In early 2023, Tesla launched its FSD Hardware 4.0 – now known as AI4 – an improved version of Hardware 3 with various advantages. This hardware launch initially came off to a rocky start with FSD and Autopilot not being available to freshly delivered vehicles.
Today though, AI4 is the next step as Tesla strides towards full autonomy. While Tesla hasn’t abandoned HW3 or declared it as legacy yet – and doesn’t seem to plan to, it’s still important to be able to figure out what hardware your vehicle has. This is especially true for those who have paid for, or are subscribed to FSD – as it seems that going forward, AI4 will receive major FSD updates before hardware 3, which will require optimization.
So, let’s go over what AI4 offers in terms of improvement, the fact that there is no retrofit path from Hardware 3, and finally, a few easy ways to tell FSD Hardware 3 from Hardware 4/ AI4.
HW4 / AI4 Improvements
AI4 brought along several improvements, including new cameras, new electrical and wiring harnesses, and most of all – improved processing power.
The new cameras bring improved resolution for better details. The rear camera on AI4 has a resolution of 1448x938 vs 1280x960 on Hardware 3. However, there’s a much larger differences in the front cameras. HW4/AI4 has a resolution of 2896x1876 while HW3 has a resolution of 1280x960. That’s a huge improvement in quality - additionally, that telltale red tint that they have ensures better performance in low-light conditions. The video below compares the difference between HW3 vs HW4.
Musk previously said that HW4 is about 3-5x faster than hardware 3, although all of that compute power isn’t being utilized yet. We’ll likely see the full power of HW4 come into play with the divergence of HW4 later this year.
How to Tell If You Have HW3 or HW4 / AI4
There are a few easy ways to tell if you have Hardware 3, or AI4. Sadly, Tesla doesn’t provide any information in the app or vehicle that simply tells you which FSD hardware you have, so here are a few ways to tell them apart.
Note the telltale red glint of the HW4 cameras
Not a Tesla App
Delivery Date
The first is based on your model and delivery date. If you purchased Model S or X, you’ll likely have AI4 if you purchased after March 2023. If you have a Model Y, it’s after late May 2023 for vehicles made in the United States. The updated 2024 Model 3 has HW4, but if you have a 2017-2023 Model 3, you’ll have Hardware 3.
Red Camera Lenses
Next, if you’re not sure of the delivery date of your vehicle, or want to confirm, take a look at the vehicle itself. HW4/AI4 has cameras with red lenses – the easiest place to see this is on the front cameras – where there will be 2 red lenses and one black (fake) lens. AI4 got rid of the 3rd front-facing camera since the cameras now have a higher resolution.
The repeater cameras are also slightly different, with the same red tint, but include a smaller and narrower turn indicator.
HW4 (top) and HW3 (bottom) repeater cameras
Not a Tesla App
No Retrofit to HW4
Elon Musk and Tesla have confirmed that unlike AP 2.5 or AP 2, Tesla does not intend to offer a retrofit for older vehicles. This isn’t a surprising move, especially given the fact that there is an entirely new wiring and cooling harness for the compute unit in AI4.
This, in turn with AI4’s different form factor, means that it isn’t feasible to upgrade HW3 vehicles to AI4. A retrofit would be a complex and expensive task that would likely require building a custom solution that would fit into HW3 vehicles. It also comes with other complications such as overwhelming Tesla Service. Instead, Tesla will continue to do it the software way – by optimizing and updating the FSD models to perform well on Hardware 3.
Tesla’s been on a roll with Supercharger improvements lately, from the 325kW charging update for the Cybertruck, to 500kW with V4 Superchargers coming next year. While those improvements have been limited to the Cybertruck, Tesla didn’t put all their focus on their new flagship vehicle, but looked at their more affordable vehicles as well.
LFP Battery Heating
Tesla’s Superchargers can now heat LFP Batteries - those that are in the Model 3 and Model Y Rear Wheel Drive variants. This applies to Long Range and Standard Range models, which saw a limited run. This is another update included as part of the 2024 Tesla Holiday Update - which really arrived with a lot of unannounced new features and capabilities.
