Loony's BEC Roadster Build Thread

[voucht]

Originally Posted by davidimurray

I'm a bit late to the party on this, but just a thought on radiators and fans. The big area in the middle of the fan(where the motor is) acts as a dead area that cool air cannot pass through. So your fan is only drawing air through the area of the 'donut' where the blades spin around. It is common to see fans mounted set back from the rad with a shroud from the rad to the fan to ensure all the air is drawn through the rad and the full surface area is used. On my car I used a Clio rad with a 10" fan mounted 4" behind the rad and a little folded up aluminium shroud to support the fan/duct air.

Hi,

Sorry David, I don't agree with that.

What you say is true if the fan is mounted in front of the radiator. In that case, yes, the motor area completely obstructs the airflow (as well as the, rim, spokes, etc. do).

But when the fan is fitted behind the radiator, the air passes through the core anyway, even on the the motor area (it is not like 100% of the airflow is obstructed but the motor : there are air turbulences there too in this configuration).

If you make the balance between this very small obstruction on the motor area and the loss of efficiency of the fan if it does not touch the core, it is still much more interesting to have the fan sticking as close as possible to the core.

If the fan runs, it means that the engines needs cooling as soon as possible, and it has to be immediately and completely efficient. It will not be if it is not touching the core, because it will be sucking more air coming from between the fan and the radiator than through the radiator (air, like all fluids, always takes the easiest way )

You say it is common to see fans mounted set back from the rad, but I've never seen electric fans mounted 4'' from the radiator, and it sounds way too much to me. Perhaps the "shroud" you are talking about is a kind of air-duct (I didn'd really understand this), in which case it might be OK, but I'm very sceptical about the fan's efficiency if mounted that far from the radiator without no well-sealed ducting.

No bad feelings or nothing personal about that David, it is always hard for me to put the necessary nuances in this language which is not my mother tongue, and I hope I am not sounding offending or anything like that. It is just a different opinion (and only my humble opinion) and nothing more