Most people outside of Japan probably haven't heard of Pro Stock Racing yet. It's only been in business for three years, but in that short time frame it has established itself as a tuning specialist among owners of GT-Rs and Zs alike. Its quick success has come through offering a simple tuning philosophy: concentrate on the things that make a car fast rather than getting lost in the details. Pro Stock Racing's R32 Skyline GT-R perfectly embodies this philosophy; it's a car built for extreme power and fast times around the Holy Grail of the time attack scene in Japan, Tsukuba Circuit, but at the same time retains its unmolested stock looks. After seeing it in action at the recent Rev Speed Lab Battle event, we decided to stop by the impressive Pro Stock facilities to take a more in-depth look at what makes this car so special.
Before the Pro Stock Racing shop was even set up, Jin-san, the owner, built what has to be to this day the most outrageous R34 GT-R time attack car in existence, the Pro Stock Advan R. The car was meant to run and prove itself at the '07 Lab Battle in Tsukuba, but Jin decided to dedicate all his efforts to setting up Pro Stock Racing as a brand and concentrate on cars that couldn't be ignored at the time. So the BNR34 was put on the backburner and all-new R35 and 370Z (the most popular sports cars currently on sale in Japan) demo cars were developed. Despite having an irresistible itch to show the world what the Advan R can really do - it's built for 52- to 53-second lap times at Tsukuba, after all -Jin had another car he wanted to complete first, his personal burgundy GT-R.
He began building the R32 way before Pro Stock Racing was even an idea and felt he owed it to himself to complete it so he could move on to other projects. Jin is a very successful businessman, and when he sets his mind to something, he's the kind of guy who always achieves what he sets out to do. The emphasis on tuning has been to create an extremely powerful engine with broad midrange torque, all managed by the stock Nissan ECU.
Jin is a firm believer that with the right equipment and know-how, remapping the stock engine management is the best way to not only extract the best performance out of the car but also guarantee a level of safety and margin that Japanese aftermarket or piggyback units can't match. The ECU remapping service is what has made Pro Stock a well-respected tuner in such a short period of time, getting more and more interest from dissatisfied owners who have had bad experiences with poorly mapped cars. This Skyline GT-R shows just how far you can go with the stock "brains."
What differentiates the Pro Stock R32 from other cars we have seen is that it's a dedicated time attack car that looks pretty much stock on the outside and manages to remain street legal - just barely. Underneath the factory body lays a fully prepped chassis, spot-welded and stiffened with the sort of rollcage you normally only see in race cars. The interior is fully stripped out - only a driver-side Recaro bucket seat remains, surrounded by the bare essentials like a Nismo Alcantara steering wheel, a Racepack LCD dash unit and HKS gauges. The air conditioning has been removed, leaving space in the center console for the carbon switch panel, where digital modules like the HKS boost controller and lap timer are located. The Pro Stock ECU sits on the passenger-side footwell for easy access and so everyone can see that even a car of these capabilities can be managed with an OEM system.
Jin likes to use proven components, which is why he has teamed up with Öhlins to create his own lineup of Pro Stock suspension kits. The specially valved dampers are mated to 18-kg/mm springs at the front and slightly softer 16-kg/mm ones at the rear.
Ikeya Formula, which has been collaborating with Pro Stock since the Advan R was built, supplied its full BNR32 pillow-ball suspension arm and link set, replacing the aged Nissan pieces and rubber bushings. This not only helps set the car up for serious circuit use, but thanks to roll center adjusters, really helps set the geometry accurately. Jin originally used to run Brembo 6-pot monoblock calipers at the front, but he has recently upgraded to drool-inducing Brembo Racing calipers. The pot count remains the same, but these race-only items cost an obscene amount of money due to their light magnesium-alloy forged construction and titanium pistons. These calipers are mated to two-piece PFC dimpled 380mm rotors, the same kind used - in slightly smaller 343 mm size - at the rear. To get the best brake balance, the stock rear 2-pots are retained, but they're mounted on custom-made brackets.
