had been preparing mental notes on what he thought could be done to ‘take it to the next level’.

After discussions with John Whittaker of Brisbane Tuning and Turbo Centre, a full-scale attack was launched on the new HSV. John says everything was done in one big hit – there were no dribs and drabs modification here!

Not wanting to pull apart the Calloway engine, Doug decided bolt-on products were the way to go. A big ‘800hp’ version of the latest Vortech supercharger is bolted to the front of the block using parts supplied in an off-the-shelf CAPA kit. Brisbane Tuning and Turbo has modified the CAPA kit to incorporate a Gilmer belt drive system and an in-house developed water injection system with a high-pressure electric pump.

With the big Vortech whirring to the tune of 12 psi and a relatively high 9.8:1 static compression ratio, an effective intercooler is essential. The CAPA air-to-air intercooler kit is installed with custom mandrel bent and polished plumbing. Heat exchange is further helped along with fitment of a nitrous spray bar. The spray is triggered by the programmable management system and a manual switch which opens the bottle. The large nitrous bottle can be found in the boot.

With 5.7 litres of boosted C4B, you’re talking a lot of gas flow. Brisbane Tuning and Turbo has fabricated a set of big-bore headers leading into a twin 3 inch mandrel system with high-flow cats and mufflers. Nice. Very nice!

On the intake side, a K&N pod filter inside the front left guard protects the compressor, there are twin Bosch Motorsport blow-off valves and a 78mm HSV throttle body feeds the stock intake manifold.

Not afraid to spend bux where it’s needed, Doug ripped out the factory engine management system and whacked in a top-line MoTeC M800 programmable unit. This controls a set of huge 1000cc injectors working with modified rails, bigger lines, a surge tank and a ‘1000hp’ pump fed by a low-pressure lift pump. Not much is left of the standard fuel system.

All of this is hung on the back of a bog-stock C4B engine. The C4B engine already boasts CNC-ported heads, an aggressive cam and upgraded valvetrain – a major advantage over lesser model LS1s.

Brisbane Tuning and Turbo carefully programmed the M800 management system to provide as much power as possible while still allowing detonation-free use of 98 RON pump fuel. The fuel and ignition maps were tickled until the in-house Dyno Dynamics chassis dyno showed a sizeable 423kW at the treads. Peak power is reached at around 6100 rpm and there’s good, useable torque through the rev range. An aftermarket oil cooler and power steering cooler have been added to ensure temps stay out of the red.

The stock Holden/HSV driveline is strong bugger and there hasn’t been any need to upgrade the stock T56 ‘box. The clutch is a custom Brisbane Tuning and Turbo part and the stock Hydratrak diff has been exchanged for a KAAZ mechanical type unit with a 3.9:1 ratio (the same as standard). A modified tailshaft and new rear axles are also installed.

Rather than mix ‘n’ match suspension components, Doug’s GTS Coupe runs coil-overs, swaybars and bushes the same as used in Peter Brock’s Targa race car. Brisbane Tuning and Turbo can be thanked for sourcing the parts and installation. The Targa suspension set-up provides a liveable ride together with excellent balance – as you’d expect.

Brake-wise, huge six-pot HSV front calipers team with DBA slotted and drilled replacement discs and competition pads to ensure powerful braking. The rears are standard HSV four-potters with less aggressive aftermarket pads.

But forget about the lowered stance and muscular looking brakes – this machine never fails to grab attention with its yellow paint, abundant carbon fibre and Supercar-style rear wing.

Brisbane Tuning and Turbo farmed out the job of laying up a new carbon bonnet (with vents which are effective in cooling the intake manifold), front splitter and Group A under-body rear diffuser. It’s all custom and magnificently finished. The wiper arm surround panel, mirrors, front engine bay trim, valve covers, fuse box and front strut bar are a mixture of genuine and imitation carbon fibre. And the rear wing? Well, let’s just say it arrived together with a reinforced boot from a very high profile race car.

Keen Holden fans might recognise the 18 inch wheels. These are the same as slated for fitment to the stillborn 427ci (7-litre) production coupe and are clad in Dunlop road/race rubber.

Inside, the trim is pretty much stock HSV GTS with splashes of aftermarket carbon fibre trim. A boost gauge and nitrous level gauge are hidden away from prying eyes.

So where to next for this road-reg supercar?

Well, at the time of writing, a competition sump and diff cooler were being stirred into the mix and there are discussions about upping the cubic capacity count with an alloy 427ci-er. Doug plans to build the car that HSV never had the guts to carry through with.

Oh, and we should mention that Doug has also bought a new HSV Coupe 4 (AWD) that won’t stay standard for very long...

Contact: Brisbane Tuning and Turbo Centre +61 7 3393 1588

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