What Porsche Owners and Engine Builders Should Know About Nikasil Cylinder Plating

Nikasil cylinder plating has played an important role in Porsche engine technology for decades. Long before many modern engines began using thermal spray coatings, aluminum-silicon bores, or other advanced cylinder surface technologies, Nikasil helped make lightweight aluminum cylinders practical for high-performance engines.

For Porsche owners, Nikasil is often associated with aircooled 911 engines, racing engines, and high-performance cylinder sets. For engine builders, it remains one of the most important cylinder bore technologies to understand because it requires the right inspection, honing, cleaning, piston ring selection, and break-in procedures.

LN Engineering has extensive experience with Nikasil and Nickel Silicon Carbide cylinder platings through its Nickies cylinders, watercooled sleeves, and Porsche cylinder reconditioning services. 

What Is Nikasil?

Nikasil is a nickel-silicon carbide cylinder bore plating developed by Mahle in the 1960s and is still used today by Mahle Motorsport in their Porsche piston and cylinder sets. It was originally created to provide a hard, wear-resistant surface for aluminum rotary engine housings, allowing seals to run directly against an aluminum component that would otherwise be too soft for long-term durability.

The same basic idea applies to piston engines. Aluminum offers excellent heat transfer and reduced weight, but it needs a durable wear surface for the piston rings. Nikasil provides that surface by electroplating a nickel matrix containing silicon carbide particles onto the cylinder bore.

Silicon carbide is extremely hard, and when it is properly distributed in the nickel matrix, it creates a durable surface for the piston rings to run against. This allows an aluminum cylinder or aluminum engine block to retain the heat-transfer advantages of aluminum while providing a wear surface suitable for high-performance operation.

Why Porsche Used Nikasil

Porsche was one of the early manufacturers to use Nikasil in high-performance piston engines. The technology was used in Porsche racing engines and later became well known in production aircooled Porsche engines.

Compared with cast iron liners, Nikasil-plated aluminum cylinders offer several advantages. They transfer heat efficiently, reduce weight, allow tighter piston-to-cylinder clearances, and provide excellent wear resistance when paired with compatible rings and proper surface finish.

For Porsche engines, these advantages are especially important. Aircooled engines depend heavily on efficient heat transfer, and high-performance engines benefit from reduced friction, improved ring seal, and stable cylinder geometry.

Nikasil vs. Cast Iron Cylinders

Traditional cast iron cylinders and sleeves are durable and familiar to most engine builders, but they do not transfer heat as efficiently as aluminum. A cast iron sleeve installed in an aluminum cylinder or block can create a thermal barrier because the two materials expand and transfer heat differently.

Nikasil allows the piston rings to run on a very hard plated surface while still allowing the aluminum cylinder to transfer heat efficiently. This can help the engine run cooler, maintain more consistent clearances, and support improved performance.

Nikasil and similar Nickel Silicon Carbide platings are also oleophilic, meaning they have an affinity for oil. This helps support lubrication at the ring-to-cylinder interface and contributes to reduced friction compared with many traditional iron or steel cylinder surfaces.

What Is NSC Plating?

NSC stands for Nickel Silicon Carbide. It is a nickel-silicon carbide composite plating similar in function and performance to Nikasil. 

In simple terms, NSC plating uses very small silicon carbide particles suspended in a nickel matrix. One useful way to think about it is like concrete: the silicon carbide particles act like the rock, while the nickel acts like the cement holding everything together.

Once plated and honed, the result is a thin, hard, durable cylinder bore surface that supports the piston rings while preserving the heat-transfer benefits of an aluminum cylinder.

Why Surface Finish Matters So Much

Nikasil is much harder than cast iron. That hardness is one of its greatest advantages, but it also means that the surface finish must be correct before the engine is assembled.

On a conventional cast iron cylinder, the rings may wear in against the bore during break-in. With Nikasil, the cylinder surface is so hard that the rings cannot be expected to correct an improper finish. If the bore is too rough, the rings can wear prematurely. If it is too smooth, the rings may not seat properly. If the valleys are not right, oil retention can suffer.

