If you’re living the modified lifestyle, you most likely picked your ride cause it can make big power. But to Denver denizen Justin Mangnall, traction is where it’s at.
"One New Years Eve, I was driving my SL500 from Glenwood Springs to Denver and got stranded on Eisenhower Pass in a snow storm,” Mangnall starts. "I tried driving down the pass on the wrong side of the road and almost hit a plow head on. All of the hotel rooms were booked, so I slept in my car for two days. And I watched Subarus pass me while I sat there stranded. All of a sudden, I wanted a performance car that wouldn’t leave me stuck in the snow.”
As soon as Mangnall got yanked from the snow bank, he found and bought an STi that fit the bill. Immediately he swapped in his buddy's used first-gen Perrin rotated-mount 35R turbo, RC 1200 cc injectors and a few electronic goodies that made for a beefy 510 wheel horsepower. "But the block wasn’t built, and I knew it was a ticking time bomb,” he reveals. And after a couple of blissful years, the fun came to a screeching halt when the flat 4 grenaded itself.
After the requisite six-month mourning period, Justin was ready to move on. The wife signed off on him doing the build he always wanted, which replicates the V-mount look on WRC cars. "Scotty at MoFab had been the only one to ever work on the car, and he has always been super creative on pushing the limits.” So Justin contacted Scott Molitor and Denver-based MoFab.
MoFab is a performance-based fabrication studio that specializes in Japanese performance cars like Hondas, Mitsubishis, Nissans and, of course, Subarus. Owner Scott Molitor is a NASA racer and hillclimber who’s spent 10 years building a solid reputation for impressive work—a big reason why Justin flipped him the STi’s keys. (Molitor also owns a sick 2.5 RS; I’ll be breaking that bad boy down from soup to nuts for your reading pleasure soon.)
After pulling Justin’s blown motor, MoFab’s first step was to build a bulletproof foundation. So Denver’s SUBA Performance put together a new short block that included new case halves, Cosworth bearings, a strengthened, nitrided crankshaft, Manley rods and CP pistons.
In preparation for the new bullet, the MoFab crew added stability for the extra power by way of a Cusco engine and trans mount, and an Agency Power pitch stop mount. When the short block was done, MoFab assembled the long block and added ARP head studs and factory gaskets. Reliable lubrication comes by way of a stock oil pump, a Cosworth baffle for those high-g corners and a Moroso pan; the stock oil fill was deleted in favor of a baffled MoFab air-oil separator/catch can, which routes and fills much easier.
To support the required airflow, the MoFab techs bolted up a couple of ported cylinder heads from Heads by Drew. The freer-flowing heads benefit from a valve job, as well as cleaned-up intake and exhaust ports for smoother, higher airflow. The valve train and intake manifold remained stock, but the tumblers were ported and polished.
Two things about the STi’s MoFab V-mount intercooler: one, you could fire up the Google and compare it to the Predator’s gaping, fanged maw. And two, a V-shaped intercooler system is just the coolest—figuratively, and probably literally as well. This custom fabricated setup is made from a Bell core and MoFab end tanks, and complemented with 2.5-inch aluminum hot-side piping and 3-inch aluminum cold-side piping.
When air flows through the cone air filter, it gets almost immediately compressed and heated up in the Garrett GTX3076R turbo. Then the V-mount gets the atmosphere chilled in a hurry and pushes it along to the straight-shot intake piping with blow through MAF, which provides the ECU with more precise air temp and volume readings. Then, it passes it along to the waiting engine. That air gets combined with juice through ID1000 fuel injectors; they’re fed from an in-tank Bosch 044 pump through custom MoFab lines. And once the flat 4 has done its thing, spent gases are exhausted through HKS’ headers into the hot-side of the Garrett, through the up-pipe/downpipe and a catback.
Keeping this complex engine chilled is a dual-pass MoFab radiator, which starts with an AFCO core and utilizes dual 10-inch fans and a custom shroud. There’s also a MoFab coolant pressure and overflow tank mounted where the compressor used to sit. Combined, this setup keeps the AEM temp gauge’s needle out of the redline—unlike the boost gauge.
