Jube

iTrader: (43)

That's the key to all of this, every track and driver can yield different findings with this stuff. Try different things, it's ok, just keep close tabs on temps (motor, esc and bats). I personally like a slower car, it's easier to drive smooth. These systems are crazy powerful and rarely do we use all of the available power.

Emmeth

I agree that a lower Kv motor is more efficient on 6s.

Told that I would like to hear your opinion comparing a Truggy motor 1550 vs a 1350.

A buggy 1400 is fair but I have seen on track that truggy ones are better both in torque and speed, trust me.

Hate2Looz

iTrader: (27)

That's the thing, why have all this motor, if you can't use it? Even outdoors,
I never had my 1900/4s combo turned up over 80% and even then, I could
over jump even the largest of triples. What good is that? I always ran my
10th scale stuff so it was just enough and that is what I plan to do with my
8th stuff. I've already taken a bunch of guff from buddies saying that I'm
putting way to little motor in these cars but we'll see whos laughing when
it all comes down.

dangerwr

iTrader: (5)

How is this setup more efficient if temps are a concern as posted below? Ok, you can run a 1400Kv on a 6S and have similar performance as the 1900Kv on a 4S. You can use a 3000mAh pack and get the same run times but if you are running hotter I am at a loss to understand how this setup is more efficient. Comments?

Also, there are trade-offs with everything you do when is comes to power. From what I understand is that slightly higher temps are the result of running higher voltage but using less current.

Jube

iTrader: (43)

Your understanding is 180* off

8ight-e

iTrader: (58)

Higher voltage leads to lower amp draw which also results in less heat, but the track, the driver and many other factors effect temps.. even ambient temps.

AMPS = HEAT no matter what so you can only compare to your own setup really.

say we need 700watts

14.8v x 47amps (more heat)
22.2v x 31amps (less heat)

Now keep in mind i agree a 4s setup doesn't generate too much heat in a truggy or a buggy if you are setup correctly and have no mechanical issues avg temps under 170 even in extreme ambient temps is common (quite a bit lower if using mechanical brakes).

Going off here a little as others also tend to think if you want more run time you cannot count only the reduced amp draw of being that big of a deal as it doesn't drop it all that dramatically. Still basic math will help you figure out how long a pack is going to last you in your setup.

hyperion cx packs (25c/50c) easy choice to show weights as they have all 3 pack sizes and will result in very similar run times

14.8 x 5000= 74000 494g
18.5 x 4000= 74000 501g
22.2 x 3333= 74000 545g

**keep in mind only a 4s is roar legal.

Seeing these numbers what has to happen to get additional run time (assuming top speed is dialed the same on each setup) you MUST get more mAH that I have listed above at each voltage, so if you want a 6s setup to last longer than a 4s setup you best get a 4k or better lipo, but notice even at 3300 range you are already heavier than a 4s lipo pack so additional mAH = additional weight.

To be honest with you in a typical buggy (375mah/min), obviously other factors can increase or decrease this, all you would need to do a 10min a-main is a 4s 4000 pack, 5s 3200, 6s 2600 but that is cutting it pretty close to LVC in most cases on most setups on most tracks.


Sorry for a little tangent there

dangerwr

iTrader: (5)

So you are saying that one would realize lower temps with 6S on a 1400kV motor? This would make sense if people are claiming better efficiency and why many are switching to this setup. I trust your judgment--so are the runs times really comparable?

Jube

iTrader: (43)

My temps are generally in the 135-145 range on the motor and 3 LEDs on my rx8 90*+ temps on loose outdoor tracks. My 6s 35c 3000 pack yields me the basic same runtime as my 4s setups did at a 100g savings. These are my findings and everyone will be different because of driving styles and track differences. One thing u must think about is when people talk about their runtime they never consider how bad they suck and how much time they spent on their lids waiting on marshals lol. If my car is always upside down, it doesn't use any mah. If I'm getting lapped 3 times in a qual then my car isn't doing the same amount of "work" as the fast guy. Clear as mud? Lol

Casper

iTrader: (34)

Even though your amps are down your resistance is up!

R = E / I. So as voltage (E) increases and amps (I) go down resistance goes up!

The motor is not working as hard though as you gear them way down.

for same wheel speed you would gear a 4S 1700kv motor 16/45 you would gear a 6S 1400kv 13/45.

As you know lower gearing is easier on the motor and draw is even less. The taller you gear the more amp draw.

It really has to do with proper gearing and lower amp draw. Batteries are rated in mAh. If your amp draw is decreased significantly (in this case 33% less with 6S over 4S for the same power) your system will run hotter if you are actually using the same power but your runtime goes up drastically.

Now you think since you are geared so much lower with what should be consisdered to have more torque.

It is much easier for the 1400 on 22.2V to move the car. It is not working as hard and drawing less overall amps to do it.

