Stormtrooper Evolved: WTAC’s Wildest WRX
Survival of the Fastest

If there’s a single constant throughout the life of a race car, it’s change. Evolution if you will. The automotive embodiment of a ‘survival of the fittest’ ethos.

I’d consider myself something of a regular now at the Yokohama World Time Attack Challenge, with five media swingers to prove it collecting dust in my ‘junk’ room at home. And with five consecutive years of attendance, the concept of race car evolution becomes a glaringly obvious phenomenon during a casual pit lane stroll.

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Radical aero revisions sprouting fore, aft and sometimes laterally. Billet blocks lurking stealthily beneath a maze of pipework and wiring. Even wheel and brake combo alterations catch the eye of the seasoned WTAC attendee.

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Seeking out these overt and slightly less obvious details makes the World Time Attack Challenge car geek nirvana, inviting expectation from both teams and spectator alike. Will these changes perform? Will they be effective enough to have shaken up the leaderboard as the sun sets over the Saturday night podium?

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Somewhere towards the middle of the pit garage ranks, sat a stark white Subaru with the weight of expectation rivalling the downforce produced by its giant rear wing. Speaking to Scotsman Andy Forrest and his partner Lisa, you’d have sworn it was all in a day’s work to spirit a car over 15,000 kilometres from home base, to a relative unknown circuit, and have a crack at the biggest and best time attack bash on the planet.

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Anyone who was at WTAC a couple of years back should remember the car, although perhaps not how you’d expect. You couldn’t blame Andy if he’d sooner forget, but the wild GC8 Subaru WRX only managed to get through a day and a half of testing before destroying a gearbox. This proved terminal, rendering the WRX an aerodynamic paperweight for the weekend.

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Even then, the WRX presented an evolutionary form. Conceived via a bet with Lisa, Andy originally built the EG33-powered WRX within a month, with a goal of cracking a 9-second pass on the drag strip. That goal was achieved with relative aplomb, but as quarter mile ETs dipped into the mid 7-second zone and the costs began escalating, Andy made the call to focus on a new challenge.

As the pursuit of one perfect lap, time attack served up the impetus to evolve to a circuit specification. In Andy’s words, “we made the car handle,” and in that first year the six-cylinder Subaru swept every event in the Scottish Super Lap series.

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In WTAC 2015 form, the WRX landed at Sydney Motorsport Park a slightly more conventional looking beast – if such an understatement can suffice. Wide arches, the stock-looking front bar featuring bulky winglets pairing with a tall rear wing, was at least a development from the comparatively subdued Scottish time attack guise.

Besides the eventual gearbox breakage – a broken output shaft on the custom 6-speed sequential creating mass carnage and a workload too daunting to consider – Andy also mentions the times weren’t up to par. “I drove that track as hard as I’d driven at home, but we were still 12 seconds off the pace.” Regardless, Andy’s appetite for aerodynamic grip had been whetted.

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Andy admits showing up to the track as a spectator was painful, but ultimately it left him determined to develop the car and return.

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So, that expectation. Andy suited up in Sydney with a bunch of goals in mind. First, to be the fastest Subaru over the course of the weekend. Second, to be the fastest of the European contingent. Thirdly, to make the Top 5 shootout on the Saturday evening. And finally, a stretch goal: to stand on the podium.

Boss Mode
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To achieve the goals, the WRX has been significantly levelled up. Versus the previous incarnation it’s difficult to pick a place to begin running through the changes. The obvious, perhaps, is the most polarising aspect of the car: the aesthetic.

Outwardly, the WRX looks quite unlike any other Subaru that’s preceded it. The resulting silhouette is streamlined, courtesy of bespoke carbon fibre bodywork flowing over massive 18×11-inch RAYS Volk Racing TE37SLs.

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But it’s all about function. It’s no real surprise that a prominent name among the WTAC pit is responsible for the design of the WRX’s look, and exterior function. Andrew Brilliant of AMB Aero set about concocting a recipe that would work with the WRX’s four-door shell.

The pointy end is also the cleverest. Andy described the AMB ‘Infinity Wing’ second elements on either side of the splitter as presenting an infinite lift to drag ratio. In layman’s terms, the drag created by these elements is pulling sideways; the wing on the left pulls right and vice versa. The net result being an effective zero drag creation, while generating front downforce.

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The elongated nose reduces frontal area and flows neatly across the front arches, not before permitting high-pressure air to enter the front and exit through the hood slot, a common trick to create downforce while cooling the radiators. A flat floor covers the entirety of the underside, morphing into two large tunnels at the car’s rear. This works to slow down the air velocity as it exits the underbody, creating a low pressure zone beneath the car and improving aerodynamic grip.

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Out the back is a behemoth dual-plane wing. In Andy’s words, “I wanted a big wing, so I got a big wing.” It’s tough to argue with that.