That is why proper honing and plateau finishing are critical. The honing process must expose the silicon carbide particles, establish the correct crosshatch, and produce the right balance of peak height and valley depth.

Profilometry and Quality Control

A visual inspection is not enough to verify a Nikasil cylinder bore. Surface finish should be checked with a profilometer, which measures surface texture and helps confirm that the bore has the correct finish for ring sealing and oil control.

Important surface finish values include Ra, Rpk, Rk, and Rvk. These measurements help evaluate the roughness average, reduced peak height, core roughness, and reduced valley depth of the bore surface.

LN Engineering verifies cylinder geometry and surface finish as part of its quality control process. Bore geometry, ovality, taper, and surface finish all matter because ring seal depends on more than simply having a clean-looking cylinder.

Can Nikasil Cylinders Be Reused?

In many cases, Nikasil-plated cylinders can be reused if there is no visible damage and no measurable wear beyond acceptable limits. However, the cylinders and pistons must be inspected and measured carefully.

If the cylinder is in good condition, it may be possible to re-ring the pistons after the cylinder has been properly deglazed and thoroughly cleaned. This does not mean aggressive honing is always appropriate. Nikasil plating is thin, and unnecessary material removal can create clearance problems or compromise the plating.

As a general rule, if the cylinder has significant wear, scratches that catch a fingernail, chips, nicks, cut-through, worn spots, excessive ovality, or taper, the cylinder should be evaluated for replating rather than simply being reused.

Can Nikasil Cylinders Be Re-Honed?

Nikasil cylinders can sometimes be lightly honed, but this must be done carefully. The plating is thin, and piston-to-cylinder clearance must always be considered.

Removing too much material can increase clearance and lead to piston slap, oil consumption, poor ring seal, or other problems. If wear is beyond what can be corrected safely, stripping and replating is the better repair path.

This is where experienced Porsche cylinder reconditioning matters. The goal is not simply to make the bore look better. The goal is to restore the correct geometry, surface finish, and compatibility between the bore, piston, and rings.

When Should Nikasil Cylinders Be Replated?

Nikasil cylinders should be replated when the original plating is damaged, worn through, chipped, scratched, or no longer within specification. Damage can come from dirt ingestion, poor air filtration, foreign object debris, overheating, improper assembly, or normal wear over a long service life.

The replating process generally involves stripping the existing plating, inspecting the bare aluminum bore, repairing or correcting damage where possible, preparing the surface, electroplating the new Nickel Silicon Carbide layer, and then diamond honing the cylinder to final size and finish.

This process restores the wear surface while retaining the benefits of an aluminum cylinder. In some cases, damaged bores can be bored slightly oversize and plated back to the correct finished dimension. In more severe cases, additional repair steps may be required.

Ring Compatibility Is Critical

Piston ring selection is one of the most important considerations when working with Nikasil-plated cylinders. Not every ring material or coating is appropriate.

Historically, phosphate-coated cast iron rings have been commonly used with Nikasil bores. Chrome-faced rings should not be used with Nikasil. Chrome nitride, ductile iron, plasma-moly, and soft gas-nitrided rings may be compatible depending on the application, piston design, and bore finish.

Even when the correct rings are selected, the surface finish and cleaning process still matter. If the cylinder is not finished or cleaned correctly before assembly, the ring faces can be damaged by contamination or an improper surface profile.

Cleaning Nikasil Cylinders Before Assembly

Cleaning is one of the most commonly overlooked steps in engine building. Freshly honed Nikasil cylinders must be cleaned thoroughly before assembly because honing debris and abrasive residue can remain in the crosshatch and surface valleys.

If that contamination is left behind, it can damage the piston rings, cylinder walls, and piston skirts during break-in. Proper cleaning also affects profilometer readings, which means surface finish should ideally be checked after cleaning, not only before cleaning.

LN Engineering recommends careful cylinder cleaning procedures and emphasizes that the final cleaning step is critical. A clean bore helps improve ring seal, reduce blow-by, reduce oil consumption, and prevent avoidable wear.

Assembly and Break-In Considerations

Engines with Nikasil cylinders require proper assembly practices. A tapered sleeve ring compressor is strongly recommended because it applies even pressure to the rings and helps reduce the risk of ring distortion or cylinder damage during piston installation.