Engine bays don’t get this clean on their own—especially since there's an over-abundance of coolant and fuel lines, and a mess of wires. MoFab clearly got all Type A on this puppy. First came the shortening, lengthening and rerouting; next came the re-looming, re-wrapping and deleting of all unused plugs. And because this mill would be putting out a ton of heat, a blanket and heat wrap from DEI was employed, and reflective gold wrap was used on the engine bay’s electronic components. Add to that high-quality touches like revolutionary Vibrant VanJen clamps and Phoenix Industries AN fittings, and you’re left with a stunning engine bay.
While initial dyno runs only put down 430 whp and 450 lb-ft on 14psi due to a fuel issue, Mangnall is looking for around 560-575 whp and over 600 lb-ft on 24-25psi. "The car is tuned on open source,” Justin explains, "as the factory computer is great for that if you aren’t looking to change maps on the fly. Mac Autosport had done all the tuning in the past, and Nick is someone that I trust for a safe and powerful tune.”
Despite the added power and torque, a stock 2005 STi trans holds its own—though it’s enhanced with an Exedy flywheel and twin-disc ceramic clutch. The stock driveshaft and axles funnel the power to four beautiful, black, 18x9.5-inch Advan RZ-DFs wearing BFG g-Force T/As. BC Racing’s BR Type coilovers improve handling and control at increased speeds, and Hawk HPS brake pads help bring the high-altitude fun down to a controlled halt.
Justin enjoys his newfound [reliable] power and handling while sitting in stock seats, though he’s anchored with a harness bar and 5-point harnesses. He keeps tabs on the mechanical goings-on via an Autometer liquid-filled fuel pressure gauge, as well as AEM gauges for coolant temp, oil pressure, wideband O2 and boost. Further interior upgrades, including new seats, are just around the corner.
All of this goodness happens under a modded yet deceivingly vanilla wrapper. A carbon fiber hood wearing aero catches uses a reversed scoop for venting the post-intercooler air.
The front bumper is a modified stocker, as the upper crash beam and lower radiator mount was removed to fit the V-mount intercooler. Rear flares add some extra attitude, and a full wrap by Impacted Wraps & Graphics completes the look. But without closer inspection, this STi could pass for plain Jane—a fatal miscalculation for would-be challengers.
The entire build encompassed one full year—but in that time, MoFab was able to transform this STi into a beautiful, reliable street rocket that fulfilled Justin’s dream. "Scotty understood my idea of what a factory V-mount Subaru would look like, and built it beyond my expectations for sure.” And you never know: when the snow starts flying, it’ll probably make one hell of a tow vehicle, too.
Build at a Glance
2005 Subaru STi
Built by MoFab
Short Block by SUBA Performance
New Case Halves
Nitrided / Reinforced Crank
Heads by Drew Head Job
Factory Subaru Gaskets
ARP Head Studs
Cusco Engine Mount
Agency Power Pitch Stop Mount
Ported and Polished Tumblers
HKS Exhaust Headers
DEI Heat Wrap, Blanket and Foil
Garrett GTX3076R T3 .63 Turbocharger
MoFab Custom V-Mount Intercooler Setup
MoFab Custom Dual-Pass AFCO Radiator
Vibrant VanJan Clamps
Injector Dynamics 1000cc Injectors
MoFab Custom Fuel Lines
Bosch In-Tank 044 Experimental Fuel Pump
MoFab Motorsport Air-Oil Separator / Catch-Can
MoFab Custom Coolant Pressure & Overflow Tank
Moroso Motorsports Oil Pan
Cosworth Oil Baffle
Stock 2005 STi Transmission
Exedy Twin-Disc Ceramic Clutch & Flywheel
CUSCO Transmission Mount
Autometer Liquid-Filled Fuel Pressure Gauge
AEM Coolant Temp, Oil Pressure, Wideband AFR, Boost Gauges
SMY ClusterMaker Gauge Pod
Sparco Harness Bar
Modified OE Front Bumper
Full Exterior Wrap by Impact Wraps & Graphics
Rear Fender Flares
BFG G-Force TA
Advan RZ-DF 18x9.5
Hawk HPS Pads
BC Racing BR-type Coilovers
Cusco Front and Rear Strut Brace