I am running a 5 port sirio 15 in my ntc3 ft on a very short oval track. The traction is very good. I was told the 3 port motors are bettery for tracks under 80 foot straights. Is this true???? My motor is getting old and was wondering if I should go evo 3 or os 12tz port???? Any ideas????? Thanks

3 port = more low end torque, good for short, small, tight and alots of turns (parking lot layout) track....
5 port = more high end HP, good for large....etc complete opposite to 3 ports.

However, that doesn't mean 3 port does not have top speed, or 5 ports has no low-end torque....no engines are perfect, just they are better on 1 thing then the other.

OS 12 TZ is a good sub $200 enigne...at least, the parts support is a little better then SIRIO.

i would go with the .12 os tz or the sts D3R i just got the sts and the os is on its way