Speed Difference, 1600KV VS. 1800KV on 4S?

[Checkmateguy01]

Simple question, all things equal (i.e. hull, batts, ESC) how much of a difference would there be between running a 1600 KV motor versus an 1800 KV on 4S lipo? Noticable difference? I did post this question in a "Spartan" thread too, which is what i'm debating on, 1600 or 1800kv, but as a general question i figured i'd ask here. Again, i will be sticking with 4S! Thanks!

[monojeff]

All things are not equal no matter how you spin it.
Each kv rating has its benefits and disadvantages.
Lower kv will spin a larger prop and higher kv will spin a smaller prop faster.
Larger props do not always work well on some boats so smaller prop higher kv would be better.
If I were you I'd run the 1800kv motor and go from there if you are staying with 4s.
It's a good middle of the road kv and will be able to use both small and decent sized props to get some good speed.
Be careful anything over 45mm be sure to check temps on everything.

[kevinlew211]

Simple question, all things equal (i.e. hull, batts, ESC) how much of a difference would there be between running a 1600 KV motor versus an 1800 KV on 4S lipo? Noticable difference? I did post this question in a "Spartan" thread too, which is what i'm debating on, 1600 or 1800kv, but as a general question i figured i'd ask here. Again, i will be sticking with 4S! Thanks!

Why you asked? are you try to get more speed with your 4s setup? if yes then get 2000kv motor, x442, x642 or even P220, btw, you will notice the diff between 1600kv and 1800kv but not much and not worth to buy a new motor, 1600kv is 5s setup and 1800kv is hot 5s setup but still. What kind of you esc? what kind of 4s pack and 1p or 2p, and you running Spartan mono, is it right?

[BHChieftain]

For a 4S setup a 1600kv is "generally" on the low side. My 4S setups are:

29" mono: 2200kv with x440 to x442 prop
29" OPC tunnel: 2030kv with m440 prop
1/10 shovelnose hydro: 1600kv but turning a whopping x447 prop

I was running a 1600kv on the mono, but to get decent speed the prop diamater got too large and I got too much chine walking-- performed much better with more RPM and less prop diameter.

Chief

[dogg]

General consensus seems to be to aim between 2000kva and 2200kva for a fast 4s set-up. What motors are the ones youre considering?
Chief said it all with the chine walking, spartans have a bad name for it and as Chief alluded to in his thread, the prop size can greatly affect this.

I'd be reading up on what most "fast" setups are on the spartan that work well and duplicate that....

[Checkmateguy01]

Why you asked? are you try to get more speed with your 4s setup? if yes then get 2000kv motor, x442, x642 or even P220, btw, you will notice the diff between 1600kv and 1800kv but not much and not worth to buy a new motor, 1600kv is 5s setup and 1800kv is hot 5s setup but still. What kind of you esc? what kind of 4s pack and 1p or 2p, and you running Spartan mono, is it right?

No, not looking for more, or less for that matter, speed out of my 4S set-up in the Spartan. I currently have the Castle 1800kv motor in it, but last season I burned up another traxxas ESC. I was real happy with how the boat runs with 1800kv motor, my Daytona cat has the leopard 1800kv and it runs great too on 4S. The reason I asked is becuase both the OSE and Kintec "Spartan Upgrade" package comes with the 1600kv Leopard motor (and a Seaking 180 ESC), I wondered if there was a direct reason for that and If I bought that package would I see a big difference in speed on 4S, which I plan to stick with as a "lake basher".

[kevinlew211]

I'm glad you happy with lower kv speed (me too, but most peoples dont) with your spartan, now you can get leopard 1600kv or even 1800kv with seaking 180esc, x442-445 and good 4s lipo, perfect "lake basher" boat and full of reliability.
Peoples, they will give you anykind of kv option but, the question is: how long the boat can run and how hot their system will get? after the day, the basic rule is still the same.

