As the spring mount at the top of the shock absorber assembly, the top mount absorbs more than a quarter of the vehicle’s weight in impact forces when driving on uneven roads, playing an indispensable role. Today, let’s take a closer look at it!

The function of the top layer

The shock absorber top mount is made of rubber and serves to cushion and dampen vibrations. When the spring is fully compressed, the vehicle body is subjected to a significant impact transmitted from the wheels; without the cushioning provided by the shock absorber top mount, this intense impact would not only damage the shock absorber but could also cause the wheel hub to deform.

The top rubber on shock absorbers also provides sound insulation. When tyre noise is generated by contact with the road surface, the top rubber helps to dampen this noise, preventing excessive noise from being transmitted into the cabin; furthermore, it reduces the direct impact on the vehicle body when the tyres encounter bumps on uneven surfaces.

It is precisely thanks to the shock-absorbing top rubber that we need not worry about the car sustaining damage from severe vibrations when driving on bumpy roads. When the tyres hit a dip, the shock-absorbing top rubber also helps to keep the body of the car stable.

Top-to-bottom clearance

There is often a gap between the shock absorber top mount and the retaining ring; the exact size of this gap varies depending on the vehicle model and design specifications. This gap is intentionally incorporated to enhance damping performance. Under normal circumstances, a gap of less than 20 mm in the front shock absorber top mount is considered normal. However, this figure varies from vehicle to vehicle, and specific details should be checked against the vehicle’s technical specifications.

However, if the gap is too large or too small, this may adversely affect the vehicle’s handling and safety.

To be more specific, excessive clearance may cause abnormal noises. Conversely, insufficient clearance may result in the shock absorbers becoming too stiff, which will also detract from the driving experience.

The cause of excessive or insufficient clearance between the top rubber and the shock absorber is the ageing or damage of the top rubber.

Signs of damage to the top layer

Ride comfort is reduced, and unusual noises may be particularly noticeable when driving over bumps or speed bumps; this is a warning sign that there is a problem with the suspension system.

Tyre noise increases, and in severe cases, a rumbling sound can even be heard.

The vehicle veers off course; even when driving in a straight line, the steering wheel may pull to one side, and the vehicle may still be unable to maintain a straight course after correction.

When turning the steering wheel whilst stationary, a squeaking noise may be heard; in severe cases, this may even cause the vehicle to pull to one side whilst driving.

If any of the above symptoms occur, you should immediately have the vehicle inspected by a professional or have the parts replaced as necessary. It is worth noting that there is no fixed schedule for replacing shock absorber top mounts; instead, this should be done as soon as any issues are detected, based on the actual condition of the vehicle, to ensure driving comfort and safety.

Tips for Extending the Life of Your Top Sheet

The worst thing you can do to the top mounts is to drive over speed bumps and rumble strips at high speed. As long as you slow down—reducing your speed before you reach the speed bumps or rumble strips, rather than braking as you go over them—this will benefit the shock absorbers, top mounts, engine mounts and indeed all the rubber cushioning components on the chassis.

• Contact Us for Vehicle-Specific Bushings: natasha@nafurancar.com

Why can’t you hear the sound of metal scraping against metal when a car is driving on a bumpy road?

Why do we often say that a car feels ‘soft’ or ‘stiff’? How is this achieved through suspension tuning?

That’s right—it’s all down to the car’s bushings! Bushings serve to absorb shocks, reduce friction, extend the life of components and enhance comfort. Who would have thought such a small component could have such a powerful impact!

In a car’s chassis, the various components and articulation points are not mechanically linked; instead, they are connected by rubber bushings made primarily from rubber. These bushings are positioned at the endpoints of the suspension geometry—in other words, at the points where forces are concentrated. Lateral, longitudinal and vertical forces from the chassis all act upon the surface of the rubber bushings, subjecting these rubber components to heavy loads over extended periods.

The quality of the bushing design directly reflects the performance of the vehicle, so high-quality bushing design is of paramount importance!

The bushings used in cars are mainly divided into rubber bushings and hydraulic bushings. Why are hydraulic bushings considered ‘superior’?

Hydraulic bushings provide a better stiffness curve

Hydraulic bushings feature a complex structure and are among the most technically sophisticated and high-value-added products in the bushing category.
The internal cavity of the bushing is filled with hydraulic fluid; when subjected to external pressure, this allows for varying degrees of stiffness, providing an improved stiffness curve that helps enhance the vehicle’s overall driving performance.

Hydraulic bushings provide excellent shock absorption

Compared to standard automotive rubber bushings, the most significant improvement offered by hydraulic bushings is that they break the direct correlation between the softness of the rubber and the damping characteristics of the bushing.

As shown in the diagram above, the outer layer of the hydraulic bushing is still made of the familiar rubber material, but inside the rubber, numerous chambers and channels have been designed and filled with hydraulic fluid.
Consequently, when the suspension moves and compresses the hydraulic bushing, the hydraulic fluid flows to the opposite side, where it generates damping through hydraulic pressure. In this way, the hydraulic bushing ensures shock absorption in the initial stage using soft rubber, whilst simultaneously providing damping force in the final stage to prevent unnecessary vibrations, delivering a suspension effect that is soft at the front and resilient at the rear.
If, at this point, the vehicle’s suspension tuning is also of a high standard, the chassis will be able to handle road bumps with ease, delivering a superior ride quality to the occupants.

The hydraulic suspension system on the Nafurancar is designed in accordance with the original factory specifications, ensuring the same high standards as the original equipment. This enhances not only the driving performance of the entire vehicle, but also the driving experience for passengers.

I. Composition of the Air Conditioning System & Introduction to Components

Composition of the Air Conditioning System:

Automotive air conditioning systems typically comprise the following components: compressor, condenser, receiver-drier, expansion valve, evaporator, blower fan, throttle valve, and ventilation system.

