# motor size vs power and range



## ZeroGasoline (Jul 30, 2008)

All things being equal (system voltage, driving habits, other electronic components, motor efficiency...) I would expect you'd get similar range with a larger motor.

Things to consider:



The new and larger motor probably weighs more, this would reduce your range.
A more powerful motor MAY require less energy to move the car along the road, this would increase your range.
If you have a more powerful motor, chances are you'll want to use that power and that will effect your driving habits (not in a good way). This will decrease your range of course.
If you're changing system voltages that would be a completely different conversation as there are many more things to consider. If you're just switching out motors, the above should hold true.


----------



## jfbrink (Aug 15, 2008)

Hi,

I'm reviving this old thread to get some more feedback on this topic. Specifically, I'm looking at the merits of the an 8" motor vs. a 9" motor. 

Let's say that everything is equal (you even make up the weight difference between the two motors). Then let's look at this graph: 










(from the Belktronix website)

Since the Warp 8" (and Impulse 9") uniformly take about 25% more amps than the Warp 9" to produce equal torque, that strongly suggests to me that one could expect around 25% less range when using a Warp 8". 

In my conversion, I'll have to do a bunch more fabrication to fit the Warp 9", but if I'm going to see that much difference in range, it is worth it. 

Any thoughts on this? Is my simplistic reasoning far off the mark? 

Thanks,

Jesse.


----------



## Stunt Driver (May 14, 2009)

Seems like you have the point. Where graph comes from?

I am looking at a 9" myself for a Fiero conversion.


----------



## rillip3 (Jun 19, 2009)

Without some more granularity it's kind of hard to say. I'm going to make some guesses here, feel free to make your own.

It looks to me like the warp9 is hitting 100 "torque" (I'm going to guess ft-lb, they really should label it), at around 265 A, while the Warp8 is using about 380 A to get to that same torque. That's a difference of 115, or about 35%

But still, 385 is not unreasonable for that amount of torque. What you're really looking at here is only going to affect acceleration, once you're maintaining speed, torque really isn't all that important. If you want to drive more like a muscle car, I'd say go with the 9. If you're looking for street car like performance, I'd say go with the 8 and make the conversion easier on yourself. You might also want to check out the dimensions on the ADC 9, it's a good compromise between the two, and the ADC 9 may provide enough of a difference in length to make the fabrication/engineering easier on you, depending on what challenge you're facing.


----------



## CNCRouterman (May 5, 2008)

Are these torque vs amp comparisons at the same voltage and rpm?
If not, can you really draw any range based conclusions?


----------



## jfbrink (Aug 15, 2008)

CNCRouterMan: The parameters are the same for each curve, so they are directly comparable. And correspond well to the numbers on other independent/manufacturer graphs I have; this one just combines things conveniently. 

Rillip3: To me, it seems there is enough resolution to see that at *any* level of torque, the 8" takes an average of 25% more amps as the 9". Since torque is *always* being applied if the vehicle is moving, it seems that you get significant energy savings (assuming you drive in the same manner with both motors) from the 9". 

Stunt Driver: This particular graph comes from the Belktronix website. Other graphs, from the manufacturers, show similar numbers. 

Since my previous reply, I've changed my design somewhat so that the difference between an 8" and a 9" doesn't matter so much for installation. But, I am still intrigued at the seeming difference between them in terms of power usage. And the 9" seems a better choice in that regard.

Jesse.


----------



## major (Apr 4, 2008)

CNCRouterman said:


> Are these torque vs amp comparisons at the same voltage and rpm?


Hi CN,

The torque per amp is independent of voltage and RPM. So it doesn't matter.



> If not, can you really draw any range based conclusions?


I'd say not. You need to know the RPM and voltage for each motor along with the torque per amp. Or in other words, the power.

Think about it. Any difference in the torque at a particular current level from that graph could be compensated by a different gear ratio.

Such a graph is only useful if you have a fixed gear ratio and a set current limit and need to calculate the maximum tractive force for the different motors.

Regards,

major


----------

