So we finally have got some much needed rain in our area. As I stood outside and had a few drinks and watched the thunderstorm, I wondered how the vents work. How do they (air vents and scope) stop water from getting in but then allow the air to get in/out? Or do they not stop the water from getting in and the water/rain gets on your engine and turbo?

I guess I could always lift my hood and figure it out myself but I thought I'd ask the community about it.

 

As air crosses over the nose it 'pulls' out heat from the 2 smaller front vents, and 'pushes' air behind the motor (exhaust manifold) in the main one. Kinda like a convection oven

 

I understand that. What I'm wondering is what stops the openings from allowing only air to transfer between these vents/scopes and not water?

 

Water will still get in but even with a car wash it doesn't seem like a lot of water is in the engine bay.Plus when you are driving in the rain the turbo is hot so it will just evaporate a way

 

What about when my car is chillin in the drive way and its raining its @ss off outside?

 

It will just have to wait until you drive it than.If you think about it all of the motor,turbo,tranny,ecu are all on the outside.The only place that is not on the outside is where you sit you got guys running turbo under the back of the car where the exhaust is and they are fine.

 

I hose down my engine bay!

 

There are rain "guards" in the front vents and one in the center one. They direct water into the hood which it then runs down out of some holes in the front on the underside.

 

I don't think water gets in. Sometime after a car wash I would open the hood and thats when the running water stuck on the vent would drop a few down on the engine cover but if I avoid opening the hood then water is directed elsewhere away from the engine.
Heres a link to a blog on the perrin website about air vents on the x
http://blog.perrinperformance.com/2008-evo-x-posed/

I'll be worry more about something like this, maybe its got its own reason. FQ400 hood.

 

Water doesn't hurt your engine; it's designed to handle the elements. Hell, look at the Jeeps and Land Rovers with snorkel airboxes...those engines get fully submerged under water (not that I'm suggesting you try it with the Evo).

 

Take a look at the older model hoods. They have Enormous vents that easily catch a lot of water. When i wash my car i can see the water getting down in there. And when i start it up a bunch of steam comes up out of the vent. Mitsu had to have thought about this when designing the car, so i dont even worry about it. (They obviously know better than I do.) Just my .02

But that being said, I do sometimes wonder that if getting water in the bay can be detrimental to the exhaust manifold and turbo, especially when hot. I know that repeated heating and cooling can weaken a metals integrity, but really how much can a little rain/water from a wash cool these parts? What do you guys think?

 

Yes repeated cooling and heating of metal is not always good. Think of it this way, you take a frying pan that is really hot, put it in water to cool and it will warp. The thing is, that much water is not getting on the parts like the turbo and manifold to cool it off rapidly enough. Yes you might have some droplets on there, but its not like its being dunked into a cold bucket of water. Plus those parts are much stronger than something like a frying pan.

Just like Kracka said, Jeeps and other 4x4s have snorkels and fully submerge their engine bay and its ok, as long as serious amounts of water doesn't get into the engine, everything will be fine.

 

The vents are heat extractors as well as mitigating some of the air pressure that builds up under the hood. Race cars use large vents on the hood and fenders to extract heat and release the aerodynamic pressure caused by airflow into the engine bay. We can thank Chaparral for this idea back in the mid 60's.

Take note of the fact that the driver's side vent is open while the passenger vent is strictly cosmetic. Even while at a standstill in the rain, the amount of water getting in is nominal and once under way, the air coming out of the vents should pretty much negate any water trying to get in. When I wash my car, I put a towel under the open vent to soak up water.