Introduction to Air Conditioning System Components—HVAC Air Conditioning Assembly:

The air conditioning unit employs mode selection dampers to direct cold or warm airflow to specific vents, such as footwell, face, or defrost outlets. Temperature control dampers blend cold and warm air to achieve the desired outlet temperature. The internal/external air mix damper regulates the proportion of cabin and external air, directly influencing temperature, air quality, and defrosting/demisting functionality.

Introduction to Air Conditioning System Components—Condenser:

Function of the condenser: to cool the refrigerant.

The condenser integrated with a dryer, wherein a liquid receiver dryer is installed at the end of the refrigerant circuit within the condenser, facilitates simplified air conditioning system design and enhances the reliability of the refrigeration system.

Introduction to Air Conditioning System Components—Compressor:

The compressor serves as the ‘heart’ of the air conditioning system, analogous to the engine's role in a vehicle—it is the driving unit.
In conventional air conditioning systems, the compressor is driven via an engine belt.
The compressor must exclusively draw in and expel gaseous refrigerant.
Its internal mechanism contains numerous moving parts, necessitating sufficient lubricating oil to lubricate these components.

Introduction to Air Conditioning System Components—Air Conditioning Piping:

The air conditioning piping system comprises key components such as aluminium tubing, flexible hoses, and pipe fittings, which collectively connect all elements of the air conditioning system. Aluminium tubing and flexible hoses are tightly joined via crimping techniques, though minor variations in crimp dimensions may exist between different models and manufacturers. To mitigate potential damage from engine vibration, flexible rubber hoses are employed for the lines connecting the compressor's suction and discharge ports. Their flexible design effectively absorbs vibrations, enhances system sealing integrity, and extends the service life of the piping. Many manufacturers have also developed nylon air conditioning hoses, which are utilised in mass-produced vehicle models.

II. Refrigeration Principles of Air Conditioning Systems

The operational principle of refrigeration systems relies upon the continuous vaporisation and liquefaction of refrigerant. The entire refrigeration cycle comprises four distinct operational stages: compression, condensation and heat release, throttling, and evaporation. During compression, the low-temperature, low-pressure refrigerant gas processed by the evaporator is compressed by the compressor into a high-temperature, high-pressure gas, which is then delivered to the condenser. During the condensation and heat release stage, the high-temperature, high-pressure refrigerant gas gradually condenses into a liquid while releasing heat. The subsequent throttling process, via the expansion valve, transforms the refrigerant from a high-pressure to a low-pressure state. Finally, the evaporation process occurs within the evaporator, where the refrigerant absorbs a significant amount of heat before re-entering the compressor, thereby achieving the cooling of the vehicle's interior.

III. Precautions for Air Conditioning Refrigerant Pipe Assembly

When installing air conditioning pipework and connecting components, the method of fitting and tightening joints is critical.
When removing pipe plugs, first inspect the O-ring for integrity and apply lubricant evenly to its sealing surface. For threaded pipe joints, also apply lubricant evenly to the external threads. When applying lubricant, observe the following points: 
The lubricant applied must be compressor-grade lubricant, PAG or equivalent grade.
Lubricate threaded sections to prevent seizing after tightening.
To prevent moisture absorption, promptly reseal lubricant containers after use.
To maintain internal cleanliness of system components such as piping, remove plugs only immediately prior to installation. Refit promptly; do not leave exposed to air for extended periods.  
Clamp-type joint connection: Insert the lubricated clamp plate's blind hole vertically through the double-ended stud. Simultaneously insert the clamp joint vertically into the corresponding mounting hole. Avoid tilting during insertion to prevent O-ring damage. Once seated with parallel faces, hand-tighten the nut until resistance is encountered. Subsequently, use a torque ratchet or wrench to tighten the bolt to specification, marking the tightened position. The tightening torque for M8 nuts is 15–20 N·m; for expansion valve nuts (M6), it is 6–10 N·m. 
Threaded joint connection. Insert the lubricated sealing ring end into the threaded joint end. Align and insert vertically until the front face of the plug head contacts the threaded joint. Hand-tighten the nut, then secure the threaded joint end with an open-end spanner. Tighten the nut end using a torque wrench, marking the tightened position (see figure below). Tightening torque specifications: High-pressure pipe fitting (M16×1.5 threaded joint): 12–15 N·m Low-pressure pipe fitting (M24×1.5 threaded joint): 30–35 N·m.

Note: When tightening threaded joints, it is essential to use two spanners simultaneously to avoid deformation of the pipework.

Connection of dual clamp joints. First position the end of the high-pressure clamp within the fork slot of the low-pressure clamp. Align and push the compressor interface in parallel. Once the clamps are flattened, inspect the O-ring position for misalignment or extrusion. Hand-tighten the bolts until resistance is encountered, then use a torque ratchet or wrench to tighten to specification, marking the tightened position (see figure below). The tightening torque for the compressor tail bolts (M10×1.25×35) is 20–30 N·m.

Supplementary Notes on Air Conditioning Pipe Installation:

Minor damage to O-rings during pipe installation may compromise sealing integrity, leading to refrigerant leakage.
Following installation, verify that pipes do not interfere with or exhibit free movement relative to surrounding vehicle components. Address any friction or interference promptly through adjustment, and secure pipes prone to free movement with appropriate fastenings.
Moving components such as the engine throttle cable and oil dipstick must never be bundled together with air conditioning piping. This prevents abrasion of the air conditioning lines, which could lead to refrigerant leakage.

As the automotive industry increasingly prioritises weight reduction, fuel economy and cost-effectiveness, aluminium alloys have become the material of choice for manufacturing automotive air conditioning piping due to their light weight, high strength, excellent thermal conductivity and corrosion resistance. As a key component carrying high-temperature, high-pressure refrigerant, the safety and reliability of air conditioning piping are of paramount importance. The wall thickness of the piping is a core design parameter that determines its strength, weight, cost and durability. Excessively thin walls may lead to leaks or even ruptures under extreme operating conditions, posing safety risks; conversely, excessively thick walls increase material costs and the overall vehicle weight, running counter to the trend towards lightweighting.