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Working in tandem with the aero is a revised suspension setup. The WRX used a conventional MacPherson strut arrangement previously, but Andy himself has engineered a bespoke double-wishbone arrangement at both ends. The only concession to the rules is the retention of original shock towers, hence the pushrod actuation of the remote reservoir front dampers.

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The rear however hangs off a custom tubular structure, meaning Andy’s been able to dispense with the bulky pressed-steel subframe. Like all of the engineering on the car, the fabricated rear arms are Andy’s own work, offering minimal obstruction as they pass through the underfloor tunnels.

Mechanically Speaking
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Squashed between the tunnels is the most significant change to the running gear since 2015 – Andy’s installed an R35 Nissan GT-R transaxle at the rear. In his mind, the benefits of lightning fast dual-clutch shifts and the ability to place the mass at the rear of the car justifies the additional heft of the unit.

Just like a GT-R, it’s shifted by paddles. In fact, with the assistance of EcuTek software, Andy’s managed to retain an OEM R35 control unit. It permits traction control and use of the R35 active diff, inclusive of torque split between front and rear wheels. The byproduct is those distinctive GT-R shifts. It’s a trait that draws attention to the car before it’s even in view, familiar yet unusual when paired with the snarl of the H6 engine.

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Drive is taken to a repurposed Escort Cosworth front diff via a propshaft, outputting to a very unconventional chain drive to the front axle. Naturally, durability is the question on inquisitive lips. Andy simply shrugs it off, mentioning the chains are capable of handling 600hp Harley-Davidson drag bike duties.

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All of this is because the engine now sits further back against the firewall courtesy of the driveshaft relocation. The front diff is normally located in line with the front axle, with the boxer engine slung out in front. Weight distribution is now massively improved, albeit posing some packaging changes.

One of those was the turbo install. Previously running a twin-turbo layout, the EG33 now breathes through a Precision PT6870 lurking beneath a cover where there’d ordinarily be a passenger seat. Andy reckons response is much the same, with around 1,200hp on tap with a hit of nitrous oxide. Without nitrous, pushing 2.0bar (29.4psi) of boost the combination is good for numbers in the 1,000hp region.

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Internally, the engine retains its 2015 spec. Now displacing 3.6 litres courtesy of a 79mm stroke and a 98mm bore, inside it’s a far cry from its SVX/Alcyone 3.3-litre 220hp spec. There’s an Arrow crank, forged Mahle pistons, custom AFP cams and ported heads. The whole shebang’s topped with a patriotic “St Andrews Cross blue” front-facing inlet manifold with a set of 1,300cc injectors supporting the hefty output, all under the watchful gaze of a Syvecs S88 ECU.

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Inside it’s all racecar. The high carbon fibre sills make for an entrance reminiscent of an LMP car, but once inside it’s a businesslike environment. A complement of AiM displays ensure the Subaru’s vitals are kept monitored in the dash binnacle, while hanging from the cage is the requisite GPS lap timer. Sitting on the tunnel is a Life Racing PDU keypad, allowing quick access to a number of controls communicated by a CAN system. Turning up the wick is as simple as selecting a given map via a couple of rotary switches. Andy mentioned they started off on about 600hp for the weekend, before dialling it up incrementally as the car and circuit became increasingly comfortable.

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Braking? No problem with giant 2-piece rotors being squeezed by 6-pot Alcon calipers front and rear. But check out that pedal box. Two pedals in a race car is without a doubt unusual, and it’s also interesting to note the use of a fly-by-wire throttle arrangement. Again, it’s an exercise in control; the ability to vary throttle body behaviour electronically is integral to managing 1,200 horsepower beneath the right foot.

For Andy, Lisa and the team, WTAC has undoubtedly been a rollercoaster experience. From hope, to heartbreak, to a dogged determination and rise from the ashes. How did the car dubbed Project Storm by virtue of its stormtrooper-esque aesthetic, respond to the changes and importantly were the AFP team’s goals realised?

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Fastest Subaru? Check. Fastest European entrant? Absolutely, by about 2.2 seconds over the stonking Audi R8 1:1. Top 5 shootout? You bet. Podium? Not quite, but after experiencing Andy’s creation, and hearing the self-assurance in his voice when he says the team has unfinished business with WTAC, don’t be surprised when the growling H6 mounts another attempt for 2018 with sights set firmly on challenging for top honours.

The WRX is the poster child for the evolution of a time attack racer. Survival requires the fittest, and with every change Andy and the Subaru get that little bit closer to the top.

Richard Opie
Instagram: snoozinrichy



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Matthew Everingham

Oh wow, now I wish I spent a little bit more time in Andy's garage. Such an extreme, but extremely well built little motor vehicle!


First glimpse makes me thought that's a kouki S14, lol


It has a bit of that from a frontal perspective, huh?




Longnose wrx for the fkn win.


