Tsukuba SLB lap time: 58.368 seconds There are a few noteworthy players who have cemented themselves as the grandfathers of JDM, and Susumu Koyama-the man who until early last year was the vice president of JUN Auto, one of the most respected tuning shops and parts manufacturers-is one of those men.
Koyama-san was the man who helped JUN become what it is today, the brains behind all the crazy projects the company has undertaken over the years-from the 249-mph Bonneville Z32 300ZX to the Hyper Lemon R33 GT-R and the 4WD Z33 350Z (to name a few). Back in 2005, a collaboration began between JUN and Team Orange, where Koyama-san was entrusted with building Kumakubo's controversial RWD Impreza. He then became Team Orange's chief mechanic, which led him to create the RWD EVO X that was used in the '09 D1 Championship. It was during last year that Koyama-san decided to leave JUN and head north to Nihonmatsu in Fukushima-ken, the home of Ebisu Circuit, as a permanent member of Team Orange. Until last December, that is
Out of nowhere, Koyama-san showed up to the Rev Speed Tsukuba Super Lap Battle with a creation built by his new venture, the Koyama Racing Labo (KRL). The brand-new EVO X was intriguing from the start, putting down a solid 58.368-second lap in the car's first shakedown test.
This car is all about pushing the boundaries of development and taking a car that was originally deemed untunable (because of its all-aluminium engine) and proving everyone wrong. Koyama is no stranger to the EVO X and its new 4B11-he built the JUN EVO X time attack car and Kumakubo's D1 Grand Prix RWD EVO X-so he knew exactly what he needed to do when jumping into this project. The KRL EVO X is set to become not only the fastest CZ4A in Japan but will also be shipped off to China later on this year to take part in the 57th Macau Grand Prix endurance race in November. Needless to say, it not only needs to be very powerful but also strong and bulletproof to take on the demands of endurance racing. A few months ago, Koyama started this project with a bare EVO X shell. A lot of time was spent prepping the chassis for the build, which included heavy doses of spot- and seam-welding as well as welding in reinforcements to high-stress areas. A custom rollcage was fabricated and fitted into the stripped-out interior, which does away with any kind of trim from the standard car, including the dashboard that was replaced by a simple carbon-fiber piece. Air jacks have also been installed to help the pit crew get under the car easily and change wheels quickly. The interior is kept minimalistic with only a driver-side carbon-Kevlar Recaro SPA bucket seat. The center console houses a custom switch panel and a Blitz boost controller and is tilted toward the driver to make the controls easily reachable when strapped down with the HPI racing harnesses. All stock instrumentation has been binned and replaced with a Racepack IQ3 dash unit and data logger, a very advanced piece of equipment that allows the driver to flick through a multitude of engine parameters.
Exterior-wise, the car may look familiar because it's fitted with pretty much the same M-sport kit that Kumakubo's D1 CZ4A runs, albeit with a few minor alterations. The M-sport front bumper features a more aggressive contour with a bigger gaping front grille, helping to force feed fresh air to the intercooler and radiator. Carbon canards and a carbon underspoiler help generate more front-end downforce to keep those front tires nice and planted around the twisty bits. M-sport side skirts and front fenders help enhance the EVO's profile while the carbon front and rear doors from Top Mix help shave weight from the body. M-sport also supplied the rear bumper, which introduces side air ducts and an aggressively styled rear diffuser. The Top Mix carbon trunk lid is joined by a carbon Sard GT-wing to keep the rear end planted at higher speeds.
Koyama was up until the wee hours of the morning the night before our photo shoot to complete the air intake on the KRL FRP hood, which forces air toward the external wastegate. He also had to build an air guide that directs air from the central air intake directly onto the exhaust manifold, an area that suffers from extreme heat build-up on the EVO X. (This part was actually removed for the pictures because it completely covers up the manifold and turbine.) The car's aesthetics are completed with race-inspired carbon mirrors from M-sport and a set of Enkei Sport RC-T4 18-inch wheels wrapped in sticky 275/30ZR18 Hankook Ventus TD semi-slick tires.
Koyama's relationship with some of Japan's most noted names in the manufacturing of high-end performance parts means his EVO X is fitted with some of the best components out there, including the Zeal Super Function Type-E adjustable suspension kit. These race dampers sport remote piggyback tanks for easy adjustments and are mated to KRL prototype suspension links, which are still in the testing stage.
Braking is up to the most advanced calipers Endless has to offer, the Mono 6 (six-pot monobloc calipers) at the front and the Mono 4 (four-pot) at the rear. Joining these are e-slotted two-piece rotors, 380mm up front and 330mm at the rear, topped off with special race Endless pads that combine to make a braking system that wouldn't be out of place on a Super GT car.
