The 1G Eclipse and the MHI TD05: A Performance Rite of Passage

The first-generation Mitsubishi Eclipse, alongside its Diamond Star Motors (DSM) siblings—the Eagle Talon and Plymouth Laser—holds a legendary status in the tuner world. From 1990 to 1994, these cars packed the 4G63T engine, a cast-iron block with forged internals that, in its original 14B turbocharged form, pushed 195 horsepower to the crank. Industry enthusiasts quickly realized the 4G63T's potential. The restrictive 14B turbocharger runs out of breath past 5,000 RPM, leaving significant headroom on the table. The definitive solution for extracting that hidden power is the MHI TD05 turbocharger upgrade.

However, simply bolting on a larger turbo is a recipe for disaster. This guide provides a comprehensive roadmap that covers turbo selection, critical supporting modifications, a meticulous installation walkthrough, and a realistic cost breakdown, ensuring your 1G Eclipse not only makes more power but does so reliably.

The MHI TD05 Family: Choosing the Right Variant for Your 1G Eclipse

Mitsubishi Heavy Industries (MHI) produced the TD05 turbocharger in several variants, each offering a distinct power band and driving experience. The "TD05" designation refers to the turbine wheel diameter (5 inches or roughly 12.5 cm). Understanding these differences is essential before making a purchase.

EVO III 16G: The Gold Standard

The EVO III 16G is widely considered the ultimate upgrade for a street-driven 1G DSM. It features a large 16G compressor wheel (68mm) and the upgraded TD05H turbine wheel. This combination provides a spool threshold nearly as quick as the stock 14B but pulls hard all the way to redline. It easily supports 300 to 400 wheel horsepower with the correct supporting mods. The factory EVO III setup also features a larger wastegate actuator and a more efficient compressor housing.

This specific variant requires drilling the stock 1G exhaust manifold to 10mm to accommodate the larger studs, a simple but critical step.

Big 16G vs. Small 16G vs. 20G

  • Small 16G: A direct bolt-on upgrade that uses the stock 14B compressor cover. It offers a minor power gain but spools identically to the 14B. It is often not worth the effort unless a 14B has failed and a replacement is needed.
  • Big 16G: A generic term for a 16G wheel in a larger compressor housing. It performs admirably, offering strong mid-range power. However, the EVO III 16G has largely superseded it in value.
  • 20G: This features a 68mm compressor wheel on the inducer side but a larger exducer. It requires significant supporting modifications, including an upgraded fuel system, larger injectors (750cc+), and a front-mount intercooler. The 20G creates tremendous heat and is best suited for drag racing or high-boost applications. Spool is significantly later than the 16G.

For 95% of 1G owners seeking a responsive, daily-drivable powerhouse, the EVO III 16G is the unequivocal choice. It builds boost by 3,000 RPM and pulls violently to 7,500 RPM, transforming the car without sacrificing low-end drivability.

Why Upgrade? The Real-World Benefits and Expected Gains

The stock 14B turbocharger is efficient up to roughly 14-15 PSI of boost. Beyond that, it becomes a heat pump, pushing hot, high-pressure air that leads to engine knock. The TD05 family, specifically the 16G, is designed for higher pressure ratios. Upgrading delivers the following performance characteristics:

  • Sustained Top-End Power: The 14B falls off sharply after 5,500 RPM. The 16G pulls hard all the way to the 7,000 RPM fuel cut (and beyond with a tune).
  • Improved Torque Curve: A larger compressor wheel moves more air volume, increasing the area under the torque curve. The car feels significantly faster at highway speeds.
  • Consistent Boost Control: The stock 14B often spikes boost. The larger integrated wastegate on the EVO III 16G provides more stable boost control, especially when paired with an aftermarket manual boost controller (MBC).
  • Higher Ceiling for Future Upgrades: A properly supported 16G build leaves room for cams, ethanol (E85), and larger injectors without changing the turbocharger.

Important note on fuel economy: At light throttle cruise, fuel consumption remains identical to stock. Under wide-open throttle, you are consuming more fuel to produce significantly more power. Efficiency, in terms of power per fuel unit, often improves due to the compressor operating in a more efficient island.

Before You Begin: The Critical Supporting Mods

Installing a TD05 turbocharger without addressing the fuel, tuning, and intake/exhaust systems is a path to engine failure. The following supporting modifications are non-negotiable for a reliable build.

Fuel System Upgrades

The stock 450cc injectors and 10-year-old fuel pump cannot supply enough fuel for a TD05 running any measurable boost. A lean condition under boost causes detonation, which will quickly destroy a 4G63T.

  • Fuel Pump: A Walbro 255 lph (W255) is the standard. It provides ample fuel for up to 500 whp. Crucial: This pump overpowers the stock fuel pressure regulator. You must install an aftermarket Adjustable Fuel Pressure Regulator (AFPR) and a fuel pressure gauge to avoid rich idle and flooding.
  • Injectors: 650cc to 750cc injectors are ideal for a 16G. These provide a 50% duty cycle safety margin at your power target. For an 18G or 20G, look for 850cc to 1050cc injectors. Matching injectors to your tuning solution is critical.

