I think Mitsu folks have it there for a reason, knowing they're pretty smart to have built the Evo and evolved it to the nice fast machines we're running, let's trust them enuf and leave it on! :-)

Wael

 

Yes . that is why is better for the aero dinamics too.
the front of the car is like a parachute. The vent is one way to let the air escape.
If you remove it ,there will be some turbulence and will slow it down the airflow, wich is coming out from the engine bay.
So you got two problems with that.
One is more drag -less airflow. Two less airflow = less cooling.

 

do you not understand the basics of how an aeroplane wing works?

the bump in front of hole creates a pressure field that pulls air out of the engine bay.

the ideas of air escaping and entering that some of you people are coming up with is hysterical.

Kaiten2 has said that the vent is to stop air going down into the hood and what is worse is that you agreed with him.

has anybody here taken basic physics?

 

Ok...no need to act like a know-it-all ***** there...
You might see some advantages in taking out the vent if you are on a road track with the engine running at high rpms constantly, but for daily driving its pointless

 

the post just get better and better

 

My understanding is that the "bump" in the hood itself creates the main aerodynamic force that "pulls" the air from the engine bay. Based on that, my thought is that the louvered shield simply helps keep water out of the engine bay while not reducing the effect created by the hood itself.

Thinking a little further in to it, the louvers my help extent the low pressure area created by the hood and reduce turbulence, which could actually increase the effect. I want to say that the Coriolis effect is the correct term, but I'm not completely sure ...

 

That is actually incorrect, in fact it does not cool better, in fact it makes things worse.

Some stated it before but let me clarify. Look at the front of the stock hood and notice the slight bump on it that exists just right before this vent. This vent creates lower air pressure to pass over it because the bump makes wind speed through it at a faster rate. This is similar to how a wing works on a plane. Everyone knows hot air rises and so as it slowly rises through the vents it isn't immediately forced back into the engine compartment because of this bump. Once the hot air gets to a certain point about 1 inch above the vent the higher faster moving low pressure air created by that bump grabs the hot air and literally pulls it out of the vents.

The main difference between having the vent fin cover on and off is that because of the angle of the fins on the cover it assures that air that is coming from this bump does not go into the engine compartment keeping the hot air inside and also causing a backlog of air being less aerodynamic on the firewall between the engine and the passenger compartment.

They designed it for a reason fellas.. You have to keep in mind that air is moving at an angle not just stationary. I'll draw a picture if I can to help illustrate.

 

In essence, they both provide cooling but the angle of the fins on the hood give it more time for hot air to rise without having the cooler air coming over the bump to push it back into the engine bay. It's all about the timing..

 

^^
I know what you're saying that that's the best argument so far... but I'm not convinced that you need to help the low pressure area by adding a barrier with directional fins.

I've been wanting to buy one of those surface heat sensors for checking rotor temp. so If I pick one up I'll bring the vent to my next track day and test under the hood temps after sessions with any without to see if there is a radical change in temp caused by removing it.

unless anybody's got a wind tunnel they want to loan out.

 

Another argument that I would like to make is that the angled fins on this vent also provide a sense of floor/barrier for the hot air to be swepped. Think of it like this. We all agree that the air that comes over the bump of the hood creates a low pressure and thus creates a high speed of air to move across it. This air helps pull the hot air out of the engine. That we all agree on.. What the argument is how much is that hood helping and if it's obstructing air or helping more air pass through it.

Now think of it this way.. imagine you where standing on the hood with a broom, and you start sweeping over the hood vent area. Lets assume someone was undernead the hood the engine was removed and for the sake of experimenting they had a big pipe or something and they where pushing schredded cheese through it. as it comes up the vent area you with the broom sweeps it in the direction towards to back of the car imitating wind passing over it and pulling the hot air out. if you have the vent cover with the fins on it; as you sweep some pressure from the broom pushes down into the vent but because of the angled fins it creates a sort of a floor where the cheese cannot go back into the engine and instead with your brushed stroke it helps push it out. if you had no angled fins and only an open hole, when you brushed the broom over it some of it might go back into the engine compartment.. more so than if you had angled fins creating a sort of floor or barrier. you might get more air near the back end of the vent becausea floor is created because of the hood but in the front most of the cheese would just get pushed towards the back and possibly back into the engine bay.

I know this example is a big weird but if you think about it.. it helps.

The angled fins provide a floor that without the cover would not be there and would let more hot air to get pushed back into the engine compartment.

 

^^
in this example you don't account for the air entering the front of the engine bay. the air enters the nostrils (for those with 8s) also under the hood where the stock intake collects from and passes the radiator and goes over the turbo area then in my theory gets pulled up and out more freely then if a metal plate blocks it.

 

I believe that the real reason they put the louvers is so that people will look at it and think that it is like a race car, since they think that Mitsubishi would not have put it there if it was not functional. Whether it is in fact functional is secondary to the "it looks like a race car" thing. Like the wing and the vortex generators. And the brake air guides and the Brembo on the brakes. And the Momo wheel and Recaro seats. And the SE lip, etc.

Maybe it does aid cooling and maybe not, but even if it does it is probably not enough of a difference for anyone but people who actually race it to notice a difference. I mean, how many people run without the wing? Or the VG?

 

I see your point but you have to keep in mind, that this isn't just some type of metal plate it is in fact a vented plate with angled fins to guide air not block it.

In reality putting your point into perspective you actually achieve more air flow helping the hot air exit the vent better because of the angle of the fins.

Assuming this is the front of the car =(===/=/=/=/ the = sign is air, and the / are the angle of the fins, Notice how the angled fins will dig into the engine bay a bit and pull some of the air out through the middle of the hood instead of flowing to the rear of the car. This will all happen after it gets to the turbo..

 

yeah, but not you're assuming the low pressure area created by the bump is not doing a good enough job of "encouraging" air to get pulled out and thus the hot air travels back to the firewall.

I don't think either of us can figure this out on paper. temp readings immediately after a few hard sessions will be needed to prove/disprove the in motion effectiveness. obviously at low speeds / not moving without will cool better.

 

i never use mine.. aside from some water spots i have had no probs in 4 years.