The Mitsubishi Lancer Evolution IX has long been a benchmark in the world of turbocharged four-cylinder performance. Its 4G63 engine, twin-scroll turbocharger, and MIVEC variable valve timing make it a formidable platform right off the showroom floor. But even with 286 factory-rated horsepower at the crank, serious enthusiasts know the Evo 9 can do more. In this article, we follow a real-world build that uses GSC S1 camshafts and 1000cc fuel injectors as the foundation to deliver 350 horsepower at the wheels.

The Evo 9 Engine: 4G63 Powerhouse

The heart of the Evo 9 is the legendary 4G63T, a 2.0-liter iron-block inline-four that has earned its place in motorsport history. The block itself is cast iron, closed-deck, and features a forged steel crankshaft with a stroke of 88 mm. The connecting rods use a cracked-cap design and the pistons are cast but factory-oil-jet cooled. This robust bottom end can safely handle 350–400 whp with proper fueling and tuning, which makes the platform ideal for the upgrades we describe here. The cylinder head on the Evo 9 includes Mitsubishi’s MIVEC system on both intake and exhaust camshafts, enabling variable valve timing across the RPM range.

Stock, the 4G63T produces approximately 247–260 horsepower at the wheels depending on the dyno and condition. The twin-scroll TD05HR-16G6 turbocharger builds boost quickly and delivers a broad torque curve, but its airflow potential tops out around 300–320 whp before the compressor wheel becomes a restriction. To reach a reliable 350 whp, the turbocharger must be upgraded, and the engine’s breathing and fuel delivery must be optimized to match the increased airflow.

Building a 350 WHP Package

This build revolves around two key components: a set of GSC S1 camshafts and 1000cc fuel injectors. But these cannot stand alone. After discussing the core parts, we’ll cover the supporting modifications that make the whole package work on both pump gas and a factory-style ECU tune.

GSC S1 Camshafts

GSC Power Division’s S1 camshafts are designed as the first step beyond stock cams for the 4G63. They are available in both MIVEC and non-MIVEC variants; for the Evo 9, the MIVEC-compatible S1 cams are used. The S1 profile offers 272 degrees of advertised duration and 0.410 inch lift at the valve. Compared to the factory camshafts, the S1s increase both lift and duration on the intake and exhaust sides, allowing the engine to ingest and expel more air at higher RPMs while still maintaining driveability at low speeds.

One of the most compelling aspects of the S1 camshafts is that they do not require valve spring upgrades for RPMs below 8000. The stock springs are capable of handling the S1 ramp rates, making installation relatively straightforward. When paired with a proper tune, the S1 cams typically add 20–30 whp over a stock cam setup at the same boost level. In this build, the S1 camshafts shift the powerband slightly upward, pulling strongly from 4000 RPM to the 7500 RPM redline.

1000cc Fuel Injectors

To supply enough fuel for 350 whp, the factory 560 cc/min injectors are no longer adequate. Upgrading to 1000 cc injectors provides a generous safety margin. The specific injectors in this build are high-impedance units from FIC (Fuel Injector Clinic) with a flow rate of 1000 cc/min at 43.5 psi (3 bar). These injectors are direct plug-and-play with the stock fuel rail and harness, requiring only a change to the injector scaling in the ECU map.

Using larger injectors also lowers injector duty cycle, which improves atomization and cooling at high load. With the stock 560 injectors, duty cycle may exceed 80% near the fuel cut limit when pushing for 350 whp, risking lean conditions. The 1000 cc injectors keep duty cycle well below 60% even at peak power, leaving room for future upgrades. A high-quality set like the Injector Dynamics ID1700 would also work, but the 1000 cc size is perfect for the 350 whp target on 93 octane pump fuel.

Fuel System Overview

In addition to the injectors, a Walbro 255 lph or AEM 340 lph fuel pump is recommended to maintain fuel pressure under high flow. The stock pump can keep up until about 330 whp, but at 350 whp the pressure may dip. In this build the owner installed a Walbro 255 in-tank pump along with a rewire kit for consistent voltage. The factory 4G63 fuel pressure regulator is sufficient at this power level, though a small adjustment to base pressure can fine-tune the dead-time compensation table during tuning.

Upgraded Turbocharger

Reaching 350 whp on a 2.0L engine requires a turbocharger capable of flowing roughly 44–47 lb/min of air. The stock TD05HR-16G6 twin-scroll turbo peaks at about 36 lb/min. This build uses a Garrett GT3076R with a 0.63 A/R turbine housing, single-scroll T3 flange. While this sacrifices the factory twin-scroll response, the GT3076R delivers a noticeable mid-range punch and pulls hard to redline. To maintain spool characteristics, the builder selected a turbine housing with a divided inlet and fabricated a twin-scroll up-pipe adapter. The result: full boost by 3700 RPM, only 300 RPM later than stock.

Intercooling and Induction

An upgraded intercooler is a must. The stock top-mount intercooler becomes a heat sink once boost exceeds 22 psi. This build uses a ETS (Extreme Turbo Systems) 3.5-inch core front-mount intercooler with cast aluminum end tanks. Charge air temperatures drop by 20–30°F during a full-throttle pull, keeping the intake air density high and reducing the risk of knock. On the intake side, a 3-inch intake pipe and an HKS Racing Suction Reloaded air filter reduce restriction. The MAF sensor is relocated after the filter to ensure accurate airflow readings.

