Inside an 820 WHP Mazdaspeed3 Built by Grocery Getter Performance

There are Mazdaspeed3 builds with a few bolt-ons, and then there are builds where nearly every part of the car has to work together toward the same goal.

This 2012 Mazdaspeed3 falls firmly into the second category.

We originally built the car for our customer and friend Aaron with one goal in mind: make it a street-driven straight-line monster that could hang with virtually anything, without turning it into a miserable car to live with when the throttle wasn't pinned.

The car has since changed ownership, but all of the photos and video in this feature were taken while it was still in Aaron's hands and in the configuration shown here.

Grocery Getter Performance built the car around a serious engine, turbo and fueling combination while addressing the drivetrain, suspension, traction and interior needed to support it. After calibration by Jorge / JTune at House of Boost, the finished combination laid down 820 wheel horsepower and 684 wheel torque on a Dynojet at 40 psi.

And the number on the dyno sheet only tells part of the story.

What Grocery Getter Performance Built

Kotzur Racing handled the engine build itself, and Jorge / JTune handled the final calibration. Outside of those two specialties and tire mounting, Grocery Getter Performance handled essentially the rest of the car.

That included the engine installation, turbo system, fueling system, clutch and drivetrain work, suspension and chassis setup, custom shifter fitment, catch-can setup, interior hardware and the many small changes that turn a pile of high-end parts into a complete car that actually works together.

This wasn't a one-time assembly either. The car has been in this general form for years, with additions, refinements and adjustments made over time to keep improving how it performs and how it behaves on the street.

Building the MZR for the Power

At the center of the build is an MZR engine built by Kotzur Racing.

The block received a Darton wet-sleeve conversion and 88.5 mm Manley pistons paired with Manley I-beam connecting rods. The factory crankshaft was retained and keyed.

Up top, the combination uses pinned Kelford 247-C cams, a ported cylinder head and Supertech valvetrain components including beehive valve springs and retainers. ARP studs complete the foundation.

Grocery Getter Performance's coil-pack rotation bracket helps clean up the top of the engine and is one of several GGP pieces incorporated into the finished car.

Even with the large Kelford cams, the car still has a healthy idle. There is noticeable cam chop, as you'd expect, but fuel trims are good, oil pressure is strong and the car retains the amenities that make it a real street car rather than a stripped dyno-only build.

Precision 6266, Blacksmith Performance Fabrication Top Mount and Hood-Dumped Wastegate

The turbo system makes it immediately obvious that this isn't a conventional bolt-on Mazdaspeed3.

A Precision 6266 turbocharger sits on a custom top-mount exhaust manifold fabricated by Blacksmith Performance Fabrication (@blacksmithfab), with a TiAL external wastegate venting through the hood.

It gives the engine bay a completely different appearance from a factory-location turbo setup and makes the hardware behind the power impossible to miss.

JMF Intake, Dual-Fuel Strategy and C85 Port Injection

Feeding the engine is a JMF intake manifold combined with a Damond Motorsport port-injection plate.

The fueling strategy is split between two systems. The factory tank carries 93-octane fuel for the direct-injection system, while a separate auxiliary tank carries C85 for the port-injection system. Injector Dynamics ID1050 injectors deliver that C85 through the Damond plate.

At 820 wheel horsepower, the engine, turbo and fuel system can't be treated as unrelated upgrades. They're one combination, and the dual-fuel setup gives the car the fuel delivery needed to support the rest of the package.

Getting the Power Through the Car

Making power is only useful if the rest of the car can deal with it.

The transmission is paired with an XClutch 9-inch twin sprung ceramic clutch, while the factory shifter arrangement was replaced with a custom-fitted Acuity full-replacement shifter.

The clutch is one of the most surprising parts of the entire build. Pedal effort is very close to stock, not remotely like the brutally stiff single-disc clutches people often associate with high-power street cars. There is a little chatter, but not much. It is easy to take off from a stop, easy to creep in traffic and easy to drive normally despite holding power levels far beyond what many much harsher clutches are asked to survive.

Putting 820 WHP to the Ground

Putting more than 800 horsepower through the front wheels presents an entirely different problem.

The car rides on VMS Racing wheels wrapped in Hoosier drag radials, with Fortune Auto 500 Series coilovers controlling the chassis.

A TB Performance Mazdaspeed3 traction bar further addresses front-end movement and traction under acceleration.

