Hi

I'm planning on renovating a 1:10 scale RC from aliexpress, which I want to spice up with shifting, speed capping each gear so you'd have to "shift up" after a given speed using Raspberry Pi somehow.
The plans are still very raw, I have a lot of work to do and a lot of planning to make, but as I'm a pretty newcomer in the world of RCs, I really need some advice.
The "final product" would be a 1:10 replica of given cars, I really wanna go for LMDhs and GT3 cars, so the speed limit of them would be the 1/10 of the original car's performance, trying to mimic the handling, weight, grip, aero etc. as accurately as possible.
Do you have any recommendations what type of DC motor I should use, or anything that could improve the effectiveness of the car given the idea behind?

Thank you in advance!

First, I would find an RC car that runs near 20mph and see how slow that feels. It is hard to get a 1/10 car to mimic the performance of a full scale car. While the size is 1/10th, the weight is WAY less. A 2000lb full scale care would weigh 200 pound in 1/10 scale. Our cars weigh 3-4 pounds. So, scale handling and performance is going to be hard to mimic.

Real car grip is greatly affected by the inertia of all that weight being thrown around. Our cars have 1-2% of the weight, so the physics don't scale.

You could certainly do it with a Pi, but an Arduino would also work and maybe smaller and easier. Need something with 3 PWM channels. Way I see it working is that the throttle from the receiver goes to your adruino as well as the output from 3rd channel on your receiver to be the gear changer. The adruino would control the "gears", so say you're in 1st gear and you pull full throttle on the radio, the adruino would output say 20% throttle to the ESC until you hit the 3rd channel up on your radio, which would cause an up shift, then would output say something like 40%.

But honestly you probably won't notice anything other than an artificial speed limiter when pulling full throttle.

I would go with a sensor brushless motor. You would have more consistency.

Why do you want to limit the speed for different gears? Just curious.

I'd go even further and call it pretty much impossible. Our cars will never look and feel like the originals when moving. Plus you probably don't have a track in 1/10th scale to run them on realistically, even if they did.

This is not correct - but a common mistake. You can't just divide weight by 10. Weight does not depend only on the length but on the volume of the object. A 1/10th scale car has not only 1/10th of the length, but also 1/10th of the width and 1/10 of the height, so the volume is actually 1/1000th (10x10x10) of the real car - and that is pretty close to the weight of our models. 1300-1400g x1000 is 1300-1400kg - not a completely unrealistic weight for a real size car.

like running an ol TH400 slush box in the RC car. I think i have seen 3 speed trannies for 1/8 off road nitro.
Those shift on simple physics and not electronically.
You would have to keep RPM tabs on the motor, and then program whatever it is to shift at certain points (if doing an auto instead of semi-auto) to the next gear. I'd be curious on the amount of force needed to do this from a servo/pneumatic valve.