Overview of Crankshaft Subaru Ee20z: Composition, Mechanical Properties, and Applications

Types of Crankshafts for Subaru EE20Z Engine

The crankshaft in the Subaru EE20Z engine is a critical mechanical component responsible for converting the linear motion of the pistons into rotational motion, which ultimately powers the vehicle. This 2.0L horizontally opposed (boxer) diesel engine is primarily used in Subaru models such as the Forester, Impreza, and Legacy, and is also found in select Suzuki diesel applications. Due to its high compression ratio and torque output, the crankshaft must be engineered for durability, balance, and efficiency.

Several types of crankshafts are used in the EE20Z engine, each designed with specific materials and structural features to meet performance, longevity, and comfort requirements. Below is a detailed breakdown of the most common crankshaft variations found in this engine platform.

Cast Iron Crankshaft

Made from high-strength cast iron, this crankshaft is designed for durability and cost-effective manufacturing in standard production engines.

Advantages

• Excellent wear resistance under normal operating conditions
• High damping capacity reduces engine vibrations
• Cost-effective for mass production
• Stable performance in daily driving scenarios

Limitations

• Heavier than forged alternatives, increasing rotational inertia
• Lower tensile strength compared to forged steel
• Less suitable for high-performance or high-torque modifications

Best for: Stock applications, fuel-efficient daily driving, OEM replacements

Forged Steel Crankshaft

Manufactured through a forging process that compresses steel under extreme pressure, resulting in a stronger, more resilient component.

Advantages

• Superior strength and fatigue resistance
• Lighter weight improves engine responsiveness
• Ideal for high-torque and performance tuning
• Better grain structure enhances longevity

Limitations

• Higher manufacturing and replacement cost
• Requires precise balancing and installation
• Less vibration damping than cast iron

Best for: Performance builds, modified engines, heavy-duty use

Counterweighted Crankshaft

Features integrated counterweights to balance the reciprocating forces of opposing pistons in the boxer engine layout.

Advantages

• Reduces engine vibration for smoother operation
• Improves longevity of engine mounts and connected components
• Enhances driving comfort, especially at higher RPMs
• Optimized for the EE20Z’s horizontally opposed configuration

Limitations

• Slightly more complex design and manufacturing
• Potential for imbalance if damaged or improperly serviced
• May require dynamic balancing during rebuilds

Best for: All EE20Z applications, especially where smoothness and reliability are priorities

Expert Tip: When rebuilding an EE20Z engine, always inspect the crankshaft for scoring, cracks, or journal wear. If upgrading to a forged crankshaft, ensure proper balancing of the rotating assembly (including pistons, rods, and flywheel) to maximize performance and engine life.

Why Crankshaft Choice Matters in the EE20Z

The Subaru EE20Z’s diesel operation generates high cylinder pressures and torque, placing significant stress on internal components. The crankshaft must not only withstand these forces but also maintain balance to prevent premature wear on bearings and seals. Additionally, a well-designed crankshaft contributes to fuel efficiency by minimizing internal friction and ensuring smooth power delivery.

Because the EE20Z uses a flat-four (boxer) configuration, inherent vibration from opposing piston movement is mitigated through precision engineering—especially via counterweighted crankshafts. Choosing the right type ensures optimal performance, whether you're maintaining a stock engine or building a more powerful variant.

How to Choose a Crankshaft for Subaru EE20Z Engine

Selecting the right crankshaft for a Subaru EE20Z engine is a critical decision that impacts engine reliability, performance, and longevity. The EE20Z, a 2.0L turbo-diesel boxer engine used in models like the Forester and Legacy, demands precision components due to its horizontally opposed configuration and high-torque output. Choosing an incompatible or low-quality crankshaft can lead to imbalance, vibration, premature wear, or catastrophic engine failure.

Below are the key factors to consider when selecting a replacement or performance crankshaft for your EE20Z engine, with detailed insights to help you make an informed decision.

1. Material and Construction: Strength Meets Durability

The material used in crankshaft manufacturing directly influences its ability to withstand stress, torsional forces, and fatigue over time. Subaru typically uses two types of crankshafts: cast iron and forged steel.

Cast Iron Crankshafts

Commonly found in stock EE20Z engines, cast iron crankshafts offer good durability and cost-efficiency for standard driving conditions. They are manufactured through a casting process, which is less expensive but results in a more brittle structure compared to forged alternatives.

Best suited for daily drivers and moderate use, they may not hold up well under high boost, increased RPM, or performance tuning.