Engine Management and Tuning

You cannot simply increase fuel pressure and hope for the best. The stock 1G ECU runs in open-loop until it sees mass airflow, and it cannot compensate for larger injectors or altered airflow characteristics.

  • ECMLink V3: This is the gold standard for DSM tuning. It allows you to reflash the stock ECU, control injector size, adjust timing maps, and data-log every critical parameter. It supports SD (Speed Density) tuning, which is highly recommended for upgraded turbos.
  • Socketed ECU and EPROM Chip: A budget-friendly alternative is a socketed ECU with a custom chip from a trusted tuner. This provides a tuneable base map but lacks the real-time adjustability of ECMLink.
  • Wideband O2 Sensor: A wideband air/fuel ratio gauge is mandatory. You need to see exactly what your car is doing under load. Innovate, AEM, and Zeitronix are reliable brands.

Intake and Exhaust Flow

The stock 1G sidemount intercooler (SMIC) and restrictive exhaust are bottlenecks for a TD05 upgrade.

  • Front Mount Intercooler (FMIC): A proper FMIC is the single best investment for consistent performance. It lowers intake air temperatures, prevents heat soak, and allows you to run more aggressive timing. An ETS, VRSF, or custom kit is highly recommended.
  • Exhaust System: A 3-inch turbo-back exhaust (from the O2 housing back) is required. The stock 2.1-inch system strangles the turbo. A 3-inch downpipe, test pipe (or high-flow cat), and cat-back system provide the flow necessary to prevent backpressure that would otherwise cause boost creep.
  • Blow-Off Valve (BOV): The stock 1G plastic bypass valve is prone to cracking and leaking under higher boost levels. A 1G BOV modification kit (crush mod) or an aftermarket replacement (Greddy Type RS, Tial Q) that is recirculated back into the intake is necessary to maintain stable idle and prevent stalling.

Detailed Installation Guide for the MHI TD05 on a 1G DSM

This section provides the mechanical steps necessary for a successful installation. Safety and precision are paramount.

Preparation and Workspace

  • Park on a level surface. Disconnect the battery ground terminal.
  • Drain the coolant and oil into appropriate containers.
  • Obtain a full gasket kit for the turbo install (manifold to head, turbo to manifold, O2 housing to turbo).
  • Soak all exhaust manifold studs in penetrating oil (PB Blaster) 24 hours before disassembly. Snapping a stud is a common, time-consuming problem.

Step 1: Removing the Stock Setup

Carefully remove the heatshields, intake pipe, turbo-to-intercooler pipe (L-pipe), and downpipe. Unbolt the oil feed and drain lines. Remove the coolant lines. Finally, unbolt the exhaust manifold from the cylinder head (working from the center outwards). Tip: Label all bolts and hoses.

Take photos for reference.

Step 2: Prepping the New Turbo and Manifold

  • Port the manifold: The stock 1G manifold's outlet is slightly smaller than the EVO III 16G's inlet. Port-matching the manifold to the turbo gasket is a free power gain that improves spool.
  • Install a 90-degree oil feed adapter: The stock 14B oil feed line is not directly compatible. Use a high-quality -4AN stainless steel braided oil feed line. Install the oil filter housing to turbo fitting with a restrictor if your turbo is journal bearing (most MHI are).
  • Drill the manifold to 10mm: The EVO III 16G uses larger studs (10mm) than the stock 14B (8mm). Accurately drill out the manifold holes. Use new 10mm studs and nuts.

Step 3: Installing the Turbo

Position the new gasket between the manifold and the turbo. Torque the turbo-to-manifold bolts to 40 ft-lbs. Install the downpipe and O2 housing with a new gasket. Torque to 45 ft-lbs. Use high-temperature anti-seize on all threads for future disassembly.

Step 4: Connecting Fluids

  • Oil Feed: Connect your new -4AN line to the oil filter housing port. Do not overtighten the aluminum fitting into the block.
  • Oil Drain: This is the most critical line. The turbo's oil drain is gravity-fed. It must slope downward from the turbo to the oil pan without any restrictions. Do not kink the drain line. Use a -10AN or -12AN drain line.
  • Coolant Lines: If your TD05 is water-cooled (most EVO III 16Gs are), properly route the coolant lines. An aftermarket coolant line kit is highly recommended to eliminate the restrictive stock hard pipes.

Step 5: The Critical Check: Clearance

Do not skip this step. With the turbo and manifold installed, rotate the engine over by hand (using a socket on the crank pulley). Listen for any contact between the compressor wheel and the compressor housing. Also, check that the wastegate actuator can open fully without contacting anything. The 1G water pipe running near the compressor outlet often needs a small dent for clearance.

