Tesla continues to optimise manufacturing, with the FSD Hardware 4 computer, also called HW4 or AI4, now under examination. The computer supports driving assistance in newer Model 3 and Model Y cars. According to analysis by the well-known hacker Green, the revised version had a simpler, leaner design, reflecting cost reduction and engineering simplification as Tesla prepared for AI5.

Fewer components, the same goal

Green found that several components had been removed from the revised board and associated wiring. The most noticeable changes included:

  • removing some secondary connectors
  • eliminating the small batteries dedicated to the board’s internal clock
  • and removing the copper ground cable, replaced by a direct connection to the vehicle chassis, a common automotive practice

Although apparently small, these changes could mean lower material costs and simpler manufacturing processes, two central elements of Tesla’s approach.

Structural simplification of HW4

The changes were not only about saving money.
Using the vehicle chassis as an electrical grounding point could reduce wiring weight and complexity, making factory assembly work easier.

Removing the small batteries dedicated to the RTC, or Real-Time Clock, module also allowed it to rely on the vehicle’s low-voltage battery for continuous power, reducing the number of components that might fail over time.

At manufacturing scale, each unused connector or component represents an avoidable cost. Tesla appeared to be applying lean manufacturing even to less visible details.

Preparing for the next step: AI5

The revision came as Tesla prepared to introduce AI5, which this November 2025 report expected to enter mass production in 2026. Why keep optimising HW4 if a replacement was approaching? The argument was scale: the report projected more than two million vehicle sales before the complete transition, so small savings repeated across those volumes could have a substantial financial impact. These were projections made at the time.

It was also considered likely that some HW4 refinements drew on testing and knowledge accumulated during AI5 development. The revised HW4 already included a front bumper connector for fitting the front camera.

What to expect

The changes suggested more than simple cost cutting: Tesla was rationalising the vehicle architecture with the aim of faster production, fewer materials and improved reliability over time.

HW4’s development therefore represented an intermediate step towards AI5 and an example of Tesla revisiting processes as well as products.

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Giorgio Rebecchi

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Giorgio Rebecchi
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