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Tuner Jim Riedel Builds “Hellafunctionality” into His WRX STI

The brutal-looking 2006 WRX STI sits on a lift, awaiting some finishing touches on its enormous 6-piston Brembo® calipers. Completing the work is the proud owner, Jim Riedel. At first glance, Riedel does not seem like the type to create a monster vehicle capable of flinging him around a racetrack. A self-described closet nerd with an affable demeanor, hipster-issue beard, and undercut hair style, you might assume he uses a fixed-gear bicycle as his primary mode of transport. But this couldn’t be further from the truth, as evidenced by various dyno sheets for his vehicle with high scores that easily crest the 550-horsepower mark.

You Never Forget Your First

For most automotive enthusiasts, there is a distinct point in time that initially got their gears turning –their first glimpse of a sports car, or the first family trip to a track. For Riedel, that first magic moment didn’t arrive until auto shop class in high school, where he discovered he enjoyed the science behind how vehicle components work. Fast-forward a few years, and Riedel was building upon his automotive skills in an automotive technology and management program at the Pennsylvania College of Technology. Riedel loved the acceleration and all-wheel drive of his mom’s 2005 Forester 2.5XT, but sensed the need to take things to the next level. He eventually acquired his own Subaru; a high-mileage 2004 WRX.

At this point, his life started to turn into a positive feedback loop. What Riedel was learning in school he was applying in both maintenance and modifications. What he wanted to improve on the WRX was being discovered via racing. How to make such improvements was being answered in school, which in turn led to more mods and further fostered his innate curiosity and natural passion. A few years later, while working as an automotive service adviser, a well-maintained 2006 WRX STI made an appearance outside Riedel’s window. Before anyone else could snap it up, he quickly gathered his finances, and with visions of velocity in his head, he began making mild modifications to his new vehicle. The desire to further learn, research, and modify led to a job application at Subaru of America, Inc. Riedel was selected as one of a handful of Service Management Associates, a group of candidates that showed great potential and a strong interest in learning all things technical about Subaru vehicles. Since then, he has quickly risen through the ranks, acquiring a second Subaru along the way. With this new Subaru covering his everyday transportation needs, Riedel decided it was time to go crazy on the WRX STI.


Various turbo setups came and went, with one resulting in a track-day engine fire. There were the countless engine tunes. More adhesion became a requirement, so wider tires were purchased. The 275/35 19 Dunlops didn’t quite fit, so on went the fender flares. The massive amount of newfound grip was overwhelming the suspension, so Racecomp Engineering Tarmac 2 coilovers soon arrived in the mail. When teased that you could still see daylight between the tires and the fender flares, Riedel responded in his signature cut-to-the-chase Long Island drawl: “I don’t give a (HONK!–ed.) about stance or wheel gap. It’s ‘hellafunctional.’” This relentless devotion to hellafunctionality also caused the WRX STI to spawn a fuel cell, twin fuel pumps, tubular rear subframe, roll cage, and 6-piston Brembo brakes. That unswerving focus on functionality expanded beyond the vehicle to include the garage that includes everything from a lift to a projector that puts most home theaters to shame, perfect for pulling up factory service manuals in high-definition glory.

The Journey, Not the Destination

When probed why he didn’t just buy a supercar instead of creating a supercar slayer, Riedel responds that the enjoyment he derives from the build far outweighs buying something off the shelf. To Riedel, the vehicle is his habit, and he's quick to point out that it’s a productive one that has spawned new habits, as Riedel now plans on learning how to machine and weld. There aren’t many bolt-on upgrade parts that he hasn’t tried and tested, so it’s custom parts for him from here on out. 

Learning through Teaching

During the weekdays (and occasionally nights and weekends), Riedel is a technical training manager. He’s responsible for developing coursework for Subaru technicians, ensuring they have the necessary skills to diagnose each component in a Subaru vehicle. This has given him unique insight into his build. Riedel was proud to show how he adapted the vehicle’s original fuel-pump controller to his twin-pump setup. Whereas most modified vehicles run poorly when the aftermarket auxiliary pump abruptly turns on and off, Riedel’s modified Subaru fuel-pump controller progressively ramps the fuel delivery up and down. Fellow Subaru tuners are confounded by his vehicle’s smoothness as it claws its way up the torque curve. In that same vein, the focused approach he uses to build and improve his WRX STI also works on the job. Modify, push the limits, see what needs tweaking, make improvements, repeat – it’s a positive feedback loop that continues to serve Riedel well.