Exhaust System

A free-flowing exhaust is critical for turbo spool and maximum power. This car runs a 3-inch stainless steel downpipe with a high-flow catalytic converter (optional for street legality) and a 3-inch cat-back exhaust with a single straight-through muffler. The stock exhaust manifold is retained since it performs well up to 400 whp, but the factory O2 housing is replaced with a Grimmspeed divorced wastegate O2 housing to reduce backpressure and improve flow around the wastegate.

Engine Management and Tuning

The factory Evo 9 ECU uses a flash-based system that can be reflashed using a tactrix cable and open-source software (ECUFlash) or a dedicated tuning suite like EcuTek. In this instance, the ECU was reflashed by a calibrated tune from Boostin Performance. The final calibration included adjustments to injector scaling, MAF calibration, ignition timing, boost control duty cycle, and the MIVEC mapping. The MIVEC maps were advanced on the intake side between 4000 and 6500 RPM to take advantage of the S1 cam profiles, producing a smoother torque curve.

Boost pressure is controlled through a Mac boost solenoid and is set to a peak of 26 psi tapering to 23 psi at the redline. The air/fuel ratio is tuned to 11.5:1 at full load for safety on 93 octane fuel, with ignition timing held conservative (16–18 degrees at peak torque) to avoid detonation.

The Dyno Session: Validating the Build

After the modifications and initial street tuning, the Evo 9 was strapped to a Mustang MD-500 dynamometer at a local shop. Ambient conditions were 72°F and 29.92 inHg, representing a standard day. The car was left in fourth gear (1:1 ratio) and run from 3000 RPM to 7600 RPM. Three pulls were performed, with the best run producing 353.4 whp and 325 lb-ft of torque.

The power curve climbs steadily after 3800 RPM, with peak torque at 4400 RPM and peak horsepower at 7100 RPM. The torque curve flattens nicely between 4200 and 5500 RPM, providing strong in-gear acceleration. The air/fuel ratio holds a steady 11.4–11.6:1 across the pull, and boost peaks at 26.2 psi before settling at 23.5 psi near redline. No knock activity was detected on the factory knock sensor or a secondary audible knock detector.

The 350 whp milestone was achieved with margin. The injector duty cycle measured 58% at peak power, confirming ample headroom. The turbo is working within its efficiency island; the temperature of the compressor outlet was 215°F and post-intercooler air temps were 106°F. These numbers indicate a robust setup that can handle sustained pulls at the track.

Drivability and Reliability

A common concern with aggressive cams and larger turbos is loss of low-end torque. However, the combination of the MIVEC-equipped GSC S1 cams and a quick-spooling GT3076R means the car feels nearly stock below 3000 RPM. Off-boost throttle response is crisp due to the retained stock intake manifold and proper ignition timing. The owner reports that daily commuting in traffic is comfortable; the idle quality is only marginally rougher than stock, and the smell of raw fuel from the larger injectors is negligible.

Reliability-wise, this build respects the factory safety margins. The boost level is well within the fuel and octane capabilities. Oil temperatures during aggressive driving stay below 240°F with a stock oil cooler. The owner installed an aftermarket oil pressure gauge and temperature gauge to monitor vitals. At 350 whp, the 4G63T’s bottom end is under moderate stress; with proper maintenance (oil changes every 3000 miles, synthetic 5W-40), this engine should see a long service life.

Cost vs. Performance

Building a reliable 350 whp Evo 9 with these specific parts is not inexpensive, but it offers a strong power-to-dollar ratio compared to other performance cars. Here is a rough breakdown of the components used:

  • GSC S1 MIVEC camshafts: $849
  • FIC 1000 cc injectors: $399
  • Garrett GT3076R turbo kit (including manifold/downpipe): $2,200
  • ETS front-mount intercooler kit: $1,095
  • Fuel pump and rewire: $199
  • Tuning (reflash and dyno time): $750
  • Miscellaneous (gaskets, oil, plugs, MAF adapter): $200

Total parts and labor (if self-installed): approximately $5,700. A professional installation would add $1,000–$1,500 in labor. For that investment, the car transforms from a stock 260 whp car into a 353 whp machine that runs on pump gas and retains a/c and power steering. Compare that to buying a newer sports car with 350 whp stock—a 2024 Subaru WRX STI or Ford Focus RS costs more than double that amount.

Conclusion

Achieving 350 wheel horsepower from an upgraded Evo 9 using GSC S1 camshafts and 1000cc injectors is not just possible—it’s a well-worn path that delivers real, repeatable results. The combination of improved cylinder head flow from the cams and a fuel system that can deliver ample gasoline allows the 4G63T to reach its potential with a sensible turbo upgrade. This build stays true to the philosophy of the Evo 9: an everyday performance car that can surprise far more expensive machinery on the road and track. For those looking for a turnkey 350 whp setup, the parts list above is a proven recipe. The Evo 9’s aftermarket continues to thrive, and builds like this ensure the legend remains relevant more than a decade after production ended.