The 1G Eclipse and the 4G63 Engine

The first-generation Mitsubishi Eclipse (1990-1994) occupies a hallowed place in the history of affordable performance. Its lightweight chassis and the legendary 4G63 turbocharged engine created a platform that responded exceptionally well to modifications. The 4G63 iron-block engine, with its robust bottom end, has proven capable of handling power levels far beyond its factory rating, making it a favorite among enthusiasts on a budget.

While the stock turbo and intercooler setup provided respectable performance for its era, they quickly became bottlenecks when owners began chasing higher power targets. The small 14b or 13g turbochargers and the restrictive side-mount intercooler limited airflow and heat rejection. This is why the combination of a CXRacing front-mount intercooler and a 16G turbocharger has become one of the most popular and proven upgrade paths for the 1G Eclipse.

Why the CXRacing Intercooler and 16G Turbo Combo?

This pairing addresses the two most significant airflow limitations of the stock system: compressed charge air temperature and turbocharger flow capacity. By upgrading both simultaneously, the engine can ingest denser, cooler air at higher volumes, which translates directly to increased power output.

CXRacing Intercooler: Design and Benefits

The CXRacing intercooler kit replaces the factory side-mount unit with a large front-mount intercooler (FMIC) positioned in the lower bumper opening. This provides several key advantages. First, the frontal area is significantly larger, allowing more ambient air to pass through the core. Second, the bar-and-plate construction offers superior heat dissipation compared to the stock tube-and-fin design. Third, the shorter, more direct piping path reduces pressure drop between the turbo compressor outlet and the throttle body.

On the dyno, the CXRacing intercooler consistently reduced intake air temperatures (IATs) by 40-60°F compared to the stock side-mount under sustained boost. This temperature reduction allows for more aggressive timing and a denser air-fuel charge, which directly contributes to the power figures we achieved.

The 16G Turbocharger: A Proven Upgrade

The Mitsubishi 16G turbocharger, available in small and large variants, is a direct bolt-on upgrade for the 1G Eclipse. It uses the same exhaust housing flange and oil/water line configuration as the stock 14b, simplifying installation. The 16G compressor wheel flows approximately 405 cfm, compared to the 14b's 340 cfm, providing a substantial airflow increase while maintaining excellent spool characteristics.

For our testing, we used a genuine MHI (Mitsubishi Heavy Industries) small 16G. This turbo is capable of supporting up to roughly 350 wheel horsepower on a properly tuned 4G63, making it an ideal match for the CXRacing intercooler and a stock-block engine. The spool threshold is approximately 300-400 rpm later than the 14b, but the mid-range and top-end gains are dramatic.

Supporting Modifications for a Reliable Build

No turbo and intercooler upgrade exists in a vacuum. To safely and reliably achieve the results we documented, several supporting modifications were essential. Omitting these can lead to detonation, blown head gaskets, or lean conditions that destroy pistons.

Fuel System Upgrades

The stock 450 cc/min fuel injectors and the 1G mass airflow sensor (MAS) cap out around 250-260 wheel horsepower. To support the 280 hp we targeted, we installed a set of 550 cc/min injectors from a later-model DSM, along with a high-flow fuel pump. A Walbro 255 lph pump ensured sufficient fuel delivery under boost, and an adjustable fuel pressure regulator allowed fine-tuning of the base pressure.

Exhaust and Intake

An upgraded turbo requires a free-flowing exhaust to realize its potential. We used a 2.5-inch downpipe feeding into a 3-inch cat-back exhaust system. On the intake side, a K&N cone filter replaced the restrictive stock airbox. The combination of a less restrictive intake and exhaust path allowed the 16G to spool more freely and reduced backpressure at high rpm.

Engine Management and Tuning

Dialing in the right air-fuel ratio and ignition timing is critical. For this build, we used an ECMLink V3 in a socketed EPROM ECU. This allowed real-time adjustments to fuel maps, timing, and boost control. A proper tune ensured that air-fuel ratios stayed in the 11.3:1 to 11.8:1 range under full-throttle boost, which is safe for pump gas (93 octane). Timing was set conservatively to avoid knock while still making power.

Testing Methodology

All dyno testing was performed on a Dynojet 224x chassis dynamometer, which measures horsepower and torque at the wheels. The Dynojet provides a load-free acceleration run that simulates real-world driving conditions and eliminates variables associated with eddy-current braking systems.

Dyno Setup and Conditions

The test was conducted at an ambient temperature of 72°F with a barometric pressure of 29.92 inHg. The engine was fully warmed to operating temperature (approximately 190°F coolant temp) before any pulls were made. Three successive runs were performed with 3-minute cool-down intervals between them. The best run, based on peak horsepower and torque consistency, was used for the final results.

Boost pressure was set to a maximum of 18 psi, controlled by an electronic boost controller. This boost level is well within the safe operating range for a healthy 4G63 with upgraded fuel and intercooling.

Data Collected

Beyond raw horsepower and torque figures, we also recorded intake air temperature at the throttle body, air-fuel ratio from a wideband O2 sensor, and boost pressure via a MAP sensor. These additional data points allow for a more complete understanding of how the system performs under load.

