This is interesting. I have been experimenting quite a bit with differnet set ups in my rc8. My 1512 1.5d (3300) on 4s geared 12/46 doesn't run any hotter (45,000 +/- rpms)than when I run it on 3s. I pretty consistently get motor temps in the 150s.

I also have a 1509 1.5y (2400kv) that I run occassionally on 4s. I was actually thinking of bumping it to 5s to see if the motor runs better. Geared 14/46 it is a tad faster than a nitro, but I want a little more low end punch. The 1509 on 4s 5000 is good for 20 minutes. I was hoping to gear it down, bump the voltage to get a litlte more power and a little increase in run time.