The 1700 on 14.8V is geared taller to to keep up with overall speed and is working harder drawing more amps.

high volt systems have more punch as well.

I was running 2100 on 11.1V. Geared way up to get top end (21/43). It had the legs to keep up but lacked bottom end of the 1700 4S system. I was using less battery on the 1700 4S system.

8ight-e

iTrader: (58)

Well said about the driving skills Also everyone has to keep in mind two 4s packs can be 100g different in weight, roar legal requires a hard case.. most tracks do not require this and it's really not needed iMO. Almost no 6s lipo's come in hard packs... so pick any pack well.. 6s packs can very by 100grams just from buying a 25c vs a 35c pack as well.

My tekno 8ight w/ lektron 2200 runs around 130-155 w/ 4s hyperion lipo's depending on the track and ambient temps, but I do run mechanical brakes. I typically run well and work my buggy as many laps as most and can push a 5000mah pack w/ my setup to around 14minutes, if I can stay really smooth maybe a bit longer.

8ight-e

iTrader: (58)

You're basically saying what I did, higher voltage = less amps to do the same thing to have less amp draw means it is easier work.. also note if you don't change your gearing you gain nothing. I'd also argue the peak amp spikes are much more similar btw the two as well which is why you don't see huge run time gains based on 'how much battery you have' (I've done both) even though avg amps are down. See above as obviously you are using far less mAH but to achieve the same result but to get the voltage you have to carry more cells even though smaller typically net the same weight and don't really gain much other than reduced temps in some cases. As far as punch goes, to be frank.. 4s systems have too much punch and have to be dialed down for fastest lap times.. so that is a mute point unless you just want to drag race. I even run a tekno clutch on mine now as well... protects the drive train and gives a even smoother response.

PS w/ brushless motors torque "punch" is more about the ability of the battery than gearing.. especially if you just change from a different KV motor in the same line, if your battery can provide the amps the higher you gear the more effective torque you will have but at a cost, chewing up runtime and causing more heat... then you can start another whole debate on 25c, 35c, 45c lipo's because you can hit a 45c lipo a LOT harder w/ amp draw (speed and torque) and have the same run time as a 25c pack geared way down.. with a 45c (true rating) packs ability to provide more amps you will also have a cooler system, especially the battery and ESC. So really depending on your setup, you could get some of the same runtime and heat savings benefits by simply buying better lipo's vs changing to a 6s setup, for that matter reducing the IR between the ESC and battery and motor as well... lol it's really endless they are all tied together.

SpEEdyBL

iTrader: (1)

There seems to be a little confusion on motor heat.

Heat in = I^2*R, so yes higher current = considerably higher temps if you only look at that, BUT...

Consider motor A = 2000 kv
Motor B = 1000kv same design.

If motor A is a 1 turn, it means motor B is a 2 turn of the same winding style because # turns is inversely proportional to kv.

Since motor B has twice the number of turns, the coils must be about 1/2 as thick in order to fit inside the same space. Motor B therefore has 4 times the resistance as motor A because its coils are twice as long and half as thick.

Therefore,

If you run twice as much voltage in motor B in order to get the same RPM as motor A, you only need 1/2 the current to get the same power, BUT motor B has 4 times resistance so:

Motor heat of A = Motor heat of B

In reality, higher turn motors are wound better than lower ones. They fill in the space better and make a more uniform coil. So you can argue that lower kv motors are slightly more efficient in that respect, but its not because they draw less current. The main difference is heat in the esc and wires since their resistances are fixed. Lower current will definatly mean lower temps in those componts. In summary, high voltage is good for getting power to the motor more efficiently, but not for running the motor more efficiency itself.

How the motor performs itself depends on the voltage it's being supplied. Too high a voltage to the motor will overexcite it causing it to spin faster and draw current causing heat. The lower kv motors handle more voltage because they are less demanding, dont spin as fast and generally run better because 6s is a lot better at supplying the necessary power through the esc and wires than 4s is to an even more demanding motor.

lbckevin

iTrader: (107)

Enough of this talk about voltage...

Frank or Casper...

Would you guys mind, posting your setup for indoor clay tracks ?

Jube

iTrader: (43)

Just race and have fun. There are many variables and all are small. I prefer my 6s system mearly for the weight savings, not cause of power,heat or efficiency. They all are "close enough".

Casper

iTrader: (34)

I run this setup but 55 pistons and 37.5wt oil in the front.

http://www.losi.com/ProdInfo/Files/L...6_DrakeStd.pdf

I am trying some heavier diff setups but have not hit the track with them yet. I will let you know how it works after I run ;-)

The above setup works really well at WC. My car always seems to work really well at WC.

I am running the inclined spindles and blocks now as well. Helps with middle off steering. They are not cheap though.