Forged Steel Crankshafts

Made from high-grade steel billets that are forged under extreme pressure, these crankshafts offer superior strength, ductility, and resistance to cracking. Forged units are the preferred choice for performance builds, towing applications, or modified EE20Z engines where reliability under stress is paramount.

Though more expensive, their extended service life and ability to handle higher horsepower make them a worthwhile investment for enthusiasts.

2. Balance and Counterweights: Ensuring Smooth Operation

The horizontally opposed (boxer) layout of the EE20Z engine inherently produces unique vibration characteristics. A properly balanced crankshaft with precisely engineered counterweights is essential to minimize harmonic vibrations and ensure smooth power delivery.

Factory crankshafts are dynamically balanced to exact specifications. When replacing or upgrading, it's crucial that the new crankshaft undergoes professional balancing—either individually or as part of a balanced rotating assembly (including pistons, rods, and flywheel).

Improper balance can lead to excessive engine vibration, accelerated bearing wear, and potential damage to motor mounts or internal components.

3. Brand and Compatibility: Trust Matters

Not all crankshafts marketed for the EE20Z are created equal. OEM (Original Equipment Manufacturer) Subaru crankshafts guarantee perfect fitment and adherence to factory tolerances. Reputable aftermarket brands like CP-Carrillo, Eagle, or K1 Technologies also offer high-quality forged options designed specifically for Subaru diesel engines.

Avoid generic or unbranded crankshafts that lack proper testing or certification. Always verify compatibility with the EE20Z engine code and confirm whether the crankshaft includes correct reluctor ring positioning, oil passages, and journal dimensions.

Warning: Using a crankshaft designed for a gasoline boxer engine (e.g., EJ20 or FB20) in an EE20Z diesel application can result in mechanical failure due to differences in stroke, weight, oiling system, and strength requirements.

4. Precision Machining and Tolerances: The Devil Is in the Details

Precision machining ensures that all journals, fillets, and oil holes meet exact dimensional standards. Tight tolerances are vital for maintaining proper oil clearance, reducing friction, and preventing premature bearing failure.

Look for crankshafts that have been ground to OEM specifications or better, with surface finishes that promote lubrication retention. High-quality units often come with micro-polished journals and rolled fillets to enhance fatigue resistance.

If rebuilding the engine, always have the crankshaft inspected by a machine shop for straightness, journal wear, and surface cracks—even if using a used OEM unit.

5. Performance Requirements: Match the Crankshaft to Your Goals

Your intended use should dictate your crankshaft choice:

Keep in mind that increasing engine output places greater stress on the crankshaft, especially in diesel applications where low-end torque is substantial.

6. Price and Budget: Long-Term Value Over Short-Term Savings

While OEM and forged crankshafts carry a higher upfront cost, they offer better long-term value through improved reliability and reduced risk of engine damage. A failed crankshaft can lead to extensive collateral damage, including broken connecting rods, damaged cylinder walls, and oil system contamination.

Important: Never compromise on crankshaft quality when rebuilding an EE20Z engine. Always pair the crankshaft with compatible components (rods, bearings, pistons) and follow proper installation procedures, including correct torque specs and engine break-in protocols. Consult a qualified mechanic or engine builder for complex installations.

Commercial Opportunities for Subaru EE20Z Crankshafts

The Subaru EE20Z diesel engine, known for its reliability and performance in models like the Forester and Impreza, presents a growing aftermarket demand for high-quality replacement and performance components. The crankshaft, a critical engine component responsible for converting piston motion into rotational power, is especially vital for engine rebuilds, performance upgrades, and fleet maintenance. This guide explores key commercial markets and strategic approaches for wholesalers and distributors targeting customers seeking genuine or upgraded Subaru EE20Z crankshafts.

Automotive Workshops & Mechanic Garages

Independent repair shops and specialized diesel service centers are primary end-users of aftermarket crankshafts. These businesses frequently perform engine overhauls on aging EE20Z-powered vehicles, particularly in regions where diesel Subarus remain popular for their fuel efficiency and durability.

• Offer bulk pricing and trade accounts to encourage repeat business from established garages
• Provide installation support materials (torque specs, alignment guides) to enhance service quality
• Partner with shops to supply complete short-block rebuild kits (crankshaft, bearings, gaskets)
• Promote precision-balanced, OEM-spec crankshafts to ensure smooth engine operation

Business Advantage: Workshops value reliable supply chains and technical support—position your brand as a trusted partner in engine rebuilds.

Online Auto Parts Retailers

E-commerce platforms specializing in Japanese or Subaru parts can significantly expand your market reach. These retailers cater to DIY enthusiasts, importers, and international buyers searching for hard-to-find diesel components.

