they keep cool due to good quality hardware and design....if you have those 2 things there is no need for a fan, and stay away from a Quark

i have seen afew posts about v2's with the same problems as v1's

side note, will running my 2.5df on 5 cell cause extra heat?

So far the V2 mmms have been okay- only 4 known failures reported.
Your 1515 2.5d is only a 1650kv motor, so it will do just fine on 5 or 6s lipo- just afjust gearing accordingly.

but the 1521 will be better because it has a slightly higher kv rating and its more powerful so i can gear it higher and get better top speed without sacrificing any low end.
with a more powerful/bigger motor, will that use up more battery even though it says it has the same amps?

a 1515 would be plenty of power for you and good luck with your drivetrain you will need upgrades....I get 50 mph with my Revo and that is about as fast as you want to go with a MT

Heh, 40mph is scary enough- you need alot of space and smooth ground to use all that speed... *said the voice of (limited) experience*

nah, when you have an entire park all to yourself... acers of land... you just wanna go as fast as you possibly can. 50mph is too slow lol - 60 minimum!

if you are interested in over the top vehicles check out these 2 threads

http://www.rc-monster.com/forum/show...&highlight=xtm

http://www.rc-monster.com/forum/show...&highlight=xtm