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When Volkswagen handed over their ID.4 electric motor to Munro & Associates, they did something rare in the auto industry: they invited a no-holds-barred teardown on camera. And we delivered.
This permanent magnet (PM) motor offered a compelling look into how VW is approaching the global EV market—with a strong focus on modularity, cost reduction, and long-term reliability. Here’s what we found.
Global Design Strategy: Modularity Over Integration
Unlike Tesla, which integrates motor mounts into its castings, Volkswagen opted for a flexible, bracket-based design. The ID.4 motor can be installed across various platforms and suspension setups, making it ideal for a manufacturer with global reach and a wide portfolio. This strategy sacrifices some part count reduction but gains adaptability—key for scaling worldwide.
In practical terms, this modularity means VW can support multiple product lines with a common drivetrain. This is crucial for fleet vehicles, delivery vans, and future pickups where design constraints vary widely. It’s a smart move for cost control and engineering efficiency at scale.
Gearbox Simplicity and Bearing Reduction
The gearbox was the first point of entry—and a surprise. VW uses just three bearings instead of the typical four. Thanks to tight tolerances and accurate spline alignment between the motor shaft and gearbox, this reduction cuts friction and improves efficiency without sacrificing durability.
However, the bearings are smaller than those used by Tesla. It’s a bold move, and while it may not support million-mile aspirations, it’s likely tuned for a more standard vehicle lifespan.
Notable detail: Volkswagen uses RTV sealant throughout. It’s clean, leak-resistant, and robust for long-term sealing. The use of RTV over traditional gaskets streamlines production and simplifies assembly, aligning well with lean manufacturing goals.
Cooling System Innovation: Less is More
Volkswagen has taken a streamlined approach to thermal management. Coolant flows first through the inverter, then into the stator housing, eliminating the need for:
- An oil pump
- An oil filter
- A separate heat exchanger
This “serpentine loop” efficiently wicks heat away while simplifying the system—a major win in both cost and complexity. Small squirt holes help bleed air, and the overall architecture shows smart system integration.
This strategy highlights VW’s deep understanding of what truly needs to be cooled. Electronics—particularly the inverter and IGBTs—are more sensitive to heat than the motor itself. Prioritizing these elements yields better thermal control and reliability without added components.
Housing Materials: Smart Aluminum Choices
The motor housing uses different casting processes depending on the part:
- High-pressure die cast (383/384 aluminum) for outer shells
- Low-pressure die cast (3105 aluminum) for the center section
Volkswagen explored extrusions for weight and cost but ultimately stuck with die casting. It strikes a balance between manufacturability and performance, and Munro’s material tests confirmed the consistency. These casting choices reduce machining needs and improve thermal performance, further reflecting a lean engineering mindset.
Hairpin Stator Wins on Fill Factor
VW opted for a hairpin-wound stator, beating traditional wire winding methods by delivering a 60% slot fill versus just 46%. This increases power density and allows for optimized magnet use.
By reducing reliance on rare-earth materials like dysprosium and neodymium, VW scores big on both cost and supply chain resilience. The hairpin method also enhances thermal conductivity and supports more efficient manufacturing through automated winding processes.
Rotor Construction: Innovative, Yet Over-Bolted
The ID.4 rotor uses four long bolts to compress laminates and secure the internal magnetic assembly. It’s effective but raises concerns:
- Threaded fasteners are prone to loosening from vibration and thermal cycling.
- Munro recommends radial riveting or snap fits instead—faster, more reliable, and better for automated assembly.
Despite the bolt-heavy design, VW has cleverly avoided adhesives and optimized for manufacturability. However, the philosophy of “design for Bob”—Munro’s shorthand for blindfolded, one-armed assembly—suggests that snap-fits or rivets would be more reliable in mass production.
Magnet Array: Clever Noise Abatement
During our teardown of the ID.4, we found that Volkswagen’s rotor features a delta-style magnet layout with unique offsets designed to reduce noise—akin to how high-speed rail cuts rail joints on a bias to minimize clatter.
This attention to acoustics matters. EV buyers notice noise, and VW’s smooth pattern shows thoughtful NVH engineering. Compared to the abrupt transitions in older layouts, the gradual tapering seen in the ID.4’s magnetic pattern provides a smoother torque delivery, helping eliminate tonal vibration.
Skeletonized Laminates: Lightweight with Integrity
Every gram counts in EVs. VW’s laminates are skeletonized—removing unnecessary material while maintaining structural and magnetic integrity. This strategy helps reduce mass and cost while boosting motor responsiveness.
The magnet slots are cleanly cut, with optimized air gaps and clear thermal paths for heat dissipation. VW’s attention to this detail indicates a serious effort to reduce material waste and increase efficiency without over-engineering.
Inverter Architecture: Vertical Assembly with Caveats
Volkswagen’s inverter is vertically stacked, supporting Munro’s ideal “top-down” assembly flow. That’s great for automation and lean manufacturing.
But here’s the issue:
There are far too many threaded fasteners—dozens, in fact.
These screws complicate assembly, lower quality scores, and make service unlikely. As Sandy Munro puts it, “No one’s fixing inverters.”
Instead, VW could improve by moving to:
- Snap fits
- Thermal adhesives
- Glued seals for non-serviceable parts
Despite this drawback, the inverter’s performance is strong. It includes an effective bleed resistor glued into place, bus bars that are easy to access, and a large capacitor for smoothing voltage delivery. Each layer of the stack is well-cooled, and the EMIC seal on the lid prevents electromagnetic interference—an often-overlooked but vital feature.
Assembly Philosophy: Designed for Automation
Munro’s teardown revealed that the ID.4 motor design largely supports robotic assembly. Most major components drop in vertically, simplifying automation. The coolant passages align with precision. The inverter stack is modular. And with fewer adhesive bonds, disassembly (for recycling or diagnostics) becomes easier.
Where VW still lags is in its reliance on threaded fasteners. These add complexity and risk during thermal cycling and vibration. Eliminating them—or using Loctite, thread-forming screws, or snap features—could further improve reliability and cost.
Final Thoughts: A Global Contender
Volkswagen’s ID.4 electric motor exemplifies thoughtful, cost-aware engineering. From the elimination of oil-based cooling systems to compact winding strategies and quiet rotor design, VW shows it can play ball in the EV space—and maybe even challenge the big names.
What We Loved:
- Smart modular motor mounts
- Reduced bearing count
- Efficient cooling via coolant-only loop
- Hairpin stator with better fill factor
- Lightweight laminated rotor with clever noise design
- Top-down assembly approach
What Could Be Better:
- Too many threaded fasteners
- Overreliance on bolted assemblies
- Missed opportunity for more automation-friendly fasteners
Volkswagen may not have reinvented the EV motor, but they’ve refined and adapted it well to suit global manufacturing needs. With a few tweaks—particularly in fastening strategy—they could push even further toward lean manufacturing excellence.
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