Keeping Your Cool in a Tiger

An Article by Dan Walters
September, 2001

Page 4

More Fans Stuff:

.... A common replacement fan is the famous "flex-fan." The perfect flex-fan (or variable pitch fan) pushes air at the same flow rate regardless of RPM. As the RPM increases, the air being pushed by the fan also pushes the flexible fan blades back causing the fan to "flatten out" as the RPMs go up. One misconception is that a flex-fan "flattens out" by RPM alone. A flex-fan spinning in a vacuum would not flatten out, regardless of RPM. Another misconception is that once flattened out, a flex-fan BLOCKS air. It is possible for a vehicle to be moving through the air faster than a cooling system fan pushes air. But at that point the air pushes the fan around (instead of the fan pushing the air) and a flex-fan would increase it's pitch and allow more air to pass through than a rigid fan! Flex-fans have a limit to the amount of air that they push. However, an engine has the potential to generate more heat as the RPMs go up, A flex-fan may not keep up. If the airflow is insufficient the fan is blamed when in fact it is the choice of fan that is the problem.

.....One problem I have not heard about the stock Tiger fan is that the blades fly off. The same cannot be said about some flex-fans. One advantage of most flex-fans is the position of the blades. If you have an over sized radiator, fan clearance is a problem. Flex-fans typically have the mounting surface near the front edge of the blades yielding more clearance than original equipment fans.

The Fan From Hell

.....An example of a FAN FROM HELL is the Ford fan part number C9DZ-8600-A (ID number CF-C9DE-A ). This fan has 6 ridged blades and needs some modification to fit a Tiger. Another thing to consider is that the stock fan belt path has very little contact with the water pump pulley, which limits the power applied to the fan and water pump. In this case, the FAN FROM HELL may be counter productive or at least hard on the fan belt. A quick way to verify adequate fan belt tension is to attempt to turn the generator/alternator pulley by hand. Keep an eye on fan belt tension when using the FAN FROM HELL

....Overall, Maybe the stock fan is not a bad idea after all! They may be the next hot stock Tiger part at the swap meets. You heard it here first.