What kv brushless and what battery for 4WD Truck Open & Rally Open?

MojoManDan · 04-06-2009, 01:37 PM

Hey Guys,

I decided I'd like to enter the Open classes for both 4WD truck and Rally at the 2010 Indoor Offroad Nats. I was wondering what kv brushless motors you guys used for these open classes at previous Nats races, and what type of battery (2s or 3s lipo, or NiMH).

Thank you!

MojoManDan · 04-08-2009, 01:24 PM

Well, in case anyone was wondering, I decided to go with a 6800kv motor from Castle

. As far as 2s vs 3s lipo or NiMh battery, I am still undecided...

Psycho Man · 04-09-2009, 04:28 AM

MojoManDan,

I would have to say that your motor choice was a good one, at least to start out with. I see so many racers just go out a get the highest KV motor they can and struggle because they have too much motor for the infield. It always depends on the track layout. If it is wide open then you can get away with higher KV, if it is really technical then you could go even down to a 5400kv. As far as batteries go, most sanctioned racing limits you to 2s LiPo cells. Just like your motors, if you want to be competitive, try not to go out there and get the biggest LiPo you can get. Size and weight obviously play a big part in the balance of you car/truck, so I would get a battery that is just big enough (MAH) to last your race. I really don't run off-road much anymore, but at the On Road Nat's in our M18's we ran a Psycho Cells 35C 1150mah pack. The pack is small enough to place some of the electronics on the battery side of the car, for much better balance. That particular pack might not be suited for off road truck because of the extra draw of the big tires, but I think you get my point. I hope this helps.

Psycho Man

MojoManDan · 04-09-2009, 12:35 PM

Hey Psycho Man,

Thank you very much for your in-depth input. I agree about "too much motor", but I figure that the throttle could always be "dialed down" to a controllable level. I'd like to have power in reserve, rather than come up short with a particular setup. In any event, I am still too new to know whether an overpowered car can in fact be "dialed down" enough to be controllable for someone fairly new like myself.

Regarding 2s vs 3s for sanctioned events, the Indoor Off-Road Nats did allow the use of unlimited battery voltage for the open classes. So, I was wondering whether most people used 2s or 3s, in addition to their fantastic driving skills.

If I am not mistaken, the On-Road Nats had a voltage limit of 7.4, so only 2s lipos were allowed...I think

Unfortunately, it boils down to experimentation and practice, which are things I don't have time for (nor a track) except at the Nats once a year. I have yet to even consider fore/aft and lateral balance in my cars!

Thanks again!

Psycho Man · 04-09-2009, 01:22 PM

MojoManDan,

You are correct about Off Road Nats. I had to go back and look at the rules. As I said, I don't really get a chance to run Off Road anymore. That being said, the same principles can be applied to the 3s LiPo cells, especially since you are throwing around even more weight. I would want to keep them just big enough to make runtime but not a whole lot more. Otherwise you are just carrying un-needed weight to balance out. I'm not sure if I fully agree with 3s LiPo cells in racing, but I don't make the rules. I can see them in oval racing, but just not sure how I feel about anything else regarding 3s LiPo cells. But hey, if people want to run them, then I will sell them.

Psycho Man