Quote:
Originally Posted by dfink
Does anyone know the actual required CFM to cool the engine.
|
Here's a couple of data points - I'm sure others could build on this from the various spec books/workshop manuals - also depends on auxialliary oil coolers...
993 fan blows 1010 litres per sec at engine speed of 6100 rpm (at max power) with pulley ratio of 1.16 (reference Porsche tech spec book)
2L 911S fan blows 1390 litres per sec at engine speed of 6100 rpm (max power at 6900 rpm) (reference Porsche workshop manual)
And some racing engines with flat fans.....
908 3L 8 cyl = 14hp (ref Mezger IME 1972)
"the cooling properties of the 917
12-cylinder engine are superior to all of Porsche’s earlier
air-cooled racing engines. This holds for the engine
temperatures as well as for the power requirements of the
cooling air blower drive" (ref Mezger IME 1972)
"The cooling blower is arranged horizontally above the
engine. It has a diameter of 330 mrn (13 in) and supplies
the cooling air for the engine at a rate of approximately
2400 l/s at the rated engine performance. The blower is
driven via bevel gears at a ratio of 17: 19 of engine speed.
As already mentioned, at maximum engine power the
power input to the blower is 17 hp, i.e. 2.7 per cent of the
engine performance. Of the entire cooling air volume
65 per cent is used to cool the cylinder heads and 35 per
cent for the cylinders." (ref Mezger IME 1972)
John