One look under the hood and you know that Pro Stock takes its engines very seriously. Replacing the stock BNR32 motor is an N1 unit sourced from the V-spec II Nur BNR34, easily recognizable via the light metallic bronze engine covers. The engine didn't stay in its original configuration for long, being totally dismantled and sent in to a trusted machine shop for prepping. First off, the block was bored out and torque-plate honed to ensure the best possible tolerances once everything was assembled. The fully balanced HKS Step II 2.8-liter stroker kit then followed, adding almost 200cc extra capacity to the RB26. The head was shaved and its water jackets were cleaned out from casting residue before it was ported and polished. Special valve guides were fitted and new valve seats were cut to accept larger valves. HKS 272-degree duration and 10.2mm lift camshafts take care of valve actuation, allowing each of the cylinders to suck in a larger air and fuel mixture. The HKS T04Z takes care of compressing filtered air at a maximum of 1.6 bar before channeling it through the core of the HKS intercooler. From there, it heads to the engine via the Nismo GT plenum, which equalizes flow to each of the six cylinders. Some 800-cc/min injectors, topped up by a pair of Bosh Motorsport fuel pumps, take care of the rest. Pro Stock called in the help of Fujitsubo to fabricate a high-flow 90mm front pipe and full titanium exhaust system of the same diameter.
A small screamer pipe was also made up for the HKS external wastegate. The motor is kept cool via an HKS oil cooler as well as a Calsonic radiator, and seeing how the car spends most of its time lapping circuits, an air separator tank has also been added. The Pro Stock ECU handles all engine parameters and allows the RB28 to crank out 720 hp at 8200 rpm, 100 rpm shy of the redline.
Most impressive, however, are the 564 ft-lbs of torque available at 5600 rpm, giving the R32 explosive acceleration out of corners. To channel all this twist to the four wheels, Jin decided to ditch the stock transmission in favor of a Getrag 6-speed from the R34 GT-R, fitted along with an Exedy triple plate clutch. The driveline is beefed up with a pair of ATS carbon differentials at both ends, and to keep everything within operating temperature a pair of ARC coolers were added, one for the transmission, the other for the rear differential.
Jin hired Nob Taniguchi to take care of the driving at the '10 Tsukuba Lap Battle, where he managed to lap in a best time of 58.779 seconds, reaching a top speed of 128.5 mph on the back straight. With a time like this, Jin is finally satisfied and has decided that the car is done. He has deregistered it and put it up for sale, hoping to find interested buyers overseas to help promote the Pro Stock name internationally. Now what everyone wants to know is when will Jin take out the Advan R for a full on attempt at smashing the Tsukuba lap record?!
Specs & Details
'91 Nissan Skyline GT-R
Engine Nissan RB26DET inline-6
Engine Modifications N1 block, oil pump; Trust extended oil sump; Reimax oil pump; HKS step II 2.8-liter stroker kit, 1.2mm metal head gasket, Dynamic-balanced HKS crank, 272-degree 10.2 camshafts, stainless steel exhaust manifold, T04Z turbine, GT-II external wastegate, intercooler, oil cooler, billet fuel rail, 800cc fuel injectors; high-performance valve guides; re-cut valve seats; polished & ported head; Pro Stock Racing 90mm front pipe & titanium exhaust by Fujitsubo; Pro Stock Racing V-intake pipe, high-flow AFM, collector tank, lightweight radiator fan pulley, oil catch can; Trust Airinx filters; Nismo GT inlet plenum; Bosh Motorsport fuel pumps; Sard adjustable FPR; Splitfire ignition coils; Calsonic radiator w/ Pro Stock Racing air separator tank; Billion power steering reservoir tank
Engine Management Pro Stock Racing ECU
Drivetrain BNR34 6-speed Getrag transmission; ARC Magic transmission cooler, differential cooler; Exedy triple plate clutch; balanced flywheel & clutch cover; ATS carbon LSD (f/r); 3.9 final drive
Suspension Pro Stock Racing track-spec adjustable suspension by Öhlins; Eibach springs 18 kg/mm (f) & 16 kg/mm (r); Full Ikeya formula BNR32 pillow-ball suspension arms & links; Auto Select billet aluminum strut tower bar
Interior Fully spot-welded stripped and reinforced shell; Pro Stock Racing custom multi-point race rollcage w/side-impact cross bars; carbon-fiber door cards; Recaro racing seat; Takata 4-point racing harness; Nismo Alcantara steering wheel & boss; Racepack data logger; custom carbon instrument panel; HKS boost & exhaust temperature gauges, Circuit Attack Timer, EVC boost controller; custom carbon-fiber center console & switch panel; BNR34 stock gear knob
Exterior
Nismo front bumper w/ intercooler air vents, bonnet grille spoiler, rear lip spoiler; Moonface tow hook; Craft Square carbon side mirrors; Top Secret rear fender finisher
Wheels, Tires & Brakes Volk TE37 wheels 18x9.5" +15mm (f/r); Yokohama Advan A050 M-Compound tires 265/35R18 (f/r); Brembo Racing forged monoblock racing 6-pot calipers; PFC 2-piece dimpled floating discs (f/r), race-compound brake pads