The 1G Eclipse: A Legendary Platform for Performance

The first-generation Mitsubishi Eclipse (1990–1994) shares its underpinnings with the Eagle Talon and Plymouth Laser, forming the core of the DSM (Diamond Star Motors) enthusiast community. Its lightweight unibody and factory turbocharged 4G63 engine—available in 135 hp and 195 hp variants—make it an ideal candidate for serious power upgrades. With proper aftermarket support, a 1G Eclipse can reliably produce 400–600 hp or more. This article details the brands that deliver proven, trustworthy performance parts for this iconic platform, helping you choose components that match your goals and budget.

Categories of Performance Parts for the 1G Eclipse

Before diving into specific brands, it’s important to understand the main upgrade paths. Each category contributes to overall power, reliability, or handling. Common categories include:

  • Engine components: internals (rods, pistons, cams), head work, and turbo upgrades
  • Fuel system: larger injectors, high‑flow fuel pumps, and adjustable pressure regulators
  • Intake and exhaust: cold air intakes, header/downpipes, and cat‑back exhausts
  • Engine management: standalone ECUs, piggyback systems, and tuning software
  • Cooling and drivetrain: upgraded radiators, intercoolers, clutches, and LSDs
  • Suspension and braking: coilovers, sway bars, bushings, and big brake kits

Top Brands for 1G Eclipse Performance Parts

The aftermarket for DSMs is mature, but not every brand is equal in fitment, quality, or customer support. The following brands have earned consistent praise from the 1G Eclipse community for their reliable power gains and durability.

1. Mitsubishi Motors (OEM+)

While not an aftermarket tuner brand, genuine Mitsubishi parts remain the gold standard for reliability. For stock‑replacement or mild upgrades (e.g., a factory EVO III 16G turbo upgrade), OEM components ensure plug‑and‑play compatibility. Note that many genuine Mitsubishi parts are still available through dealerships or online retailers like Mitsubishi Parts Central. For those building a daily driver, using OEM gaskets, seals, and timing belts eliminates guesswork.

2. HKS

HKS has been a dominant force in Japanese performance since the 1970s. Their product line for the 4G63 includes:

  • Turbo kits: The HKS GT‑II 3037 kit is a popular choice for 500‑hp street builds, featuring a ball‑bearing center cartridge for spool.
  • Exhaust systems: The HKS Hi‑Power cat‑back (3‑inch) reduces backpressure and produces a deep tone.
  • Intercoolers: HKS air‑to‑air cores (e.g., Type S and Type R) are direct‑fit for the 1G and support over 400 hp.
  • Boost controllers & blow‑off valves: The HKS EVC and SSQV (Sequential Blow‑Off Valve) are iconic DSM upgrades.

Enthusiasts report that HKS parts generally require minimal modification to fit, though some exhaust hangers may need slight adjustment. The brand’s reliability record is excellent, and their turbochargers often outlast cheaper alternatives.

3. Greddy (Trust)

Greddy, known in Japan as Trust, offers a broad range of DSM‑specific parts. Their most notable offerings include:

  • Greddy 24R and 20G turbo kits: Designed for the 1G, these kits include a manifold, wastegate, downpipe, and oil/water lines. The 20G is a favorite for quick spool and 400‑hp potential.
  • Exhaust systems: The Greddy EVO 2 cat‑back uses a straight‑through muffler for minimal restriction.
  • Intercooler kits: Greddy’s front‑mount intercooler (FMIC) kits are among the best‑fitting aftermarket options for the 1G bumper.
  • Oil catch cans.

Greddy’s reputation for quality is long‑standing. Many 1G owners pair a Greddy 20G with 780 cc injectors and a fuel pump to break 400 whp on pump gas.

4. AEM

AEM specializes in engine management and induction systems. Key parts for the 1G Eclipse include:

  • AEM Infinity ECU: A full standalone engine management system that replaces the factory wiring. It offers native support for boost control, flex‑fuel, and data logging. For the 4G63, plug‑and‑play harnesses are available.
  • AEM Cold Air Intake: Improves air flow over the restrictive stock airbox. The filter uses a dry‑flow media that requires no oil.
  • AEM Wideband UEGO: Essential for tuning, especially when moving to larger injectors and turbochargers.
  • AEM Boost and Fuel Pressure gauges.

AEM’s engine management products are widely used by DSM tuners. The Infinity ECU has replaced the older EMS‑4 as the company’s flagship, offering better resolution and expandability.

5. Eibach

While power is exciting, handling keeps the car planted. Eibach is the go‑to brand for spring and sway bar upgrades on the 1G:

  • Eibach Pro‑Kit Springs: Lower the car about 1.2 inches while improving spring rates. They work well with factory shocks.
  • Eibach Sway Bars: 26 mm front and 24 mm rear bars reduce body roll dramatically. Using upgraded end links (from Moog or aftermarket) is recommended.

Many 1G owners combine Eibach springs with Koni Yellow shocks for a budget‑friendly yet effective suspension setup. The Pro‑Kit also maintains adequate ride quality for daily driving.