Consequently, the scientific and precise definition and calculation of the wall thickness of aluminium tubes used in automotive air conditioning systems are of paramount importance for ensuring product quality, controlling costs and enhancing vehicle performance. This report will systematically review the basis for defining wall thickness, analyse the underlying calculation theory, and present a complete calculation process from parameter selection to result analysis.

I. Definition of Wall Thickness in Automotive Air Conditioning Aluminium Tubing and Relevant Standards

1. Definition of wall thickness

From a physical perspective, the wall thickness of an aluminium tube refers to the distance between its outer and inner walls, which can be simply expressed by the formula: wall thickness = (outer diameter – inner diameter) / 2. However, in engineering applications, the definition of wall thickness extends far beyond this. It is a comprehensive engineering concept, primarily divided into the following two aspects:

Nominal wall thickness: This is the standard wall thickness value specified on design drawings for identification and ordering purposes. It is an idealised commercial specification, such as 1.0 mm, 1.5 mm, etc.

Minimum Allowable Wall Thickness: This is the thickness that the pipework must satisfy at its weakest point, as calculated from the design and taking into account all safety factors. Due to unavoidable dimensional deviations (tolerances) during the manufacturing process, the actual wall thickness of the product will vary from the nominal wall thickness. Therefore, the core objective of the design is to ensure that, even under the maximum negative tolerance, the actual wall thickness remains greater than or equal to the calculated minimum allowable wall thickness.

2. International automotive industry standards (SAE/ISO)

SAE (Society of Automotive Engineers): The SAE has published a large number of standards relating to automotive components. For example, SAE J2064 is a standard concerning high-quality air conditioning hoses,. Although no SAE standard specifically addressing the calculation of wall thickness for rigid aluminium tubing was found in the search results, relevant standards set out clear requirements for the system’s pressure rating and performance characteristics (such as pressure resistance). These requirements, in turn, influence the design inputs for wall thickness.

ISO (International Organisation for Standardisation): Similar to SAE, ISO also has standards relating to piping and pressure; for example, ISO 8434-2 defines the pressure ratings for pipe fittings. However, once again, no specific ISO standard has been found that directly addresses the calculation of wall thickness for aluminium tubing used in automotive air conditioning systems.

Overall, the definition of wall thickness for aluminium tubes used in automotive air conditioning systems is a multi-standard, multi-tiered process. It is guided by specialised standards such as T/QCKT 003-2011, whilst drawing on the design principles of general-purpose pressure piping standards such as GB/T 20801 and ASME B31.3 for specific calculation methods.

II. Theoretical Basis and Key Parameters for Wall Thickness Calculations

1. Core computational principles

An aluminium tube for automotive air conditioning is essentially a thin-walled cylinder subjected to internal pressure. The fundamental purpose of calculating its wall thickness is to ensure that the hoop stress generated in the tube wall material remains below the material’s allowable stress under all operating conditions.

The most fundamental and widely used calculation model is derived from the theory of thin-walled pressure vessels; its simplified formula (also known as a variant of the Barlow formula) is as follows:

δ = (P × D) / (2 × [σ]) + C

Where:

•  δ (or t): The minimum wall thickness required for the calculation (mm)

•  P: The design pressure of the piping (MPa)

•  D: The outer or inner diameter of the piping (mm); this varies slightly depending on the specific formula used, but the outer diameter is typically employed for conservative calculations

•  [σ] (or S): The allowable stress of the material at the design temperature (MPa)

•  C: Wall thickness allowance due to factors such as corrosion, erosion or machining (mm); for internally clean air-conditioning systems, this value can usually be taken as 0

•  More complex formulas, such as those provided in ASME B31.3, also introduce factors such as the weld joint factor (W), the mass factor (E) and the material-specific temperature correction factor (Y).                     t = (P × D) / (2 × (S × E × W + P × Y))

These factors make the calculation results more accurate and safer, but the basic principle remains unchanged.

2. Analysis of key input parameters

Accurate wall thickness calculations depend on precise input parameters.

Design Pressure (P):

Design pressure is one of the most critical input parameters in wall thickness calculations. It is not simply the average operating pressure of the system, but rather the most severe pressure value the system is likely to encounter over its service life, with a safety margin added to this value.

Pressure zones: A vehicle’s air conditioning system is divided into a high-pressure side and a low-pressure side. The high-pressure circuit (from the compressor outlet to the expansion valve) is subjected to higher pressures.

Pressure range:

•  The operating pressure on the low-pressure side is typically between 0.15 and 0.25 MPa (1.5–2.5 bar).

•  The operating pressure on the high-pressure side is typically between 1.3 and 1.7 MPa (13–17 bar), but varies significantly depending on factors such as ambient temperature, engine speed and refrigerant charge.

•  Industry standards and practical testing indicate that the operating pressure on the high-pressure side should not be less than 3.5 MPa. Some standards even require a leak-free pressure hold test at 3.53 MPa.

Basis for selection:

Consequently, when calculating the wall thickness of high-pressure pipes, the design pressure (P) is typically set at a value significantly higher than the average operating pressure—for example, 4.0 MPa or even higher—to account for all possible transient peak pressures and to provide the safety margin required by standards.

Allowable stress ([σ] or S):

The allowable stress is the maximum stress a material can withstand without undergoing permanent deformation or failure. It directly reflects the material’s ‘resistance’.

Common materials:

Aluminium tubes for automotive air conditioning systems are typically made from aluminium alloys that offer good strength and machinability, such as 3103-H12, 6063-T6 and 6061-T6.

