Originally Posted by
Troy Carter
3.9 isn't enough gear for boosted. Start around 6:1 and add boost to your liking. You may be able to go lower but I would start there for boosted and work my way down if I was running 21.5.
For F1 4.0 is right for 21.5 boosted starting point. At 6:1 the motor will top out almost immediately on the straight. With the torque there will be a lot of wheel spin in the twisty bits.
Without boost, on rubber tires we were running the same motors @ 2.75 to 3.25 FDR and they're coming off under 130 without fans. The only thing I can think of is that the light weight of the car decreases the amount of torque required from the motor to make it go.
I have another on order for my CRC WTF-1.