I am wondering if it would be easily done to take the twin fan setup off of a tpi car and swap it onto a tbi car and then piggy back the secondary fan so that it turns on with the primary (left and right). Then your tbi could function off of the stock fan switch and such. Just an interesting idea for a cheap cooling upgrade.

 

Can be done. You will need to know how your fan on the TBI is turned on. Most of the TBI units I have looked at use the fan switch in the block and the AC pressure switch. Consult a wiring diagram for you specific application. Assuming you use the system mentioned you will need to have TWO fan relays. One relay cannot handle the current of two fans without failing in a short time. The fan switch should handle both relay coils without a problem.