As you can imagine, under the hood is where this EVO X really inspires. Koyama certainly likes to push the limits with every project car he takes on, and this build required a lot of custom and special-made parts. The bottom end has an all-new KRL stroker kit that pushes capacity to 2,281cc, a bit off the 2.3-liter mark; it's comprised of a special crankshaft, lightweight H-section connecting rods and 86.5 mm forged pistons. Sealing the aluminium block to the head is a 1.2mm KRL metal head gasket that makes sure the engine can cope with all the boost the oversized turbine can throw at it. The head is fitted with KRL 264-degree camshafts on the intake and wilder 272-degree ones for the exhaust side along with adjustable-slide-type cam pulleys.
Koyama called in the help of Blitz on this project, which supplied a prototype turbocharger to be used on the 4B11 along with a custom-made exhaust manifold. Boost control is up to the Blitz Type-E external wastegate that barely fits cramped between the engine and firewall. Koyama explains that this is one of the biggest problems of the new-gen engine, which due to tightening emissions control, has been rotated 180 degrees compared to the 4G63 that powered the previous generation of EVOs. This helps keep the exhaust side hotter, helping the catalyst do a better job of cleaning exhaust gases, something that isn't the priority on a performance-tuned engine. For this reason, Koyama has had to direct as much cooling air as possible to this area.
While at Ebisu, D1 driver Naoto Suenaga took the EVO X out for a series of set-up runs, and Koyama was very happy the new vents worked well to keep the exhaust side much cooler. Once the air has been sucked in from the custom carbon KRL airbox, it's then compressed and sent on to the Blitz intercooler that Koyama positioned in a wide V-mount configuration with a Koyo radiator. This allows for the best possible cooling to be achieved as well as keeping piping to a minimum to help throttle response. The pièce de résistance, however, is the NTS billet intake plenum that works wonders for increasing engine response and supplying an equalized amount of air to all four cylinders. This is joined by the new NAPREC 80mm mechanical throttle body, replacing the far-too-modern-for-its-own-good electrical throttle system of the stock 4B11. Fueling is handled by four Sard 1,000cc injectors, fed by a Sard fuel pump that works hard in the car's trunk.
Koyama fitted an 80-liter ATL fuel cell, a requirement when building a car for an endurance race like the Macao Grand Prix. Koyama has yet to put the EVO on a dyno to measure the figures, but if he had to make a wild guess he would expect the engine to deliver more than 600 hp and somewhere in the region of 485 ft-lbs with excellent midrange torque. To help handle all that power, an ORC twin-plate clutch was fitted along with a modified version of the stock Mitsubishi 5-speed transmission, featuring an NTS micro-finish-coated gearset and a special KRL shorter fifth gear to help the car get the most out of short to medium circuits in Japan. Upgraded ATS carbon LSDs fore and aft take care of distributing proper torque to each of the four wheels.
Seeing Suenaga drive the EVO around the Higashi course at Ebisu was quite a sight as he came up the main straight well over 124 mph, a pretty incredible speed to achieve on the tough uphill straight. Even Kumakubo showed up for a quick drive to sample Koyama's creation. His comment after a few laps, "This car is scary fast!" If a guy that's used to going sideways at 112 mph says something like that, you know it's an impressive car. This is, without a doubt, another great car from one of the greatest JDM tuning gurus out there.
Specs & Details
'08 Koyama Racing Labo
Mitsubishi Evo X
Max Power 600 PS
Max Torque 67 kgm
Engine Mitsubishi 4B11T inline-4
Engine Modifications KRL 86.5mm forged pistons, H-section connecting rods, stroker crankshaft for 2,281cc, 1.2mm metal head gasket, performance camshafts, adjustable cam pulleys, cam belt, lightweight water pump pulley, lightweight alternator pulley, carbon-fiber airbox and filter system; NTS micro polished ported head, Blitz custom exhaust manifold, Type J external wastegate, Type J V-mount intercooler, oil cooler; Koyo racing radiator, Blitz/KRL prototype turbocharger, KRL custom exhaust manifold cooling air guide, front pipe, exhaust system, intercooler piping, custom intercooler end tanks; Samco silicon intake hose, NAPREC 80mm mechanical throttle, NTS aluminium billet intake plenum, Sard fuel pump, fuel pressure regulator, 1,000cc injectors, air-separator system; KRL/NTS/Team Orange purple engine cam cover
Engine Management KRL original ROM flash ECU, HKS F-Con V Pro piggyback ECU
Drivetrain ORC special twin plate clutch and lightweight flywheel, NTS micro-finished gearset, KRL original 0.82 fifth gear, ATS carbon LSD (f/r)
Suspension Zeal Super Function Type-E adjustable dampers w/ remote piggyback tanks, 13 kg/mm springs (f), 15 kg/mm (r), KRL prototype adjustable suspension links
Wheels, Tires & Brakes Enkei Sport RC-T4 18x9.5" +30; Hankook Ventus TD tires 285/30/ZR18; Endless Racing 6-pot monoblock calipers (f), 4-pot monoblock calipers (r), 2-piece e-slotted 380mm rotors (f), 2-piece e-slotted 330mm rotors (r), Endless Special brake pads