Bought a hardly-used IR T31 off a friend. He said it was loud, but man, it was EXTREMELY loud. You could literally feel it through the floor in the shop (and this is with insulating pads). Other thing, it got hot. Hot enough that filling the tank from dead empty to shutoff you could smell the paint (it was bubbling off). Payed 500.00, so it was cheap enough but I knew that I couldn't run this thing, christ it was going to make moisture like you read about, and drive me crazy with the racket. It did have a Baldor 7 1/2 HP motor so it was worth the 500.00. I ordered a Eaton 10 HP Quiet pump for 450.00, a belt plate, Motor pulley kit (to slow it down to 600 RPMs), belts, an a run-on valve (another 100.00 all together).
Had to mount the pump up on some angle-iron to level it out with the belt adjustment plate, and make up some lines but it was fairly straight forward. The IR had less outlets on the tank so I had to make due, although the run-on valve is much more accessible on mine than the way Eaton has theirs.
The IR ran at a much higher RPM so I would say that that was one of the reasons for noise/heat. The Eaton runs at 600 (you can see the difference in the flywheels). I will say the IR was no slouch for CFM but that is the only thing I can say good. So the difference you ask (besides being REALLY quiet)??.
The IR pump took 6 Minutes, 44 seconds to fill the tank from dead empty to shutoff..
Eaton pump took 3 minutes, 25 seconds to do the same.
The IR pump took 44 seconds from low air to shut off (app. 140 to 170)
The Eaton pump took 28 seconds.
So big difference. PLUS the Eaton built very little heat. I could grab any part of the pump and it was just warm (from no air to shutoff) The IR pump was no only hot, it was bubbling the paint off.
My compressors have their own room and you can barely hear the Eaton, where you FELT the IR through the floor besides the noise. I am very very pleased, and Eaton's service was top-notch. I had to get them to send me another set of belts (the one's they sent were wrong) and I needed another one-way valve because the IR was a double-flare. I needed a pipe thread for a adapter. They sent the belts/valve right out with no money/CC, and said send the belts back in the same box, we sent a UPS tag and put a check for the valve in the box. You can't beat that it this day and age.....