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offroad mod motor choice

offroad mod motor choice

Old 08-07-2011, 06:43 PM
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I have heard a higher wind motor produces more torque eg.8.5, 9.5. as compared to a 6.5. I am a little confused about torque with brushless motors.

The 6.5 would obviously have more top end, but does this mean the bottom end is LESS than a 8.5/9.5 ?

so for example, if we were to accelerate both cars with a 6.5 and 9.5 with their ideal FDR for say example a short distance of 5 meters to simulate a corner to corner quick squirt of the throttle, which car would get there first?

and how much distance would it take for the 6.5 to overtake the 8.5, or would it be straight away?

how can a 8.5 have more torque than a 6.5?

sorry about the noob questions, if I could put both motors in the same cars and do a test run, I would.
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Old 08-07-2011, 10:04 PM
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Yes, the HIGHER wind produces more torque but less top end.
Lower wind produces LESS torque but HIGHER top end.

But that is just initial torque... The faster motor (ie lower wind) will get there faster. The 6.5 will be MUCH faster than the 8.5 but may actually be slower if there isn't enough traction to lay that power down.

I have noticed many mod drivers go to an 8.5 because it can be much smoother in its powerband than a 6.5 or even a 5.5...

Another thing is I have seen a good driver compete in a mod class with a 13.5! So that just proves a good driver with a well setup car doesn't need gobs of power to be competitive!
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Old 08-08-2011, 12:15 AM
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Geared properly, the faster motor should have more power all around, but in 2wd classes, most mod motors have more torque than the car has traction so it doesn't really matter. A good starting point is 10.5 - 8.5 in 2wd classes, and a couple turns lower in 4wd. An experienced driver on a big or high traction track may be able to handle more, but if you're just getting into modified motors, I wouldn't start with anything much faster.
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Old 08-08-2011, 02:43 PM
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Originally Posted by captain stacker

how can a 8.5 have more torque than a 6.5?
It kind of comes back to your middle school science. To put it simply the more turns you have the larger the magnetic field so it can " pull " your rotor around harder. The less turns the less of the magnetic field but lower resistance so it can switch faster and get you rotor spinning faster.
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Old 08-08-2011, 02:50 PM
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See i get the whole difference in power band going from a 7.5 to a 10.5 but what confuses me is when you start changing rotors.. a high torque rotor is suppose to up your torque and lower your Rpms.. well that makes me think a 7.5 with a HT rotor is no diff than a 9.5 motor.. ?
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Old 08-08-2011, 06:04 PM
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Originally Posted by 1Fastpede
well that makes me think a 7.5 with a HT rotor is no diff than a 9.5 motor.. ?
Not quite. You'll have the kV rating of about an 8.5, but with additional torque. There's a reason why HT rotors aren't ROAR approved, they simply make more power.
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