The 1G Eclipse, particularly the turbocharged GSX and TSi models, remains a beloved platform for performance enthusiasts. Its 4G63 engine is legendary for its strength and tuning potential. One of the most effective modifications to unlock significant power is upgrading the factory turbocharger. This comprehensive guide walks you through maximizing power with a 16G or 20G turbo upgrade, covering installation tips, supporting modifications, tuning, and a detailed cost analysis to help you plan your build.

Why Upgrade from the Factory 14B Turbo?

The stock 14B turbocharger on the 1G Eclipse is a capable unit, but it runs out of breath around 250–280 wheel horsepower. For enthusiasts looking for more power without sacrificing daily drivability, a 16G or 20G turbocharger is the next logical step. These turbos bolt directly onto the stock exhaust manifold and O2 housing, making them a popular “drop-in” upgrade. However, to realize their full potential, you must address the engine’s air, fuel, and ignition systems.

Turbocharger Comparison: 16G vs. 20G

16G Turbocharger Overview

The 16G is available in two main variants: the small 16G (from the Evo I-III) and the big 16G (common aftermarket upgrade for DSMs). It features a larger compressor wheel than the 14B, flowing roughly 40% more air. Spool is very quick — full boost arrives around 3000–3200 RPM. Power potential ranges from 300 to 380 wheel horsepower on pump gas with proper tuning. This turbo is ideal for street-driven cars that need responsive power for daily driving and autocross.

20G Turbocharger Overview

The 20G uses an even larger compressor wheel, capable of flowing enough air for 400–500 wheel horsepower. It spools a bit later, reaching full boost around 3500–3800 RPM. The trade-off is higher top-end power. A 20G is best suited for drag racing or high horsepower street builds where mid-range and top-end punch is prioritized over instant spool. It requires more extensive supporting modifications and a stronger fuel system.

Quick Decision Guide

  • Choose a 16G if: You want a fast-spooling, fun street car with reliable 350 HP, minimal lag, and a stock-like driving experience.
  • Choose a 20G if: You are chasing 400+ HP, plan to run race gas or E85, and are willing to upgrade the fuel system, intercooler, and clutch.

Critical Supporting Modifications

A turbo upgrade is only as good as the supporting systems. Installing a 16G or 20G without upgrading fuel delivery and cooling is a recipe for detonation and engine failure. Below are the essential upgrades.

Fuel System Upgrades

  • Fuel Injectors: For a 16G, 550–660cc injectors are sufficient. For a 20G, start with 750–1000cc injectors. Use high-impedance injectors for plug-and-play compatibility.
  • Fuel Pump: A Walbro 255 lph (or equivalent) rewire kit is mandatory. A rewired 255 pump supports at least 450 HP. For higher power on E85, consider a 450 lph pump.
  • Adjustable Fuel Pressure Regulator (AFPR): The stock regulator cannot handle the flow of a 255 pump, causing over-pressurization. An AFPR ensures stable fuel pressure.

Air Intake and Intercooling

  • Hard Intercooler Pipes: Replace the stock rubber pipes with aluminum or silicone pipes to prevent boost leaks and increase flow.
  • Front Mount Intercooler (FMIC): A large FMIC is necessary for a 20G; a 16G can work with a upgraded sidemount, but a FMIC is strongly recommended to reduce intake temperatures.
  • Intake Pipe and Air Filter: Upgrade to a 3-inch intake pipe with a high-flow air filter (K&N or similar).

Exhaust System

  • Downpipe and O2 Housing: The stock O2 housing is restrictive. Upgrade to a 2.5- or 3-inch tubular O2 housing and a full 3-inch turbo-back exhaust. This reduces backpressure and allows the turbo to breathe.
  • External Wastegate (Optional): If you plan to run high boost (25+ psi) with a 20G, an external wastegate provides better boost control and eliminates boost creep.

Engine Management and Tuning

  • ECU Tuning: The stock ECU cannot handle the airflow of a 16G/20G. Options include: a chip-tuned ECU (e.g., from ECMLink), a standalone system (like AEM or Haltech), or a piggyback (such as SAFC). ECMLink is the most popular and feature-rich choice for DSMs.
  • Wideband O2 Sensor: A wideband air/fuel ratio gauge is essential for safe tuning. Install a sensor in the downpipe and monitor real-time AFRs.
  • Boost Controller: A manual or electronic boost controller allows precise adjustment. Electronic controllers (Apexi AVC-R, Turbosmart E-Boost) offer in-cabin adjustability and boost-by-gear.

Step-by-Step Installation Guide

While a professional installation is an option, many enthusiasts tackle this project themselves. Below is a condensed guide for installing a 16G or 20G turbo on a 1G Eclipse.

Tools and Supplies Needed

  • Metric socket set (10mm, 12mm, 14mm, 17mm, 19mm)
  • Wrenches (10mm, 12mm, 14mm, 17mm, 19mm)
  • Torque wrench (ft-lb and in-lb)
  • Penetrating oil (e.g., PB Blaster)
  • Gasket set (turbo manifold, O2 housing, oil return line)
  • New copper crush washers for oil feed/return lines
  • Anti-seize compound
  • Jack stands and floor jack

Step 1: Prepare the Vehicle

Disconnect the battery. Drain the engine oil and coolant. Remove the intercooler piping, intake pipe, and air filter box. Remove the heat shield over the turbo. Label and disconnect all vacuum lines and sensors.