• Supply exclusive SKUs or branded packaging to help retailers differentiate their offerings
• Provide high-resolution product images, compatibility charts, and detailed descriptions for SEO optimization
• Enable drop-shipping options to reduce inventory burden for online sellers
• Support retailers with marketing content (blogs, videos) explaining crankshaft function and upgrade benefits

Growth Tip: List products on major marketplaces (eBay, Amazon, CarParts.com) through partner retailers to increase visibility.

Automotive Manufacturing & Reconditioning Companies

Companies involved in engine remanufacturing, crate engine assembly, or EV/diesel hybrid conversions may require certified crankshafts in volume. The EE20Z’s compact boxer layout makes it attractive for niche applications, including marine, industrial, or custom vehicle builds.

• Offer OEM-reconditioned or forged performance crankshafts for industrial applications
• Provide material certifications (SAE steel grade, heat treatment reports) for compliance-sensitive buyers
• Support private labeling for companies building branded engine packages
• Explore B2B contracts for long-term supply agreements with remanufacturers

Strategic Opportunity: Position your crankshafts as core components in "renewed engine" programs targeting sustainability-conscious fleets.

Performance & Racing Specialists

Enthusiasts modifying EE20Z engines for increased power, especially in rally or track-prepped Subarus, demand high-strength crankshafts capable of handling boosted performance. Forged or nitrided crankshafts offer superior fatigue resistance under high RPM and turbocharged conditions.

• Develop a performance line with counterweighted, micro-polished crankshafts for balanced high-RPM operation
• Market to tuners as part of Stage 2+ engine builds requiring internal upgrades
• Partner with turbo upgrade and engine management firms for bundled performance packages
• Highlight tensile strength, dynamic balancing, and fatigue testing data to appeal to technical buyers

Performance Edge: Offer crankshafts compatible with stroker kits to increase displacement and torque output.

Automotive Education & Training Institutions

Technical schools, community colleges, and vocational training centers use real-world components like the EE20Z crankshaft for hands-on engine diagnostics and rebuilding courses. These institutions often purchase parts in bulk for classroom use or student projects.

• Supply non-functional or cutaway crankshafts for demonstration purposes at reduced cost
• Create educational bundles with pistons, connecting rods, and bearings for complete engine disassembly labs
• Provide technical diagrams and curriculum support materials to instructors
• Offer institutional discounts and warranty programs for teaching fleets

Long-Term Investment: Building relationships with educators fosters brand recognition among future mechanics and engineers.

Fleet Operators & Government Agencies

Government fleets, rental companies, and utility services operating diesel Subarus may seek reliable replacement crankshafts to extend vehicle service life. These organizations prioritize durability, warranty coverage, and cost-per-mile efficiency.

• Offer extended warranties and volume discounts for fleet maintenance contracts
• Provide rapid replacement programs to minimize vehicle downtime
• Highlight corrosion-resistant coatings and fatigue-tested materials for high-mileage applications
• Support with maintenance logs and part traceability for compliance reporting

Operational Benefit: Reliable crankshafts reduce unscheduled repairs and improve fleet availability.

Strategic Recommendation: Focus on building a multi-channel distribution strategy that combines direct B2B sales with online retail partnerships. Emphasize product quality, technical documentation, and after-sales support to differentiate from generic suppliers. Consider launching a certification program for preferred installers to build trust and brand loyalty in the Subaru diesel community.

Additional Strategic Considerations

• Compatibility Assurance: Clearly label crankshafts with EE20Z-specific part numbers and model year coverage (e.g., 2008–2020 Forester diesel variants)
• Quality Certification: Highlight ISO, IATF 16949, or JASO compliance to build buyer confidence
• Global Export Potential: The EE20Z was widely used in Europe, Australia, and Japan—target international markets with localized packaging and support
• Aftermarket Branding: Develop a sub-brand (e.g., "SubDrive Pro" or "BoxerCore") to establish identity in the Subaru performance community
• Sustainability Angle: Promote crankshaft remanufacturing and recycling programs to appeal to eco-conscious buyers

Frequently Asked Questions: Subaru EE20Z Engine

The Subaru EE20Z is one of the most distinctive diesel engines in the automotive world, known for its innovative engineering and robust performance. As the first mass-produced horizontally opposed (boxer) diesel engine, it combines Subaru’s signature low-center-of-gravity design with the efficiency and torque of a diesel powerplant. This section answers common questions about the EE20Z engine, covering its off-road capabilities, versatility beyond Subaru vehicles, and fuel economy advantages over gasoline engines.

