Mitsubishi 4G63 Engine: Power, Problems & Potential

The Mitsubishi 4G63 engine is nothing short of a motoring icon, widely celebrated as one of the greatest four-cylinder engines to ever emerge from Japan. Its reputation stems from its remarkable performance capabilities, even in its factory-standard form, and its pivotal role in elevating vehicles like the Mitsubishi Evolution to legendary status within the automotive world. This engine isn't just a piece of engineering; it's a foundation for high-performance builds, a source of both immense pride and, for some, considerable frustration. Understanding the nuances of the 4G63 requires a journey through its history, its technical specifications, its notorious Achilles' heel, and the myriad ways enthusiasts continue to push its boundaries.

What is the 4G63 Engine?

At its core, the 4G63 is a 2.0-litre inline-four engine produced by Mitsubishi. While many enthusiasts primarily associate it with the high-performance turbocharged variant, the 4G63T, it's important to recognise that the 4G63 nomenclature actually encompasses a broader family of engines, including naturally aspirated versions. The 'T' simply denotes the presence of a turbocharger, which is where the engine truly shines, delivering astonishing power figures that can easily reach well into the 400 horsepower range with minimal modifications from stock.

This powerhouse engine found its way into a diverse range of vehicles, not just the globally acclaimed Mitsubishi Evolution line-up (from Evo I to Evo IX). In the North American market, it was a cornerstone of the Diamond Star Motors (DSM) collaboration between Mitsubishi and Chrysler. During the mid-1990s, DSM vehicles like the Mitsubishi Eclipse, Eagle Talon, and Plymouth Laser became highly sought-after, offering an accessible entry point into the world of turbocharged all-wheel-drive sports coupes, long before the Subaru WRX and Evolution officially arrived stateside.

Mitsubishi's engine coding system provides a clear insight into the 4G63's fundamental characteristics: the first digit ('4') signifies four cylinders, the second ('G') indicates a petrol engine, the third ('6') denotes the engine family, and the fourth ('3') specifies the model within that family. This system confirms the 4G63 as a petrol-powered, four-cylinder engine that, in its various iterations, consistently delivered performance. The naturally aspirated 4G63 was found in models like the first-generation Mitsubishi Eclipse RS and GS, while a smaller 1.8-litre variant, the 4G93, also existed, adhering to the same logical nomenclature.

The Infamous "Crankwalk" Phenomenon

Despite its many accolades and incredible performance potential, the 4G63 engine is sadly also known for a severe and often catastrophic flaw: crankwalk. This issue, primarily affecting specific generations of the 4G63, refers to the undesirable axial movement of the crankshaft within the engine block. It typically stems from a prematurely failed thrust bearing or, in some documented cases, mis-machined engine girdles that lead to improper clearances. Regardless of the root cause, the outcome is consistently detrimental to the engine's health and longevity.

The early signs of crankwalk can be subtle but quickly escalate. Owners of affected DSM or Mitsubishi vehicles might first notice their engine cutting out or shutting off during left-hand turns, a peculiar symptom related to the crankshaft shifting and affecting sensor readings. In more advanced stages, the problem becomes audibly apparent: a distinct clicking or grinding sound can be heard, particularly when the clutch pedal is depressed. This noise is often the crankshaft physically making contact with and damaging the crank position sensor, a clear indication of excessive axial play. Unfortunately, once crankwalk is confirmed, the engine is usually beyond repair, necessitating a complete engine replacement.

The prevalence and severity of crankwalk had significant repercussions, not just for individual owners but also for Mitsubishi as a whole. Many believe this reliability issue played a substantial role in Mitsubishi's decision to discontinue the Evolution line, despite its global popularity and strong competition with rivals like the Subaru WRX STI. The controversy surrounding crankwalk led to a major scandal, tarnishing Mitsubishi's reputation for reliability and highlighting a perceived lack of accountability from the manufacturer. It remains a cautionary tale in automotive engineering and a significant footnote in the otherwise stellar history of the 4G63.

Variations of the 4G63T: Six-Bolt vs. Seven-Bolt

Within the world of the turbocharged4G63T, enthusiasts often discuss two primary variations, distinguished by a seemingly minor detail: the number of bolts on their crank snout. These are commonly referred to as 'six-bolt' and 'seven-bolt' engines, and the distinction carries significant weight within the tuning community.

