6S Firma 2050Kv motor Vs. 8S Firma 1250Kv motor?

[DeltaNova]

I'm currently confused on the benefit of upgrading to 8S or just sticking with the stock 6S. In my limited understanding of these motors I would think that the 6S 2050Kv motor is faster and better than the lower 1250Kv 8S motor due to the 6S having a higher Kv. Can anyone explain the difference, pros, and cons of upgrading? I plan on putting in a 160A ESC for the 8S setup too.

 

[Cheez]

Example #1:

A 2500 Kv motor and a 2S Li-Po battery at 7.4 volts



(2500 x 7.4) = 18,500 RPMs



the same Kv motor on a 3S Li-Po battery at 11.1 volts



(2500 x 11.1) = 27,750 RPMs​

Example #2:

A 4800 Kv motor and a 2SLi-Po battery at 7.4 volts



(4800 x 7.4) = 35,520 RPMs



the same Kv motor on a 3S Li-Po battery at 11.1 volts



(4800 x 11.1) = 53,280 RPMs​

What this all means is that if you have a motor with a higher Kv then it will have more top end speed but less efficiency than a lower Kv motor at the same voltage . So a higher Kv motor produces more heat and it will handle less voltage than a lower Kv motor.



If you have a motor with a lower Kv then it will have a lower top end speed but it will have better efficiency than a higher Kv Motor at the same voltage. So a Lower Kv motor is more efficient than a higher Kv motor so it produces less heat. This means that it will be able to handle more voltage and that means more possible speed.



I usually like to suggest using a motor that is balanced in the middle of the two extremes, it will give you the best of both worlds. That is of course unless you have a very specific goal in mind for your RC. If you are a speed freak like I am then you can opt for the higher Kv rating. If motor heat is an issue then it is sometimes advisable to use a lower Kv rating with a higher voltage battery to get the same effect.

The big thing to remember when using Kv for your Brushless Motor Ratings is that your Brushless Motor and ESC will each have a maximum input voltage (battery cell count) that is allowed. So if either your motor or ESC has a lower maximum voltage then you must use this to calculate your top RPMs. If you go over the recommended voltage then you have a high chance that something will fry in your setup.​

 

[DeltaNova]

Wow! Great explanation! Learning has occurred. I didn't even have this thorough of an understanding with my EDF jets. Thanks! I like to upgrade things, but i think the 6S setup that comes with the new felony will give me plenty of speed and power and I can save the 8S upgrade for a time down the road after I've mastered it's stock setup. The only upgrade for now is maybe the radio to a DX5 PRO and the handbrake. Thanks again.

 

[LibertyMKiii]

Much like your experience with planes there are other considerations.
#1 is weight. I think you can get everything you are looking for out of a 6s setup.
Running 2x 4s batteries will be heavier and cost more money. It may also show weaknesses in your LiPo charger.

To be honest as you had mentioned in other posts being out of the surface side of the RC hobby for a while, you may be shocked how potent the factory 6s setup is. Unless you want to go beyond 100 mph the factory motor and ESC will be more than enough power to get you in trouble with curbs, trees, cars etc...

My honest opinion is try it out first and see if you want more from it. Another side note is that 8s can be a bit "punchy" where power comes on very abruptly. Good aftermarket radios can help tune that out, but overall 8s power on a 6s car can result in damaged differentials, dog bone pins, or bent dogbones at an earlier time.

 

[jondilly1974]

I can also tell you that diffs often don’t like 8S power. Don’t ask me how I know ?

 

[DeltaNova]

Thanks for the feedback gents. Upgrading to 8S in a car apparently requires the consideration of a few more variables than in my jets. You change a motor and ESC to 8s in a jet and you immediately get higher top speeds, impressive vertical performance, and the added weight stabilizes the plane in gusty wind, but in a car it increases the risk of damage and reduced control in comparison. You're confirming more and more that the stock setup is where I need to be to be completely happy. My car gets here next week Tuesday and I can't wait.

 

[Samfwu89]

Has anyone tried to put 8s on the spektrum 2050kv motor with success? I know that the arrma felony esc were having issues with cut off and horizon has been shipping out the 160a 8s esc to run with the same motor. You guys think the motor can handle it?

 

[3d-rc.myshopify.com]

Has anyone tried to put 8s on the spektrum 2050kv motor with success? I know that the arrma felony esc were having issues with cut off and horizon has been shipping out the 160a 8s esc to run with the same motor. You guys think the motor can handle it?

sure. a 3s motor will handle it..... question is how long lol. 8s would blow the magnets off in a short time.

 

[jondilly1974]

Has anyone tried to put 8s on the spektrum 2050kv motor with success? I know that the arrma felony esc were having issues with cut off and horizon has been shipping out the 160a 8s esc to run with the same motor. You guys think the motor can handle it?

I have tried it for speed runs and melted the bullets off ?????

 

[IRONWORKER]

I can also tell you that diffs often don’t like 8S power. Don’t ask me how I know ?

The above statement should strongly be considered before going the 8s route.... I never had any major diff problems until i used a set of pull out K8 electronics in my Talion.... 8s was too much power, too much weight & too many problems.

An on road setup might be fine but in a high traction off road setup 8s & Arrma diffs don’t play well together

 

[QMAN]

I have tried it for speed runs and melted the bullets off ?????

