6S Firma 2050Kv motor Vs. 8S Firma 1250Kv motor?

[flynlw]

So the major issues I ran into after the 1250kv upgrade were the diffs. I locked both, and was way over geared. The locks kept coming loose at the cups. So now I'm down to front locked with hr lock, and 500k in the rear. 27/42. Its finally coming together, and it's all my fault cause I had one foot in on making it a drag, and one on making it rocket...I finally understand all the friends who told me you can't have it both ways, .

So now its going straight up drag! Even about to try out a new belt kit that I'm hoping gives me a little more pop out the gate, we'll see

 

[jondilly1974]

thanks for the link, could you help me with what values are need highlighted in the photo it would be great!

View attachment 158697

The important thing here is knowing which diff you are plugging in and make sure you use the appropriate tire height for that diff.

Example: Felony Front
Diff Pinion: 15
Diff Spur: 42
Tire Diameter: 100mm

Example: Felony Rear
Diff Pinion: 14
Diff Spur: 45
Tire Diameter: 107mm

 

[Gatekeeper]

Okay, so I understand the whole kv rating. Heres my question. If I have something with a 6s 1900kv rated motor, how is it an "upgrade" to go with the 8s 1350kv setup that the manufacturer has suggested? Someone please help me understand.

 

[jkflow]

'Upgrade' is subjective.
In this specific case, the lower kV will be more efficient and run cooler if things are equal.
To make it equal, you would need 8S (2x 4S) and a larger pinion to get to equal rpm.
You can debate all day long if this is an upgrade.

 

[BudUMfan]

I just got this setup for my infraction also. I haven’t ran it yet. I’ll try both 6 and 8S

 

[Anthony jaques]

Example #1:

A 2500 Kv motor and a 2S Li-Po battery at 7.4 volts



(2500 x 7.4) = 18,500 RPMs



the same Kv motor on a 3S Li-Po battery at 11.1 volts



(2500 x 11.1) = 27,750 RPMs​

Example #2:

A 4800 Kv motor and a 2SLi-Po battery at 7.4 volts



(4800 x 7.4) = 35,520 RPMs



the same Kv motor on a 3S Li-Po battery at 11.1 volts



(4800 x 11.1) = 53,280 RPMs​

What this all means is that if you have a motor with a higher Kv then it will have more top end speed but less efficiency than a lower Kv motor at the same voltage . So a higher Kv motor produces more heat and it will handle less voltage than a lower Kv motor.



If you have a motor with a lower Kv then it will have a lower top end speed but it will have better efficiency than a higher Kv Motor at the same voltage. So a Lower Kv motor is more efficient than a higher Kv motor so it produces less heat. This means that it will be able to handle more voltage and that means more possible speed.



I usually like to suggest using a motor that is balanced in the middle of the two extremes, it will give you the best of both worlds. That is of course unless you have a very specific goal in mind for your RC. If you are a speed freak like I am then you can opt for the higher Kv rating. If motor heat is an issue then it is sometimes advisable to use a lower Kv rating with a higher voltage battery to get the same effect.

The big thing to remember when using Kv for your Brushless Motor Ratings is that your Brushless Motor and ESC will each have a maximum input voltage (battery cell count) that is allowed. So if either your motor or ESC has a lower maximum voltage then you must use this to calculate your top RPMs. If you go over the recommended voltage then you have a high chance that something will fry in your setup.​

Also remember more torque on lower kv allows for gearing up to retain higher speeds