Extensively Modified Mugen EP3 Civic Si Turbo Build - 400HP Honda Tune

Introducing the Mugen EP3 Civic Si Turbo

The Mugen EP3 Civic Si Turbo is an exciting performance car built over 3 years by passionate Honda enthusiasts. This highly modified Honda Civic Si shows what's possible when you combine creativity, skill, and quality aftermarket parts.

The owner documented the 3-year build process on YouTube, sharing the blood, sweat, and grease that went into creating this beast of a Honda. With a big turbo, upgraded internals, and custom body work, this Civic Si puts down some serious power while retaining its daily drivability.

Starting with a Base Civic Si

The build started with a 2002 Honda Civic Si, the classic EP3 generation known for its high-revving naturally aspirated VTEC engine. This was an ideal platform to build upon thanks to the Civic's lightweight and rigid chassis.

Though the stock Civic Si was no slouch, the owner knew there was untapped performance potential in the 2.0L 4-cylinder engine. With some carefully chosen upgrades, big power gains could be extracted from the K20 motor.

Bolting on Forced Induction

The centerpiece of the build was the addition of a large turbocharger kit fromHTTPConnection.This included a GarrettGT2871R turbo, Tial wastegate, and all supportingplumbing and hardware.Custom stainless steel turbo headerswere fabricated to connect the turbo to the stock exhaust manifold.

With 6-7psi of boost from the turbo, the Civic Si's power output jumped from 160hp to over 300hp at the wheels. This level of boost was safe on the stock engine internals. There was much more in store after building the engine to handle higher boost.

Built Motor and Increased Boost

In preparation for more boost, the engine was torn down and rebuilt with forged internals including JE pistons, Eagle rods, and ARP studs. This built bottom end could now reliably run 15-20psi of turbo boost pressure.

With supporting fuel system upgrades like high flow fuel injectors, fuel pump and regulator, the Civic Si was hitting 370hp at the wheels on a conservative 18psi of boost. With even more boost pressure, 400+ wheel horsepower figures were achievable.

Extensive Body Modifications

While the engine bay got some nice upgrades, the exterior received even more attention. The owner went all out modifying the bodywork to create a custom widebody look.

Custom Over-Fenders

To accommodate the wider track stance, custom over-fenders were fabricated for the front and rear. Made from fiberglass, these bolt-on arches widen the body by several inches to create an aggressive, ready-to-race appearance.

Properly fitted over-fenders are key to getting that competition look while allowing wider wheels and tires to fit. Gone are the days of zip ties and heartache!

Front Lip Spoiler and Rear Diffuser

Adding even more visual drama are the front lip spoiler and rear diffuser pieces. Made from lightweight fiberglass, they create actual downforce while giving the car a tuned aerodynamic look.

The front lip spoiler is a crucial piece in managing airflow traveling under the car. Out back, the rear diffuser cleans up underside air movement for reduced drag.

Side Skirts and Rear Spoiler

Continuing the aero theme are side skirts and rear spoiler. The side skirts smooth out air along the sides of the car, helping reduce turbulence. A carbon fiber GT wing puts downforce on the rear axle while looking right at home on this road rocket Civic Si.

Wheels, Tires and Suspension

No tuned Civic build would be complete without proper wheels, tires and suspension upgrades. This Mugen EP3 sits dramatically lowered on coilovers and is ready to carve corners.

Lightweight Wheels

The widened fenders allowed fitting 18x9” lightweight wheels all around. Not only do these wide rims fill out the fenders nicely, they reduce unsprung wheel weight for better acceleration, braking and handling. Matte bronze paint adds some custom flair.

Sticky low profile tires sized 235/40R18 provide the huge contact patch necessary to put all that turbo power to the ground. Large cross-drilled brake rotors and calipers ensure this Civic Si stops as well as it goes.

Dialed-In Suspension

The OEM suspension was swapped out for an adjustable coilover setup with pillowball upper mounts. This allows dialing in the perfect ride height while maintaining crisp suspension response.

Stiffer anti-roll bars, strut bars, and chassis bracing sharpen handling precision and reduce chassis flex. Upgraded suspension bushings ensure steering input is transmitted directly to the wheels.

Interior Upgrades

The interior remains largely stock appearing, retaining the classic simple EP3 Si cabin. Appearances can be deceiving though, as there are several key upgrades made.

Bolstered Seats

The stock seats were replaced with a set of Sparco racing buckets. These providemuch better lateral supportwhen drivingenthusiastically. High bolsters and deep shoulder wings keep the driver planted and focused on driving.

Matching red 4-point cam lock harnesses attach to the seat frame, offering protection during hard cornering. Custom door panels were fabricated to allow mounting the shoulder belts.

Steering Wheel and Pedals

A suede covered steering wheel from NRG replaces the stock tiller, adding style while also improving grip. Down below, aluminum pedal covers spruce up the footwell while providing better traction.

Gauges monitor boost, air/fuel ratio, oil pressure and temperature. A wideband O2 sensor helps tune the motronic ECU for optimal power and response.

Conclusion

This extensively modified Mugen EP3 Civic Si shows what's possible when imagination and skill come together. The owner meticulously implemented a 3-year plan, documenting the process along the way.

Now boasting over 400hp in a lightweight package, this turbo Civic Si is a testament to the strong Honda tuning scene. With custom widebody work and track-ready suspension, it's ready to perform on road or track.

After hundreds of hours of work, the owner can finally enjoy the fruits of this labor. For him and the partners who helped make it possible, this Civic Si represents a dream fulfilled. The passion behind this build is what makes it so special.

FAQs

What year model Honda Civic Si was used for this build?

The base car was a 2002 Honda Civic Si (EP3 generation). This was an ideal platform to build upon thanks to its lightweight chassis and high revving 2.0L VTEC engine.

What size turbocharger was used on the Civic Si?

A large Garrett GT2871R turbocharger was chosen for this build. At low boost levels, it can safely produce over 300 wheel horsepower on the stock engine internals.

How much power is this Mugen EP3 making?

With supporting engine upgrades, the Civic Si is making around 370 wheel horsepower on 18psi of boost. With more aggressive boost levels, over 400 wheel horsepower is achievable.

What suspension upgrades were done?

The OEM suspension was replaced with an adjustable coilover setup and upgraded sway bars. This allows dialing in ride height and handling precision.

What interior upgrades were performed?

Upgrades inside included Sparco racing seats, 4-point harnesses, a suede steering wheel, aluminum pedals, and additional gauges for monitoring engine parameters.