Dry assembly should be avoided. At minimum, the bores should receive appropriate light lubrication, and the pistons, rings, and wrist pins should be lubricated with a suitable conventional, non-friction-modified oil or appropriate piston assembly lubricant.

Break-in is also critical. The engine needs load after initial startup and camshaft or valvetrain break-in so that cylinder pressure can help seat the rings. Excessive idling, overly rich running, fuel washdown, or using friction-modified synthetic oil too early can interfere with ring seating.

Depending on the engine, rings, oil, tuning, and break-in procedure, ring seating may take time. Some oil consumption during early break-in can be normal, but the correct oil, proper load, and careful monitoring are important.

Nikasil Streaking Is Not Always Bore Scoring

After break-in, Nikasil cylinders may show streaking that can be mistaken for bore scoring during borescope inspection. In many cases, light streaking is simply transfer from the rings or piston coatings as the parts wear into each other.

This type of streaking is often cosmetic and may diminish with continued normal operation. True scoring, damaged plating, or material transfer must still be evaluated carefully, but not every visible mark in a Nikasil cylinder is automatically a failure.

Why Porsche Owners Should Care

For Porsche owners, Nikasil matters because it is part of what makes many Porsche engines durable, efficient, and capable of high performance. When maintained properly, Nikasil-plated cylinders can last a very long time.

However, the same technology that makes Nikasil effective also means that rebuild work must be done correctly. The wrong honing procedure, incorrect piston rings, poor cleaning, improper assembly lubrication, or poor break-in can lead to oil consumption, poor ring seal, smoking, or premature wear.

For anyone rebuilding an aircooled Porsche engine, repairing a watercooled Porsche engine, or evaluating used cylinders, the key is measurement. Bore condition, piston clearance, ovality, taper, surface finish, and ring compatibility should all be verified before final assembly.

LN Engineering Nikasil and NSC Cylinder Services

LN Engineering offers Nikasil and NSC cylinder solutions for Porsche engines, including Nickies cylinders, watercooled sleeves, and cylinder reconditioning services. These solutions are designed for engine builders and Porsche owners who want the benefits of aluminum cylinders with a durable Nickel Silicon Carbide wear surface.

Whether the goal is restoring original Porsche Nikasil cylinders, repairing damaged aluminum engine blocks, or building a performance engine with modern cylinder technology, the process requires experience, proper equipment, and careful quality control.

Learn more about LN Engineering’s Nikasil and NSC cylinder plating process here:

Nikasil and NSC Cylinder Reconditioning and Plating for Porsche Engines

Final Thoughts

Nikasil remains one of the most important cylinder bore technologies used in Porsche engines. It offers excellent heat transfer, low friction, strong wear resistance, and long service life when used correctly.

For Porsche owners, the takeaway is simple: Nikasil is a proven technology, but it must be inspected, serviced, and rebuilt properly. However Porsche has moved away from Nikasil, as have other manufacturers, and are now using coatings like APS and PTWA.

For engine builders, the takeaway is even more important: Nikasil cylinders require correct measurement, compatible piston rings, proper honing, thorough cleaning, and careful break-in. When those steps are followed, Nikasil and NSC-plated cylinders can provide exceptional performance and durability in both street and performance Porsche engines.

Bore Scoring, Modern Cylinder Coatings, and What Porsche Owners and Shops Should Know

Bore scoring remains one of the most talked-about issues in the watercooled Porsche community. For many Porsche owners, the subject can be confusing because not every modern Porsche engine is affected in the same way, and not every engine with aluminum cylinder bores carries the same risk.

At the same time, modern cylinder bore technology has changed dramatically. Today’s Porsche engines, along with many other modern performance engines, use advanced bore materials and coatings that require a very different approach to inspection, repair, honing, piston selection, and ring compatibility.

That is why understanding which engine is in the car matters. It is also why owners, shops, and engine builders need to recognize that modern cylinder coatings cannot always be evaluated or repaired like traditional cast iron cylinders.