The change is pretty interesting - Superchargers of the V3 and V4 variety can now pre-heat batteries for Model 3 and Model Y vehicles equipped with LFP battery packs. That means those vehicles are able to get back on the road faster when it's extremely cold. Of course, Tesla still advises you to precondition before you arrive, saving drivers time and money.
Max de Zegher, Tesla’s Director of Charging, also commented on the new feature. Essentially, Tesla is inducing an AC (alternating) ripple current through the battery to warm it up. Keep in mind that Superchargers are DC charging. That means it is possible to get a cold-soaked LFP vehicle on the road 4x faster than before, assuming that it didn’t precondition at all and that it is in the worst-case scenario (below 0ºF).
In essence, Tesla is using some engineering magic to turn the circuits inside the LFP battery into an electric heater - and powering that heater through the Supercharger. An AC ripple current is a small oscillation in the DC charging current that generates heat through electrical resistance, warming up the battery. Those ripples are a byproduct of converting AC to DC and back - so Tesla is using the onboard charger to induce those ripples to warm up the battery. Definitely an innovative technique that’s really only possible with the versatility of the NACS connector.
We’re hoping Tesla can implement this across their full lineup of vehicles, but we’ll have to wait and see how it is trialed across LFP vehicles first and if it is even possible on vehicles with 2170 or 4680 battery packs.
Tesla launched two FSD updates simultaneously on Saturday night, and what’s most interesting is that they arrived on the same software version. We’ll dig into that a little later, but for now, there’s good news for everyone. For Hardware 3 owners, FSD V12.6.1 is launching to all vehicles, including the Model 3 and Model Y. For AI4 owners, FSD V13.2.4 is launching, starting with the Cybertruck.
FSD V13.2.4
A new V13 build is now rolling out to the Cybertruck and is expected to arrive for the rest of the AI4 fleet soon. However, this build seems to be focused on bug fixes. There are no changes to the release notes for the Cybertruck with this release, and it’s unlikely to feature any changes when it arrives on other vehicles.
FSD V12.6.1 builds upon V12.6, which is the latest FSD version for HW3 vehicles. While FSD V12.6 was only released for the redesigned Model S and Model X with HW3, FSD V12.6.1 is adding support for the Model 3 and Model Y.
While this is only a bug-fix release for users coming from FSD V12.6, it includes massive improvements for anyone coming from an older FSD version. Two of the biggest changes are the new end-to-end highway stack that now utilizes FSD V12 for highway driving and a redesigned controller that allows FSD to drive “V13” smooth.
It also adds speed profiles, earlier lane changes, and more. You can read our in-depth look at all the changes in FSD V12.6.
Same Update, Multiple FSD Builds
What’s interesting about this software version is that it “includes" two FSD updates, V12.6.1 for HW3 and V13.2.4 for HW4 vehicles. While this is interesting, it’s less special when you understand what’s happening under the hood.
The vehicle’s firmware and Autopilot firmware are actually completely separate. While a vehicle downloading a firmware update may look like a singular process, it’s actually performing several functions during this period. First, it downloads the vehicle’s firmware. Upon unpacking the update, it’s instructed which Autopilot/FSD firmware should be downloaded.
While the FSD firmware is separate, the vehicle can’t download any FSD update. The FSD version is hard-coded in the vehicle’s firmware that was just downloaded. This helps Tesla keep the infotainment and Autopilot firmware tightly coupled, leading to fewer issues.
What we’re seeing here is that HW3 vehicles are being told to download one FSD version, while HW4 vehicles are being told to download a different version.
While this is the first time Tesla has had two FSD versions tied to the same vehicle software version, the process hasn’t actually changed, and what we’re seeing won’t lead to faster FSD updates or the ability to download FSD separately. What we’re seeing is the direct result of the divergence of HW3 and HW4.
While HW3/4 remained basically on the same FSD version until recently, it is now necessary to deploy different versions for the two platforms. We expect this to be the norm going forward, where HW3 will be on a much different version of FSD than HW4. While each update may not include two different FSD versions going forward, we may see it occasionally, depending on which features Autopilot is dependent on.
Thanks to Greentheonly for helping us understand what happened with this release and for the insight into Tesla’s processes.
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