What an incredible machine! (Especially when you take a look at THAT rear end)
The only "stock" item on this car is... tail lights? XD


The car retains the std subaru chassis and floorpan between front and rear suspension mounts, oem pillars, rear 1/4's and roof.


The firewall, shock towers for sure - rules state this stuff has to remain OEM.


Finally, I was awaiting this feature!

Too bad it's pretty much impossible to see the drivetrain on the running car, you could probably do a feature on it alone. Still wonder if the DTM Calibra was the main inspiration for those chain drives, or has anyone ever seen a setup like this before? I haven't.


There is no space for a front differential in line with the driveshafts now I have moved the engine back and down to help with the centre of gravity. The chains were just an idea I came up with to fit around the confines. The car runs a 50:50 front to rear weight distribution now vs 65:35 of the previous H6 build using conventional Subaru trans set up.


Hi Andy, let me start off by saying I truly admire the car, and the build quality.

But, there are a couple of issues. One, what kind of wheel spindles are you using? Obviously, you can't use the OEM Subaru spindles because they are setup for MacPherson strut suspension.

Next, the diffuser design leaves a lot to be desired. For one, it is probably too big consider you are running a front splitter. A diffuser is supposed to be tuned to the air mass flow passing through it. If you starve the diffuser of air, or the air does not follow the contours of the diffuser, then you won't be getting any real downforce, or at least, you won't be getting the downforce you COULD have.

To clear up the diffuser issue, I would recommend that apply flowviz paint, and see if the air is remaining attached to the surface of the diffuser. Depending on the outcome of the flowviz tests, you can then modify the diffuser properly. From what I can tell, the roof of the diffuser is far too high, and the flow is unlikely to stay attached. The only way to remedy this problem is lower the height of the diffuser. Also, in order for a diffuser to work optimally, you need to introduce strakes that take any turbulent airflow and straighten it out. These are the vertical panels that you see on cars like Ferrari diffusers, and on F1 cars.


Hi Joe
Your skills are wasted here if you can simply look at a car picture and work out its aerodynamic efficiency! I used to think I could do that as well! Now I fully trust the professional aero design on this car that has been CFD, wind tunnel and track designed/proven. Much of the detail is not obvious from the pics but I can assure you it works....and works well. As an aside, most cars don't run such large tunnels as they are limited on height or volume by their regulations (intended to slow them down)


Haha thanks for that reply, I thought that he must be a genius too, many experts in internet comments. Go hard, I love the cars you put out, good luck with the car and future races.


Thanks for the reply, yeah, I was aware of the reasoning behind this drivetrain layout, just wondered if you went "I have seen something like this before..." or pragmatically engineered away without outside influence, which it apparently was. I'm working in a motoring museum, so have come across all sorts of unusual or downright bonkers technical solutions.


I've never come across it... and speaking with Andy, it's an elegantly simple solution to a relatively complex issue. There was much more that could be said about it, and how much drive it actually doesn't need to deal with. Andy explained the car was essentially RWD from around 100km/h upwards.


Can anyone explain what that damper and spring set up is in front of what appears to be the pushrod converted steering rack?! Madness...


There is a 3rd spring set up that only operates under high aero loadings (when both fronts compress at same time) This allows softer main spring settings to improve mechanical grip and still supports the car with 1000kg+ of aero loading. The steering is via a lever system to keep the linkage pivots where I need them for correct alignment (ackerman, bumpsteer etc)


That I believe is part of the anti-roll bar setup - Andy did mention that at this point it wasn't in use, he may chime in and fill you in some more I hope! The steering rack relocation was something else I wanted to touch on, but space constraints!


Some of my all time favorite articles show the detail of the insane engineering which go on behind these builds. I would seriously like to see this car with all of the panels off. Keep up the good work!




The benchmark has been set, I'm expecting some big things from your build now young man! :P

Seb Agent-Orange Betts

Would love to know more about the steering setup on this with the rack being mounted up top & the column running between the manifold & block it looks nuts


It's not that weird because he gutted the stock suspension. It makes sense that he would have to relocate the steering rack. Although, I cannot understand how we would not get bump steer with the rack in that location.


It is in exactly that position to eliminate bump steer!


Okay, I see some weird assembly hanging off it, and it looks like it 'offsets' the steering rack. Also, it looks like you would be getting Anti-Ackerman effects because the steering rack is mounted forward of the hub.


awesome stuff


The steering shaft is routed through the intake manifold.

Carlos Lucas Diaz Hernandez

machine no limit
Que onda las maquinas de hoy, son sobrenaturales


All this awesomeness and no video :(


From the pictures of the rotors, it looks like he's giving the brakes about all they'll take. Suppose it's not surprising with all that power and still keeping them inside 18" wheels. Wonder if that'll change next year...


We only have these tyres up to 18"


Fantastic pictures and story Richard, Andy keep up the great work, looking forward to seeing the development that you make as you learn more about the circuit and the car, such a great story you have going.