A Family Affair

At any given time, Riedel says, at least 16 different parts are in the process of being shipped to his house. And the lifestyle is catching; his wife Nicole, citing the need for a faster vehicle, bought a WRX and swapped in a bigger turbo. The original turbo was repurposed as a centerpiece for their dining room table. Their dog, Frankie, loves hanging out in the garage, supervising the two as they work on their vehicles. As often happens with Subaru enthusiasts, passion for their vehicles has created indestructible bonds.

Jim Riedel’s Steel Gray Metallic 2006 WRX STI


Bottom End

•    2011 STI block
•    11mm oil pump
•    Cosworth baffle tray
•    Subaru heat-treated crank
•    ACL HX bearings     
•    Eagle rods/Weisco pistons
•    ARP Custom Age 625+ head studs
•    Supertech Nitrated +1mm oversized valves
•    Supertech dual valve springs
•    Kelford STI-B cams for AVCS
•    Killer B motorsport oil pickup and pan
•    Gates® Racing timing belt
•    ATI super damper
•    Cosworth 160-degree thermostat
•    Koyo® Hyper V-Core 36mm radiator
•    Perrin upper and lower hoses
•    ACT® 13-lb lightweight flywheel
•    ACT 6 puck sprung clutch with HD pressure plate

Bottom end of Riedel's '06 WRX STI engine.
Photos: Gordon Yeung

Top End

•    Garrett GTX3076.63AR
•    TurboXS turbo back exhaust with V-band joints
•    Tial® MVR 44mm external wastegate, water cooler and plumbed into downpipe
•    Cosworth intake manifold
•    TurboXS type-H blow-off valve
•    TurboXS electronic boost control solenoid
•    Ported TGVs
•    Crawford Performance V2 air oil separator
•    Beatrush engine and trans mounts
•    TurboXS front-mount intercooler
•    3-inch IC piping with Vibrant Performance® Vanjen clamps
•    Setrab oil cooler

Top end of Riedel's engine. Photo: Gordon Yeung

Fuel system - Flex Fuel

•    Injector Dynamics® ID1000cc injectors
•    Aeromotive 15-gallon stealth fuel cell
•    Aeromotive A1000 fuel pump
•    Aeromotive fuel pump controller
•    Aeromotive billet fuel rails
•    Aeromotive Pro-Series fuel pressure regulator

Flex Fuel system in the 06 WRX STI. Photo: Gordon Yeung


•    Tuned by Jermaine at TurboXS w/ COBB Accessport
•    585whp/ 540wtq at 31psi on E85
•    460whp/480wtq at 24psi on pump gas

Suspension & Chassis

•    Racecomp Engineering Tarmac 2 coilovers
•    MSI front and rear camber plates
•    Whiteline 29mm front sway
•    Whiteline 24mm rear sway
•    Whiteline Anti-Lift Kit
•    Whiteline roll center kit
•    Whiteline front and rear strut bars
•    Carbing aluminum front subframe
•    Beatrush skidplate
•    TSS Fab tubular rear subframe
•    TSS Fab tubular rear lateral links
•    TSS Fab tubular rear trailing arms and mounts
•    TSS Fab tubular T-bar
•    Enkei NT03-M 18x9.5
•    275/35 18 Dunlop® Direzza Star Specs


•    Brembo 6-piston front/4-piston rear brake calipers
•    Brembo 355mm 2-piece rotors
•    Goodyear® braided lines
•    GrimmSpeed® master cylinder brace 
•    Driveshaft Shop carbon drive shaft
•    Driveshaft Shop 600-hp rear axle bars
•    Perrin rear differential cover


•    Autopower Industries® 6-point cage
•    Sparco® Evo2 GRP seats
•    Autopower rear seat support
•    Sparco 6-point harnesses
•    Sparco suede steering wheel with quick release
•    SPA Multi-Flo AFFF fire suppression system
•    Optima yellow battery relocation with quick disconnect

Exterior & Misc.

•    Kaminari® carbon-fiber hood
•    Aerocatch® hood latches
•    Karlton Lew’s fender flares
•    Big Country Labs rear wing
•    APR Performance carbon-fiber front splitter
•    APR Performance Formula GT3 side mirrors
•    Subaru WRX STI V-Limited front lip
•    BENEN Industries tow hooks
•    Baked/painted headlights – charcoal and tint on corner marker
•    ’04 taillights with blue “Batmobile” tint
•    Defi Racer Red gauges
•    Exhaust Gas Temperature gauge
•    Innovate LC-1 wide-band AF sensor
•    VBG-1 center vent boost gauge