6. Walbro

Fuel delivery is critical for boosted engines. Walbro’s 255 lph (liters per hour) fuel pump is the standard upgrade for DSMs:

  • Walbro 255 lph (GSS342): Drop‑in replacement for the in‑tank pump. Supports up to 450 hp on pump gas, and up to 600 hp with proper injectors and tuning.
  • Walbro 450 lph (F90000267): For high‑boost or E85 builds. Requires a larger fuel line or twin‑pump setup.

Installation is straightforward: remove the rear seat, access the fuel pump cover, and swap the unit. Most tuners recommend using the 255 lph pump for street cars to keep noise lower than the 450.

7. BC Racing

For coilover suspension, BC Racing offers outstanding adjustability without breaking the bank:

  • BC Racing BR Series Coilovers: 30‑way adjustable damping, ride height adjustable via the shock body, and pillow‑ball upper mounts. Spring rates of 8 kg front / 6 kg rear are common for street use.
  • BC Racing DS Series: A budget alternative with slightly less dampening range, but still a dramatic improvement over stock.

BC Racing coilovers are popular because they offer a true coilover design (spring over shock) that allows independent height and preload adjustment. Many 1G owners report significant improvements in cornering grip and feel.

8. Forced Performance (FP)

Forced Performance is a DSM‑focused turbo builder known for custom wheel designs and rebuildable cores:

  • FP 68HTA: A hybrid of the EVO III 16G, featuring a larger compressor wheel. Capable of 400 hp with excellent spool.
  • FP Green (55 lb/min): A popular street/strip turbo for the 1G, supporting 500 hp on a well‑built engine.
  • FP Red and Black: For extreme builds over 700 hp, requiring fuel system, head work, and cams.

FP turbos come with a reputation for reliability and strong customer support. They are often recommended over generic eBay units because of tighter tolerances and better warranty.

9. Magna Fuel (formerly Aeromotive)

Fuel pressure regulation is essential after upgrading injectors. Magna Fuel’s FPR (fuel pressure regulator) kits are direct‑fit for DSMs:

  • Magna Fuel 13105: Adjustable from 20–75 psi, designed for return‑style fuel systems. Includes a mounting bracket and gauge port.

Pairing a Walbro 255 pump with a Magna Fuel regulator and a set of FIC (Fuel Injector Clinic) injectors (1000 cc or 2150 cc for E85) creates a robust fuel system for any power level.

Choosing the Right Parts for Your Goals

Not every upgrade is necessary for every build. Consider the following tiers:

  • Stage 1 (225–300 hp): Stock turbo with boost controller, 2.5‑inch exhaust, fuel pump rewire, and intake. Budget: $500–$1,000.
  • Stage 2 (350–450 hp): EVO III 16G turbo, 3‑inch exhaust, 650‑780 cc injectors, Walbro 255 pump, FMIC, and a basic tune (e.g., using a SAFC or ECMlink). Budget: $2,000–$3,500.
  • Stage 3 (500–650 hp): FP Green or HKS GT‑II, forged rods and pistons, larger cams, 1000 cc+ injectors, standalone ECU, upgraded clutch, and LSD. Budget: $6,000+.

Always plan your fuel system and engine management before adding a large turbo. Many builders skip the supporting mods and ruin engines—don’t be that person.

Installation Tips and Common Pitfalls

Installing performance parts on a 1G Eclipse requires patience. The engine bay is tight, and 30‑year‑old hardware can snap. Key advice:

  • Use penetrating oil (e.g., Kroil or PB Blaster) on exhaust bolts for 24 hours before disassembly.
  • When upgrading the intercooler, you may need to trim the bumper support or radiator fan shroud.
  • For fuel pump installation, replace the rubber hose inside the assembly with submersible fuel hose to prevent leaks.
  • Always torque turbo bolts to factory specs—over‑tightening cracks the manifold.
  • Join communities like DSM Tuners or DSM Talk for model‑specific guides and troubleshooting.

Suspension and Driveline Upgrades to Match Your Power

Adding 100+ hp without addressing suspension and tires is dangerous. Recommended upgrades:

  • Coilovers: BC Racing or Tein Street Basis for adjustable height and stiffness.
  • Strut tower bars: Add rigidity to the unibody. Companies like RM Racing and OBX offer bolt‑in bars.
  • Clutch: South Bend Clutch (SB Clutch) or ACT are trusted for DSMs. For 400 hp, use a heavy‑duty organic disc; for 500+, use a six‑puck ceramic.
  • Limited slip differential (LSD): A Quaife or Kaaz LSD helps put power down in corners and off the line.

Final Recommendations

Building a 1G Eclipse is a rewarding journey. The aftermarket ecosystem is robust, and the brands listed above have decades of proven results. Start with a solid baseline—fresh timing belt, maintenance, and boost leak test—before adding power. Use reputable vendors like Extreme PSI and STM Performance for genuine parts. Research your specific model year (1990 manual vs. 1990 automatic have different ECU and wiring quirks). With careful planning and quality components, your 1G Eclipse can deliver exhilarating performance that rivals modern sports cars.