Motor size per kv question.

[stadiumyamaha]

I have a pursuit that I've been running for years that truly my favorite sport boat. I'm running a castle 1515 2200kv motor in it and cant hardly over prop it withing reason on 4s. Runs low fifties and stays cool. Sometimes drop a set of 5s in just for kicks and still stays cool although its pushing my comfort zone on RPMs.

I've bought a new hull that I'm building in a similar fashion but want to change things up a bit by increasing my KV to 2600kv with a TP 40mm motor.

Question is, If I should run the 74 or 83mm can? My thinking is that the 83 would be the better choice as it will be able to swing a slightly bigger prop with all things being equal. They do offer a 92mm but that a lot of motor for that hull.

Any input with experience in this issue would be much appreciated.

[HTVboats]

Going to a larger motor I would not increase the KV's. More Kv's means more shaft speed (friction) and it also makes prop selection more difficult. It also makes it far easier to increase amps and heat. I have TP 4050 3Y in my 33' P mono (40x82mm-2100KV). It runs well in P class and if I went larger I would stay under 2100kv to turn larger diameter props. Right now I pull 189-200 amps with heat race props and more motor would require more ESC cost.
Mic

[ray schrauwen]

Remember that a Castle is a 1Y wind and quite efficient.

[Speed3]

Don't know if it too late but a motor that you can also look at for 4s is the leopard 4092 2080kv.

This motor might be possible the most powerful 4s motor available. Provide you have good cells and everything properly soldered. I did a catalog with one.

The motor max out at 34067rpm unloaded at 16.3volts.

This the part that shock me loaded it was able to swing a x642 at 32131rpm.

For reference many motors ranging from 1740 to 2000 plus kv cannot turn a x642 that fast on 6s.

So the leopard 4092 2080kv on 4s is put out more power than many put out on 6s.

[Fluid]

....This motor might be possible the most powerful 4s motor available....So the leopard 4092 2080kv on 4s is put out more power than many put out on 6s.

Hmmm, this makes no sense at all. First, an x642 is a tiny prop for such a huge motor, especially on only 4S. How do you know that a 2000 Kv motor of the same size will spin an x642 slower than 33,000 rpm on 6S? What does “loaded” mean? A 30” rigger or a 36” mono?

IME the Leopard line of motors are decent sport motors but lack the efficiency of higher quality motors like TP, Castle and Neu. This means they run hotter because more of the battery energy is turned into heat, nor rpm.


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[Moonie]

Don't know if it too late but a motor that you can also look at for 4s is the leopard 4092 2080kv.

This motor might be possible the most powerful 4s motor available. Provide you have good cells and everything properly soldered. I did a catalog with one.

The motor max out at 34067rpm unloaded at 16.3volts.

This the part that shock me loaded it was able to swing a x642 at 32131rpm.

For reference many motors ranging from 1740 to 2000 plus kv cannot turn a x642 that fast on 6s.

So the leopard 4092 2080kv on 4s is put out more power than many put out on 6s.

I think your on to something. I have to strongly agree with you.

[Speed3]

I have seen many datalogs, of many different motors. Bigger and smaller cans, 4s and 6s.

When I made the statement that this leopard 4092 2080kv might be the most powerful 4s motor, I said that because, based on the datalogs I saw non is close too that kind of performance on 4s. I have a tp 4060 1950kv and that I had to be putting out around similar power to the leopard on 4s but the leopard maybe actually be the more powerful one on 4s.

I would like to make something clear. You will not get close to those type of power levels out of the leopard 4092 2080kv with out very powerful lipos.

I will share an experience. I used to run a leopard 4092 1730kv a lot on 4s and thought it was decently fast. Then bought the 2080kv 4092 hoping for more speed and it ran around the same speed on 4s that I was getting with the 1730kv. I also bought the tp 4060 1950kv again hoping for more speed. The tp ran slower that the 1730kv leopard 4092.

I made an upgrade with the cells and that made a huge difference. The tp gain 8mph from the cell change. The leopard 4092 2080kv gain 4.5mph from the same cells.

I purchase some even better cells and gained even more speed with the 2080kv 4092.

The same upgrades did not improve the performance of the 4092 1730kv it remained the same.

This thought me that lower kV motors can reach they peak with much weaker batteries than the higher kV counter part.

My 4s battery is recording .2v loss at 53 amps. 16.3v to 16.1v at 53 amps. So at a 106amps it will drop to 15.9v from 16.3v. I am sharing the performance of my cells to give an idea what my motor being supplied with to put out the power I am getting. If the cells are weaker the performance will be less.