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BrianG · 09.01.2006, 01:32 PM

I think there are a few reasons for the difference in L vs XL (or vs S for that matter):

Efficiency. There is an ideal rpm range where each motor is at its most efficient. To get that RPM, you apply the required voltage based on the kv value. Since an XL motor has a lower kv for a given turns count, you would need more voltage to get that ideal rpm. Running an XL with the same voltage as an L of the same turns won't be as efficient.
Weight. Well, of course the XL will weigh more, not to mention the battery weight for the higher voltage requirements.
Cogging: A lot depends on the controller firmware, but if you use a low kv motor on low voltage, it isn't going to spin very fast and the controller may have a harder time to read rotor position at low speed driving.
Power matching. For a relatively light (6-9lb) truck, you probably don't need tons of torque, so an L will suffice. Just like an S size works for 4-6lbs, and an XL works well for ~9 and up (to a limit of course).

That's my $0.02.

	(#6)
BrianG RC-Monster Admin Offline Posts: 14,609 Join Date: Nov 2005 Location: Des Moines, IA	09.01.2006, 01:32 PM I think there are a few reasons for the difference in L vs XL (or vs S for that matter): Efficiency. There is an ideal rpm range where each motor is at its most efficient. To get that RPM, you apply the required voltage based on the kv value. Since an XL motor has a lower kv for a given turns count, you would need more voltage to get that ideal rpm. Running an XL with the same voltage as an L of the same turns won't be as efficient. Weight. Well, of course the XL will weigh more, not to mention the battery weight for the higher voltage requirements. Cogging: A lot depends on the controller firmware, but if you use a low kv motor on low voltage, it isn't going to spin very fast and the controller may have a harder time to read rotor position at low speed driving. Power matching. For a relatively light (6-9lb) truck, you probably don't need tons of torque, so an L will suffice. Just like an S size works for 4-6lbs, and an XL works well for ~9 and up (to a limit of course). That's my $0.02.