[ByronRACE]

Direction of rotation doesn't matter if you don't care how much air it moves; or how hot that air gets...yes, it will move air.

This pump is not straight-vane. Efficiency drops sharply if the helical impeller is spun backwards. Also, the direction of the impeller is reverse of the direction of the discharge vent, the pump becomes very inefficient because it's throwing the air in the direction opposite the discharge. If you spun the hell out of an XX-Trim backwards, you'd probably get about half the flow it's capable of, and lots more heat, and possibly put the impeller and engine itself at risk (vanes are not designed to resist flex in that direction, they break, go through motor).

You would make more power with a smaller YS-Trim (what I'm running), which is designed for reverse rotation. And, if you really want a blower this big and need reverse rotation, Procharger has offerings in this flow range and bigger.

Two belts and an idler won't fix this problem unless you drive the idler on the back side of the belt, give it a good 50% wrap, then bring the belt back around and return it to the crank with more idlers and all. It would be messy. If you're going to do that, you may as well just drive the blower off the back-side of the belt using a double-sided cog belt (if you can find one). I'm not aware of any double-faced cog belts that can handle this kind of drive power. And, most power cog belts come apart when back-bent. That's why I went with a 50mm wide GT-2 belt; it's one of the few that can be back-bent. My catalog doesn't show any double-faced GT2's however. It would be a challenge, and would take 2 idlers I think...but it could be done if you could source the belt.

In any event, yeah, it bugs me. If you spin it backwards, sure...it'll move some air. I'm hoping whoever put this together didn't say "Yeah, it's backwards but eh, who cares"...not on an engine this nice. That would indeed be a shame.

Byron