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A friend and I started building a car for top speed runs. While researching esc's I noticed most of them have a 3.5 limit on motors using 2s or 6.5 limit if using 4s.

My question is if everything else is the same (gearing, tire size, etc) would a 3.5 motor on 2s be faster or the 6,5 motor on 4s?

If you know the kV rating on the motors, and you know the voltage of the batteries, you should be able to calculate the maximum RPM of both combos and compare them.

EDIT - Examples:

-Combo one: 3.5T motor = 9150 kV x 7.4V = 67,710 RPM
-Combo two: 6.5T motor = 6600 kV x 14.8V = 97,680 RPM

Upping the voltage probably will have a more significant impact than changing the motor.

forget the car motors, go with the 4 - 6s plane/boat motors and load up on smaller/lighter packs

like above if you want top speed cars you need airplane ESC's and Neu's motors, and lots of Lipo's


in this hobby money=speed

fastang wrote:A friend and I started building a car for top speed runs. While researching esc's I noticed most of them have a 3.5 limit on motors using 2s or 6.5 limit if using 4s.

My question is if everything else is the same (gearing, tire size, etc) would a 3.5 motor on 2s be faster or the 6,5 motor on 4s?

ESCs used to have a theoretical switching maximum of 64,000rpm... dunno if it still applies

if you're after top speed runs you need to gear up, not rely on crazy high motor rpms.
Keep the revs sane and rely on the torque of electric motors.

Higher voltage also has electrical switching efficiencies.

Above all else horsepower is king. Castles big 50V esc and a Neu motor is ample. I feel that normal 540 sized motors lack the horsepower needed to "make it really happen" Yeah they're quick but if you want to go fast you need to horsepower up.

Above all else horsepower is king. Castles big 50V esc and a Neu motor is ample. I feel that normal 540 sized motors lack the horsepower needed to "make it really happen" Yeah they're quick but if you want to go fast you need to horsepower up.

This. With the exception of Formula 1 cars, that's how it's done with 1:1 cars, too. The quickest cars in the world don't use especially high revving engines. They use big power with tall gearing. 330+ MPH top fuel cars have no transmission; they use a slipper clutch and 8,000 horsepower fire breathing nitro engines to accelerate from 0-300 MPH in under 5 seconds.

If you want a really fast 1/10 or 1/8 electric RC, go with a torque monster 700 series motor and gear it to the moon.

That's how I went about it with my nitro top speed vehicle:



No trans; just a heavy duty clutch set-up directly driving a 3:1 differential. Top speed with the Novarossi .28 turbo engine is still unconfirmed at this time, but it was 88 MPH with the LRP engine.

Regardless of gearing, "horsepower" as it relates to electric RC cars is a function of motor & battery. How much power you create is dependent on motor & battery. The most powerful motor will be a gutless wonder with insufficient voltage pumped into it. Conversely, take a modest motor and over-volt it, you'll make plenty of power...until the motor fries, that is.

Gearing just determines the balance between torque & top speed, it has no bearing on power.