Howdy!

Thanks (RIP!) to RC Crew Chief's YouTube channel, I'm looking at torque curves, timing, boost, efficiency and getting slightly less confused.

But what does throttle mean? Say in default 'blinky' type modes, is throttle purely telling the ESC to try and supply between 0% and 100% of ESC rated current to the motor?
Lots of ESC's claim 150+ Ampere continuous, which would be a huge amount. Batteries might not do that, gears might not last, things overheat, cars spinning out..
So with a certain ESC and motor, what is the definition of full throttle?

The ESC controls throttle output using PWM - pulse width modulation. The percentage of the throttle dictates the percentage of the duty cycle. So a 50% throttle means the ESC is powering the motor half of the time and idle the other half. It switches really quickly, and most high end ESCs lets you specify how quickly, that's the drive frequency setting. It's typically between 2kHz and 32kHz.

Full throttle basically means it's on the whole time, and the drive frequency becomes irrelevant. The current rating of the ESC is just how much it can handle without failing. Peak current happens under hard acceleration from a dead stop. The ESC doesn't dictate how much current flows, the motor does.

Thanks, I take back what I said, I'm not getting less confused at all

I've seen that the load on the motor is a big one. With the same motor, the load from a very light car geared to do 10mph will be much lower than a heavy car geared to do 100mph.

I've also seen those engine dyno curves, using a flywheel test machine. Does that mean if you change the flywheel weight, you drastically change the torque and power curves you're going to see from the same motor?

But if the motor decides how much current it wants in a situation, how do things like turbo and boost work? If the ESC can't simply put more current into the motor, how is the motor understanding it needs to work harder?

A flywheel inertia dyno should still give the same general results regardless of what flywheel you use - the torque and power output of the motor should be the same. The difference will be in how quickly it accelerates - too light and you won't be able to capture enough data due to the sample rate limitations, too heavy and you might burn out the motor or sensors with prolonged high current draw.

Turbo and boost affect the timing of the motor. Boiling it down very simply, it's the same thing as adjusting the endbell on the motor but doing it electronically. So it's really just altering the parameters of the motor, rather than "pushing" more power into the motor. I'm not sure how familiar you are with the concepts of electricity, but in general a power source (ESC in this case) provides a voltage, and the load (motor in this case) pulls a current that's dependent on the input voltage and the parameters (resistance/impedence etc) of the load. Pretending a motor is just like a resistor (it's not, it's way more complex), Ohm's law says the current is voltage divided by resistance.

Torque is the measure of the force that can cause an object to rotate about an axis. So yes if you change the the flywheel weight, you will change the required torque.

You'll change the required torque for the same amount of acceleration, but that's not how motors behave. It'll output the same torque, but will accelerate at a different rate.

The motor actually gets full battery voltage at all times - the ESC simply sends it in high-frequency on-off pulses - and it widens those “on” pulses as you give it more throttle until eventually you hit full throttle and the pulse is just fully on with no off.

Also - What gigaplex said is correct. Adding mass to the flywheel or any part of the rotating drivetrain will only show up as a tq/hp loss when using an inertia-type dyno that only calculates torque by measuring the rate of acceleration instead of measuring the actual torque like a brake dyno does.