Help! Limp mode?

[Dvdbrthn]

Good morning! So straight to the point: my Granite will run like a scalded dog for about 30 seconds.

Here is the setup:
Castle Knockoff Dilwe 4900kv Motor
ESC120a Drfeify off Amazon
Sococon 3S 7600mah 120c Battery
Slipper Clutch (Relevant later)

So the issue is it runs perfect for about 30 seconds. I mean literally tire shredding amazing. Then it slows WAY DOWN for about 15 seconds like it is in a limp mode...then NOTHING. Wait for about 3 solid minutes and it'll take off like a bat out of Hades again for about 30 seconds and then slow down again...then just sit there looking at me all stupid.

My first thoughts were it was overheating, but Temp on ESC has never exceeded via laser thermometer 157 degrees and motor never over 130.

Second thought was battery was discharging so quickly it was simply depleting and I was hitting low voltage. But that wouldn't explain why it will revert back to previous running conditions, And have the same issue on 2s...(I have ordered 3s 6000mah 60c. And adapter plugs to try this 120a setup on 4s. Awaiting delivery)

So I swapped my previous Spektrem Firma 85a ESC out for this 120a. Same issue if not worse.

So I got noodling the issue and doing some research, and it dawned on me that this whole issue started after I replaced my spur gear for the 3rd time for a higher quality one, as I had busted 2 previous cheap options. I can't imagine this would be the culprit as I've adjusted it every which way possible. If ANYTHING I feel like I can't get this $60 slipper clutch tight enough and it always sounds like it's slipping and has never cogged.

At this point, I need help. I've educated myself as best I can on everything I've thought could be causing this and I'm just at a loss.

I GREATLY APPRECIATE you guys and any input you may have.

Thank You!

 

[Hector_Fisher]

What kind of flashes is it doing on the ESC when it goes into limp mode? What pinion are you running? i wouldn't recommend running that motor on 4s, FYI. That rotor is very like to grenade itself at those RPMs. It's already running a risk being on 3s.

If I had to guess, it sounds like the truck might be overgeared and causing the battery voltage to dip too low on full throttle, thus causing the ESC to trigger LVC. Then by the time you've restarted your ESC, voltage on the battery has risen back up again and you can run it.

 

[Dvdbrthn]

What kind of flashes is it doing on the ESC when it goes into limp mode? What pinion are you running? i wouldn't recommend running that motor on 4s, FYI. That rotor is very like to grenade itself at those RPMs. It's already running a risk being on 3s.

If I had to guess, it sounds like the truck might be overgeared and causing the battery voltage to dip too low on full throttle, thus causing the ESC to trigger LVC. Then by the time you've restarted your ESC, voltage on the battery has risen back up again and you can run it.

I'm not sure how it's flashing. That is a good question. I currently have a 91t Spur, 20t Pinion. What would you suggest? I primarily run at the dog park and want as much speed as possible in high grass. I run mostly on pavement in my cul-de-sac at home and that id prefer just it to be "handlable". I do have a 1900kv Spektrum Motor I could swap out for 4s. What would be your overall suggestions for tall grass setup and gearing wise? For example; Abandon this motor for the 1900kv, 120a esc on 4s and gear down to like a 16 or 18 pinion? Or just try and gear down? Thank you SO VERY MUCH! For your time @Hector_Fisher!

 

[Gordo]

Tall gearing and grass never work....

 

[SrC]

Good morning! So straight to the point: my Granite will run like a scalded dog for about 30 seconds.

Here is the setup:
Castle Knockoff Dilwe 4900kv Motor
ESC120a Drfeify off Amazon
Sococon 3S 7600mah 120c Battery
Slipper Clutch (Relevant later)

So the issue is it runs perfect for about 30 seconds. I mean literally tire shredding amazing. Then it slows WAY DOWN for about 15 seconds like it is in a limp mode...then NOTHING. Wait for about 3 solid minutes and it'll take off like a bat out of Hades again for about 30 seconds and then slow down again...then just sit there looking at me all stupid.

My first thoughts were it was overheating, but Temp on ESC has never exceeded via laser thermometer 157 degrees and motor never over 130.

Second thought was battery was discharging so quickly it was simply depleting and I was hitting low voltage. But that wouldn't explain why it will revert back to previous running conditions, And have the same issue on 2s...(I have ordered 3s 6000mah 60c. And adapter plugs to try this 120a setup on 4s. Awaiting delivery)

So I swapped my previous Spektrem Firma 85a ESC out for this 120a. Same issue if not worse.

So I got noodling the issue and doing some research, and it dawned on me that this whole issue started after I replaced my spur gear for the 3rd time for a higher quality one, as I had busted 2 previous cheap options. I can't imagine this would be the culprit as I've adjusted it every which way possible. If ANYTHING I feel like I can't get this $60 slipper clutch tight enough and it always sounds like it's slipping and has never cogged.

At this point, I need help. I've educated myself as best I can on everything I've thought could be causing this and I'm just at a loss.

I GREATLY APPRECIATE you guys and any input you may have.

Thank You!

View attachment 317093

Very Nice neatly done rig you have there. Attention to detail....
Looks like you covered all your bases.
Personnally 4900 kv is rather way high IMHO.
Have you tried another Lipo yet?
What color ESC leds do you get when it stops running. Flashing Red or Green?
Red is for LVC, Green is when it Thermal Cuts. ( Temp cutting)
If you changed out the ESC and Lipo, but running the same motor and issue is still there, Could be the motor?? Same with the Spur gear. Maybe you are simply way overgeared for that high KV motor???
I don't see how the slipper clutch is the cause at all. But it should be tighter no doubt.
And I wouldn't run 4s with that 4900 kv motor. The RPM's will be way too high. Open the motor and have a look see, clean it out and lube the BB's if all looks good.