Not Every Porsche Engine Commonly Experiences Bore Scoring

Although bore scoring is a real concern on certain Porsche engines, it is not accurate to say that every modern Porsche engine is equally prone to the problem. Some engines and model families are not commonly associated with bore scoring, while others require more careful inspection due to their design, materials, piston skirt coatings, ring packs, oiling behavior, operating temperatures, and long-term wear patterns.

LN Engineering has published a detailed guide covering Porsche models that do not commonly experience bore scoring, along with important context about which engines are more susceptible and why.

Learn more about Porsche models without bore scoring

For Porsche owners, this information is especially useful when shopping for a used Boxster, Cayman, 911, Cayenne, Panamera, or Macan. A proper pre-purchase inspection should always consider the specific engine family, not just the model badge on the decklid.

Why Modern Cylinder Bore Technology Matters

For decades, engine builders were accustomed to working with cast iron cylinders or iron sleeves. Those materials could often be bored, honed, and reconditioned using familiar procedures. Modern engines are different.

Many current aluminum engines use engineered bore surfaces instead of conventional iron liners. These include Alusil, Lokasil, Nikasil, PTWA, APS/SUMEbore, and other thermal spray systems. These technologies are not experimental. They are proven production solutions used by major manufacturers across domestic, European, and Japanese platforms.

The advantage is clear. Aluminum blocks with advanced bore surfaces can reduce weight, improve heat transfer, reduce friction, and support modern fuel economy and emissions requirements. The challenge is that these surfaces require the correct repair strategy.

A shop cannot assume that a modern Porsche cylinder can be treated like an older cast iron bore.

Alusil and Lokasil Cylinder Bores

Alusil, Lokasil, and related aluminum-silicon bore technologies use a hypereutectic aluminum-silicon surface. After machining, the aluminum matrix is selectively removed so that silicon particles are exposed. These exposed silicon particles become the load-bearing surface for the piston rings.

When properly manufactured and finished, this type of bore can provide excellent heat transfer and reduced weight. However, the surface depends on the correct exposure of silicon. If the silicon is not properly exposed, or if the silicon particles are damaged during machining or honing, the bore may not support the oil film and tribofilm needed to protect the pistons and rings.

That is one reason bore scoring can occur. The piston, rings, oil, cylinder finish, and operating conditions all have to work together.

From a rebuilding standpoint, Alusil and similar bores require compatible pistons, skirt coatings, and ring materials. Conventional assumptions about piston rings do not always apply. For example, conventional plasma-moly top rings are not appropriate for exposed aluminum-silicon bores. Correct ring selection is essential.

Nikasil and Electroplated Cylinder Coatings

Nikasil and other nickel-silicon carbide coatings have long been associated with high-performance engines. These coatings are hard, durable, and thermally conductive when paired with compatible rings and proper lubrication.

However, Nikasil coatings are thin. Once finish-honed, they are typically only a few thousandths of an inch thick. That means there is very little margin for overbore correction. If the cylinder is scratched, worn, out of round, or has surface finish problems, the proper repair is usually stripping and replating rather than simply honing more material away.

Ring compatibility is also critical. Low-tension ring packages are typically required, and chrome-faced rings are generally not the preferred choice for Nikasil. Cast or ductile iron rings may be used in some OEM applications, but the final ring package must be selected based on the bore material, coating, piston design, and intended use.

This is especially important for shops rebuilding Porsche engines. A cylinder that looks acceptable visually may still have an incorrect surface finish, ring compatibility issue, or coating problem that prevents a successful rebuild.

PTWA, APS, SUMEbore, and Thermal Spray Cylinder Bores

Many modern engines now use thermal spray coatings instead of traditional liners or electroplated coatings. PTWA (Plasma Transferred Wire Arc) uses a steel wire that is melted, atomized, and sprayed onto a prepared aluminum bore. APS, or Atmospheric Plasma Spray, uses powdered material instead of wire. SUMEbore is one example of an APS-based technology.

These coatings allow manufacturers to retain the weight and heat-transfer advantages of aluminum while creating a bore surface that behaves more like iron from a tribological standpoint.

Porsche has used modern sprayed bore technologies in later horizontally opposed engines, including 718, 991.2, and newer applications. VW, Audi, Porsche V8 engines, Ford, Nissan, and other manufacturers have also used thermal spray cylinder technologies in production engines.

