Archie X of Sydney is very controlled person. You might argue that his monster power XR6T is pretty wild – and it is! – but when it comes to modification, Archie knows it’s wise to do things in stages. There’s no point changing everything at once and not having any idea what’s going on.
So when the standard performance of his auto trans ’03 XR6 Turbo grew ho-hum, Archie allocated himself a budget to install an APS (Air Power Systems) Phase 2 upgrade. The Phase 2 brings a high-flow stainless exhaust, high-flow air intake, upgrade injectors, an additional fuel pump and UniChip control. The valve springs were also upgrade at this time. Upshot? Power increased from 195kW to 268kW at the wheels, as measured on Croydon Racing Developments’ Dyno Dynamics chassis dyno. An easy gain of almost 40 percent.
Archie recalls that the on-road performance of the XR6T was absolutely transformed with the Phase 2 kit but the standard gearing wasn’t exactly optimized for fun. With the stock 3.45:1 diff, the car could reach only the end of second gear before shattering the speed limit. A shorter diff ratio and some extra power would wait for the next round of mods.
A few months later, Archie returned to Croydon Racing Developments for Round Two – a step up to APS Phase 3 spec and a new diff centre. With Phase 3 hardware attached (the biggest difference being a big front-mount intercooler), Archie’s XR6T cranked out a massive 330kW at the treads along with truly spectacular torque across the rev range. As it turns out, a little too much torque...
Within half an hour of picking up the Phase 3 equipped XR6T, Archie had busted the trans. Fortunately, North Mead Autos had acquired some experience tweaking XR6T transmissions so Archie laid down the cash for a ‘trans tickle’ and installation of a trans fluid cooler. This was followed by a trip to Diff Technics for installation of a 4.11:1 diff – the diff swap being a pretty time-consuming job in the IRS Falcon sedan. Archie says the shortened diff ratio made a tremendous improvement in driveability and feel – cruising at 60 km/h, the engine is now operating at the beginning of its powerband. Simply stab the throttle and you’re g-o-n-e. Unfortunately, this combination of mods isn’t kind on rear tyres...
Archie had a blast with his 330kW ATW XR6T because, let’s face it, there’s not much on the street that can come close. Still, Archie felt there was more power waiting to be released with some further refinement – so, after waiting patiently, the next project was to improve power while retaining the standard engine internals and turbocharger.
Interestingly, the next move involved replacement of the factory exhaust manifold. Croydon Racing Developments whipped up a custom tubular manifold and united it with the standard turbocharger in a ‘high mount’ configuration. Braided steel lines channel oil to and from the ‘charger. Initial testing showed that the new exhaust manifold made if difficult to control boost – the turbo was constantly overboosting. The solution was to add a 50mm external wastegate.
On the opposite side of the head, a Nizpro intake plenum was bolted on with custom mandrel bent pipes linking the to the APS intercooler. Fitment of the Nizpro plenum also involved relocating the battery to the boot.
At the time of writing, the fuel delivery system was yet to be finalized. The existing APS fuel system remains in service but it appears that 450cc injectors aren’t enough to prevent this baby from running lean. A Flash Tuner is being used to control fuel, ignition timing and cam phasing while a Blitz electronic boost controller tells the wastegate what to do.
With much sorting yet to be completed, the car has so far pushed out 340kW at the wheels but fuel system tweaks should allow Archie to meet his goal of 370 – 380kW at the wheels. As it is, the Nitto street-legal semi-slicks have a hard time remaining intact...
Some of that patented Archie self control dictates that there are no immediate plans for further modification – he knows when he’s got enough. Nevertheless, if the existing engine throws in the towel, Archie would have the perfect excuse for a performance built engine along with maybe a high-flow compressor.
Archie says he’s glad to have modified his XR6T in stages. Sure, anyone can go out and get it done in one big splash but doing it progressively – the Archie way - ensures the project never ‘runs off the rails’ and it keeps you content over a longer period.
Yep, with his XR6T nearing 400kW at the treads, Archie is a model of self control!
Croydon Racing Developments +61 2 9648 4264