Honeywell ABV DU144 and DU145

[John.g]

Is there a reason for the apparent completely different settings on these.
For example if I require a flowrate of 480LPH at a pump head of 6M then I set the index on the DU144 to 0.5
But I cant see how this is achieved on the DU145, even if I set the index to 6, the minimum flow is almost 800LPH at a pump head of 6M??

 

[John.g]

The DU145 is the angled version so wonder why the apparently different characteristics.