These coatings are thin, often around the same 0.1 mm class as electroplated coatings. In many cases, there is effectively no overbore margin. If the bore is damaged, the solution may require recoating, replating, boring, or sleeving depending on the engine design and the extent of the damage.

Why Honing Modern Coated Bores Requires Caution

Modern coated bores cannot be honed casually. Nikasil, PTWA, APS, SUMEbore, and similar coatings often leave very little room for material removal. A shop attempting to “clean up” a cylinder without understanding coating thickness may remove too much material, alter the surface finish, or compromise the coating entirely.

Surface finish validation is especially important. A bore may appear clean and usable to the naked eye, but still have an unsuitable finish for ring sealing. Conversely, some thermal spray bores may show visible porosity that is part of the coating’s intended oil-retention structure.

This is where profilometry becomes essential.

Surface Finish Measurement and Profilometry

Surface finish measurement is one of the most important steps when evaluating modern cylinder bores. A handheld profilometer, such as a Mitutoyo SJ-210, is commonly used, but the stylus tip size, filtering method, and interpretation of the data matter.

Conventional cast iron surfaces are often easier to evaluate using standard methods. Porous thermal spray coatings can be more difficult because larger stylus tips may bridge narrow valleys and under-report true valley depth. Robust filtering and smaller stylus tips may provide a more accurate understanding of the bore’s actual surface structure.

Cleaning before measurement is equally important. Honing debris, folded material, embedded contamination, or residue in the coating’s valleys can distort profilometer readings. A bore should not be evaluated until it has been properly cleaned.

For engine builders, the key point is that a visual inspection alone is not enough. Measuring bore geometry and surface finish before and after reconditioning is essential.

Ring Compatibility Cannot Be Ignored

Modern bore technologies require compatible piston rings. The ring face coating, ring tension, bore material, oil film behavior, and cylinder finish must all be matched.

For example, modern PTWA and APS thermal spray bores are often paired with advanced ring coatings designed for high load, low friction, and boundary lubrication conditions near top dead center. CrN-faced steel rings and HVOF-applied cermet coatings are examples of ring technologies used in severe modern applications.

Under boosted or high specific-output conditions, the ring-to-liner interface experiences higher cylinder pressure, greater contact stress, and reduced oil film thickness. Choosing the wrong ring can lead to accelerated wear, poor sealing, oil consumption, or scuffing.

This is why shops should not assume that a ring package that works on cast iron will work on Alusil, Nikasil, PTWA, APS, or SUMEbore.

What Porsche Owners Should Take Away

For Porsche owners, the most important takeaway is simple: know which engine is in the car.

Bore scoring risk depends on the specific engine family, cylinder technology, piston design, operating history, maintenance habits, oil choice, and inspection results. Some Porsche engines are not commonly associated with bore scoring, while others deserve careful evaluation, especially when symptoms such as ticking noises, elevated oil consumption, metallic debris, or visible cylinder damage are present.

A qualified Porsche specialist should use the correct inspection methods, including borescope inspection where appropriate. In some cases, oil analysis, compression testing, leakdown testing, and careful evaluation of engine noise may also be useful.

Read LN Engineering’s guide to Porsche models without bore scoring

What Shops and Engine Builders Should Take Away

For shops and engine builders, the takeaway is even more important. Modern cylinder coatings cannot always be repaired using traditional assumptions.

Thin coatings such as Nikasil, PTWA, APS, and SUMEbore leave very little margin for honing. Before attempting to re-ring, hone, or recondition a modern coated cylinder, the builder should identify the bore technology, measure geometry, validate surface finish, clean the bore properly, and confirm piston and ring compatibility.

Depending on the condition of the bore, the correct repair path may include recoating, replating, boring, sleeving, or replacing the cylinder block or crankcase component. The wrong repair can lead to poor ring seal, oil consumption, scuffing, and premature engine failure.

Modern Cylinder Coatings Are Here to Stay

Modern bore technologies are not a temporary trend. They are now part of mainstream engine manufacturing. Alusil, Lokasil, Nikasil, PTWA, APS, SUMEbore, and related systems have all been used successfully in production engines.

