7XL Vs 8L on 12 cells..which is better?

[Bmr4life]

can a 7xl take 14 cells? and how many amps would it pull with 12?

[maxxdude1234]

The 7XL will be fine on 14 cells. You'll need a 9920 controller to handle the current. The actual current figures they give for motors are not very accurate.

[squeeforever]

Originally Posted by Rtsbasic

That doesn't add up, because on only 12 cells the only way to get a lot of speed is through pulling a lot of amps..correct? So presumably if I geared an 8L to hit 40mph, and geared a 7XL to hit the same speed (via steeper gearing), they would both need to draw the same power to get to that speed? Would the 7XL get there faster because its bigger rotor = more torque?

actually thats incorrect. the 7xl will NOT have to pull the same amount of amps to get to the same speed because of the higher gearing thus not having to work so hard. basically the torque allows you to gear higher for more speed while not pulling as many amps and having a higher efficiency.

also, i think that you should get BETTER runtime because of the motor pulling less amps.

[Rtsbasic]

So the general concensus is that a 7XL runs cooler, draws less amps so easier on controller, has more torque in general, and if geared appropiately will hit a higher top speed than an 8L in spite of revving a lot lower (29,000rpm on 12 cells vs 41,000rpm), while not really affecting runtimes? The bit that confuses me, is the 7XL generates more power, while pulling in less amps than an 8L, you can only put out what goes in, and the efficency difference can't be that big can it? Or is it possible for it to pull the same number of amps but because the bigger surface area and larger rotor its able to do it without heat problems?

Which brings me to my next question :) What sort of top speed is realistic to hit with a 7XL on 12 cells? Mtroniks say a stock weight emaxx will do 50mph with their 8L/Truck ESC combo on 12 good cells, but I find that a bit hard to believe. In summer I go to a local bash meeting every weekend thats held on a very big field, so lots of top end is important to me when I go to this (mostly because there's only about 3 of us that run electric..against 20-30 nitro buggies and trucks, lagging behind some dudes stock savage would suck).

[RC-Monster Mike]

The efficiency difference is actually pretty minimal between these two motors. I think that if they are geared for the same overall speed, runtime would be about the same with either motor. The 8L would accelerate a little quicker than the 7xl, but the 7xl would run a bit cooler. Both will work quite well with 12 cells. The 7xl will be a much better option for 14 cell use, and would allow more speed and runtime with the extra batteries. For 12 cells, the 8L is a pretty nice motor, but the 7xl would get my vote due to its ability to dissipate the heat better, which will allow back to back battery packs with less heat. Both motors will be pretty impressive on 12 cells with good batteries, though. And I would use a 5mm shaft regardless of the motor used. The 1/8" shaft will need care when mounting the pinion(keep it close to the motor) to prevent damage to the shaft.

[coolhandcountry]

The brushless has alot better zip to getting up to speed. If you ran truck that can out accelerate the others on the track. You can beat them with the acceleration not the over all speed. My savage is decent on top end. By the time it gets there I have reached top speed slowed turned and back up again with my brushless.

[Rtsbasic]

I use an RC10 T3 for track running, this is purely bashing. I am comfortable with 40mph or so top speed, if I cannot get this with an 8L or 7XL on 12 cells I may get a warrior in future if I can find a good deal on one, but I'm not prepared to sink $200 into something that takes 3 months for a service, maybe i'm just spoilt by being within driving distance of Mtroniks :)

My 8L is only a 1/8 shaft. If that causes a problem at least its under warranty and I could obtain a replacement within a few days. I will take your advice and keep it as close to the motor as possible. When my Emaxx arrives i'll give the 8L a go and see what its like. Eventually I will get a 7XL as it sounds a bit better in every way, but I'm not sure there's enough difference to justify spending more dosh on another motor. Maybe i'll get it when I sell the EVX and titans..what are they worth these days?

Thanks for all the input guys, its much appreciated. Can't wait to get brushless running in my E-Maxx :) Will runtime with brushless be much difference to the titans? On a friends E-Maxx I get about 10 mins running with the titans, normally pretty close to WOT.

Originally Posted by Rtsbasic

What other slippers are there besides the strobe? I'd like to stay with 32p gears simply because my LHS stocks them, and they don't the ofna ones. I don't mind buying a couple of 5mm pinions if the motor will be more powerful. I am considering cvd's, are there any dogbone kits I could buy for the front and rear? CVD's look so damn expensive :( But then I guess everything about this car is.

I recently converted over to Revo drive shafts, stub axles and RPM Revo bearing carriers on my gasoline powered Maxx project - these seem to be really beefy, and are relatively inexpensive.
I haven't purchased any of the hi-power BL systems yet, so I can't speak to their torque versus my 23cc gas engine, but I know I pretzeled my stock maxx driveshafts almost immediately.
Using Revo shafts offered me an inexpensive alternative to CVDs. Time will tell if they hold up as well though.

[coolhandcountry]

I am not sure what nitro motor to rate the torque of a brushless to. It seems to out do my .28 savage. I have broke a few cvds to.