on transverse mounted motors such as on an xray t4 or trf417, air flow from the chassis driving direction provides sufficient airflow on the front & top of the motor when the car is moving forward. In effect this airflow creates negative (recirculating) air pressure on the back of the motor, resisting fresh airflow therefore generating compounded heat on the back of the motor. mounting the fan directly on the back of the motor eliminates negative air pressure & provides sufficient airflow where its needed.
for most racers mounting directly behind the motor is most likely due to the ease of installation & even possibly an attempt to keep the center of gravity as low as possible.
Originally Posted by Josh-n-ya
Why 8mm? Behind motor or on top? I am still playing around with this! It seems I always get my highest temps on top of motor and closer to pinion side. I see alot of guys with fans behind motors and away like probably 8mm or so. Is there a theory behind this position?