Integrating "Pressure Flaps" to Cooling Fan Shroud

[BigBoss]

Hi all,

I don't think this topic has been discussed in detail at all on the forums. I came across a cooling system report down by PSU, and they included something called a pressure flap to their shroud to counter the effects of air flow restrictions in the shroud (i.e. relative air velocity is substantially FASTER than that of the air that can be pulled by the fan alone). Question is, how many teams besides PSU have implemented this into their design, and how big of a problem can this restriction pose towards cooling efficiency for cars that don't run them?

[Will M]

BigBoss,

I tried to get a good design for a flap system but the packaging got tricky.
If you do your heat exchange calculations for average engine load with the car sitting still and your fan provides sufficient cooling then the restriction is not a problem.

However if you are careful and clever then with some good design you could down size your fan and set up the fan speed to turn off at higher speeds to reduced energy consumption!

It is a good idea to look into it but the details will be specific to your car.

-William

[BigBoss]

Will,

For us, it's definitely something to look at. I don't think the previous cooling guy had considered it. Hopefully I can devote enough time & resources to it this year.

[Scott Wordley]

It can definitely be beneficial.

Fan shrouds are great below a certain road speed, but become restrictive above that speed.

Lightly sprung blow off flaps allow the fan to pull a lot of air at (car) rest and low speeds, then the flaps open up and flow extra air at high speeds when the restriction of the fan/shroud starts to limit cooling flow.