Some pretty good info I found at our french sister-website
www.germanlook.org :
Early 911 245 mm fan with 1.3: 1 pulley ratio 1390 ltr/sec @ 6100 rpm
1976-77 five bladed fan with 1.8:1 pulley ratio 1265 ltr/sec @ 6000 rpm
1978-79 226 mm fan with 1.81:1 pulley ratio 1380 ltr/sec @ 6000 rpm
Turbo fan with 1.68:1 pulley ratio 1500 ltr/sec @ 6000 rpm
964 fan with 1.6:1 pulley ratio 1010 ltr/sec @ 6100 rpm
New twin turbo with 1.8:1 pulley ratio 1210 ltr/sec @ 6100 rpm.
Early 911 245 mm fan with 1.3: 1 pulley ratio 1390 ltr/sec @ 6100 rpm
..................diameter (mm).........rpm.........pulley ratio....speed (ft/sec)
early 911................245..............6100.......... ..1.3 ..............334
76-77 5 blade..........245..............6100............1. 8...............462
SC.......... ...............226..............6100............1. 8...............426
.
930..........................245.............6100. ..........1.68...............431
964/993................... 279.............6100............1.6............... 468
993tt.........................279.............6100 ............1.8...............526
1965-74/75...... 110 mm crank..................95 mm fan pulley
1976-77... ........130 mm crank..................83 mm fan pulley
1978-79............130 mm crank... ..............80 mm fan pulley
1980-89............120 mm crank..................83 mm fan pulley
fan sizes / blades / air flow:
1965-74/75........245 mm / 11 pales.........1.3:1 ratio..1390 liters air/sec
1975/76- 77......245 / 5 pales..................1.8:1 ratio....1265 l/sec
1978-79............226 / 11 pales ...............1.8:1 ratio...1380 l /sec
1980-89............245 mm / 11 blade.........1.67:1 ratio...1500 l/ sec
964...............279mm / 12 pales......... 1.6:1 ratio..1010 l /sec (!)
And the best part:
An original 12-blade 964 fan uses only 8,1 hp at 6100 rpm!!
I say that is WAY less than a type 1 fan at that rpm