Strength criteria:

Allowable stresses are typically determined based on the material’s yield strength or ultimate tensile strength (UTS). Yield strength is the critical point at which a material begins to undergo plastic deformation; it is the more conservative and commonly used design criterion.

Mechanical Properties of 6061-T6: According to the data, the typical mechanical properties of 6061-T6 aluminium alloy are:

•  Minimum yield strength: approx. 240–241 MPa (35,000 psi)

•  Minimum ultimate tensile strength: approx. 290 MPa (42,000 psi)

Safety factor:

The allowable stress is not simply the yield strength; rather, it is calculated by dividing the yield strength by a safety factor (SF). The value of the safety factor depends on the criticality of the application, the uncertainty of the load, the consistency of material quality, and the requirements of the relevant standards; it typically ranges from 1.5 to 3.0. [σ] = Yield strength / Safety factor

Temperature effects:

The allowable stress of a material varies with temperature. Although the operating temperature range of air conditioning piping (-40°C to +125°C) has a relatively minor effect on the strength of aluminium alloys compared to steel, it is still necessary to consult the allowable stress data tables for the relevant materials at the design temperature when carrying out precision design work.

III. Example of the calculation process for the wall thickness of aluminium tubes in car air conditioning systems

1. Preliminary Remarks

Important Notice: Following a comprehensive analysis of the search results provided, no publicly available sources have been found that offer a complete, official example of aluminium tube wall thickness calculations for automotive air conditioning systems, including specific input data and output results. Such calculations typically form part of the internal core design processes and intellectual property of original equipment manufacturers (OEMs) or Tier 1 suppliers.

Consequently, this section will construct a logically rigorous and data-reasonable hypothetical calculation example based on the aforementioned theoretical foundations and data collated from search results. The aim is to clearly demonstrate the entire process of wall thickness calculation, rather than to provide a ‘standard answer’ that can be directly applied.

2. Calculation Scenario

Subject of calculation: Aluminium tubing on the high-pressure side of a passenger car air conditioning system.

Outer diameter (D) of the tubing: 12.0 mm (a common specification).

Tubing material: 6061-T6 seamless aluminium alloy tubing.

3. Selection and rationale for input parameters

Design pressure (P):

Basis: Given the significant fluctuations in operating pressure on the high-pressure side, and in accordance with industry standards requiring a pressure resistance of no less than 3.5 MPa, and to address pressure surges caused by system anomalies (such as cooling fan failure), we have selected a conservative design pressure.

Value: P = 4.2 MPa (this value is also close to the maximum operating pressure specified in QC/T 669-2019)

Allowable stress ([σ]):

Basis: The material is 6061-T6, which has a minimum yield strength of approximately 241 MPa at room temperature. Given the stringent safety requirements for automotive components and the complex operating conditions, such as vibration and thermal cycling, we have selected a relatively conservative safety factor (SF). We assume SF = 2.5.

Calculation and values:

[σ] = yield strength / SF = 241 MPa / 2.5 = 96.4 MPa
[σ] = 96.4 MPa

Other specifications:

Outer diameter (D): 12.0 mm

Corrosion allowance (C): As automotive air-conditioning systems are sealed, clean systems, the risk of internal corrosion is extremely low. Therefore, C is taken as 0 mm.

4. Calculation Procedure

Step 1: Select the calculation formula
For clarity, we shall use the simplified Barlow’s formula mentioned earlier, which is sufficient for preliminary engineering design:

Step 2: Substitute the values to perform the calculation
Substitute the selected parameters into the formula:
δ_min = (4.2 MPa × 12.0 mm) / (2 × 96.4 MPa) + 0
δ_min = 50.4 / 192.8
δ_min ≈ 0.261 mm
Step 3: Interpretation of Results
The calculated result, δ_min ≈ 0.261 mm, indicates that, in theory, for this aluminium tube to safely withstand the design pressure of 4.2 MPa, the wall thickness at any point must not be less than 0.261 mm.

5. Analysis of Results and Final Selection

The calculated value of 0.261 mm is merely the theoretical minimum wall thickness and must under no circumstances be taken directly as the final nominal wall thickness. The following key factors must also be taken into account: Manufacturing tolerances: During the extrusion or drawing process, there will be a certain degree of variation in the wall thickness of aluminium tubes. Assuming, in accordance with a certain standard (for example, T/QCKT 003-2011, for which specific values are unavailable), the wall thickness tolerance is ±10%. This implies that, to ensure the thinnest point is no less than 0.261 mm, the nominal wall thickness (t_nominal) must satisfy:

In addition to strength, the wall thickness must also meet process requirements such as tube bending and joint connections (e.g. flaring, welding). Tubes with excessively thin walls are prone to wrinkling or cracking during bending.

Vibration fatigue resistance:

Automotive tubing is subjected to prolonged vibration, requiring sufficient wall thickness to resist fatigue failure. This is typically verified through extensive bench testing and CAE simulation, rather than through static pressure calculations alone.

Standardised Selection:

Aluminium tube manufacturers generally produce only standard specification series, such as 0.5 mm, 0.8 mm, 1.0 mm, 1.25 mm, 1.5 mm, etc.

Final decision:
Taking all the above factors into account, even if the calculated minimum wall thickness is only 0.29 mm (taking tolerances into account), the engineer would never opt for such an extreme wall thickness. Instead, they would select a wall thickness from standard specifications that not only meets the strength requirements but also strikes the optimal balance between manufacturability, fatigue resistance and cost. In this case, 1.0 mm or 1.25 mm would be more realistic and reliable nominal wall thickness options. This choice ensures a very high safety margin to account for dynamic loads and uncertainties not fully covered by the computational model.

