How to get higher top speeds without (too much) increase in temps?

[smirkracing]

Hi All,

I am looking for some advice on how to balance my temps vs my top speed (for general purpose bashing in a park).

I am running a castle 1515 motor, 2200kv, on 4s, using a Mamba Monster X ESC. Everything on the truck is basically stock (tires are backflips LP).

Currently, I think the pinion is maybe 18t (need to check) and my top speed on short grass is about 43 mph.

I'd like to be closer to 55mph, but I think if I gear up (basic math says I'd need to go at least to a 23t pinion) a lot of other things will suffer. First, the motor runs well but I think it will run way too hot with such a large pinion. Second, I love the current power deliver - wheelies even from half throttle, excellent acceleration, and generally, great overall balance of power, speed, temps.

I just want another 10-15mph for blasting across the wide open field, but I want the normal (lower) gear ratio the rest of the time.

It occurred to me that this is basically what racers want on the infield vs the straightaways... and since I have a sensored motor+esc, maybe I should try out boost?

Would it make sense to set something up such that when I'm at wide open throttle (whatever those RPMs are) for more than say half a second, the timing ramps up by 15-20? Would that add some top speed?

I've never used these features before so appreciate you explaining this to a noob!

 

[senorroboto]

Boost is worth a shot trying! Worst case it runs too hot or doesn't work for what you want and you try something else.

Realistically you are pushing the limits here for 4s on grass. That is already a fairly aggressive pinion / motor kv combo already (I'm on a 17T on a 2000kv with backflip lps, with some temp headroom to spare)

I think the only way to go faster without adding too much heat is to increase voltage and go up to 6s. Then you can increase punch/torque control to keep it manageable and not destroy difs at low speed while being faster at high speed.

 

[Hector_Fisher]

43 mph on short grass is about approaching the max you could get from 4s on a 1/8 scale truck of this size. I typically read about people running a 15-17t pinion on a ~2000kv motor. What kind of temps are you seeing with your current setup? Maybe you're overgeared?

If you want to keep heat down and get better top speed, IMO, run a lighweight 6s pack, around 3500 - 4000mah. It won't weigh anymore than the typical 5000-6500mah 4s pack and will give you the top speed without really adding any extra heat. Some people will claim that running higher voltage causes higher temps, but heat is a byproduct of current, not voltage, and my experience had shown me that running 6s instead of a high geared 4s has improved temps (MT410, Kaiju, Kaiju EXT). Just my 2 cents.

 

[PatMarcus]

Sounds about right as Im using a max8 g1/2200/19t and I get about 45 but whenever I think Im gonna hit top speed the truck "turtles" anyway. Do you have a steel diff case for your centre ? If not, highly reccomended if youre going to push it harder as my composite case melted on this combo.

 

[22livefast]

Just a warning that the boost, which is basically advanced motor timing, will heat it up considerably. If you don’t use it much, then no biggie. You can put a heat sink and fan on the motor, and thermal paste the heat sink to the motor.

 

[Mt410dude]

Add another cell brother, 5s Will get you there

 

[Mt410dude]

Also drop gearing to 14tooth pinion