The older 'six-bolt' engines, typically found in pre-1992 models, are often preferred by serious modders and builders. This preference largely stems from specific internal differences, such as the use of larger connecting rods in these earlier iterations. These more robust components are generally considered stronger and better suited for handling higher power outputs, making the six-bolt a highly desirable foundation for extreme performance builds. Consequently, engine swapping a six-bolt 4G63 into a chassis originally equipped with a seven-bolt engine has become a common and popular upgrade among the DSM and Evolution tuning crowd.

If you're considering a 1G six-bolt 4G63 swap, it's also a wise move to investigate the specific 1G cam angle sensors. Certain cam angle sensors from the first-generation Eclipse models offer the capability to adjust base timing, which is an incredibly useful feature for any tuner looking to precisely manipulate engine parameters and extract maximum performance from a turbocharged setup.

Unleashing More Power: The 4G63 Capacity Upgrade Kit

While the stock 4G63 is already a formidable engine, its true potential is often unlocked through internal modifications, particularly capacity upgrade kits. These kits are designed to increase the engine's displacement, leading to significant gains in torque and enabling the use of even larger, more powerful turbochargers. A prime example of such an upgrade is the HKS Capacity Upgrade Kit, which offers a comprehensive solution for transforming a standard 4G63 into a high-performance 2.3-litre monster.

HKS Capacity Upgrade Kit 4G63 2.3L (Step 2)

HKS, a renowned Japanese tuner, provides a racing-specification capacity upgrade kit that redesigns critical components like the connecting rods and crankshaft. This meticulous engineering ensures not only enhanced performance but also maintains exceptional quality. The kit significantly increases the 4G63 engine displacement from its original 1,997cc to a potent 2,231cc (Step 2), resulting in a remarkable increase in torque, which is crucial for spooling larger turbochargers effectively.

Key features of the HKS kit include its "Racing Specifications" offered at a competitive price, making high-level performance more accessible. Furthermore, HKS proudly states that all components are "Made In Japan," with strict supervision throughout the manufacturing, inspection, and packaging processes, guaranteeing superior quality and consistency.

Component Details:

• Connecting Rods: Through extensive CAE analysis and in-house testing, the rod's shape has been optimised. Surface processing and materials are carefully chosen to reduce manufacturing costs without compromising performance or quality.
• Crankshaft: Similarly, the crankshaft has undergone rigorous analysis and redesign to lower costs while maintaining performance. A notable achievement is the sharp reduction in weight, bringing it to only 1kg over the stock weight, which contributes to higher engine response and improved efficiency.
• Pistons: The kit includes pistons with molybdenum-coated skirts, enhancing initial fitment and reducing friction. The piston diameter is 0.5mm oversize from standard, an ideal choice for those concerned about block strength with larger bore pistons. This also offers an economical advantage, as the block can be reused with 86mm pistons in the future.

Technical Specifications (HKS Step 1 vs. Stock):

The Step 2 kit, based on feedback from the "Carbon EVO" CT230R, specifically aims for a 2.3L (2231cc) displacement, making it perfectly suited for applications with large turbochargers. It typically includes newly designed H-beam connecting rods and a lightweight crankshaft. The pistons feature nickel-plated tops and an "oval coated" skirt to improve anti-knocking properties and reduce friction. The suggested power limit for this kit is around 500ps with 60kgm of torque, beyond which the block durability may decline.

Machining Requirements:

• Cylinder boring and honing are required due to the 0.5mm oversized pistons.
• No block clearance modifications are necessary for the larger stroke crank, simplifying installation.

Should You Build a 4G63T Engine? Building Basics 101

Deciding to build a 4G63T engine can be a daunting task given the myriad of options available. Terms like "stroker" and "de-stroker" can add to the confusion. Fundamentally, engine building for increased power involves understanding material properties and tolerances, which directly impact an engine's power-holding capacity and longevity.

When contemplating a build, it's helpful to categorise potential power levels. For instance, builders often use terms like "Stage 1" or "Stage 2" to differentiate between the approximate power an engine can reliably handle. These designations imply specific components and assembly techniques, recognising that increased power generates more heat and stress on internal components.

• Stage 1 Engine: Typically features tighter tolerances in ring gaps and bearings, with a focus on lighter, less-wearing materials. These builds are generally suited for moderate power gains and offer excellent street manners and longevity for their intended power level.
• Stage 2 Engine: Designed for significantly higher power outputs, these engines utilise looser tolerances. This accommodates greater expansion from higher operating temperatures and higher oil pressures generated at elevated RPMs. While capable of extreme power, these engines might exhibit characteristics like piston rattle during cold starts due to larger piston-to-wall clearances, which can accelerate bore wear over time.

