KV vs Turns.... HELP!
 

OK so I am looking to buy a Brushless setup and I have ran into a question. I need to find a 13.5 motor.... My question is why are some motors only rated by their KV? I have read that there is No direct formula and that the numbers can vary when trying to do a KV to turn conversion. It seems like there are A LOT more options for motors when it comes to KV as opposed to Turn rating. Please let me know as much as you can and help me source a motor!

I am by no means one of the experts on this site (or any site for that matter LOL) but I'll give you what my understanding is.

KV is the speed rating usually associated with sensorless motors
Turns is how sensored motors are rated. (there are some sensorless motors I have seen listed in turns but they're very rare)

KV is the rpm rating with 1 volt running through the motor.
Turns isn't a mathematical equation, you have to do the research on each motor to find out it's KV rating to get the same info

There is no turns to KV formula because it varies from motor to motor. 13.5 turns generally is in the range of 2800KV-3100KV though.

If you are doing this for racing purposes just buy a 13.5. If it's only rated in KV it probably wont be allowed in the 13.5 class.

Thanks guys.... I noticed the Turn rated motors seemed to cost more.... now I see why... because they are sensored....

That would be why! If your just going to bash go with the KV if your going to race spend the little bit more and buy the 13.5! BTW 13.5 happens to be a great mild mod. Motor! its what I like to run!

I wouldn't assume that one is sensored and another not based on how they are rated. The turn vs kv numbers really don't correlate. Take the Hobbywing XERun sensored motors as an example. Their 8.5T is 4000kv and their 10.5T is 3200kv. Their nonsensored EZRun are rated the same. Now let's go over to Trinity with their Duo 3 motors. Their 10.5T is 4300kv. That's more than the 8.5T sensored XERun motor. Their 13.5T is 3600kv which is more than the XERun 10.5T.

kv is the most important number. Use the turn ratings as guidelines but look at kv for a better idea on how fast that motor will be, sensored or otherwise.

KV is just a measure of RPM, not power, and power is what makes cars fast.

It's dangerous to assume that more KV means a more powerful motor. Turns are what matters in a sensored racing motor.

Some motors have more advance built in than others so might seem quicker in a blinky class (there is not much in it even then), but that is not because they have a higher KV, but because they generate a little more power (at the expense of efficiency). In mod class or boosted class the motor you start with hardly matters - if anything, the advanced timing models are more of a hassle than an advantage.

kv x voltage will tell you how fast it will go. The amount of turns to get there is irrelevant. I take that back, not irrelevant but certainly less relevant.

I edited my original post to seem a little less blunt.

Now I will be blunt.

You are WRONG.

The reason , I am guessing, you are looking for a 13.5 turn motor is probably for raceing aplication. Most classes have limits on what you can run. If your motor is rated in turns then the Kv is within a certain range and are built to spec i.e nora, motors will be slightly faster or slower depending on quality of build and materials. Either way hope this helps

Sensorless motors are rated by kv because its essentially constant. Sensored motors are rated by turns instead because kv is easily altered through timing.. either on the motor, or through the esc. Even if crazy boost isn't used, a lot of mod motors run with something more than 0 degrees. Some are rated for both since a sensored motor can he used on a sensorless esc but without adjustable timing. It gets confusing when a class or esc is rated for a certain number of turns but not specified for kv though.

My suggestion to you is: Wait till Randy from Tekin or someone from
Novak comes on here to answer you. I would only take a reputable motor
companies word on this subject if it's important to you.

Good luck and I hope you get your answer soon.

OK I guess I am it. Here is the answer. Kv= RPM/voltage input. It is part of the motor equation along with Kt. Kt=torque x input amps. The higher the Kt of the motor the more power it puts out. Kv varies with the load on the motor to the point were it is zero when the motor is stalled by the load. Most manufacturers rate Kv at a certain input voltage with no load. Kv is also very sensitive to mechanical and electrical timing thus Kv can vary with both sensored or sensoreless motors because both sensored and sensoreless ESC can produce electrical timing.
Turns on the other hand probably give customers a better handle on what is going on. The lower the number of turns the more power the motor is going to put out. We also have another variable with the high slot multi-pole motors. You can either wind them in a Y or Delta configuration. These give different Power curve characteristics. Y's tend to have more Torque at the bottom end and Deltas tend to have higher top end RPM's so they feel differently.
Hope this helps without getting to technical.
Bob Novak

Thanks BOB!

Great Knowledge!