Originally Posted by Ridin' Green
The tube on the 7500 and on the 8500 are the same exact size. The only difference is at the end of the tube on the 8500. It is flared out to create a different turbulence as the air exits the tube, which is designed to allow the high CFM's to work on a slightly wider area at normal operating distances. If you were to cut that flare at the bottom of the inside radius, you'd basically have the tube end that is on the 7500/570. Trust me when I tell you, the 7500/570 fan isn't overworking the engine in the slightest. It operates at a minimum of 750 rpm's below its maximum rated power speed (max rated power speed= 8000 rpm's vs maximum operating speed of 7250 rpm's). The 8500/580 on the other hand, actually operates at its maximum rated power speed of 7200 rpm's.
I'll say that if EVERYTHING was the same (engine size/HP/impeller design?) except for the tube tips...then I could wrap my mind around this concept.
So what would happen if the 7500 tube tip was put on the 8500? Too much backpressure...&/or a possible 250mph air speed???