IV. Conclusions and Future Research Directions

The wall thickness of aluminium tubes for automotive air conditioning is not defined by a single numerical value, but is instead governed by specific standards such as ‘Aluminium Tubes and Assemblies for Automotive Air Conditioning’ (T/QCKT 003-2011), which specify general performance requirements. The minimum permissible values are determined through engineering calculations based on general pressure piping theory (e.g. GB/T 20801, ASME B31.3), and the minimum permissible values are determined through engineering calculations. The nominal values are ultimately selected by taking into account manufacturing processes, costs and standardised specifications.

Key elements of the calculation: The essence of wall thickness calculation lies in strength verification based on the principles of materials mechanics. The most critical input parameters are the design pressure (P) and the allowable stress of the material ([σ]). Determining these parameters requires a thorough understanding of the system’s operating conditions and the application of appropriate safety factors.

This study indicates that specific tables of wall thickness values, tolerance ranges and detailed official calculation examples are extremely difficult to obtain through public channels. This information largely constitutes the core technical assets of automotive manufacturers and component suppliers.

Combining theory and practice: The minimum wall thickness derived from theoretical calculations is merely the starting point for the design. The final selection of wall thickness is a comprehensive decision-making process that must take into account practical factors such as manufacturing tolerances, bending processes, resistance to vibration and fatigue, and standardised supply.

Design must take into account not only manufacturing processes but also the ease of assembly for the OEM. During the pilot production phase for a new automotive model, frequent assembly difficulties arose with the air conditioning refrigeration piping, resulting in substantial costs for subsequent design modifications. By incorporating concurrent engineering into the final assembly process, virtual assembly analysis and design constraints were applied during the development of the air conditioning refrigeration piping. This effectively reduced production costs during the manufacturing process and improved production efficiency. This paper briefly outlines the assembly and design issues encountered in the synchronous engineering analysis of air conditioning refrigeration piping, along with their solutions, and provides valuable guidance for the development of air conditioning refrigeration piping in new vehicle models.

I. Introduction to Synchronised Engineering for Final Assembly

Synchronised Engineering (SE) for final assembly is a process in which final assembly processes are integrated into the design and development phase of vehicle development. It primarily involves conducting process analyses of assembly digital models, production lines, equipment and assembly processes, and provides feasible process design changes to support the design. Its primary objective is to review issues in product design during the drawing design and digital model generation stages, taking effective measures in advance to address potential problems that may arise during process implementation, thereby ensuring the new vehicle model is production-feasible and compatible with equipment and tools.

II.  Air Conditioning Piping Assembly and Design 

1. Composition of the Front Engine Compartment Air Conditioning Refrigerant Piping

The air conditioning refrigerant piping primarily comprises the air conditioning high- and low-pressure pipe assembly, air conditioning exhaust pipe assembly II, air conditioning exhaust pipe assembly I (which may be combined with air conditioning exhaust pipe assembly II, depending on assembly considerations), air conditioning low-pressure pipe assembly I, and air conditioning high-pressure pipe assembly I (which may be combined with the air conditioning high- and low-pressure pipe assembly, depending on assembly considerations).

2. Issues with the design and assembly of the air conditioning refrigerant piping

(1) At the connection between the high- and low-pressure pipe assembly and the HVAC expansion valve, the foam padding on the clamps attached to the pipes is too thick and too rigid, causing excessive interference with the front panel and making the piping difficult to fit.

(2) The air conditioning high- and low-pressure pipe assembly comes with its own mounting brackets (secured to the engine compartment side panels and longitudinal beams). The cut-outs are circular, but the allowance for offset in the X-direction is too small; due to the combination of fitting accuracy and cumulative tolerances, the bolt holes cannot be aligned.

(3) The air conditioning refrigerant lines are connected using bolts and nuts; during prototyping, there is insufficient working space for tightening tools (such as a cordless impact wrench). The interference persists even when a shorter socket is used.

(4) It is not possible to apply refrigeration oil to the clamps during assembly of the pipe joints, and refrigerant leaks occur once assembly is complete. There is no flexible hose section connecting the high- and low-pressure pipe assemblies to the high-pressure pipe assembly; the rigid pipes are difficult to connect and prone to deformation.

(5) The piping layout is not sufficiently well-designed, leading to frequent issues such as abnormal noises and poor assembly ergonomics; for example, the piping does not run close enough to the engine compartment, and the air conditioning filling port is positioned too low to allow for refilling.

3. Design Constraints for Air Conditioning Refrigerant Piping

Design constraints are guidelines derived from a compilation of common issues encountered during the introduction of new vehicle models and the prototyping process; they are intended to identify areas requiring improvement in subsequent product designs. In response to the assembly issues outlined above, the following design constraints have been established.

(1) The foam used in the clamping plate at the connection between the air conditioning high- and low-pressure pipe assembly and the HVAC expansion valve should be made of PUR material, with a thickness preferably less than 15 mm.

(2) With the exception of the primary locating holes, all holes in the brackets on the air conditioning high- and low-pressure pipe assemblies shall be elliptical in the X-direction (e.g. 8×10, depending on the bolt specification), to accommodate cumulative tolerances. A rotational restraint mechanism (such as a locking clip) must be provided at the point where the bracket connects to the vehicle body to prevent the bracket from rotating when the bolts are tightened, which could cause deformation of the piping. The brackets for the air conditioning pipes must be designed to be mounted on the rigid pipe sections to avoid scratching the flexible hoses.

(3) When designing the system, consideration must be given to the working space required for operating pipe connection fastening tools. When using an elbow gun, the distance between the rivet head and the end of the stud must be greater than 85 mm; when using a straight gun, the distance between the rivet head and the end of the stud must be 40 mm. 

 (4) The male end of pipe fittings must face upwards in the Z-direction (no requirement for the X-direction) to facilitate the application of refrigeration oil. Rigid pipes must not be connected directly to one another; a flexible hose must be used as an intermediate connection, and the joint must be properly sealed, for example by fitting a sealing gasket. 

