Engine Louvre vents

[Martin]

Hi,
Can anyone tell me which is the more effective type of engine vent, the Le Mans style with the open holes or the louvre vent ?

[Bill D]

If it's any indication, the original race teams went to the LeMans egg crate grills because they said they allowed more hot air to escape.

I don't believe anyone has done any tests to back up that claim though.

Bill

[Big-Foot]

I would have to think that the Le Mans Egg Crates would be more efficient. They probably vent the positive pressure from under the bodyworks better than louvers since they pose less of a restriction. That said, the Louvers will provide more protection (albeit not much) when the vehicle is sitting still in the rain.
Myself - I like the Egg Crate look better..

[Peter D]

An analogy :

Think of a fast sailing skiff & how to pull water out via an automatic bailer :

- An egg-crate grill in the bilge will pull as much water in as it lets out.

- a louvre-style setup will drain the bilge pronto - that's why all auto-bailers are a "venturi-style" - sloping side against the flow, open back.

Assuming that we have a fairly even flow of air over the rear engine vent, I reckon that a louvre setup will "pull" air out of the engine bay better than a simple egg-crate grill !

Kind Regards,

Peter D.

[Mark Charlton]

I hope an aerodynamicist chimes in on this one.

Since my experience with heat problems in mid-engined cars has only been at low (or extremely high) speeds, my logic for change-over was that at low speed, the more open LeMans style would be more effective. If some day I get to do much more high-speed than low-speed driving, it would be nice to know for sure which would be better.

Oh, and I like the look of the LeMans style much more, which didn’t hurt either.

[John Fitzpatrick]

Air moves from areas of high pressure to low. If the engine compartment is at a higher pressure than your vent, air will exit. You can achieve that by pressurizing the engine compartment using a ram air scoop, etc or by lowering the pressure at the vent. Louvers do that via the Bernoulli effect if you have reasonably straight-line flow over them. You'll see a combination of those two techniques used in aircraft engine cowlings, a scoop to force air in and louvers to draw it out.