The responsibility of the modern Porsche owner, technician, and engine builder is to understand these technologies well enough to make informed service decisions.

For owners, that means understanding whether an engine is commonly affected by bore scoring and choosing a qualified shop for inspection and repair.

For shops, it means using data, measurements, and validated procedures rather than guesswork.

As engine technology continues to evolve, successful Porsche engine service will depend on understanding not only the symptoms of bore scoring, but also the cylinder bore materials and coatings behind them.

From Cast Iron to Plasma: How Porsche Cylinder Technology Truly Evolved

 

From Cast Iron to Plasma: How Porsche Cylinder Technology Truly Evolved

Porsche’s cylinder technology did not evolve by accident, nor did it follow a single straight path. Instead, it reflects decades of engineering tradeoffs shaped by cooling strategy, emissions requirements, weight reduction goals, manufacturing realities, and real-world durability. To understand why Porsche now uses plasma-sprayed cylinder bores, better known as PTWA, it’s necessary to follow the complete arc—from cast iron, through aluminum, and ultimately beyond traditional liners and coatings.

In Porsche’s early air-cooled engines, cylinder design began with cast iron barrels mounted to aluminum crankcases. Cast iron offered excellent wear resistance, stable ring sealing, and tolerance for extreme thermal swings. In an air-cooled environment, where temperature gradients are wide and uneven, iron’s dimensional stability was a strength. Weight was the drawback, but reliability came first.

Dimpled chrome Porsche cylinder

As Porsche pursued lighter engines and higher performance, air-cooled cylinder technology evolved. Cast iron gave way to aluminum “Ferral” cylinders, which used aluminum bodies with cast-in or splatter-applied iron wear surfaces. This reduced mass while retaining iron’s tribological advantages. Further refinement led to dimpled hard chrome plating, which provided exceptional hardness and wear resistance but proved sensitive to ring compatibility and long-term service conditions.

Nikasil cylinder bore cross-section

The most successful air-cooled solution was Nikasil. Nickel-silicon-carbide plating combined low friction, extreme hardness, and excellent heat transfer. In air-cooled Porsche engines, Nikasil worked extraordinarily well because the operating environment supported it. Piston motion was stable, lubrication behavior was predictable, and fuel dilution during cold starts was minimal. Properly applied, Nikasil remains one of the most durable cylinder surfaces ever used in air-cooled engines. That's why it has persisted for over 50 years.

The transition to water-cooled engines fundamentally changed the problem. Water cooling enabled Porsche to meet emissions regulations, increase power density, reduce noise, and improve drivability. It also introduced tighter packaging, closer bore spacing, water jackets surrounding cylinders, and more complex thermal behavior. The solutions that worked in air-cooled engines no longer translated directly.

Early water-cooled Porsche engines initially relied on cast iron blocks, most notably in the Porsche 924. Cast iron provided durability, but it limited displacement growth, power output, and weight reduction. The move from the 924’s cast iron block to the Porsche 944’s Alusil aluminum block illustrates why aluminum became unavoidable. The Alusil block allowed roughly a 30 percent increase in power and a 25 percent increase in displacement with no increase in weight or engine footprint. Output was also increased significantly without sacrificing longevity or durability. That was not a marginal gain—it was transformational.

Not needing to install iron or steel sleeves allows for larger bores with tighter bore spacing

From an engineering standpoint, aluminum blocks made overwhelming sense. Aluminum allowed tighter integration of oiling, cooling, and structural features, improved thermal conductivity, and supported higher compression ratios and boost levels while reducing emissions and improving fuel economy. Not having to put an iron or steel sleeve in the block also allowed for larger bores sizes without having to make the engine larger. They also run cooler that way. Extensive testing showed higher wear rates compared to cast iron, but Porsche deemed those rates acceptable within the expected service life—and history largely validated that decision.