[MAMBA2200]

i run a 2650kv on 4s its fast with a m445 prop

[Rumdog]

Te 1600 k. Motor is intended for a 6s setup

[forescott]

Are we comparing can sizes too? The spartan has a 36 mm xl can. I would think the same kv in a 40 mm leopard motor would spin a larger prop. Also have to look at efficiency. A castle motor for example would be more efficient than a hobbyking motor of the same size. The castle wil likely turn more rpm.

[Checkmateguy01]

Are we comparing can sizes too? The spartan has a 36 mm xl can. I would think the same kv in a 40 mm leopard motor would spin a larger prop. Also have to look at efficiency. A castle motor for example would be more efficient than a hobbyking motor of the same size. The castle wil likely turn more rpm.

So the Traxxas Casltle motor is probably better than the Leopards? I'm now debating pulling the the 4082 1800kv Leopard out of my Daytona/Genesis, stepping that hull up to a 2000kv motor, and putting the 1800kv motor into the Spartan. Either way, reliability is what i care about, my Daytona on 4S with the 1800 proved to be a very good combo this summer, i ran it quite a bit, had no heat issues what-so-ever and is plenty fast, but i know i can go faster just by stepping up to 5S if i want too! The Traxxas electronics have proven not to be very reliable, hence the reason i want to swap out for better equipment!

[stadiumyamaha]

I'm not sure what the deal is with mine but I put a leopard gold (which is no different than a standard) 1774kv motor in while waiting for the stock one to be replaced and is slow as Christmas.
I always thought that the stock motor was around a 1600kv but one of the guys at Traxxas told me it was more like a 2100.
I was getting great speed and handling out of the stock motor running 4s2p and a 47mm prop until I lost a bearing on the motor.

[Skullcracken]

If you use 1600kv, you definitely need 6s. You could go with the 1800kv and keep 4s for good reliable moderate speed, play around with prop size. Then bump up to 5s on the 1800kv when you want to do some fast runs.

[1945dave]

I love simple questions and generally that means complicated answers. I will try to give you a simple answer like you wanted.

Please note that I take it that what you want is a simple practical answer not just a simple theoretical answer.

The simple theoretical answer is about 6 mph. that is calculated by the unloaded rpm's on 4S power (14.8 volts) for both 1600 kv (23,680 rpm's) and 1800 kv (26,640 rpm's). This gives you with some flexibility about 2,900 rpm's to the prop difference. For a given prop again using theorectical pitch distance (how far the prop moves forward per rpm) for your actual prop a real number can be calculated. However, 6 mph will be close.

Now the simple practical answer. I did some testing exactly as you asked but using a 2,000 kv motor versas a 2,200 kv motor. Same prop, same batteries, same adjustments as far as prop depth and strut angle. While my rpm difference is also 200 rpm's like your example, just skewed a little, my actual verified performance difference in this test was 1.5 mph.

To be fair and to help others that may want additional information rather than just the simple answers, any change of just one fixed component normally would require further compensation ( different prop, different prop depth, different thrust angle) to maximize any benefit. That is, if you change the motor other adjustments may improve the overall performance of either choice in such a way as one motor and prop combination may actually perform better than a different motor and prop combination even after tweaking but you need to find this sweet spot yourself.

Hope I helped.

Dave

[Checkmateguy01]

Thanks Dave!! That's the best way to answer a "simple" question i've ever heard! In reality, talking FE anything there probably is no real simple answers due to all the variables at hand, but a general idea is what myself, and i'm sure a few others, are looking for asking "simple" questions. I never would have guessed in million years i'd be into electric boats now after many years of nitro-boat running/racing, but i really like this FE stuff, things have changed alot in the last 20 years LOL! With that said, there is quite a bit of learning to do after you break out from the RTR world. Very interesting that you got just a 1.5 mph difference, that's barely noticable if at all! With all the info i'm gonna stay with the 1800kv, i know it works good so might as well stick with it!