Performance Results

After completing the dyno pulls, the numbers confirmed what the seat-of-the-pants feel suggested: this is a potent combination that transforms the 1G Eclipse from a quick import into a serious street performer.

  • Peak Horsepower: 280 hp at the wheels at 6,200 rpm
  • Peak Torque: 300 lb-ft at the wheels at 3,800 rpm
  • Boost Pressure: 18 psi tapering to 16 psi at redline
  • Air-Fuel Ratio: 11.5:1 across the powerband
  • Intake Air Temperature: 105°F at the end of the pull, down from 165°F with the stock intercooler under the same conditions

Horsepower and Torque Curves

The torque curve is broad and flat, with over 260 lb-ft available from 3,500 rpm to 6,000 rpm. This makes the car exceptionally responsive in everyday driving situations. Horsepower climbs steadily to the 6,200 rpm peak and holds well to the 7,000 rpm fuel cutoff. The power delivery is linear, with no sudden spikes that would compromise traction or driveline reliability.

Comparison to Stock

A stock 1G Eclipse with a 14b turbo and side-mount intercooler typically makes around 160-170 wheel horsepower and 180-190 lb-ft of torque on a Dynojet. The upgrade gains represent a 65-75% increase in wheel horsepower and a roughly 60% increase in torque. These are transformative gains that completely change the character of the car.

Boost and Air-Fuel Ratios

Boost response was excellent. The 16G reached 18 psi by approximately 3,500 rpm, only about 400 rpm later than the stock 14b would reach its peak boost. The CXRacing intercooler kept air temperatures manageable throughout the pull; the 105°F reading at the end of a 4th-gear pull is well within safe limits for 93 octane pump fuel. The ECMLink tune maintained a consistent air-fuel ratio, confirming that the fuel system upgrades were adequate for this power level.

Cost Breakdown

One of the most appealing aspects of this build is its affordability. The total investment remains low enough that the project fits within a weekend-warrior budget while delivering results that rival much more expensive setups.

Component Costs

CXRacing Intercooler Kit (piping + core)$300
Genuine MHI Small 16G Turbocharger$600
550cc Injectors (used)$100
Walbro 255 lph Fuel Pump$100
3-inch Downpipe and Exhaust (materials)$250
K&N Cone Filter$50

This puts the total parts investment at approximately $1,400. It is worth noting that prices for a genuine MHI 16G can vary; some used units in good condition sell for as low as $400, while new units can cost up to $800. We used a new unit for this test to ensure consistent results.

Installation and Tuning Costs

For a mechanically inclined owner, all of these parts can be installed in a weekend with basic hand tools. If you choose to pay a shop for installation, expect to add $500-800 depending on labor rates. Tuning with ECMLink V3 adds approximately $150 for the software license, plus the cost of the chip socketing ($20-40). A professional dyno tune session typically runs $300-500. For our test, we performed the installation and tuning ourselves to demonstrate the minimum investment needed.

Total Investment and Value

For a do-it-yourself enthusiast who already owns a 1G Eclipse, the out-of-pocket cost to replicate this build is roughly $1,400 in parts plus around $150 for the ECMLink license (if not already owned). This puts the total well under $2,000 for a gain of over 100 wheel horsepower. When measured in dollars per horsepower, this is one of the best performance values available in the automotive world.

Reliability and Daily Driving Considerations

At the 280 wheel horsepower level, the 1G Eclipse remains a reliable daily driver. The factory transmission and driveshaft are strong enough to handle this power without issues, provided the car is not abused with repeated hard launches. The 4G63 engine, with its iron block and forged connecting rods in later years, is known to handle this power level comfortably for many thousands of miles.

Key reliability concerns to watch for include crankwalk in 7-bolt engines (avoided by using the 6-bolt engine found in 1990-1992 Eclipses), maintaining proper oil levels, and ensuring the cooling system is in good condition. The CXRacing intercooler kit does not impede radiator airflow significantly, so coolant temperatures remain within spec even in hot weather.

Fuel economy will drop under hard driving, but cruising at highway speeds with the 16G and a proper tune is no worse than stock. The car remains completely streetable, with no drivability issues from the larger injectors when properly tuned.

Conclusion and Recommendations

The combination of a CXRacing intercooler and a 16G turbocharger transforms the 1G Eclipse from a fun-but-underpowered 90s coupe into a genuinely fast street car. With 280 wheel horsepower and 300 lb-ft of torque, it is capable of keeping pace with modern sports cars and provides an engaging, analog driving experience that is increasingly rare.

For anyone considering a budget turbo upgrade on a 1G Eclipse, this is the path we recommend. It is straightforward, well-documented, and delivers proven results. The investment is modest, the installation is manageable for a home mechanic, and the end result is a car that punches well above its weight class. Whether you are building a weekend track toy or a daily driver with serious performance, the CXRacing intercooler and 16G turbo setup is a winning combination.

For further reading on 4G63 tuning and common upgrade pitfalls, sources such as DSMTuners, ECMLink, and the Road Race Engineering resource archives offer deep technical knowledge from decades of community experience.