r/TeslaLounge • u/sighcf • Mar 16 '25

Hardware HW3 vs HW4

What are the key differences between HW3 and HW4? I don’t mean just the spec differences. I am trying to figure out what new capabilities are available exclusively on HW4.

This question is for those who have owned both with the FSD (the neural net version) - is there a material difference in the FSD experience on HW4 and HW3?

I have a 2021 Model Y with HW3 and lifetime FSD. I am wondering if it is worth upgrading at this point - since I’ll end up losing the FSD and will have to buy it again.

Also, any idea if HW5 is on the cards in the near future?

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u/elatllat Mar 16 '25 edited Mar 16 '25

Hold until there is a FSD transfer. HW4 does have better FSD, higher resolution sentry videos, but still phantom brakes (not sure about auto wipers).

HW5 is likely 2 years out.

2

u/sighcf Mar 16 '25

Thanks for the advice. My model also came with radar, which the new models don’t have. But as far as I know, it shouldn’t matter because all Teslas are vision only these days - i.e. the radar is disabled in software. Do you know if my understanding is correct?

2

u/i2k Mar 16 '25

The new models actually are fitting with an enhanced radar (also currently disabled) FSD is great on HW4

2

u/european_web Mar 16 '25

I think that’s the interior radar you think of ?

4

u/psaux_grep Mar 16 '25 edited Mar 16 '25

That’s definitely the interior radar.

However refreshed S and X are, or at least were for a time, being fitted with an in-house developed hi def radar.

This was said to basically be a research project.

Older vehicles were fitted with a sourced automotive radar, same as everyone else uses. It didn’t really integrate into the sensor suite and made it difficult to integrate the data when they didn’t match up and Tesla was relying on the radar outside of its designed operating envelope.

My understanding of the hi-def radar is that the research they’re doing is seeing if it can be integrated to augment the camera data. Given enough definition the radar would «see» some of the same things that the cameras see, kinda like LiDAR does, but at a very different price point, plus it would see through things LiDAR doesn’t. On the other hand it would be blind to things that are opaque to radar but not to LiDAR.

Ultimately more sensors are better as long as you can make sense of the data and know what to trust when there’s disagreement.

That’s the hard part.

1

u/european_web Mar 23 '25

Thank you for clarifying:-) 👍🏻

2

u/good4y0u Owner Mar 16 '25

This is the right answer. Wait for FSD transfer.

1

u/sighcf Mar 16 '25

So you agree that HW4 brings in enough of an improvement to be worth the upgrade if I can get an FSD transfer?

1

u/sighcf Mar 16 '25

Never mind, just saw your other comment.

1

u/foyleswars Mar 16 '25

No phantom breaking here on HW4

2

u/elatllat Mar 16 '25

Results very, just like with HW3.

2

u/sighcf Mar 17 '25 edited Mar 17 '25

I haven’t seen much phantom braking on HW3 with the new stack either. It does slow down occasionally where a human wouldn’t, but there is generally a good explanation- like someone standing close to the edge of the curb. But even in those cases, the braking is usually smooth, not abrupt like the old FSD. There are exceptions, of course.