Tuning and Testing Your New Setup

Before starting the engine, prime the turbo with oil. The best method is to pull the MPI (Multi-Port Injection) fuse or disconnect the crank angle sensor (CAS) and crank the engine for 15-20 seconds. This builds oil pressure before the engine starts.

  1. Initial Startup: Start the engine and immediately check for oil leaks at the feed line and drain. Let it idle for 5 minutes, monitoring coolant temperature. Do not rev it.
  2. Check for Boost Leaks: Use a boost leak tester (a simple homemade rig or a commercial kit). Pressurize the intake system to 20 PSI. Listen for hissing. Fix all leaks before driving. A large boost leak will cause a lean condition.
  3. Base Tune: Set your base fuel pressure (typically 43 PSI with the vacuum line off). Using your tuning software (ECMLink), set your global fuel and deadtime for your new injectors. Load a base map.
  4. Test Drive: Take the car for a gentle drive. Get into boost lightly, watching your wideband. Aim for an air/fuel ratio of 11.5:1 at 15 PSI on pump gas. Do not hammer on it until you have logged a few pulls and confirmed zero knock.
  5. Data Logging: Log RPM, throttle position, airflow, knock count, and wideband readings. Adjust your fuel and timing maps accordingly.

Realistic Cost Breakdown of the MHI TD05 Upgrade

Budgeting accurately for this upgrade is essential. Costs vary wildly based on the quality of parts and whether you do the labor yourself. Below is a realistic breakdown for a properly executed build.

Component / Service Budget-Conscious Build Recommended "No Compromises" Build
MHI TD05 Turbocharger (EVO III 16G) $800 (Used, inspected core) $1,200 - $1,500 (New, genuine MHI from vendor)
Install Kit (Gaskets, Lines, Bolts) $150 (Basic gasket set + used lines) $300 - $400 (SS oil feed/drain, coolant kit, ported manifold)
Fuel System $300 (Used Walbro 255 + AFPR) $600 (New Walbro 400, AFPR, 1000cc Injectors)
Engine Management $250 (Socketed ECU + chip from tuner) $600 (ECMLink V3 with cable)
Intercooler $200 (Used sidemount + hard pipes) $800 (New ETS/VRSF Front Mount Kit)
Exhaust System $200 (Used 3" downpipe, stock catback) $1,000 (Full 3" turbo-back, stainless steel)
Gauges & Boost Control $150 (Used wideband + MBC) $500 (Wideband, boost gauge, EBC, oil pressure gauge)
Labor (If using a mechanic) $500 (If you know a guy) $1,500 - $2,500 (Professional shop rate, 15-20 hours)
Total Estimated Cost ~$2,550 ~$6,500 - $7,500

Important: These totals do not include miscellaneous consumables (fluids, tools, unexpected broken parts). Always add a 20% contingency to your budget. A cheap build is rarely a reliable build.

Common Pitfalls and How to Avoid Them

There are specific vulnerabilities in the 1G DSM chassis that you must address when adding power.

The 7-Bolt Crank Walk Issue

1993-1994 1G Eclipses use the 7-bolt engine, which is susceptible to crankshaft thrust bearing failure ("crank walk") under high stress or with poor clutch installations. If you have a 7-bolt, ensure you have a proper clutch alignment tool and consider upgrading to a well-balanced flywheel. Many high-horsepower 7-bolts run fine, but it is a known weak point that deserves respect.

Boost Creep

A common issue with the EVO III 16G on a 1G is boost creep, where you cannot control boost because the wastegate is too small. This is solved by porting the wastegate hole in the O2 housing and ensuring the flapper door fully opens. A 3-inch exhaust also helps mitigate creep by reducing backpressure.

Leaking Blow-Off Valves

The stock 1G plastic BOV leaks at anything above 12 PSI. If you are experiencing idle surging or stalling after the install, your BOV is likely leaking. Either replace it with a 1G BOV with the "crush mod" or install an aftermarket recirculating BOV.

Heat Management

A bigger turbo generates significantly more under-hood heat. If you do not have a proper heatshield, your intake air temperatures will skyrocket, leading to power loss and knock. Consider ceramic coating your exhaust manifold, wrapping your downpipe, or installing a turbo blanket.

Conclusion: The Path to 1G Supremacy

Upgrading your 1G Eclipse to an MHI TD05 turbocharger is the single most rewarding modification you can perform. It transforms the car from a forgettable 1990s coupe into a responsive, exhilarating machine that punches far above its weight. However, this path demands respect for the engineering. A successful build is not defined by the turbo alone but by the comprehensive approach to supporting modifications, meticulous installation, and disciplined tuning. By adhering to the principles outlined in this guide, you ensure that your 1G not only hits its power goals but remains a reliable, thrilling companion for years to come.

Whether you are chasing lap times or simply a massive smile on your morning commute, the TD05 upgrade is the definitive step forward for the DSMs enthusiast.

For further technical data and community support, consult ECMLink and DSMTuners.