SUB­ARU WRX STI (2005–2007)

Japanese Performance - - FEATURES -

Our fi­nal con­tender is some­thing of a left-field choice for this chal­lenge, boast­ing nei­ther a high top-speed in fac­tory trim, nor sleek aero­dy­nam­ics. But Sub­aru’s iconic WRX STI is the most pop­u­lar Ja­panese per­for­mance car of the JP era. It is also lighter than the other two con­tenders and much cheaper to buy – leav­ing a lot of cash in re­serve for some ma­jor mod­i­fi­ca­tions. And with the right ap­proach, the WRX STI can be moulded into a 500bhp+ 200mph mon­ster.

Your best Scooby start­ing point would be the 2005 to 2007 ‘Hawk Eye’ WRX STI, which boasted a longer wheel­base, sharper steer­ing, a larger-ca­pac­ity 2.5-litre boxer engine for UK mod­els, and DCCD. Pro­drive pro­duced a Per­for­mance Pack (PPP), which took a stan­dard STI from 276bhp to 316bhp. More ex­tro­vert

STI buy­ers how­ever choose the Black RB320 limited edi­tion – with the PPP, a be­spoke chas­sis (boast­ing Bil­stein dampers, Eibach springs and a lower ride height), a mesh grille and a new front lip spoiler. Ja­pan also re­ceived a Spec C and Spec C Type-ra mod­els, with the ‘WRX’ part of the model’s name dropped, sim­pli­fy­ing it to the Sub­aru Impreza STI.

The 2007 RB320 limited edi­tion (pro­duced in mem­ory of Richard Burns, the 2001 WRC World Cham­pion who had died in 2005) had 332lb ft of torque at 3750rpm, with 60mph smashed in just 4.8 sec­onds. Pro­duc­tion fi­nally ended in 2007 to make way for the all-new third gen­er­a­tion 2008 Impreza hatchback.

RE­BUILD TIME

A de­cent Hawk­eye STI will set you back just £9000, and would be the start­ing point of choice for Sub­aru tun­ing guru Matt Baker, of MB De­vel­op­ments. ‘The ben­e­fit of this model is the very strong longer-ra­tio gear­box, with a taller 5-6th gear ra­tio that will top out at over 200mph with no mod­i­fi­ca­tions needed from the driv­e­train,’ Matt ex­plains. ‘This means less stress on the engine and turbo with lower revs needed to hit the mag­i­cal 200mph fig­ure.’

With a re­vised front end they have a rel­a­tively low 0.33 co­ef­fi­cient of drag from the fac­tory, and this can be im­proved some­what. ‘Sim­ply slip­stream­ing the front-end grille and shut lines wher­ever pos­si­ble makes a big dif­fer­ence, as well as delet­ing the OEM air scoop and wing mir­rors.’ Keep­ing the big rear spoiler would be wise, though, to aid sta­bil­ity.

‘Per­son­ally, I'd also be look­ing at low­er­ing the cen­tre of grav­ity,’ sug­gests Matt. ‘It's not a must, but it does re­duce the drag and makes the car more sta­ble at the same time.’ Coilovers would be your best op­tion. Turn­ing our at­ten­tion to the engine, a set of re­place­ment forged pis­tons and con rods are a must, as well as race type bear­ings. ‘I’d rec­om­mend a set of tried and tested items such as those from ACLOR Cos­worth/mahle,’ sug­gests Matt, ‘Plus a set of up­rated 11mm or big­ger head studs and multi-layer steel head gas­kets.’ A mod­i­fied oil pump is also a must to keep the mo­tor to­gether un­der higher lev­els of stress.

‘Once the engine in­ter­nals have been ad­dressed you’ll need a larger tur­bocharger and a front-mount intercooler, as well as a high-flow 320lph fuel pump and matched larger in­jec­tors,’ Matt con­tin­ues. ‘Next up you will need a 3in ex­haust sys­tem with a sports cat or de­cat, plus a set of tubu­lar head­ers like RCM GT Spec 2 items.’ A high-flow in­duc­tion kit with a good sup­ply of cold air will also be re­quired to feed the larger turbo, along with an oil cooler to keep the oil at a work­ing tem­per­a­ture. ‘The OE water sys­tem is very good though, and th­ese rarely need touch­ing,’ Matt adds. And then it’s time for the ECU. ‘This is one of the most vi­tal parts of the build,’ Matt em­pha­sises, ‘So choose your ECU and map­per wisely. We rec­om­mend Syvecs ECUS.’

Fi­nally, you should look to shed as much weight from the car as pos­si­ble, so ditch­ing the heavy airbag equipped front seats and rear seats for lighter items makes sense, as well as re­mov­ing sound dead­en­ing ma­te­rial and un­wanted items like tools, the spare wheel/jack and seat-belt brack­ets – and adding a rollcage. Don’t at­tempt high speeds with­out one! High-speed tyres, rac­ing har­nesses and a fire ex­tin­guisher are also es­sen­tial. Matt reck­ons just over 500bhp should see a light­ened, low­ered, slip-streamed STI ca­pa­ble of 200mph. With an es­ti­mated spend of £14,000 on mod­i­fi­ca­tions and a

£9000 base car the to­tal ex­pense would be around £23,000 – un­der­cut­ting both the other con­tenders.

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