carlbellybutton10

what would be the difference in a mamba max 4600KV motor and 5700KV motor

So Cal

A 4600KV would mean that for every volt that that motor gets it turns 4600rpm, so the more KV the higher rpm. Thats what i think it means anyways. Correct me if a i am wrong

rclugnut10

My Feedback: (1)

yeah thats right but as with any electric motor made to the same specs as the one your comairing it to, more RPM = less torque, so your 4600 may be able to lift the front end no issue, the 5700 may not but it will go much faster on the top end....

and with BL motors if you want more torque and speed and more volage...

the lug

carlbellybutton10

so lower KV more top end higher KV more torque?

Access

KV is actually a measure of how quickly the torque drops off as RPM increases, among other things.

If you compare a 3000KV and a 5000KV motor, the 3000KV will have more starting torque.
But if you chart both curves, at some point they will cross, and the 5000KV will have more torque at the higher RPMs. Likewise, at the point torque is near zero, maximum RPMs are reached. If that confuses you, look at this graph.

http://arcadechamp.net/radio/DYNO/novak75vsnovak135.jpg

The 7.5 is the higher-KV motor and the 13.5 is the lower-KV motor. In this case, the point the torque curves cross is around 10,000RPM. Prior to this point, the lower KV motor has more torque, but past this point, the higher KV motor has more torque.

This only holds for motors of the same family. Motors from different families can have remarkably different levels of torque, even if they're the same size, KV, and everything else.

http://arcadechamp.net/radio/DYNO/Hacker-vs-Novak.jpg

For instance this chart shows the difference between the a 540-size Novak motor and a 540-size Hacker E40 motor, both of which are ROAR legal.

Traxxas4fun

My Feedback: (3)

no lower kv is motor torque ie the reason ie thats why they use the 2200kv mamba max motor in 1/8 scale buggies.
also thats why they use the 5700+ motors in touring cars, smaller wheels less torque to get spinning

MTboy

So if I want a motor that has good bottom and at speeds of 20-25mph can pop it up when all other conditions are good I would go with????
I would like something that gets me out of a corner quick but also at 20 mph it will hit and pull away from the pack.. Can you get both worlds in BL??

Beomagi

And just what do you think would happen if you gear down a bit to make up that torque? Consider the wattage of those motors? If the 5700 puts our more watts than the 4600 and you gear it down in the ratio of 46/57 compared to a 4600 setup - what do you think would be the difference?

The 2200kv used in 1/8 scale buggies is a completely different class of motor. It's massive - ~42mm wide, 454grams, vs the 36mm regular 5xx can motors associated with mamba max and sidewinder which is under 200grams. Having a longer can/coil effectively is equivalent to more winds.

Beomagi

One advantage of lower kv motors, is they're higher resistance, so you'll be able to volt up on them on a particular esc. 3s on the sidewinder.

As long as your batteries can supply amps, you'll have more power than you can handle. The 5700 geared down slightly will also give you tyre spinning torque, and deliver more power than the 4600 can, but with only a 2s lipo limit on the sidewinder. I'd stick with the 4600. It's a bit more versatile and efficient.

Redvanmafia

Lower KV means more torque, Low kv + high voltage + gearing = high speeds, end of story

MCSRacing

My Feedback: (2)

lower the kv more torque ...... higher the kv more rpm .....

Beomagi

That's just too simplistic an answer.
You've got pinions. Change em! Wattage and gearing is a key that's often overlooked in such statements.

usa98030

Lower kv give more low end torque and higher kv more high end power. Its like a toyota tundra engine compared to a ferraris! A truck engine probably kicks more torque ( NO WAY COMPARED TO A FREAKEN FERRARI) than a sports car but a sports engine can get that car cruising pretty fast. That why we have muscle cars and exotics. If you would also graph these they would be to lines in relation to each other so at one point they will cross and diverge

Access

Right, people focus too much on motor torque when what really matters is torque at the wheels. And in reality whatever torque you lose by going to a higher KV motor, you can gain back with lower gearing (since the motor also has higher RPMs).

Irl torque is secondary to power and efficiency. I'm yet to have a brushless setup that can't get up to speed in 2-3 seconds, traction allowing, and this was true even when I was running NIMH batteries. The high KV motors are a constant heat problem, some even with geared low, and it's rarely as efficient as a lower KV setup. The best setups for efficiency have been high voltage, low KV.