Aluminum engine blocks are not only lighter than iron but also run cooler and make more power

To avoid the mass and packaging penalties of iron liners, Porsche and other manufacturers moved toward linerless aluminum cylinder designs, including Lokasil and later Alusil. These systems rely on exposed silicon particles within a hypereutectic aluminum matrix to support piston rings after specialized honing. When the silicon exposure is correct and the operating conditions are ideal, friction is low and wear is controlled. The piston also has to have a specialized plating or coating to prevent aluminum to aluminum contact, which results in metal transfer observed as cylinder bore scoring, galling, or piston seizing.

The Audi 4.2 V8 uses an Alusil liner-less engine block; the Porsche Cayenne V8 uses the same technology

However, these systems operate within a narrow window. Extremely tight piston-to-wall clearances demand durable skirt coatings and precise lubrication. In modern water-cooled engines—subject to frequent cold starts, short trips, fuel washdown, and localized thermal loading—the aluminum-silicon interface can be disrupted. Once silicon particles fracture or become dislodged, the aluminum matrix wears rapidly, debris is generated, and bore scoring develops. This is not normal wear; it is a failure of the tribological system.

Alusil and similar hypereutectic aluminum engine blocks aren't honed conventionally - they use a special process to expose the silicon particles which support the formation of the tribofilm required to support piston and ring operation

It’s important to clarify that Nikasil was not abandoned because it stopped working. Manufacturers, including Porsche, increasingly moved away from Nikasil due to environmental and regulatory pressures. Same goes for the durable iron clad piston coatings required for linerless aluminum engine blocks - they were replaced with less durable coatings that don't hold up as well.

Failed piston skirt coatings on an engine with linerless aluminum cylinder bores result in cylinder bore scoring. For comparison, plasma spray coated engines don't require special piston skirt coatings.

The electroplating process involves hazardous chemicals and waste streams that became more difficult to permit, manage, and scale globally. As production volumes increased and regulations tightened, alternatives that reduced environmental impact and simplified manufacturing became more attractive.

Cylinder bore scoring in Al-Si engine blocks is a serious issue with Alusil and other linerless aluminum blocks with uncoated cylinder bores. 

Aluminum-silicon blocks addressed many of those concerns, but real-world service revealed their limitations under modern operating conditions, such as cylinder bore scoring.

Plasma cylinder bore coatings are applied with a rotating plasma torch

The next and current evolution is plasma-sprayed cylinder bore technology, now used in Porsche’s 718 Boxster and Cayman and 991.2 and later 911 engines. Plasma spraying applies a thin, iron-based coating directly to the aluminum bore using a plasma arc. The wire can be alloyed to deliver specific properties and also have the porosity changed to adjust oil retention. The PTWA coating becomes mechanically bonded to the block and is precision finished to retain oil and support stable ring sealing.

Plasma spray bore coatings are designed to have porosity to hold oil, allowing for smoother cylinder bore finishes for reduced friction and wear and improved cylinder sealing and performance

This approach separates the wear surface from the aluminum substrate entirely. The aluminum block provides structure and heat transfer, while the plasma coating provides durability. The system tolerates fuel dilution, thermal distortion, and real-world variability far better than linerless aluminum bores, while retaining the weight and packaging advantages that made aluminum blocks essential in the first place.

Plasma torch in operation coating a cylinder bore

Seen in full historical context, plasma-sprayed bores are not a rejection of past technologies. They represent the convergence of decades of lessons learned. Cast iron established durability. Ferral and chromal aluminum cylinders explored weight reduction while solving overheating issues. Nikasil perfected low-friction wear surfaces. Aluminum blocks enabled modern engine architecture. Plasma coatings bring those elements together in a form suited to today’s engines.

Ford has been using PTWA in serial production since 2011 with millions of engines in service worldwide - this is the single largest sample size for validation of the PTWA process

Porsche’s cylinder technology evolution reflects a consistent engineering philosophy: adapt the solution to the operating environment and constraints of the time. Air-cooled engines demanded one answer. Water-cooled engines demanded another. Plasma-sprayed cylinders are the solution that best fits the modern era while being backwards compatible with older legacy engines reliant on old or outdated technologies.