Third gear starts to become genuinely useful once the Hoosiers have some temperature in them. Fourth gear is where the car really feels like a rocket ship: the combination is moving fast enough to use the power, and the 6266 is fully in its element.

A Cockpit Built Around the Car

The interior follows the same function-first approach.

A Braum bucket seat and five-point harness sit alongside an AutoPower Race roll bar, while an Eonon Android-powered head unit keeps modern functionality in the cabin.

Engine information is handled in part through a Grocery Getter Performance defrost-vent gauge pod, fitted here with a CorkSport oil-pressure gauge. Custom vented oil catch cans were also incorporated into the build.

The Part the Dyno Sheet Doesn't Tell You

The most surprising thing about this car isn't that it makes 820 wheel horsepower. It's how normal it can feel when you're not asking for all of it.

We expected a car at this level to be something you tolerated between wide-open-throttle pulls. Instead, it is a proper street car. The clutch is manageable, the engine is healthy, the car cruises normally, the amenities still work and nothing about normal driving constantly fights the person behind the wheel.

That changes completely when the throttle goes down.

You can feel the power coming. It isn't something that sneaks up on you or that you accidentally summon. As boost rises toward the full 40 psi, the character of the car changes from civilized to violent.

The best comparison is riding a bull: once full boost is in, you hang on, keep it pointed where you want it to go and let the car do something that feels completely disconnected from how calm it was moments earlier. At full power, the acceleration is immense and fourth gear in particular feels like the car has been launched rather than accelerated.

That dual personality is what makes the build special. You always know there is enough raw power underneath you to demand respect, but the car does an impressive job of staying easy to handle until you deliberately bring that power out.

820 WHP, 684 WTQ, 40 PSI

Final calibration was performed through the COBB Accessport V3 by Jorge / JTune at House of Boost (@dialedin_supra).

The car runs its full-power calibration rather than relying on a separate low-boost street map. On the Dynojet, with the factory DI system supplied by 93 octane and the auxiliary port-injection system supplied by C85, the car produced:

• 820 WHP
• 684 WTQ
• 40 psi

The rest of the combination includes:

• Darton-sleeved MZR
• Manley 88.5 mm pistons and I-beam rods
• Keyed factory crankshaft
• Pinned Kelford 247C cams
• Ported head and Supertech valvetrain
• Precision 6266 turbo
• Blacksmith Performance Fabrication custom top-mount manifold
• Hood-dumped TiAL wastegate
• JMF intake manifold
• Damond Motorsport port-injection plate
• Injector Dynamics ID1050 injectors on C85
• 93-octane direct-injection fuel system
• XClutch 9-inch twin sprung ceramic clutch
• Custom-fit Acuity full-replacement shifter
• VMS Racing wheels and Hoosier drag radials
• Fortune Auto 500 Series coilovers
• TB Performance traction bar
• GGP coil-pack rotation bracket
• GGP defrost-vent gauge pod

Years of Refinement, Not a One-Pull Dyno Build

This combination has been together in essentially this form for years. It wasn't assembled for one glory pull and then parked. The car has been continually refined with small additions and adjustments to make it work better as a complete package.

That matters because the end result isn't just fast. It is a car that can look at home at a show, drive around normally and then completely change character when full power is commanded. In our experience, cars that look this good often aren't this fast, and cars this fast often aren't this well-rounded.

That was the biggest surprise from behind the wheel. We expected something that would only make sense at wide-open throttle. What we got was a proper street car with show-car presence and an almost absurd level of performance available underneath it.

More Than a Parts List

For us, this car represents an important part of what Grocery Getter Performance is about.

We don't just want to put performance parts into a catalog. We work on these platforms, build them, learn what works together and develop our own products from that experience.

This 2012 Mazdaspeed3 is an extreme example of that philosophy: a customer car assembled and refined by Grocery Getter Performance, powered by an MZR built by Kotzur Racing, using a Blacksmith Performance Fabrication turbo manifold and ultimately calibrated by Jorge / JTune at House of Boost to 820 horsepower at the wheels.

For Mazdaspeed3 and Mazdaspeed6 owners building anything from a basic street setup to something considerably more serious, visit Grocery Getter Performance.

Built for: Aaron
Engine build: Kotzur Racing
Turbo manifold fabrication: Blacksmith Performance Fabrication — @blacksmithfab
Vehicle build and integration: Grocery Getter Performance
Tuning & calibration: Jorge / JTune — @dialedin_supra / House of Boost, LLC
Photography & video: @andrew_drose / @the7th.branding