#enginebuild

The video from MAHLE Motorsport, presented by Daniel and Justin, provides a detailed guide on circlips used in their POWERPAK piston kits. Circlips, though small, are critical components that retain the wrist pin inside the piston and prevent catastrophic engine failures if improperly installed. MAHLE Motorsport primarily uses two types of circlips: non-tang and tang clips. Most POWERPAK kits contain non-tang clips, which should be installed with the gap positioned at either the 12 or 6 o’clock positions to reduce the risk of inertia overcoming the circlip’s spring force at high piston speeds. For tang clips, the tang must rest against the slope side of the notch in the piston.

The video walks through the installation process, recommending the use of specialized tools such as the Lock-n-Tool, along with common items like binder clips and small screwdrivers to assist in circlip installation. The presenters demonstrate the correct way to seat the clips fully in their grooves, emphasizing the importance of verifying that the circlip is not partially lifted out, which can lead to ejection and engine failure.

They also cover safe removal techniques using tools like o-ring picks, modified center punches, and small screwdrivers while warning against the use of excessive force tools such as hammers or pliers, which can damage the circlips, rendering them unusable. The video advises that circlips are generally one-time use and highlights how to inspect clips for damage after removal.

Finally, the video notes that variations in piston and circlip specifications require adapting installation techniques accordingly. MAHLE Motorsport encourages viewers to reach out with questions or concerns for further assistance.

Highlights

🛠️ Circlips are essential for retaining wrist pins and preventing catastrophic piston failure.

🔧 MAHLE Motorsport uses two main circlip types: non-tang (most common) and tang clips for high piston speeds.

🎯 Gap orientation in circlip installation is critical: non-tang clips should have gaps at 12 or 6 o’clock positions.

🧰 The Lock-n-Tool and simple office supplies like binder clips aid in safe and correct circlip installation.

👁️ Always verify that circlips are fully seated in their grooves to avoid ejection during engine operation.

⚠️ Avoid using hammers and pliers for installation/removal to prevent damage to the circlips.

🔍 Circlips are typically single-use; inspect carefully after removal to ensure they are not deformed or damaged.

Key Insights

🔩 The Critical Role of Circlips in Engine Reliability: Circlips, although small, are vital for maintaining wrist pin placement within the piston. Failure to install them correctly can lead to the clip being ejected under operating forces, causing loss of pin control and catastrophic engine damage. This highlights the importance of precision and care during assembly.

🎯 Gap Orientation Strategy Enhances Durability: Positioning the non-tang circlip gap at the 12 or 6 o’clock position strategically uses piston inertia forces to keep the clip seated securely. This simple yet effective method of orientation reduces the risk of clip failure at high RPMs, showcasing how small adjustments in assembly can significantly improve engine performance and reliability.

🧰 Specialized Tools Facilitate Proper Installation: The Lock-n-Tool, combined with common items like binder clips and screwdrivers, streamlines the installation process, making it easier to seat circlips fully without damaging them. This reflects the importance of using the right tools tailored for engine assembly tasks to increase efficiency and accuracy.

👁️ Verification of Proper Seating Prevents Failure: The video stresses the necessity of visually and physically checking that the circlip is fully seated in the groove. Even if the clip appears installed from one angle, it may be partially dislodged on the other side. This insight underscores the critical nature of thorough inspections during assembly to avoid costly errors.

⚠️ Risks of Using Improper Removal Techniques: Using excessive force tools like hammers or pliers damages circlips by deforming or twisting them, compromising their ability to maintain secure pin retention. This insight stresses that gentle, proper removal techniques are essential, and damaged clips should never be reused, especially in high-performance applications.

🔍 Circlips Are Generally One-Time Use Components: After removal, circlips should be inspected closely for signs of distortion such as loss of concentricity or size reduction. Even if they appear visually intact, subtle deformations can reduce their maximum speed tolerance and lead to failure. This insight reinforces the best practice of always using new circlips for reassembly to maintain engine integrity.

⚙️ Variation in Circlip and Piston Specifications Requires Adaptability: Differences in piston diameter, wrist pin size, clip wire diameter, and shape mean that installers must adjust their technique to each specific application. This highlights the necessity for mechanics and builders to understand the components they work with deeply rather than relying on a one-size-fits-all approach.

Understanding Piston Coatings: Types, Applications, and When They Matter

Piston coatings play a critical role in enhancing engine durability and performance—especially under extreme operating conditions. While pistons can operate reliably without coatings in moderate, well-lubricated environments, high-performance and racing applications often push materials beyond their limits. In these scenarios, coatings become an essential tool for improving wear resistance, preventing failure, and reducing friction.

This article explores the primary piston coatings used by Mahle Motorsports, including phosphate, Grafal®, and hard anodizing, and explains when and why each is used.

Why Use Piston Coatings?

Under typical street driving conditions, piston coatings may not be strictly necessary. However, when engines are pushed to extremes—due to high loads, inadequate lubrication, or elevated temperatures—coatings provide a vital layer of protection. Common failure modes addressed by coatings include:

Scuffing or galling from reduced clearances or poor lubrication

Micro-welding in the ring grooves under high temperatures

Cold start wear due to oil starvation

Fuel dilution reducing oil film strength

Thermal expansion of cylinder walls causing piston-to-wall contact

Mahle Motorsports incorporates coatings into their PowerPak and PowerPak Plus pistons to combat these risks and extend piston longevity.

Common Piston Coatings and Their Functions

Phosphate Coating (Signature Black Appearance)

Phosphate is a dry film lubricant used on the piston skirt, ring grooves, and pin bore. It reduces direct metal-to-metal contact during oil-starved conditions, such as cold starts or initial engine break-in.

Application Method: Immersion process

Usage: Suitable for both gasoline and diesel engines

Function: Provides a sacrificial layer to reduce galling and seizure risk

Thermal Properties: Not a thermal barrier coating

Removing phosphate from the piston crown (e.g., during machining for valve reliefs) does not impact the coating's protective functions on critical areas.

⚫ Grafal® Coating (Piston Skirt Coating)

Grafal is Mahle's standard skirt coating, formulated with fine graphite particles in a polymer matrix and screen-printed onto the piston skirt.

Thickness: Approximately 12 microns

Key Benefits:

Reduces friction with tight piston-to-wall clearances

Prevents scuffing during cold starts or high load operation

Designed for life-of-the-piston use, not just break-in

Application: Common on pistons used with cast iron cylinder liners

Compatibility: Works with both gas and diesel platforms

This coating is particularly valuable in applications where lubrication might be compromised, such as forced induction engines or engines running lean mixtures.

Hard Anodizing (Top Ring Groove Treatment)

Shorter top lands in some piston designs subject the top ring groove to intense combustion heat. Over time, this can cause:

Micro-welding of the piston ring to the groove

Material erosion or deformation of groove sidewalls

Mahle combats this with localized hard anodizing, which creates a hardened oxide layer on the groove’s surface. This layer improves resistance to micro-welding and prolongs the lifespan of the ring groove under extreme thermal stress.

When Should You Use Coated Pistons?

According to Chevy Hardcore, piston coatings are particularly useful in:

High RPM and racing engines

Turbocharged or supercharged applications

Engines running high compression ratios

Severe duty use like towing or marine performance

Engines with tight piston-to-wall clearances

Start-stop or extended idle conditions prone to oil dilution