A common question arises: "Should I build my engine to handle more power than I expect to need, to allow for future growth?" While it's certainly possible to over-engineer your build, the misconception is that a larger-scale build automatically translates to a longer-lasting engine. For maximum life expectancy, it's generally recommended to build an engine that precisely suits your current power goals. A "Stage 1" engine, with its tighter clearances, will typically have a longer lifespan for street use than an overbuilt "Stage 2" engine constantly operating below its design parameters, which can lead to accelerated wear from piston instability during cold operation.

Stroker and De-stroker Engines Explained

Many modern 4G63 builds incorporate components from both 4G63 and 4G64 engine geometries. The 4G64 block is essentially a 4G63 block, but it's 6mm taller. Crucially, the internal component geometry is compatible, allowing for the creation of various hybrid builds with differing displacements. This flexibility is key to customising the engine's power delivery characteristics.

The basic builds typically involve either the 4G63 block with its 88mm crankshaft or the 4G64 block with its 100mm crankshaft. While the factory connecting rod length for these engines is 150mm, many builders opt for 156mm rods to alter the rod ratio, influencing piston speed and side loading. Aftermarket crankshaft solutions further bolster these combinations, allowing for unique short-block assemblies often requiring custom forged pistons to achieve desired specifications.

Which Combination is Best? Pros and Cons

The choice of engine combination is a highly debated topic and often depends on the specific application, tuning advancements, and desired power band. Here's a breakdown of common configurations:

Maintaining Your 4G63

Regardless of whether your 4G63 is stock or heavily modified, proper maintenance is paramount to its longevity and performance. Regular oil changes with high-quality, appropriate-viscosity oil are non-negotiable, especially for turbocharged engines that operate under immense heat and stress. Monitoring the cooling system, including coolant levels and radiator condition, is also crucial to prevent overheating, which can quickly lead to catastrophic engine failure.

For modified engines, more frequent inspections and preventative maintenance are advised. This includes checking for boost leaks, monitoring fuel pressure, and ensuring that all sensors are functioning correctly. Given the potential for issues like crankwalk in certain models, paying attention to any unusual noises or changes in engine behaviour is vital. Investing in a reliable engine management system and having your car tuned by an experienced professional can also significantly extend the life of your performance 4G63 by ensuring optimal air-fuel ratios and timing.

Frequently Asked Questions (FAQs)

What is the power potential of a stock 4G63T?

A factory-standard turbocharged4G63T, particularly in later Evolution models, can often reach impressive figures of 280-300 horsepower. With basic bolt-on modifications and a proper tune, it's not uncommon for these engines to exceed 400 horsepower.

Is crankwalk fixable?

Unfortunately, once crankwalk has developed to a noticeable degree, it typically requires a complete engine replacement or a thorough rebuild involving machining the block and replacing the crankshaft and thrust bearings. It is not a simple "fix."

What's the best 4G63 for building high horsepower?

Many experienced builders prefer the earlier "six-bolt" 4G63 engines due to their stronger internal components, such as larger connecting rods, making them a more robust foundation for extreme power builds.

What are essential upgrades for a turbocharged 4G63?

Key upgrades for a turbocharged4G63 include a larger turbocharger, upgraded fuel system (injectors, fuel pump), a high-flow exhaust, an improved intercooler, and a capable engine management system with a professional tune. For higher power levels, internal upgrades like forged pistons and connecting rods are crucial.

Can I daily drive a built 4G63?

Yes, a properly built and tuned 4G63 can be daily driven. However, the level of comfort and reliability will depend on the build's "stage" and the tolerances used. "Stage 1" builds with tighter clearances tend to be more street-friendly, while extreme "Stage 2" builds might require more frequent maintenance and exhibit characteristics less suited for daily commuting.

Conclusion

The Mitsubishi 4G63 engine has undeniably carved out its place in automotive history. It's a testament to Japanese engineering, capable of delivering thrilling performance and serving as a blank canvas for ambitious tuners. While its legacy is tinged with the shadow of crankwalk, its enduring appeal lies in its inherent strength, its adaptability, and the sheer exhilaration it provides when pushed to its limits. For those willing to understand its intricacies and navigate its challenges, the 4G63 remains a top-tier choice for building a truly potent and legendary performance machine.

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