How to turn your GR Yaris into a championship-winning rally car | Top Gear
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Saturday 2nd December

How to turn your GR Yaris into a championship-winning rally car

Follow Top Gear’s foolproof, five-step guide, which is also entirely not foolproof and has steps that Paul Bunyan would struggle to summit

Yaris AP4
  1. Engine

    Yaris AP4

    Obviously, you’ll want to start here. Never mind that a rally car is only as good as its suspension, brakes, drivetrain and driver. You want the juicy stuff first. 

    Remove the engine from your GR’s engine bay. Discard the exhaust manifold. Discard the turbo. Discard the pistons. Take a similar approach to the camshafts, rockers and springs. 

    Fit gorgeous, custom-made exhaust headers. Marvel at the fact you have just three downpipes. Fit a new turbo with 1.5 bar (nearly 22 PSI) of boost, along with a pop-off valve – in case scrutineers want that sort of thing later on. Fit forged pistons, which won’t get squashed in the immense pressure and heat, destroying cylinder bores (and who knows what else) in the process. Fit stronger rockers and stiffer springs, making sure to team them with a pair of camshafts with 13mm of lift. Consider just how much lift that is in an interference engine, then machine the standard cylinder head. In what way, how much or to what end that one machines the head is one of the many questions we asked Neal Bates Motorsport’s technical director; in return, we got that ‘pause and smile’ combination that unmistakably indicates that it’s time to move on to the next question.

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  2. Drivetrain

    Yaris AP4

    Start an online store for ‘New Old Stock’ GR Yaris bits. List the following items at a price you think is reasonable: 

    -    Clutch
    -    Gearbox
    -    Front and rear differentials
    -    Driveshaft and half shafts

    So... most of it. 

    Get on the phone to Sadev and AP Racing, making sure to order a six-speed sequential gearbox and new diffs (ensuring the rear diff still has an overload clutch like the road car, to disconnect drive to the rear when the handbrake is pulled), then custom-make your own driveshaft and half shafts. Because you know how to do that, right?

  3. Suspension

    Yaris AP4

    Actually, leave all of this alone. The standard stuff is rally-ready. 

    Check date. Ensure it’s not 1 April. Then remove uprights, control arms, linkages, springs, shocks and everything else that has anything to do with suspending the GR Yaris. Then remove the sheet metal that houses the pickup and mounting points for these items. Fabricate custom shock towers and mounts in the front and rear. Be very good at welding. 

    Also, be a lifelong customer and friend of a suspension supremo. Call said supremo and ask for a full rally suspension set-up which borders on rocket science. Receive a set that offers 260mm of eerily controlled travel for the front axle and 280mm of exactly the same in the rear. 

    Do not baulk at the price. This is what these things cost. Consider extra sponsorship, possibly from some kind of energy drink company. Remember the tale of Rich Energy. Decide against energy drink sponsorship. 

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  4. Body

    Yaris AP4

    Remove everything from inside the car. Use the seats for a nice patio setting, or something. 

    Have access to a technical director, who in turn has access to (and serious aptitude with) 3D computer-assisted design. Cardboard-assisted design will do in a pinch, but might signal that your project will take a mite longer than you intended.   

    Also have access to someone who’s basically the Rodin of fibreglass. Get him to sculpt box arches that make the most of the prescribed width limits, as well as a rear hatch – complete with polycarbonate window – that looks entirely stock. Dilute this stock look somewhat by fitting a massive rear wing and the aforementioned box arches. 

    Replace side windows with polycarbonate. Discover that polycarbonate windows need window frames, which the GR Yaris lacks. Have your fibreglass sculptor sort that out. Also, a new bonnet would be nice... and some 3D-printed air vents for the bonnet, while you’re at it.

    Get rid of pretty much every piece of metal, rubber and plastic part ahead of the windscreen. You won’t need them. 

    Fabricate a new, raised transmission tunnel and connect it to a new firewall that you’ve also custom-fabricated. There’ll be some more custom fabrication to make the front all work and mount together, but you’ll sort that out. We believe in you. 

    Remove the carbon roof. This will take some serious nous that you will absolutely already have. While it’s off, fit a roof scoop. This, aside from maximum cool points, also lets air into the cabin. Also possibly mud. But that’s rallying, no?

    Also fit a roll cage that’s so incredibly stiff, it removes the need for any seam welding whatsoever. Consider the synergy of safety and speed and do that David Brent finger-interlocking thing. 

  5. Finishing up

    Yaris AP4

    Get a custom windscreen made, with heating elements hand-laid in the laminate to keep it condensation-free on colder rallies. Do not baulk at the expense. Do not consider energy drink sponsorship. 

    Buy many sets of OZ Racing rally wheels. Also amass a great stack of the Hoosier control tyres needed to compete. Marvel at just how stiff the sidewalls are. Consider hoarding OZ wheels based on looks alone. 

    Fit all the things you built or modified. Leave out all the bits you didn’t. Connect bits until they work in a fashion that resembles a rally car. Consult your technical director for guidance.

    Rally2 (nee: R5) rules dictate a 32mm restrictor, fitted ahead of the turbo. AP4 regulations allow a 34mm restrictor. Decide to be fair to the competition, which fields cars that follow Rally2 rules, and fit a 32mm restrictor, as Neal Bates Motorsport has. Or be a bit Dick Dastardly about things and fit a 34mm restrictor as per AP4 regulations, instantly liberating about 30bhp and extending top-end punch.

    Fill doors with 60 litres of shock-absorbing foam. Fight the urge to have a ‘foam party’, like your university days. Not the same foam. And you’re not the same person. 

    Fit a pair of motorsports seats, race harnesses, floor-mounted pedal box and the usual racing stuff you’ll find on proper racing machines and over-egged track cars alike. 

    Realise that this has all been quite a bit of effort and that it may have been easier to just let the pros do it. Consider placing a call directly to Neal Bates Motorsport in the future. 

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