 (5) Above the high- and low-pressure filling ports of the air conditioning high- and low-pressure pipe assemblies, there must be a clear space with a diameter of 50 mm and a height of 250 mm. Furthermore, the spacing between the high- and low-pressure filling ports must be reasonable (depending on the size of the filling nozzle).

III. Conclusion     

This paper summarises the common issues encountered during the final assembly of the refrigeration piping system for a particular automotive air conditioning unit. By incorporating SA constraints into the design phase through concurrent engineering during the early stages of new model introduction, this approach has helped to minimise design shortcomings, optimise the manufacturability of the final assembly process, and reduce production costs for the company. Furthermore, it provides valuable guidance for the development of refrigeration piping systems for new vehicle models.

Adding a turbocharger kit to your vehicle is a complex and intricate process. Forced induction conversion (adding a turbocharger or supercharger) should be undertaken with meticulous care and a thorough understanding of the concepts required for the system to function smoothly. Below is an explanation of the fundamental components that should be included in any basic turbocharger kit and their respective functions.

Turbocharger

The turbocharger component of the turbo kit is the most obvious. The turbocharger is essentially a powerful, high-capacity air compressor driven by the energy from the engine's exhaust gases. It is important to remember that not just any turbo will suffice. The turbo's capacity must be carefully matched to the engine and the desired performance.

Intercooler
Virtually all turbocharged systems require an intercooler for proper operation. An intercooler acts as an “air radiator”, cooling the air that has been compressed by the turbocharger before it reaches the engine's intake. Without an intercooler during the pressurisation process, the air becomes excessively heated, which may lead to dangerous pre-detonation.

Turbocharger Manifold and Downpipe
The turbo manifold is fitted to the exhaust stream of the turbocharged engine, housing the compressor blades where the turbocharger operates. The downpipe seamlessly connects the turbocharger to the remainder of the exhaust system, integrating it into the vehicle's existing exhaust layout.

Intercooler and Intake Piping
The intercooler and intake piping connect the turbocharger on the engine to the compressor. The outlet of the intercooler and intake manifold connects to the air filter at the intake port. The turbo piping is stronger than the stock components to handle the pressurised intake airflow at increased pressure.

Oil/coolant supply lines
Depending on whether the turbocharger is water-cooled, coolant lines may or may not be required for your turbocharger kit. All turbochargers will require an oil supply line to maintain bearing lubrication and cooling.

Fuel Management
Many turbocharger kits will require a fuel controller to ensure the correct amount of fuel is delivered to the engine under the additional boost pressure.

How does a turbocharger work?

Turbocharging works by compressing air, enabling the engine to accommodate greater volumes of air. This facilitates thorough mixing and combustion of fuel and air, thereby enhancing the engine's power output.

What are the advantages and disadvantages of turbocharging?

The advantages include an engine power increase of over 30%, with theoretically more complete combustion reducing fuel consumption and improving fuel efficiency. The greatest benefit, however, lies in emissions reduction, resulting in a lower environmental impact. This becomes particularly advantageous today as emission standards grow increasingly stringent, making turbocharging more advantageous. The drawbacks include higher operating temperatures and pressures, demanding stricter material performance specifications. Engine wear increases, resulting in a relatively shorter lifespan compared to naturally aspirated engines. Additionally, turbocharged engines produce greater noise levels. Furthermore, the time required for compressed air to convert into power output during acceleration typically spans two seconds, leading to a noticeable lag in power delivery response compared to naturally aspirated vehicles.

Where is silicone rubber applied in turbocharger systems?

Silicone is primarily employed in the C-section of turbocharger system piping, where operating temperatures typically range from 175 to 220 degrees Celsius. Certain high-temperature sections may even reach 250 degrees Celsius, necessitating silicone with exceptional heat resistance and ageing properties. NAFURANCAR's silicone products have been established in this industry for many years. Whether standard silicone, vapour-phase silicone, or heat-resistant silicone, we offer mature and stable matching solutions. These products have withstood extensive testing by numerous customers over many years, earning high recognition and trustworthiness.

Other rubber materials may not withstand operating temperatures of 220 degrees, but why not use metal components for Section C?

As metal components lack the elastic properties of elastomers, they cannot provide shock absorption and are therefore unsuitable for use in turbocharger system operating environments.

Silicone is not oil-resistant, so how does one address oil-gas mixing and oil leakage in the vortex tube?

The inner lining material for vortex tubes comprises 0.2-0.3mm fluorinated silicone rubber or 0.5-0.8mm fluorinated silicone elastomer. The reinforcement layer utilises aramid fabric laminated with calendered silicone rubber, while the outer cover features a single layer of silicone rubber. This thin inner lining layer effectively provides oil resistance. NAFURANCAR's fluorosilicone rubber products offer excellent oil resistance, superior processability, and competitive pricing, making them the ideal choice for your lining layer requirements.

What are the operational requirements for vortex tubes?

During operation, the vortex tube must not exhibit interlayer delamination, nor should its inner and outer surfaces display swelling, cracking, bulging, or other abnormal phenomena. The PVY test simulates the vortex tube's operational environment to assess its quality, primarily through pulse pressure testing and axial/radial vibration testing conducted under simulated temperature conditions.

How is that vortex tube manufactured?

The manufacturing process for silicone rubber composite hoses primarily comprises the following stages: compounding, calendering, fabric cutting, winding, shaping, vulcanisation, demoulding, cutting, assembly, and packaging. This represents the current mainstream production method, accounting for over 80% of silicone rubber composite hose manufacturing. Additionally, an extrusion moulding process exists, which reduces labour requirements while offering more consistent quality control. However, it demands higher standards in equipment, process parameters, and compound formulation. For both processes, NAFURANCAR offers suitable product solutions.

What are the future development trends for vortex tubes?