 

[Hector_Fisher]

So this was a Mega version initially right? It seems the stock pinion should be a 14t. Most of the forums posts i've seen suggest a 3000-3500kv brushless motor gives you equivalent top speed to the stock brushed motor:
https://www.arrmaforum.com/threads/which-kv-brushless-to-replace-the-stock-550.14996/
https://www.arrmaforum.com/threads/slower-after-brushless-upgrade.29430/

So if you're running a 20t pinion and 4900kv motor, then you are way overgeared. That's roughly equivalent to gearing for a top speed of 80-90mph, which would not be appropriate for bashing, especially in grass. I don't know what the smallest pinion size is you could run, but I bet if you went down to a 10t or 11t that it would be more tolerable. Likely still overgeared for a 4900kv motor, but you wouldn't be hitting LVC as soon. Otherwise, you need to run a lower kv motor.

 

[Dvdbrthn]

Thanks guys! Really appreciate you. I'll order some new pinion gears today. Have a great afternoon!

 

[Dvdbrthn]

Very Nice neatly done rig you have there. Attention to detail....
Looks like you covered all your bases.
Personnally 4900 kv is rather way high IMHO.
Have you tried another Lipo yet?
What color ESC leds do you get when it stops running. Flashing Red or Green?
Red is for LVC, Green is when it Thermal Cuts. ( Temp cutting)
If you changed out the ESC and Lipo, but running the same motor and issue is still there, Could be the motor?? Same with the Spur gear. Maybe you are simply way overgeared for that high KV motor???
I don't see how the slipper clutch is the cause at all. But it should be tighter no doubt.
And I wouldn't run 4s with that 4900 kv motor. The RPM's will be way too high. Open the motor and have a look see, clean it out and lube the BB's if all looks good.

So it IS in fact flashing red for LVC. How do I rectify this situation? 85a Spektrum ESC, primarily running Sococin 3S 7600mah 120c batteries. Thank you in advance.

So it IS in fact flashing red for LVC. How do I rectify this situation? 85a Spektrum ESC, primarily running Sococin 3S 7600mah 120c batteries. Thank you in advance.

I also dropped gearing. Same issue.

 

[Hector_Fisher]

So it IS in fact flashing red for LVC. How do I rectify this situation? 85a Spektrum ESC, primarily running Sococin 3S 7600mah 120c batteries. Thank you in advance.

I also dropped gearing. Same issue.

What gear did you install and how long did the truck last this time?

 

[Dvdbrthn]

What gear did you install and how long did the truck last this time?

A 12t and it lasted longer. A few minutes. Fully charged pack. 12t is the smallest I had in 5mm bore.

 

[rotauq]

Hector already made the correct diagnosis, just to add some more info

A 4900kv/1400W is 2S max. And I don't think you can gear down far enough to make it run fine on 2S.
If it wasn't for the slipperclutch, it probably wouldn't even come from its place. And that clutch you don't want to exceed it's max intended rpm's which will be around 30k (under load). fyi on 3S a 4900kv motor wants to go to ~55k rpm under load and demands a lot from the battery if it's doesn't get there.

Also, after wet mud, high grass is the second highest load causing surface. Generally people gear down to pinion 1-2T just to deal with this surface

If you indeed have a 1900kv on hand, that would be more suitable and perfect for 4S.
kv does not make your car faster, Watts do. higher kv only moves your gearing out of optimal range.

 

[Dvdbrthn]

A 12t and it lasted longer. A few minutes. Fully charged pack. 12t is the smallest I had in 5mm bore.

It does also sound like it's coging a bit now at low speed and braking. Haven't had time to readjust the slipper. I'm still at work.

Hector already made the correct diagnosis, just to add some more info

A 4900kv/1400W is 2S max. And I don't think you can gear down far enough to make it run fine on 2S.
If it wasn't for the slipperclutch, it probably wouldn't even come from its place. And that clutch you don't want to exceed it's max intended rpm's which will be around 30k (under load). fyi on 3S a 4900kv motor wants to go to ~55k rpm under load and demands a lot from the battery if it's doesn't get there.

Also, after wet mud, high grass is the second highest load causing surface. Generally people gear down to pinion 1-2T just to deal with this surface

If you indeed have a 1900kv on hand, that would be more suitable and perfect for 4S.
kv does not make your car faster, Watts do. higher kv only moves your gearing out of optimal range.

Thank you! So am I looking for something in the 3000kv range on 3s for grass bashing and hoping that fixes the issue? I already installed that 1900kv motor in my son's typhon on 4S with a 120a esc. It's doing very well. He is happy with it.

 

[rotauq]

It does also sound like it's coging a bit now at low speed and braking. Haven't had time to readjust the slipper. I'm still at work.

Thank you! So am I looking for something in the 3000kv range on 3s for grass bashing and hoping that fixes the issue? I already installed that 1900kv motor in my son's typhon on 4S with a 120a esc. It's doing very well. He is happy with it.

Standard it has a 3200kv 3660 motor. Don't go far above that 3200kv (anything lower you can easily compensate with a bigger pinion)
If you can fit a 3665 or 3670 in there, you could have that little more power. Just some budget amazon examples. Safer choice is a higher quality motor like Hobbywing 3660SL or castle 1412-3200kv

 

[Hector_Fisher]

If you are looking to run in 4s, get something closer to 2300 to 2800 kv.
Hobbystar is another good option, for a medium between Rotauq's good suggestions. 3660 is a common size for this platform. I believe a 3665 or 3670 may fit, but can't confirm.
For running 3s suggestion: https://a.co/d/3EekUue
For running 4s suggestion: https://a.co/d/6ystvI8