Using my layman’s calculations…
2250W / 149kV * 192kV = 2899W
2899W / 70A * 80A = 3313W
Now we’ve only got an 18% increase needed to get to 4032W. Does the extra Copper account for that? Likely.
Higher KV doesn’t equal higher watt rating.
The amp rating is only half the equation. They don’t vary voltage in their spec.
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Two motors, same can size, all other factors being the same, the higher KV motor will produce more power.
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The amp rating just comes from the thickness of the conductor. To lower the KV you need more turns, more turns means thinner wire. It would also mean there is more length of wire, which would further raise the resistance and lower the maximum current rating.
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The higher KV motor will draw more power if simply dropped in the same system without changing anything else. The higher KV in this case increases the load.
The watt rating of the motor is unchanged by KV.
If instead, we double the voltage of the 100 KV motor it will have the same RPM and draw the same watts as the 200 KV motor.
None of this has much effect on the ability of either motor to output watts while remaining at a safe temp.
So why does the rated power output increase as motor kV increases?
Less turns, so presumably uses thicker wire to fill in the same space.
In the Hobbyking specs? I gave some speculation a few posts back.
Most spec pages I’ve seen don’t have this relationship.
Originally you were looking for an example, I gave you one. I’d love to completely understand what’s going on there.
On the Hobbyking page? My guess is like I said they just test motors at 12s and they draw way more watts with higher KV.
Another example would be using a 6374 to spin a prop.
A 6374 100kv run at 20s would spin the same rpm as a 6374 200kv at 10s and the load from the prop will draw the same watts.
Take the same example and run both motors at 10s. In that case the 100kv will pull roughly half the watts as it runs at 1/2 speed (ignoring any rpm/watt curves specific to that particular prop rpm range).
Okay so ignoring the kV, the 18g weight and 10A increase is all we should be looking at?
I would just look at the weight to get a sense of how much power the motor can supply without overheating. A heavier 6380 will run cool longer than a lighter 6374.
Weight would also be a good indicator of peak torque.
The KV should be considered along with the voltage to get a good rpm for whatever gearing and wheel are used. I’d expect a 100kv motor fed 20s to run equal more or less to a 200kv motor fed 10s in the same system with the same size motor.
All this is a roundabout way of saying an 18s esc is great for keeping the esc cool and maxing the watts it can output, but there isn’t an advantage or disadvantage at the motor provided the KV is adjusted down to match the rpm of a typical 12s system.
Should caution that running a low KV motor to make up for limited gearing to enable larger tires might not pan out well. Since the voltage is the same and the wire size goes down with the KV the heat produced at a given amperage increases.
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These videos lay it out well. Lots of other factors to consider like air gaps between wires of different sizes, skin effect, max erpm escs can handle, and “the magic erpm number”
Kv seems to be the most easily varied variable in a setup because they’re nearly efficient across the board as long as you choose the right kv for your purpose.
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Staying at higher Kv is fine but most of the 190 kV motors I’ve tested sound like an angry swarm of bees at 18-20s so I am not sure how long they will last in that operating range.
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I was asking about 16S though. Theoretically would they be fine, or does going up in Voltage mean going down in kV?
I’m asking because ideally wouldn’t we want to have a 80kph capable board that you’re mostly only riding at 40kph?
It just depends on the motor, the ESC will drive it fine but it becomes a question of whether the bearings are rated for that speed etc.
Having a board that is rated beyond the speed you plan to ride at generally means taking a hit to efficiency in the power stage of the ESC. So if you run into thermal problems with ESC you’ll want to go down in KV.
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Are you saying we shouldn’t ride slow? 
I’m saying you should design the max speed of your board to be a speed you plan on going. Instead of 190 kV motors on 12s I could rewind them to be 380 kv. Theoretically my top speed would double and the motors efficiency will remain about the same at the same speed and load, but I will also draw twice the amps at half the voltage from the ESC to get the same power. Twice the amps means four times the losses in the power stage.
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I think it depends on your goal and what you care about and are able to mitigate e.g. if I want a board that can go up to 80kph, then that’s what I build to.
That doesn’t mean I’ll spend a lot of time even close to that. In practice it may mean I spend a lot of time at 60kph and below, which is just fact for a lot of people not on a racetrack.
As long as I’m able to design my system to manage the heat generated, and I’m okay with the compromises, it shouldn’t matter how I use it.
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Yes definitely, but I generally don’t advise someone to build a board to go over 40 mph because it seems like a good way to crack your skull open and when you do it you end up wasting a bunch of power for your regular riding. You asked if you can do it, the answer is generally yes but should you do it I think the answer is usually no. But it all depends on goals, I just want to be clear that it is an engineering question and there are tradeoffs with efficiency.
Just like right now when people build 12s setups we tell them to go around the 150-210 kV range, when you go 18s I’d recommend to go in the 100-150 kV range. Everything still works if you don’t do that but you might get some undesirable performance trade-offs. I also don’t think any of us are yet sure what the long term effects of running a 190 kV motor at those higher RPMs will do to the bearings.
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