Step 2: Remove the Stock Turbo

Unbolt the O2 housing from the turbo (three bolts). Unbolt the downpipe from the O2 housing. Remove the turbo-to-manifold bolts (four nuts). Carefully lift the turbo assembly out — it’s heavy. Separate the oil feed and water lines. Clean the manifold mating surface thoroughly.

Step 3: Prepare the New Turbo

Check the oil ports and verify that the 16G/20G has the correct oil restrictor (if journal bearing). Install the new oil return line gasket and copper washers. For a 20G, consider using a stainless steel braided oil feed line for reliability.

Step 4: Install the New Turbo

Place the new turbo onto the manifold with a fresh gasket. Torque the manifold nuts to 35–40 ft-lb in a crisscross pattern. Reconnect the water lines and oil feed line. Install the O2 housing with a new gasket — for a 20G, use a 2.5-inch or 3-inch O2 housing. Reinstall the downpipe and the intercooler piping.

Step 5: Reassemble and Check for Leaks

Reinstall the intake, air filter, and all vacuum lines. Fill the engine with fresh oil and coolant. Start the engine and let it idle. Check for oil leaks around the turbo, and water leaks at the coolant lines. Boost leak test using a compressor and a boost leak tester tool.

Any leaks must be fixed before tuning.

Step 6: Break-In Procedure

Drive gently for the first 200 miles, keeping boost under 10 psi. This allows the turbo bearings to seat and the seals to break in. After break-in, perform the initial tuning session.

Tuning for Power and Safety

Proper tuning is the most critical step after a turbo upgrade. Untuned, a 16G or 20G will cause knock, detonation, or melted pistons. Use ECMLink or similar to adjust fuel maps and ignition timing. Target air/fuel ratios of 11.0–11.5 under full boost (gasoline). For daily driving, boost levels of 15–18 psi with a 16G are safe; a 20G can run 18–22 psi on pump gas.

On E85 or race fuel, you can push significantly more boost. Always monitor knock count (aim for 0–3 counts maximum) and exhaust gas temperature (below 1600°F).

Potential Pitfalls and Solutions

  • Boost Creep: Common with 20G turbos on stock exhaust. Solution: port the wastegate passage, use a larger flapper door, or go external wastegate.
  • Oil Leaks from Turbo Drain: Ensure the return line is not kinked and is angled downward. Use a reinforced rubber hose or braided line.
  • Fuel Starvation: The stock fuel pump cannot keep up. A rewired 255 pump is mandatory for anything over 14 psi on a 16G.
  • Clutch Slipping: Stock clutch will fail quickly with 350+ HP. Upgrade to a stage 2 or 3 clutch (e.g., ACT, South Bend).

Detailed Cost Analysis

Below is a realistic budget for a 1G Eclipse 16G or 20G turbo upgrade. Prices are estimates and may vary by brand and condition.

Turbocharger

  • 16G (new aftermarket, e.g., MHI EVO III Big 16G): $600 – $900
  • 20G (new aftermarket): $950 – $1,300
  • Used (eBay or forum): $300 – $500 (riskier, but possible)

Installation Costs (DIY vs. Shop)

  • DIY: $0 labor, plus cost of gasket set (~$40) and new fasteners (~$20)
  • Professional installation: $500 – $1,000 depending on labor rate and location

Supporting Modifications (Minimum for 16G)

  • Fuel injectors (660cc used set): $150 – $250
  • Fuel pump (Walbro 255 with rewire kit): $120 – $180
  • AFPR: $150 – $250
  • Wideband O2 sensor: $150 – $200
  • ECMLink V3 (used): $500 – $600
  • Boost controller (manual): $40 – $60
  • Front mount intercooler kit: $300 – $600
  • 3-inch exhaust (cat-back): $400 – $800

Additional Items for 20G Build

  • Larger injectors (750cc+): $200 – $350
  • 3-inch O2 housing: $100 – $200
  • External wastegate kit: $400 – $700
  • Clutch upgrade: $400 – $700

Total Estimated Cost

  • 16G budget build (DIY, part used): $2,000 – $2,500
  • 16G premium build (new parts, professional install): $3,500 – $4,500
  • 20G build (new, with all supporting mods): $4,500 – $6,500

Note: Prices do not include tuning session fees (typically $200–$500 per hour on a dyno). A safe tune usually takes 2–3 hours.

Performance Expectations After Tuning

  • 16G at 18 psi (pump gas): 300–330 whp, 320–340 wtq
  • 16G at 22 psi (E85): 350–380 whp, 370–400 wtq
  • 20G at 20 psi (pump gas): 370–410 whp, 390–430 wtq
  • 20G at 28 psi (E85/race fuel): 450–500 whp, 450–480 wtq

These numbers are achievable with proper tuning and a healthy engine. The 4G63 bottom end is stout enough for 500 whp on stock internals, but the transmission (especially the FWD) becomes a weak point above 400 whp. Upgrade to a stronger clutch and consider a limited-slip differential (LSD).

Final Thoughts

Upgrading a 1G Eclipse with a 16G or 20G turbocharger is a proven path to serious horsepower. The 16G remains the best all-around choice for daily drivers who want quick spool and reliable 350 HP. The 20G is for those who live on the track or crave 500+ HP bragging rights. Whichever you choose, invest in supporting modifications and professional tuning — shortcuts will lead to broken parts and wasted money. The DSM community is rich with resources; consult forums like DSMTuners and ECMLink's knowledge base for guidance.

With careful planning, your 1G Eclipse can be transformed into a truly exhilarating machine.