Originally Posted by kubota57
Well I know y'all have way more experence with the 570/7500 and 580/8500 than I do but by looking at the two together was just trying to figure out why the 570/7500 produced more air speed than the 580/8500. I was just thinking by the end tube difference between the two beings the 570/7500 had smaller end tube that is what made it create more air speed. I previously had a shindiawa 630 and it was great just wanted something a little more powerful. Might should have got the 7500, but for the money difference i figured what the heck.
The air speed has nothing to do with the tube ends, which BTW, are the exact same on both with the exception of the added couple inches to make the 580's tip flare out. If you cut the 580's tube end at the bottom of the radius for the flare, you'll have the same tip as the 570's. I looked all that over before buying mine in 2011. They both have a slow taper on the inside compared to what the outside of the tube end looks like.
The speed comes from the difference in fan design and engine RPM's. The 570 has a maximum power speed of 8000 RPM and a recommended engine max speed of 7250 RPM, which means it is running at the lower speed at WOT so it isn't laboring as hard at WOT to run its fan design at its most efficient speed.
The 580 has a maximum engine power speed of 7200 RPM's, and a maximum recommended engine speed of 7200 RPM's which means it has to run at its maximum power to produce the air speed/CFM it does with its particular fan design, which in turn means shorter engine life. Switching nozzles according to the guy I mentioned above in a previous post does nothing for speed, but cuts down on its ability to spread the air flow since that is what that extra curl out at the end is designed to do (according to what Husqvarna told me on the phone).