Do you have upgraded fans? Maybe its time to solder them on!

 

[jkflow]

@QMAN I've melted the bullets off my stock Firma 2050 motor just with the Firma 160 ESC on 6S. Not just once but 3 times i.e. at first I thought it was just marginal soldering from the factory but it's simply too much for the bullets. The motor is still ok though.
I've moved to larger bullets.
This is on an Infraction.

 

[SrC]

8s on a 2050kv motor well exceeds its capabilities if not geared correctly. On paper you are easily pushing that Firma 2050 motor well over 68k RPMS if speed running.
Some have stated the older BLX2050 did better running 8s. I checked this older Arrma motor variant on my analyzer and actually is 1920'ish KV, consistently all of them I have. Cant speak for the Firma variant of the 2050.

 

[Catrinis4chaos]

Hey guys I have a felony with a 1250kv spektrum motor with 160 amp esc. running 35/45 on 6s today I got 71 mph. Heat was not an issue. I have 8s I'm going to run. Will the power from 6s to 8s make that much of a difference in speed? I'm looking to go over 100mph and was looking for advice on what way to go to achieve that. Thanks in advance

 

[Killacam]

Hey guys I have a felony with a 1250kv spektrum motor with 160 amp esc. running 35/45 on 6s today I got 71 mph. Heat was not an issue. I have 8s I'm going to run. Will the power from 6s to 8s make that much of a difference in speed? I'm looking to go over 100mph and was looking for advice on what way to go to achieve that. Thanks in advance

Jump from 6s to 8s will make a huge difference. Lots of people over 100 mph with that esc/motor combo.

 

[Isaac]

So my 1250kv on 8s should hit over 100mph ?
Hi so so sorry just making sure I read right so I got that 1250 kv 160a spektrum set up so does that mean my felony should hit 100 on 35/45
So running the 1250kv 160a versus the 2050kv 150a 1250kv should be faster ?

 

[jondilly1974]

Hey guys I have a felony with a 1250kv spektrum motor with 160 amp esc. running 35/45 on 6s today I got 71 mph. Heat was not an issue. I have 8s I'm going to run. Will the power from 6s to 8s make that much of a difference in speed? I'm looking to go over 100mph and was looking for advice on what way to go to achieve that. Thanks in advance

So my 1250kv on 8s should hit over 100mph ?
Hi so so sorry just making sure I read right so I got that 1250 kv 160a spektrum set up so does that mean my felony should hit 100 on 35/45
So running the 1250kv 160a versus the 2050kv 150a 1250kv should be faster ?

Here is a link to a website where you can plug in your numbers and get a theoretical top speed for your given setup.

https://www.radiocontrolinfo.com/information/rc-calculators/rc-car-calculator/

Pro-tip is to reduce your cell count here by 1 cell to adjust for voltage sag during your run. Usually I find this calculator to be almost spot on if this is done. Otherwise it will give you an unreasonable number.

For example, if running 6S, put 5 in the cells box. Look up your diff gear ratios if you aren’t aware of them. Tire heights too.

 

[Sloclone100]

Much like your experience with planes there are other considerations.
#1 is weight. I think you can get everything you are looking for out of a 6s setup.
Running 2x 4s batteries will be heavier and cost more money. It may also show weaknesses in your LiPo charger.

To be honest as you had mentioned in other posts being out of the surface side of the RC hobby for a while, you may be shocked how potent the factory 6s setup is. Unless you want to go beyond 100 mph the factory motor and ESC will be more than enough power to get you in trouble with curbs, trees, cars etc...

My honest opinion is try it out first and see if you want more from it. Another side note is that 8s can be a bit "punchy" where power comes on very abruptly. Good aftermarket radios can help tune that out, but overall 8s power on a 6s car can result in damaged differentials, dog bone pins, or bent dogbones at an earlier time.

LMK: The Limitless, partially complete in upgrades needed, if you at a one-step idea, could you use 6-8 3000Mah. I have a great charger. I don't even see it around anymore, This sucker peculates.

 

[Cwimp84]

Hey guys I have a felony with a 1250kv spektrum motor with 160 amp esc. running 35/45 on 6s today I got 71 mph. Heat was not an issue. I have 8s I'm going to run. Will the power from 6s to 8s make that much of a difference in speed? I'm looking to go over 100mph and was looking for advice on what way to go to achieve that. Thanks in advance

Ive got 2 infractions and 1 felony. My felony is my mainly speedruns, its got a swapped from 150 to 160a Firma ESC and still running 2050kv. I love those motors anyway. My point though , at the moment i run 26/43 and I stay in 90-102mph with that Gearing . Big fans on everything, 6s cap pack as well.

 

[flynlw]

Here is a link to a website where you can plug in your numbers and get a theoretical top speed for your given setup.

https://www.radiocontrolinfo.com/information/rc-calculators/rc-car-calculator/

Pro-tip is to reduce your cell count here by 1 cell to adjust for voltage sag during your run. Usually I find this calculator to be almost spot on if this is done. Otherwise it will give you an unreasonable number.

For example, if running 6S, put 5 in the cells box. Look up your diff gear ratios if you aren’t aware of them. Tire heights too.

thanks for the link, could you help me with what values are need highlighted in the photo it would be great!