Did You Know? The EE20Z engine was introduced in 2008 and primarily used in the Subaru Forester and Legacy models in select international markets, particularly in Europe and Japan. Its unique design makes it a favorite among diesel enthusiasts and off-road adventurers alike.

What makes the Subaru EE20Z engine suitable for off-road and adventurous driving experiences?

The Subaru EE20Z engine stands out in off-road and adventure-oriented applications due to its innovative horizontally opposed (boxer) configuration and specially engineered diesel crankshaft. This layout positions the engine’s mass lower in the chassis, significantly lowering the vehicle’s center of gravity. As a result, vehicles equipped with the EE20Z experience improved balance, reduced body roll, and enhanced traction on uneven terrain—critical advantages when navigating rocky trails, steep inclines, or loose surfaces.

Beyond stability, the boxer design inherently reduces engine vibrations, translating into a smoother and more comfortable ride during prolonged off-road excursions. Additionally, the EE20Z delivers high torque at low RPMs—typically around 350 Nm (258 lb-ft) from just 1,800 rpm—which allows for confident crawling over obstacles without frequent gear changes. This combination of mechanical balance, smooth power delivery, and strong low-end torque makes the EE20Z an excellent choice for drivers seeking reliable performance in rugged environments.

Can the EE20Z engine be used outside of Subaru vehicles?

Yes, while the EE20Z was originally developed and engineered exclusively for Subaru’s lineup—particularly the Forester diesel and Legacy diesel models—it has found applications beyond factory automotive use. Due to its compact dimensions, durability, and efficient power output, the EE20Z has been successfully adapted for use in marine environments, including small boats and auxiliary power systems. Enthusiasts and marine engineers have praised its reliability and resistance to vibration, which are essential qualities in marine propulsion systems.

Moreover, the engine’s modular design and widespread availability in certain markets have made it a popular candidate for custom conversions and alternative vehicle builds, such as off-grid camper vans or lightweight adventure rigs. With proper modifications to cooling, exhaust, and mounting systems, the EE20Z can be integrated into non-Subaru platforms. However, compatibility with electronic control units (ECUs), fuel injection systems, and emissions equipment must be carefully managed during such projects.

How does the Subaru EE20Z engine compare to gasoline engines in terms of fuel economy?

The EE20Z diesel engine offers a clear advantage in fuel economy when compared to similarly sized gasoline engines. On average, vehicles equipped with the EE20Z achieve approximately 25–35% better fuel efficiency than their gasoline counterparts under comparable driving conditions. For example, the diesel Forester could achieve around 6.0–6.5 L/100 km (36–39 mpg) on the highway, significantly outperforming the gasoline model’s consumption of roughly 8.0–9.0 L/100 km (29–33 mpg).

This efficiency stems from several key factors:

• Higher energy density of diesel fuel: Diesel contains about 10–15% more energy per liter than gasoline, allowing more work to be extracted from the same volume.
• Superior thermal efficiency: Diesel engines operate at higher compression ratios, leading to more complete combustion and less wasted energy.
• Lean-burn operation: The EE20Z uses precise common-rail direct injection to optimize fuel delivery, maximizing combustion efficiency and minimizing waste.

These characteristics make the EE20Z particularly well-suited for long-distance touring, overlanding, and fleet operations where fuel availability and operating costs are critical considerations.

Expert Tip: When maintaining an EE20Z engine, pay special attention to the glow plug system, diesel particulate filter (DPF) regeneration cycles (if equipped), and fuel injector cleanliness. Regular use of high-quality diesel and periodic long drives help keep the engine running efficiently and prevent carbon buildup.

Additional Considerations

• The EE20Z engine is not available in North American markets due to emissions regulations and Subaru’s strategic focus on gasoline and hybrid technologies in that region.
• Owners should be aware that diesel engines require specific maintenance routines, including water separator draining and cold-weather fuel additives in colder climates.
• While the EE20Z is durable, sourcing replacement parts may require importing from Japan or Europe, depending on your location.
• The engine’s noise and vibration levels, while reduced by the boxer layout, are still higher than modern gasoline engines—something to consider for daily driving comfort.

In summary, the Subaru EE20Z engine represents a unique fusion of Subaru’s core engineering philosophy with the practical benefits of diesel technology. Whether you're exploring remote trails, converting a vehicle, or simply seeking maximum fuel efficiency, the EE20Z offers a compelling blend of performance, economy, and adaptability that continues to attract enthusiasts worldwide.