Thread: Belt Driven Air Compressor - Supataool -v- Scorpion

I would be very suspicious of a comp where the FAD equals the displacement. Displacement is similar to engine displacement in a car, an arithmetic caclulation based on the bore, stroke, number of cylinders and RPM (if you are looking at L/m rather than just L as with a car engine).

It assumes that the cylinder is filled 100% at atmospheric pressure at the bottom of the stroke, and that all of the air is cleared from the cylinder at the top of the stroke, and that there is no flow restriction in the plumbing from the comp outlet to the reservoir, and then the outlet. None of these is physically possible, there will always be flow restriction around the inlet and outlet valves and ports limiting cylinder filling and evacuation, plus flow restriction post cylinder to limit flow.

Typically max FAD is in the region of 75 to 80% of pump displacement, which is in the region quoted for the other unit.

This does not mean that the second unit is grossly inferior, just that the numbers don't add up properly.

Thanks, Malb for pointing the displacement anomaly.

Should be:

Pump Displacement = 320L/min NOT 218L/mi

Thanks.

I'm confused now Where does it say the FAD is equal to the piston Displacement?

XRS12 2.2 Hp 241 L/min Piston Displacement, 186 L/min FAD

Supatool 2.5 Hp 320 L/min " " , 218 L/min FAD

IMHO the XRS12 is not a bad compressor. The pump is a "Fini" made in Italy.Every thing else is made in China.The only bad part is the pressure switch. It's a piece of sh....t. Fit a condor switch to it and you'll have a good compressor.
Not too noisy ether.

As for the Supatool....never seen one, don't know what pumps they have fitted.
Hope this helps
Cheers

Originally Posted by walro

I'm confused now Where does it say the FAD is equal to the piston Displacement?

XRS12 2.2 Hp 241 L/min Piston Displacement, 186 L/min FAD

Supatool 2.5 Hp 320 L/min " " , 218 L/min FAD

IMHO the XRS12 is not a bad compressor. The pump is a "Fini" made in Italy.Every thing else is made in China.The only bad part is the pressure switch. It's a piece of sh....t. Fit a condor switch to it and you'll have a good compressor.
Not too noisy ether.

As for the Supatool....never seen one, don't know what pumps they have fitted.
Hope this helps
Cheers

In the original post,currently displaying as
"In the red corner is Supatool. A 2.5hp, twin piston with 218L/min Free Air Delivery and Pump Displacement of 320L/min.
Price is $529."

the FAD and displacement were both listed as 218L/min, hence my comment about being suspicious of comps specced that way.

OP Aryajaide has then noted and corrected error in the post and reinforced this with the third post. The original post now represents the question more accurately, but unfortunately doesn't note that it was corrected. Therefore my original reply looks spurious.

Hope that makes sense. I did not respond with any direct comparison between the machines as I have no experience of either.

Mal

Thanks Mal, I thought there must have been a mixup with the data some where along the line.

regards
walter

I have a scorpion xr16 and the pressure switch and water trap both died very quickly, replaced them with quality and has never looked back. I would prefer on my next one to have a fully cast iron pump, but this one does the job.