Hood louvers and hood scoops - counterproductive?

[James Hunt]

I'm tossing around the idea of gifting my Bronco with some sleek hood louvers. Meanwhile, the concept of a hood scoop is doing a merry dance in my mind too.

I get the cool factor of the louvers, they're like the chimney letting out the hot air, doing their thing at whatever speed my Bronco decides to grace. But the hood scoop scenario has me in a bit of a twister. I understand it’s like inviting a cool breeze into the engine bay, but I have a nagging feeling it might turn into an overeager party guest and mess up the air flow’s groove through the radiator when we hit the highway. My worry is it might come with too much gusto, hindering the radiator and fan's chill vibe.

For the record, it’s not a beauty contest for me, it’s all about that sweet functionality.

Would love to hear your nuggets of wisdom on this!

 

[smritte]

Ok. How to say this without a bunch of pictures.
Sorry, gonna be a long explanation. If you don't want to read it, Go Louvers. Near the bottom, I explane both items.

This info is generic. Some vehicles will be effected more than others. This knowledge is used in all of my builds. This is why I don't have heating issues.

Your correct about the airflow through the radiator. I havent studied the bronco so I will keep the info generic.

Basically, the design is this. Vehicle driving over 40mph. Air hits the front. Air wants to go path of least resistance (which means, around not through). In order for it to go through the radiator, it has to pass through the grill, ac condenser, radiator whatever coolers (trans, oil, ps), lights and winch if equipped. All of these are somewhat blocking it. That means, most of the air will want to go around the vehicle, not through.

What we need to create is a lower pressure in the engine compartment. The fan will pull air but we only want that for low speeds (the fan also blocks airflow a bit).

As air flows under the vehicle, the panels underneath somewhat seal the lower front. The air going underneath creates a suction near the rear, bottom of the firewall. The front tires will create a turbulence. This turbulence will slow down the airflow. This is why there are inner fenders.

Basically, all vehicles have a flow created for the engine compartment. The more aerodynamic the body, the more important this is. Some performance cars will overheat at speed if you change the oil and leave the lower panel off. Same with the inner fenders. Some, dont care.

That's how it works. A stock vehicle should be able to move all the heat you create staying in the stock configuration. We create more heat with our mod's and towing. Examples are,
Bigger tires (did not change gears to match)- more load from the diameter as well as rolling resistance. This is why I always change gears to match tire increase.
Lift kit- more turbulence underneath
Bumpers- more weight/more load
Accessories- winch- posable airflow blockage, lights- posable more drag.
Took out the fender skirts-more engine turbulence.
Everything combined-More weight, more load, more heat.


The next part is "did the factory do a good job on grill and radiator design?"

A good example is my 96 Cruiser. It has a poorly designed system. The body and radiator design are barely able to flow enough air stock. If you add a TRD super charger, the added heat generated means you have a 50/50 chance your doing some serious cooling mods just to drive it on the street. Some people struggle with heat if they just go to 35" tires. This is because they removed a small critical part. The vehicle needs to be at 100%.



The question is, does your vehicle "need" help or do you want to help offset the extra heat your mods created? I do the latter.

Stock, the cooling system should be able to move twice the heat the engine can produce. If you overheat due to a radiator (stock vehicle), it was bad a long time ago.

Louvers. Set along the hood properly will pull heat at speed and vent heat sitting. On the to will do both, side are more for speed. Placement needs to be considered. The louvers will let water in. Even though modern car's have waterproof engines, you still don't want it sitting for a month with rain water pouring on your fuse box.

Hood scoop.
Forward facing is designed to pressurize. Now that your engine compartment is high pressure, less air goes through the radiator.
Rear facing. You better get it in the right spot. Too close to the windshield and your in a high pressure area, wrong spot in the center and your in a neutral area allowing no effect.

Rather then directly answer your question. I found it better to first explain how the system works. From there you can decide if more airflow is needed.
We modify our vehicles, therefore we should modify what's effected also. In this case its cooling. The average vehicle better be able to pull a grade at speed, with 33-35 inch tires at 100 degree ambient. This is with the stock cooling system. The system will be working harder but should be adequate.

When I build, I take everything into consideration. Better coolers, better radiator, all the seals in proper shape. On my Cruiser, I'm good with the temperature but I would benefit from louvers.

Believe it or not, I left a bunch out and just hit the basics. Remember diffrent vehicles have diffrent designs but they all work similar. If you have a problem, step back and analyze. If the vehicle is stock, something is not doing its job.

 

[Owen Hart]

Hi,
The variation in pressure created by the louvers doesn't impact the airflow through the radiator, provided that your fan shroud remains undamaged.

 

[smritte]

Correct. As long as their creating a negative pressure, they will only help. Worse case is, they do nothing at speed.
If I gave the impression above that was not my intent.

 

[MattR50]

So wait is that why on the new Jeep hoods the vents are fake? But then what about old school cars that had those big old hoods with air inducts?

 

[smritte]

So wait is that why on the new Jeep hoods the vents are fake?

Most louvers today are just for looks. Where they are on the Jeep is actually ideal, I have only seen pictures and never had one close to study whether or not to make them function. The possible issues created by making them function can be easily dealt with. As I posted earlier, worse is they make no difference.



what about old school cars that had those big old hoods with air inducts?

Those were used to force air into the intake. Depending on the style, they were called ram air or cowl.

 

[RedNeck]

Keep 'em fake. If you get out much and it crappy weather all that crap is going to get all over your motor and that will sooner or later contribute to something failing.

 

[James Hunt]

Many thanks, this really was what I needed. I’m thinking I should play it safe and focus on other areas for my upgrades.