HSV427

iTrader: (30)

Hi all, I'm relatively new to electric and would like to no how can you tell if your electric 1/10 buggy motors really has the specs the manufacture claims, for example i have had people say to me is that a real 6.5t motor or is it soft, i thought if a motor say's 6.5 then its a real 6.5, but supposedly some 6.5 are the equivalent to a 7.5t motor which really doesn't make sense, also how real are the KV numbers supplied by the manufacturer, the reason i ask is i had ready sonic mach 2 6.5t motor which claims to have 5531kv and it was super quick, then in exactly the same car with the exact same speedy gearing and lipo i fitted a tekin redline gen 2 6.5t motor which claims to have 6750kv, To my understanding the higher the kv the more powerful the motor but in this situation the tekin was a great deal slower in the exact same car as the reedy and according to the kv rating the tekin should have been a great deal quicker as it has the kv rating of most 5.5t motors, is my understanding of all this wrong, I'm really confused and would appreciate some information about how this all works with electric motors.

Mantis Toboggan

iTrader: (4)

When it comes to mod motors it really doesn't matter. If a 6.5 of whatever brand isn't enough, go to their 5.5. As for the kV thing, it is rpm per volt, but motor timing also has an effect on the kV of a motor, so that could skew the numbers some.

Really the only thing you can be sure of is a 5.5 will be faster than a 6.5 if the motors are from the same manufacture, and both are in the same condition.

Its hard to compare two motors of different winds and of different manufacture. The first motor could have been geared perfectly and the second motor could have been off on gearing and had a bearing that was starting to go, or a rotor that had gone soft because it was overheated. Two brand new motors might be a little more comparable, but I have had a brand new motor be dog slow and burn up after ten minutes, and the motor it replaced was the exact same brand and model.

Ultimately though it doesn't matter when it comes to mod, because if you need more power, then you can just go down to the next more powerful motor.

UK.hardcore

Basicly the kv rating are pointless.

because no manufacturer tells you at how much volt/amps they measure them.

and also, some motor are just duds.

Davidka

iTrader: (86)

This.

How many rpm a motor spins is not a measure of how much power it actually makes. Some are duds but most are not. I'm running a Novak SS13.5 (old silver/purple) in my 4wd buggy (we have a 13.5 class) and I'm not getting out motored by anyone, yet if I free rev the car, my tires expand far less than they do on my 17.5/2wd buggy, which is obviously slower in every way.

Dave H

Other common variables with modified motors include rotor construction/size and wire size. Which along with timing and gearing as previously mentioned can be useful for fine tuning the feel and power of the motor.

Many brands offer different rotors, high RPM or high torque, etc to adjust the powerband and feel. They might come standard with different ones. Doesn't change the absolute power a lot I don't think, but changes the powerband and feel, and the ideal gearing.

Wire size can vary which also impacts powerband and feel. For example I have some of the Novak Light motors which use a thinner wire to reduce the low end grunt, they feel significantly different compared to say a LRP X-12 which has more low end power than many. Wind to wind the LRP certainly feels more powerful.

Agree kv is a limited reference for sensored motors, only roughly useful for comparing motors of similar construction, even better from the same brand/line as mentioned. RPM is only one half of the power equation, torque needs to be considered as well, which we usually don't get much info on.

Can be complicated, but does allow for a lot of tuning for each use. Note some motors have replaceable stators, which allows for wind changes at reduced cost. Can try different winds without buying complete motors which can be helpful in finding the right one without blowing the budget.

kevinpratt823

iTrader: (12)

All these KV ratings are UNLOADED ratings. A motor with a higher KV/lower turn is not necesarrily a "faster" motor, gearing, torque, and many other things come in to play. It is certainly possible, even likely in many cases, that when you go up in kv, and don't adjust the gearing appropriately, your peak rpm, say topped out on a straight, will actually be lower. You need to adjust gearing to allow a higher KV/lower turn motor to rev out and take advantage of the power.

I see it with all my cars, but it becomes especially obvious when viewing data logging graphs with my boats. A higher kv motor, with the same prop, can actually record lower max rpm and be slower because it can't swing the prop, while if I prop down a bit(similar to lower gearing), it will allow the motor to turn higher rpms, and possibly be faster. There is always a sweet spot, more kv/lower turn isn't always the ticket for power.

HSV427

iTrader: (30)

Thanks for all the responses i now think i have a better understanding.

kevinpratt823

iTrader: (12)

It should be noted that for any given model of brushless motor, there are variances between them. The actual kv of a motor can be tested, there are a few testers on the market. I have not done it myself, but a lot of other guys building boats with twins, especially 100mph+ setups, will test motors to get a pair that matches closely.