In future, vortex tubes will increasingly adopt stable automated production processes such as extrusion. Material selection will favour high-temperature, low-pressure silicone rubber capable of strong adhesion to dense aramid fabric. Design and manufacturing techniques will prioritise thin-walled construction, alongside crucial cost-reduction requirements. NAFURANCAR Company remains committed to refining its products in alignment with OEM/customer specifications, striving to maintain a leading position within the industry's developmental trajectory.

Design considerations must encompass not only manufacturing processes but also the ease of assembly for OEMs. During the trial production phase of a new automotive model, frequent assembly difficulties arose with the air conditioning refrigeration piping, leading to substantial redesign costs later on. By implementing synchronous engineering for final assembly, virtual assembly analysis and design constraints were applied during the development of the refrigeration piping. This approach effectively reduced production costs during final assembly and enhanced manufacturing efficiency. This paper outlines the assembly and design challenges encountered in synchronous engineering analysis for air conditioning refrigerant piping, along with corresponding solutions. It offers valuable guidance for the development of refrigerant piping systems in new vehicle models.

Introduction to Synchronous Engineering for Final Assembly

Synchronous Engineering (SE) for final assembly refers to the process whereby final assembly processes participate concurrently in the design and development stages of automotive development. It primarily involves conducting process analyses of assembly digital models, production lines, equipment, and assembly procedures, thereby providing feasible process design modifications for the design team. Its primary purpose is to identify and address potential issues in product design during the drawing design and digital model generation stages. This enables proactive measures to be taken against potential problems during process implementation, ensuring new vehicle models possess production feasibility and equipment/tool compatibility.

Air Conditioning Pipe Assembly and Design

1. Composition of the Automotive Front Compartment Air Conditioning Refrigerant Piping System

The air conditioning refrigerant piping primarily comprises the air conditioning high/low-pressure pipe assembly, air conditioning exhaust pipe assembly II, air conditioning exhaust pipe assembly I (which may be integrated with assembly II depending on assembly feasibility), air conditioning low-pressure pipe assembly I, and air conditioning high-pressure pipe assembly I (which may be integrated with the high/low-pressure pipe assembly depending on assembly feasibility). 

2. Design and Assembly Issues in Air Conditioning Refrigerant Piping

(1) At the connection point between the high/low-pressure pipe assemblies and the HVAC expansion valve, the foam gaskets integrated into the high/low-pressure pipes are excessively thick and rigid. This causes significant interference with the front panel, making pipe assembly difficult.

(2) The air conditioning high/low-pressure pipe assembly incorporates its own mounting brackets (secured to the fuselage side panels and longitudinal beams). The mounting holes are circular, with insufficient clearance allowance for X-axis hole offset. Due to precision fit requirements and cumulative tolerances, bolt holes may fail to align correctly.

(3) The air conditioning refrigeration lines are connected via bolts and nuts. During prototyping, insufficient operating space for tightening tools (such as impact wrenches) may occur. Interference persists even when short sockets are used as replacement tightening tools.

(4) During assembly of the pipe joint clamping plate, refrigeration oil cannot be applied, resulting in refrigerant leakage upon completion. The connection between the air conditioning high- and low-pressure pipe assemblies lacks a flexible hose section, making rigid pipe connection difficult and prone to deformation.

(5) The pipework design is suboptimal, frequently resulting in issues such as abnormal noises and inadequate assembly rationality. For instance, the pipework routing does not sufficiently hug the engine compartment, and the air conditioning filling port is positioned too low to permit refilling.

3. Design Constraints for Air Conditioning Refrigeration Piping

Design constraints are binding specifications derived from the compilation of recurring issues encountered during the introduction and prototyping of new vehicle models. They serve to identify areas requiring improvement in subsequent product designs. In response to the aforementioned assembly issues, the following design constraints are established:

(1) The foam material within the pressure plate at the connection point between the high/low-pressure air conditioning pipe assembly and the HVAC expansion valve shall be specified as PUR material, with a thickness preferably less than 15mm.

(2) On the air conditioning high/low pressure pipe assembly bracket, all mounting holes except the primary locating hole shall be elliptical in the X-direction (e.g. 8×10, subject to bolt specifications) to accommodate cumulative tolerances. The bracket connection points to the vehicle body must incorporate anti-rotation restraints (e.g., locking clips) to prevent bracket rotation during bolt torque tightening, which could cause duct deformation. Air conditioning duct brackets must be positioned on rigid pipe sections to avoid scratching flexible hoses.

(3) During initial data design, allowance must be made for operational clearance when tightening pipe connections. When using an elbow gun, the riveting head must be positioned more than 85mm from the stud tail; when using a straight gun, the riveting head must be positioned 40mm from the stud tail.

(4) For pipe joints, the male end must face upwards in the Z-direction (no requirement in the X-direction) to facilitate application of refrigeration oil. Rigid pipes must not connect directly to other rigid pipes; one connection must incorporate a flexible hose transition. Sealing at the joint must be correctly managed, such as by adding a sealing gasket.

(5) Above the high- and low-pressure filling ports of the air conditioning pipe assembly, a clearance of 50mm diameter and 250mm height must be maintained free of obstructions. Additionally, the spacing between the high- and low-pressure filling ports must be appropriately arranged (determined by the size of the filling gun nozzle).

Conclusion

This paper summarises common issues encountered during the final assembly of refrigeration piping systems for automotive air conditioning units. By implementing concurrent engineering during the early stages of new model introduction, SA constraints were incorporated into the design phase. This approach mitigated deficiencies in product design, optimised the manufacturability of final assembly processes, and reduced production costs for the enterprise. Furthermore, it provides valuable guidance for the development of refrigeration piping systems in future vehicle models.

