A LEG­END RE­BORN

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POS­SUM BOURNE’S HILL CLIMBER RE­BUILT

THE LE­GACY LIVES ON, AS POS­SUM BOURNE MO­TOR­SPORT HAS RE­BUILT AND RE­STORED POS­SUM’S OLD WRC IM­PREZA TO KEEP UP AND SUR­PASS THE BEST REPCO’S RACE TO THE SKY HAS TO OF­FER

When you’re trusted to rebuild a car you’ve been around since its hey­day, and you’re given free rein on the project’s fi­nal out­put and public per­cep­tion — which di­rec­tion do you take it? For Pos­sum Bourne Mo­tor­sport (PBMS) owner and com­pos­ite en­gi­neer Bryan Hay­ton, the de­ci­sion was easy — the WRC-spec Subaru Im­preza would stay pe­riod cor­rect, but with some much-needed power and re­li­a­bil­ity im­prove­ments.

Orig­i­nally built in 1998 by Pro­drive, the WRC-spec Im­preza was cam­paigned by Finn rally driver Juha Kan­gas, who crashed it dur­ing Rally New Zealand. The car was then pur­chased by Pos­sum Bourne, who al­ready had a WRC Im­preza in com­pe­ti­tion, and de­cided to rebuild the crashed coupe to con­test the 2001 Race to the Sky in Cardrona Val­ley.

There was noth­ing quite like the re­built WRC car con­test­ing the moun­tain at the time — with around 447kW (600hp), Bourne won the event on his first out­ing. How­ever, 2002 wasn’t as suc­cess­ful — a blown tyre cost the race.

Af­ter Pos­sum’s pass­ing in 2003, the Subaru was pur­chased by Van­tage Doors and Win­dows (Van­tage Mo­tor­sport) and used to con­test Race to the Sky un­til 2007, driven by WRC driver Ken­neth Eriks­son, but it fell short of first place ev­ery year thanks to Nobuhiro ‘Mon­ster’ Ta­jima’s mighty Es­cudo. Since Race to the Sky’s ab­sence, the Subaru has been used for spe­cial events such as Rod Millen’s Lead­foot Fes­ti­val in 2011 and 2012, driven by Emma Gil­mour, and at the Pos­sum Bourne Me­mo­rial Rally in 2013, driven

by Cody Crocker. So when the Repco Race to the Sky event was an­nounced for 2015, Craig Vin­cent from Van­tage swung into ac­tion, en­list­ing the PBMS team to do their thing and give the Subaru what it needed to re­turn to the hill climb with a vengeance.

To be com­pet­i­tive, the team knew more power would be needed, but with a six-month dead­line to com­bat Mon­ster’s hill-climb-spe­cific ‘ Su­per 86’, head en­gi­neer Paul Hay­ton started full time on the project, and out came the drawing board. The team dis­cussed is­sues they pre­vi­ously had with the Subaru when con­test­ing Race to the Sky — the first be­ing a lack of power, but the main is­sue in the past had been cool­ing, as Paul ex­plained. “For the last three or four years, we’ve had over­heat­ing prob­lems. Be­cause of how the in­ter­cooler and ra­di­a­tor had been po­si­tioned, the ra­di­a­tor wasn’t get­ting enough air to re­main ef­fi­cient.” For the Subaru’s most re­cent out­ing, the team cut large vents into the bon­net, and de­signed a big air dam on the front bar to help ad­dress cool­ing is­sues, but for Race to the Sky this could not be done, as Bryan de­cided the WRC-spec Subaru would re­tain the pe­riod-cor­rect 2000spec bumpers and bon­net. “The prob­lem we had ini­tially was that the car had to look the same as it did in 2000. By mak­ing this de­ci­sion, we couldn’t cut any of the car up, so we had to fig­ure out a way to fit the large ra­di­a­tor and in­ter­cooler in there and make it work,” Bryan said, adding, “This was prob­a­bly one of the big­gest chal­lenges of the build.” To com­bat this, the team de­signed a very clever V-mounted in­ter­cooler and ra­di­a­tor set-up which, along with a com­bi­na­tion of air ducts de­signed in-house, works ex­tremely well. With WRC oil cool­ers for both the gear­box and the en­gine in­stalled ahead of each front wheel, duct­ing also had to be de­signed be­hind the 2000-spec bumper to chan­nel air in the right di­rec­tion.

With cool­ing un­der con­trol, PBMS en­gine builder Glen Cox started build­ing the PBMS-spec EJ20. “We de­cided to re­tain the fac­tory en­gine ca­pac­ity to help re­tain the pe­riod-cor­rect theme we were go­ing for through­out the rebuild,” Bryan ex­plained. With a work­shop full of WRC spares from the good old days, a Group A crankshaft was cho­sen, WRC en­gine bear­ings, and a bunch of PBMS-spec good­ies such as the Argo PBMS-spec con rods, PBMS-spec JE pis­tons, PBMS 14mm head studs, PBMS-spec cams, and big-port cylin­der heads — all bolted to, and in­side, the PBMS ‘ex­treme power’ 2.0-litre block.

With a block now ca­pa­ble of han­dling their ini­tial power goal, the team de­cided to make the switch from the Gar­rett turbo they pre­vi­ously ran, to a BorgWarner EFR 8374. The turbo sits up high on an eas­ily re­moved slip-joint man­i­fold, and boost con­trol is taken care of with a TiAL 46mm ex­ter­nal waste­gate. “An­other huge im­prove­ment we have made for both power and cool­ing is the use of Ethanol E85,” Paul told us. Not only is E85 cheaper than the old C16, it helps main­tain cooler com­bus­tion tem­per­a­tures — which the EJ20 des­per­ately needed. “We up­graded the fuel sys­tem while we were at it, with new Bosch fuel pumps and In­jec­tor Dy­nam­ics ID2000 in­jec­tors to han­dle the E85,” Bryan ex­plained. Once the PBMS team sorted out the fu­el­ing grem­lins which slowed progress sig­nif­i­cantly in the fi­nal week of prepa­ra­tion (due to a re­stric­tive fuel fil­ter), the Subaru was tuned on the dyno with the MoTeC M880 ECU. The team were de­lighted to see their ef­forts pay off when the Subaru churned out 636kW (854hp) at the en­gine on 42psi of boost — 75kW more than the ini­tial goal.

Back in 1998 when Pro­drive ini­tially built the Subaru, they def­i­nitely got the chas­sis, driv­e­line, and sus­pen­sion pack­age right, as none of th­ese ar­eas needed up­grad­ing be­fore Race to the Sky 2015. The Pro­drive Hew­land WRC six-speed dog box is said to be the weak­est link at the mo­ment, which con­sid­er­ing it was de­vel­oped for a car out­putting 220kW (300hp) orig­i­nally is fairly im­pres­sive — mind you, you’d hope so for $90,000 back in 2000.

What Pos­sum Bourne Mo­tor­sport has achieved in such a short time is as­ton­ish­ing — to have a ve­hi­cle per­form­ing like a mod­ern hill-climb su­per­car and ap­pear­ing as if it rolled out of the Pro­drive fac­tory in 2000 re­ally is ad­mirable. With Colin McRae’s younger brother, Alis­tair, pi­lot­ing the Subaru at Race to the Sky 2015, we think the PBMS-built Van­tage Mo­tor­sport Subaru has a real shot this year — watch out Mon­ster, PBMS has come pre­pared.

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