I'd like to get your thoughts on the topic. Would you run them on your Suzuki to help reduce under hood temps and if not, why?

During the midday sun in heavy traffic, I've noticed that the under hood temps on my 2.0L GrandV can get pretty high! My fender where the exhaust manifold is located gets really hot on the outside! You would not be able to lean onto it. I have the stock heat shield in place.

I would really like to just run one louver above the exhaust manifold to aid with keeping the temps down.. Reason i don't want two, one on each side, is because i don't want rain water falling on any electrics.. BUT is it safe if rain water got through the louvers and fell on the exhaust manifold's heat shield??

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Some info on the topic i found..

http://www.raceace.com/index.html





Video of louvers in action here

Their medium sided hi flow louvers costs $160 a pair though! 

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Here is a nice write up with some research / testing on the topic. The guy used the Pontiac Grand Prix factory louvers and they look great / very professional.. The only thing is they are difficult to find and parts.com says they stopped making them..

Link:
http://www.oman4x4.com/hoodventinstall.htm

So i know they do work, but my only fear is water getting in..

I run a set of those on the turbo tracker and they work great at venting the engine compartment heat.

Rain dripping into the engine compartment should not
worry you at all, the electrics are designed to get splashed
with water, if they weren't you would be stalled out all the
time when it rained

Wild

I found a louvered hood in the boneyard and was worried about the same thing, rain and snow, well I installed the hood and have had no problems.  I'd imagine if your plug wires are bad though, you'd get a misfire from the water.

Awesome, thanks for the responses! I will try and do some before and after under hood temperature tests (during city driving) to see exactly how much of a difference it actually makes for me.. Will post the results when I do..

It'll probably make a significant difference,  I can feel lots of heat comin out of mine when the car's sittin still after runnin a while.

One of our club members runs them on his Sammy to keep the heat down after installing the VW Fox Injection system.  He picked them up from Davesport, cut out the hood and riveted them in place.  Works great.

OK - let me the devils advocate ...

Starting with the OP post - he's in Trinidad, I'm in Guyana and these two, almost neighboring countries get more sunshine than most places in the world, including, believe it or not Saudia Arabia - how I found that out is another story, that I'm willing to share if you're interested, but is not relevant to this discussion.

Question - how are you measuring "under hood" temperatures?  All temperatures mentioned below with the exception of the indoor temp and the IAT were measured with an infrared thermomenter, the IAT reading is taken from software which reads the sensors through the ECU in real time, and also correlates with the IR thermometer reading off of the outside of the airbox, the indoor temp is a wall mounted digital thermometer.

Indoor temp, no air conditioning is 31.3*C, engine idling, vehicle stationary, in the noon day sun (11:30 am) the temp of the hood over the exhaust manifold is 77.5*C, over the intake side is 78.7*C, and over the roof at the rear, is 77.5*C - under the hood the temperature varies according to where you measure - the IAT sensor is indicating roughly 45*C, the strut brace, which is not a heat generating part and can be assumed to be at underhood temperatures is at 62*C.

Iin short the termperatures that you are concerned about (not being able to lean on the fender), bear no relationship to the running engine, or what's going on under the hood.

Louvres change the air flow dynamics and will allow hot air trapped under the hood to escape, but only under specific circumstances and these change dynamically depending on the location of the louvres and the air flow over the vehicle, which is speed related.

With the vehicle stationary and the engine running, if the temperatures are high enough to activate the cooling fan, the under hood area is a high pressure zone relative to the areas immediately adjacent and air will flow outwards through any opening - louvres if they exist, through the wheel arches and under the vehicle.

As soon as the vehicle starts to move, the dynamics change and so does the air flow - forward movement of the vehicle forces air through the grill pressurizing the underhood area, the rotating wheels cause low pressure areas under the arches, and the under vehicle area is also low pressure.

Above the hood is an especially complex area - the leading edge itself is high pressure, the area directly behind the leading edge is low pressure and as you go further back towards the windscreen it changes to high pressure (now you know why the cabin air intake is located where it is - the base of the windsceen itself is a high pressure zone.

Depending on where you locate your louvres, you will vent heat with the vehicle stationary and at low speeds, but you run the risk of reducing airflow through the radiator at higher speeds.

Oh by the way - with the engine off, (and no air flow from the fan) the hood temps over the exhaust area do rise somewhat, indicating that the normal air flow is more than adequate to cope with the heat output of the standard engine.

I don't know if they are even available or not but another thing you could check into is a header for your engine to get that hot exhaust flowing out of the engine compartment a bit better in my experience I have not seen to many exhaust manifolds that can move the air very efficiently for the purpose of cooling, in fact on my Samurai it came stock with an airline that ran from my air box to the heat shield of the exhaust manifold for the warm air choke. After I installed a header the temps went down at least a bit. Just an idea to check out good luck.   

Seems like you saved me some time there! I was planning to use an analog thermometer    placed at strategic locations to get various readings. But your IR thermometer seems to be the ideal thing!

I am aware that under the hood is a high pressure region once the radiator fan is fully active and that the ideal location for the louvers is in the low pressure zones on the hood. My front wheel arches are sealed and the main exit for hot air is out under the vehicle.

Currently with the factory design, I do believe that there is a region under the hood (high up between the strut bar and firewall) where hot air will remain trapped. By placing vents on the hood, it should help ventilate this area and keep things a little cooler..

Also, by placing the louvers in a low pressure zone on the hood (Venturi Effect!?), I should get cooling benefits both at a standstill and at speed.

I saw this test for a Jeep and was hoping the results would be similar for most vehicles..



This is the factory locations on the 1996 Grand Prix



I plan on copying the same..

Personally, I see no negative effects from additional cooling to the engine bay.. It should help increase air flow through the radiator and keep all my rubber components / sensors / battery a little cooler, which should theoretically add some extra life to the components.. Another mention is my winch which is located directly in front of my grill and it restricts air flow a little, so any extra cooling i gain would be welcomed.

May not be of any benefit where you live, but when it's really cold out they also help to keep the windsheild from iceing too. They do vent heat very well, just put your hand over them, running or not.

I would like some opinions as to which louver design to choose.. Looking mainly at cosmetics here..

Genright has a few Jeep louvers that would fit my vehicle..

Short.. 7.75" by 8"



Long.. 15" by 4"



The short installed..



The long installed..



and this is what they might look like on my vehicle..



I am thinking about only installing one long louver on the LHS over my exhaust manifold.. The one louver would look more functional than the 'ricey' look of two...

(Just gotta love the confused look on my Gf's face.. lol)

I would'nt put one of those plastic ones over an exhaust manifold.  Unless your going for the melted look.

I would'nt put one of those plastic ones over an exhaust manifold.  Unless your going for the melted look.

I decided on the square louvers from Genright. The long louvers would have fallen directly over my TPS and other sensors in the vicinity. The small squares would fall in a much safer area, so when I am washing the vehicle or leave it parked in heavy rain, no water will fall on anything important. The smaller louvers also blend better with the design of the GV hood.

The Genright louvers are made of 2mm aluminum alloy, so heat will not be an issue. Will post pics of what they look like on my GV when I install them..

You'll like them. Don't worry about water too much, I've been running mine with louvers for a few years now, and even heavy rain barley gets any water in. I get much more water in the engine compartment going through  water holes!