> they are used in the augmentor tube to suck and expel the hot air from under the cowling.
I think Buly's right. Exhaust augmentation has a big effect on ground cooling. I have the exhaust letting out into a 6 inch stainless tube which exits the cowl at the rear. The exhaust pipe stops about 2 inches short of the end of the tube. All the air expelled has to come through the NACA, into a plenum, then through the coolers. I  had a fan installed, but it didn't any measurable difference (probably because it was just circulating air) so I removed it. Without the fan  my engine stabilizes at about 195F during prolonged taxiing on a 90F day. As long as I save any significant use of power until the run-up right before take-off, I can taxi for as long as I have fuel.
John