Tesla Owner Successfully Upgrades HW3 Model 3 to HW4

For years, the standard answer to "can my HW3 Tesla be upgraded to HW4?" has been some version of "not without tearing the car apart." One developer just poked a big hole in that assumption.

Michał Gapiński — the software engineer behind the Tesla Android project that unofficially brings Apple CarPlay to Tesla screens while Tesla works on an official implementation — has successfully retrofitted a Hardware 4 (HW4/AI4) Autopilot computer into a 2022 Model 3 that shipped with Hardware 3 (HW3/AI3). He shared the work on X, confirming the car is driving and that he got the first camera working.

"It's not as bad as it seemed, the computer replacement needed some light ECU hacking." — Michał Gapiński

Gapiński is no stranger to this kind of project. He previously retrofitted the Model Y L's faster, air-cooled wireless chargers into a standard Model Y. This time the target was the car's self-driving brain.

What the Retrofit Actually Involved

The HW4 computer Gapiński used was pulled from a Model Y. Mounting it in the older Model 3 was, by his own joking description, a matter of epoxy, zip ties, and a YOLO attitude — though he noted the HW4 casing is only slightly taller, so an official "Highland" refresh bracket would bolt up cleanly if you drill the mounting holes.

The bigger technical question was wiring. Older camera cables weren't expected to play nicely with newer HW4 sensors, but Gapiński says that turned out to be a non-issue:

"It's both Fakra, you just need to adapt it to a different connector. No need to cut and replace anything."

Here's the short version of what the swap required:

• A HW4 computer (his came out of a Model Y)
• New HW4 cameras — all external cameras must be swapped to the higher-resolution units
• Custom Fakra connector adapters, so factory wiring stays intact
• Some "light ECU hacking" on the firmware side
• A mounting solution — DIY, or a Highland bracket with drilled holes

Cooling and power delivery in the 2022 Model 3 appear adequate for the HW4 computer, according to Gapiński. Interestingly, he added that upgrading an older Intel Atom infotainment unit to AMD Ryzen is actually easier than swapping the FSD computer and camera suite. His work isn't finished — "it's driving, but still a bit of stuff left to get all the features" — but the hard part is clearly behind him.

Why HW3 Owners Care So Much

This comes down to raw compute. HW3 has roughly 15% of the memory bandwidth found on HW4. That gap left HW3 cars stuck on older FSD v12.6 builds for more than a year, until Tesla publicly released FSD v14 Lite last month.

V14 Lite is a real step up from v12.6, but it still trails the main v14 branch in confidence and decision-making speed. There's a thermal cost, too — running modern neural networks on older silicon pushes the hardware hard, and there have been reports of HW3 computers overheating on v14 Lite.

Where Tesla Stands

Tesla has been fairly quiet on HW3 upgrades. The company has said a retrofit is coming for owners who bought FSD outright, and more recently confirmed it would also require the higher-resolution HW4 cameras — likely handled through temporary upgrade centers set up around the country. Tesla has also said an upgrade doesn't make sense until it solves autonomy and knows exactly what hardware that takes. Separately, Tesla confirmed that HW3 vehicles won't achieve unsupervised autonomy.

With no official program in place and a class-action claim from frustrated HW3 owners underway in Europe, community tinkerers are filling the gap. Gapiński's conclusion is pointed: Tesla could offer this as a first-party retrofit today, since it needs no new parts beyond the HW4 computer and cameras.

Should You Try This?

Honestly — no, not yet. This is a proof of concept from a developer with deep ECU experience, not a weekend project. It involves firmware modification, sourcing salvaged parts, and custom adapters, all of which carry warranty and safety implications. Treat it as encouraging news about what's possible, not a how-to guide.

What it does mean is that HW3 owners have real reason for optimism. As newer silicon arrives — including the AI4+ (or AI4.5) FSD computer Tesla teased earlier this year — projects like this one show older Teslas don't have to be permanently left behind by modern autonomy stacks.

In the meantime, the upgrades most HW3 owners can actually make today are the practical ones: keeping charging gear current, adding adapters that extend where your car can plug in, and stocking sensible roadside and safety equipment. Those pay off no matter which computer is behind your dash.