Porsche Plasma Bore Technology Explained: PTWA and RSW as the Evolution Beyond Nikasil

 

Porsche Plasma Bore Technology Explained: PTWA and RSW as the Evolution Beyond Nikasil

As Porsche engine design progressed into the modern era, one engineering challenge consistently shaped decision-making: long-term cylinder durability. Bore scoring in earlier water-cooled engines demonstrated that even advanced aluminum cylinder technologies have limits when subjected to modern emissions strategies, higher thermal loads, and increasingly tight tolerances. Porsche’s solution was not another variation of aluminum bore chemistry, but a shift to plasma-sprayed cylinder bore technology, now used in 718 and 991.2 and later Porsche sports car engines.

This technology is commonly referred to as PTWA (Plasma Transferred Wire Arc) or RSW (Rotating Single Wire). While the names differ, the underlying process and purpose are fundamentally the same. Both describe a plasma spray method in which a metal wire is energized into a plasma arc and deposited directly onto an aluminum cylinder bore to create a thin, iron-based wear surface. The differences between PTWA and RSW are largely matters of equipment configuration and nomenclature rather than function or outcome.

In practical terms, PTWA and RSW should be understood as variations of the same plasma bore coating technology, not competing or fundamentally different systems. The result in both cases is a dense, extremely wear-resistant cylinder surface that is mechanically bonded to the aluminum block and precision-finished for piston ring compatibility.

This represents a major departure from traditional cylinder designs such as Nikasil or Alusil. Those systems rely on aluminum alloy substrates to serve as both the structural cylinder and the wear surface. While effective under ideal conditions, aluminum-based bores are vulnerable to lubrication breakdown, thermal distortion, and piston instability. Once that balance is disturbed, the damage is progressive and irreversible.

Plasma-sprayed bores change that equation entirely. Instead of asking aluminum to perform a task it was never ideal for, the wear surface is engineered specifically for tribological stability. The sprayed coating resists scuffing, maintains oil film integrity, and tolerates tighter clearances without galling or smearing. This directly addresses the mechanisms that lead to bore scoring.

Another advantage of plasma bore coatings is thermal control. Aluminum expands significantly with temperature, which historically forced compromises in piston-to-wall clearance. Plasma coatings allow Porsche to manage expansion more predictably, stabilizing piston motion across cold starts, high load operation, and sustained heat. That stability is critical in modern direct-injected engines where localized temperature spikes are unavoidable.

Porsche’s adoption of plasma bore technology in the 718 Boxster and Cayman and the 991.2-generation 911 reflects a deliberate engineering pivot. Rather than continuing to refine aluminum bore chemistry, Porsche chose a surface technology already proven in high-performance and endurance applications. The move was not cosmetic or incremental—it was structural.

Importantly, this transition also marks a philosophical shift. Nikasil represented an earlier evolution in cylinder durability, replacing cast iron liners with a more advanced surface without the constraints of sleeving. Now that plating is considered a dirty operation and manufacturers are phasing this technologies out for environmental reasons, plasma bore coatings take the next step by eliminating the need for traditional liners altogether and separating cylinder wear from the aluminum block itself. In that sense, plasma spray technology can be viewed as a natural successor to Nikasil, designed for the demands of modern engines.

For Porsche owners and enthusiasts, understanding PTWA and RSW technology is essential to understanding where Porsche engine design is headed. The reduced incidence of bore scoring in these newer engines is not accidental. It is the result of rethinking the cylinder surface from first principles.

PTWA and RSW differ from APS coatings like SUMEbore or the thin-wall steel liners being used by VAG in some of the engines shared between platforms. Where PTWA and RSW make a plasma from a wire that is then applied to the cylinder bore, APS forms the plasma in a chamber before depositing it, starting from a powder instead of wire. What's in common is all of these plasma bore coatings don't require hazardous materials or special waste handling.

For those concerned that this technology is too new - rest assured, it's been around for decades, developed by Ford. Some of the earliest adopters of PTWA include Ford with its Coyote engine and even the Nissan GT-R.

As Porsche continues to refine and expand its use of plasma-sprayed bores, the message is clear. Cylinder surface engineering is no longer a compromise—it is the foundation of durability. And with plasma spray bore coatings, Porsche has embraced a solution that moves decisively beyond the limitations of traditional aluminum bore designs, proving there is life after Nikasil without fear of cylinder bore scoring.