Originally Posted by odpurple
I wouldn't say that the Spektum system needes a cap for four cell. I've heard of isolated instances where the cap solved a problem, but I've never used one on any car I've built, both with the SR3000 and the SR3500. I don't know anyone who runs one, for that matter.
Jay Bee's problem is still there with a cap anyway, so he's got a problem with something in the system.
Mr B
plug a reciever pack into that car and run it, see what happens.
The problem with the voltage drop depends entirely on the BEC on the ESC. Some ESCs don't hold their power well enough under acceleration and need the capacitor to keep the powere where it needs to be. His reciever though has the caps built in and given he is using an external capacitor as well he shouldn't be having a problem there. Though a reciever pack would be a good test to see where the problem is..