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Old 09-20-2017, 04:38 PM   #1
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Default Motor and battery upgrade, help?

Hello. I'm very new to the electric world. I bought an HPI Sprint 2 Sport and after reading a lot of stuff in the "silk purse" thread I still have some questions.

First up, what I wanna do is make it drive as close to a real car (It already does pretty much so) and put an FPV cam on top.

I did a test with my action camera on it but it was kinda heavy for the stock engine and couldn't spin much, So I was wondering if I should upgrade the motor or get driftier tyres. I like the asphalt the most. There are some cheap ones on ebay for 5-7$ four all 4 (wheel, foam, tire) but don't know if they are any good.

So far I'm on the stock NiMh battery and I wanna get some new li-po batteries and the question is how do I know what C rating should I use for this motor? I found some good Gens Ace at 30C. In case in the future I get a stronger motor does this limit my choices? I'm not a super high speed fan, I am mostly aiming for power.

Thank you!

Here is my video test. It won't let me post links yet so copy-paste it:
facebook.com/bob.corey.50/videos/1572829479403971/
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Old 09-21-2017, 02:05 AM   #2
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Max continous Amp draw (A)= Battery capacity (Ah) x Discharge rate (C)
For a example, we have a 5100mAh 3 cell Lipo battery with a 10C rating. To find the maximum continuous amp draw, we first convert the 5100mAh to 5.1Ah, and multiply that number by 10C, to give a total continuous output of (5.1 x 10) = 51A
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Old 09-21-2017, 05:15 AM   #3
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Quote:
Originally Posted by Bob Corey View Post

First up, what I wanna do is make it drive as close to a real car (It already does pretty much so) and put an FPV cam on top.

I did a test with my action camera on it but it was kinda heavy for the stock engine and couldn't spin much, So I was wondering if I should upgrade the motor or get driftier tyres. I like the asphalt the most. There are some cheap ones on ebay for 5-7$ four all 4 (wheel, foam, tire) but don't know if they are any good.
Im a Sprint 2 enthusiast and professional amateur modder... lol
Okay so when you say "drive like a real car" im guessing you dont want to race it and more want it to look realistic while its driving.?
Plus a few other questions..
Okay heres what i recommend.
Chassis - Buy Rpm heavy duty rod ends (removes slop in steering)
Upgrade front belt tensioner. Buy front Sakura D3Cs Knuckles and adjustable cvds. Buy good cheapy adjustable 55mm dampers. Make sure they sre adjustable. And throw in some light oil and springs.
MOTOR - Get a cheap brushless sensored motor and speedy with adjustable timing. Then you can tune up the timing (advance it) as you get better and want more power.
I recommend a 13.5T.
My frineds 8 year old can run it with 0 timing. And i run 45 motor and 25 esc timing 65degrees total advance. She damm near hits 90km/h with great run time and pretty good temps.

Now you have a chassis that'll steer straight. Have adjustable speed from slow to skitz. And you can adjust your preload ride height, camber, toe etc.

TIRES - Realistic = half drift/grip in my opinion.
Go hard and medium drift rubbers and see how you like em.
Get those cheapy tyres, get some foams, get some drift ones...
The tyres have so much of an affect its like a completely different feel..
P.s get a hpi rally interior body set and make a rollcage etc. Plus a rear diffuser and a light set...
Youll be in realistic scale driving heaven.!
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Old 09-21-2017, 07:55 AM   #4
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Thanks for the answers.
RPM ball cups are already on the way. The stock sloppy-ness is too much. I want to make the steering system super-tight.

I am also gonna do the front belt mod so I can fit hard case batteries if you mean this.

When I say realistic I mean the movement, I mean grip at cornering and breaking. In general the speed much higher than actual cars, considering the scale of it (that's why watching RC in slow motion is more enjoyable). I don't care about realistic looking so these other things you said might help those who care :-D

As for the motor it still sounds pretty complicated, I didn't find all these specs on a cheap motor combo, only a SkyRC Cheetah 2590kv 13.5T that says not recommended for 4WD...
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Old 09-28-2017, 10:09 PM   #5
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Can I change just the ESC so I got better control over my stock mottor, or they got certain matches?
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