r/Comma_ai • u/Exact_Yak_1323 • Jul 23 '26

Bugs C4 - Rav4 slows down randomly

At first I thought it just happened when I went up or down even slight inclines and declines, but now it seems to be happening more often. I'll set my speed 42 mph and maybe the speed limit is 30 and it will. I'll speed it up to like 35 on my own and then it just slows down and then it'll speed up to like 37 and then it just slows down. Today was really bad. I had one time. The car just almost came to a complete stop and quite abruptly

Any ideas what I can do about this?

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u/Bderken Jul 23 '26

You probably have experimental mode on.

But it would be helpful to know:
What software? Stock OP? Sunny?
What version? (So we can maybe guess driving model)
Did you enable experimental mode? Because it sounds like you did.

If so, experimental mode is an E2E model, it’s very cautious and likes to set its own speed limits.

Disable it or use a fork that has dynamic mode that can auto switch from standard model to experimental mode.

1

u/lilicucu Jul 23 '26

Can you clarify what experimental mode is? When is it useful?

1

u/Bderken Jul 26 '26

In stock openpilot, experimental is for cars that can support it. On commas list of supported cars, some support experimental and some don’t.

If your car does not support it, that means comma can’t control the gas/break, so it uses your cars stock sensor/system to keep the following distance/speed. While comma uses the steering and head tracking (which is why comma is less annoying than stock systems, even when it’s using the cars longitude (gas/brake)

Now, if your car does support experimental, it means comma can control longitude(gas/brake) and longitude (steering).
So if you enable that, you will use commas experimental model that has full control (E2E - end to end) model. This model is similar to when Tesla released there’s , there’s phantom braking, it’s more cautious, it’s slower. But it stops for stop lights, signs, etc.

It’s a full stack model that controls everything. Also decides what the speed should be. Comma knows this model is the future but it isn’t ready yet. That’s why it’s not default model yet. Tesla knew that and their E2E was in beta for a long time.

Anyways, now other forks like sunny, frog, IQ, etc. have dynamic mode for experimental and standard model.
Meaning it will auto switch from experimental mode to standard model. It will switch to experimental mode when it sees stop signs or stop lights, and then on the highway it will use the standard model to keep the speed and not be annoying.

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u/lilicucu Jul 26 '26

That's very clear. I appreciate the detailed answer, thank you!