Air impact wrench advice

[roombacurious]

This hasn't got a lot to do with woodworking but I thought I'd ask anyway...

I'm looking to buy an impact wrench and already own a small 6lt 1.5hp compressor - it's specs state 8 bar, 6 cfm. I've been looking at impact wrenches and some of them state that you need a 24lt or even larger compressor though the pressure and cfm requirements seem similar to what my compressor is rated at.
Since an impact wrench only uses air intermittently (unlike a drill or a sprayer) I thought the small compressor should be fine, but am I wrong?

Thanks

 

[jasonB]

You need to look at the FAD - Free air delivery of the compressor not the displacement which is what is usually quoted as the CFM for small compressors. You will empty the small tank before you have undone 5 nuts/studs so a larger compressor is better if you want to save time rather than effort

Having said that I did use one with a small Tiger from machine mart when I used to run a second set of mud types on my 4x4 and it worked fine, just nipped them up with a torque wrench to be sure. Just as quick with a knuckle bar.

Jason