Recently, BMW ALPINA, the exclusive independent brand under the BMW Group, officially unveiled its new brand emblem. This marks another significant milestone following the brand's formal debut as an independent entity within the BMW Group in January 2026. Paired with the previously revealed brand wordmark, the new emblem establishes BMW ALPINA's contemporary visual identity system. The brand's core proposition centres on delivering an unparalleled long-distance driving experience that combines ultimate luxury with high performance, establishing a distinct positioning differentiation from BMW's M series.

The all-new BMW ALPINA badge design harmoniously blends the brand's heritage with contemporary aesthetics, retaining the throttle body and crankshaft – two quintessential elements that underscore the brand's profound technical legacy. Within the badge, clean, crisp lines are employed to outline the emblem, maintaining stylistic consistency with the surrounding brand lettering. Furthermore, a distinctive translucent finish is applied, accentuating the modern contours.

In the production and crafting of BMW ALPINA models, these vehicles will be manufactured at the fully upgraded BMW Group facilities, adhering strictly to the brand's high production standards. Consumers are offered a wealth of personalisation options, enabling customers to create their own bespoke vehicles. Iconic design elements such as the classic exterior colour schemes and 20-spoke alloy wheels continue to be employed, having undergone detailed optimisation.

It is understood that at this stage, BMW ALPINA will focus on products developed from BMW's larger models. The first new vehicle will be the all-new B7, based on the facelifted 7 Series. This will be followed by the next-generation XB7, with future plans extending to BMW's flagship SUVs and other models. In essence, BMW ALPINA is neither an ‘enhanced BMW’ nor a ‘luxury version of BMW M’. It stands as an independent ultra-luxury brand within the BMW Group, specialising in the harmonious blend of opulent comfort and high performance. We shall see how it performs in the years to come.

The steering systems fitted to motor vehicles can broadly be categorised into three types: (1) Mechanical hydraulic power steering systems; (2) Electro-hydraulic power steering systems; (3) Electric power steering systems.

 I.Electric Power Steering System (EPS)

1. The full English name is Electronic Power Steering, abbreviated as EPS. It utilises power generated by an electric motor to assist the driver with power steering. Although the structural components differ across vehicles, the basic composition of EPS is largely similar. It typically comprises a torque (steering) sensor, an electronic control unit, an electric motor, a reduction gear, a mechanical steering gear, and a battery power source.

2. Primary operating principle: During steering manoeuvres, the torque (steering) sensor detects the steering wheel's applied torque and intended direction of rotation. These signals are transmitted via the data bus to the electronic control unit. Based on input data such as applied torque and intended steering angle, the ECU issues operational commands to the motor controller. The motor then generates an appropriate counter-torque output to assist steering effort. When no steering input is applied, the system remains inactive in standby mode, awaiting activation. Due to the operational characteristics of electric power steering, drivers typically perceive enhanced steering feel and greater stability at high speeds, commonly described as ‘steering that doesn't feel loose or vague’. Furthermore, its non-operational state during non-steering periods contributes to energy savings. This type of power steering system is commonly employed in premium saloon vehicles.

Compared to mechanical hydraulic power steering systems, electric power steering requires only electricity and eliminates numerous components. It dispenses with the hydraulic system's oil pump, oil lines, pressure/flow control valves, reservoir, and other elements. This results in fewer parts, easier layout, and reduced weight.

Moreover, it eliminates parasitic losses and fluid leakage losses. Consequently, electric power steering achieves approximately 80% energy savings under various driving conditions, enhancing the vehicle's operational performance. Consequently, it has seen rapid adoption in recent years and represents the future trajectory for power steering systems.

Some vehicles marketed as featuring electric power steering do not employ a genuinely pure electric system; they still require a hydraulic system, albeit one supplied by an electric motor. In traditional hydraulic power steering systems, the oil pump is driven by the engine.

To ensure light steering effort during stationary or low-speed manoeuvres, the pump's displacement is determined by the flow rate at engine idle speed. However, as vehicles spend most of their time travelling at speeds above idle and in straight-line motion, the majority of the oil pump's output must be returned to the reservoir via control valves, resulting in significant parasitic losses.

To mitigate these losses, an electric motor-driven oil pump is employed. During straight-line driving, the motor operates at low speed, while during steering manoeuvres it runs at high speed. By regulating the motor's rotational speed, the oil pump's flow rate and pressure are adjusted, thereby reducing parasitic losses.

II. Mechanical Hydraulic Power Steering Systems

1. Mechanical hydraulic power steering systems typically comprise a hydraulic pump, oil lines, pressure-flow control valve body, V-belt drive, reservoir, and other components.

2. This system operates continuously regardless of steering input. During sharp turns at low speeds, the hydraulic pump must deliver greater power to provide substantial assistance, thereby wasting resources to some extent. Consider this: when driving such vehicles, particularly during low-speed turns, the steering feels heavy and the engine labours noticeably. Moreover, the high pressure generated by the hydraulic pump can readily damage the power steering system. Furthermore, mechanical hydraulic power steering systems comprise hydraulic pumps, piping, and cylinders. To maintain pressure, the system remains active regardless of steering assistance requirements, resulting in higher energy consumption – another factor contributing to resource expenditure. Such systems are commonly found in economy-class saloon cars.

 III. Electronically Controlled Hydraulic Power Steering System

1. Primary Components: Reservoir tank, power steering control unit, electric pump, steering gear, power steering sensor, etc., wherein the power steering control unit and electric pump form an integrated assembly.

2. Operating Principle: The electronic hydraulic power steering system overcomes the shortcomings of conventional hydraulic power steering systems. Its hydraulic pump is no longer directly driven by the engine belt but instead utilises an electric pump. All operational states are determined by the electronic control unit, which calculates the optimal conditions based on signals such as vehicle speed and steering angle. Simply put, during low-speed, high-angle turns, the ECU drives the electric hydraulic pump at high speed to deliver greater power, reducing steering effort for the driver. At high speeds, the hydraulic control unit operates the electric pump at lower speeds, conserving engine power without compromising high-speed steering responsiveness.