[MeteorGray]

I've installed louvers on my Jeep TJ Wrangler with the 4.0L straight six engine. I did it to release extreme engine bay heat rather than for any aerodynamic benefits. At the speeds my Jeep travels, whether on-road or off, it needs the extra cooling benefits much more than any potential aerodynamic effects that might come from trying to improve on the shoe-box shape of the vehicle.

The hood louvers I installed are positioned to avoid having to cut any hood bracing, but are in places known to develop into relatively low pressure areas over the hood. This makes it more certain that the high-pressure hot air from the engine bay is easily pulled into the low-pressure air above the hood when at speed.

The louvers I installed are two rectangular-shaped Gen-Right louvers on both sides of the hood, and two somewhat-triangular-shaped Hyline louvers at the left/right center of the hood.

I've also installed a 12-inch electric radiator fan on top of the engine to blow hot engine bay air up-and-out of the louvers. This fan is used in slow-speed traveling/crawling while off-road, and I also run the fan on a timer for 10 or 15 minutes after the engine is shut down in hot weather to avoid heat-soaking everything under the bonnet. After engine shut-down in hot weather, it can get to around 300F just above the engine at the fuel rail and intake/exhaust manifold, according to the temperature gauge I installed above the engine to measure ambient engine bay temperatures.

I can't say the louvers or scavenger fan improve my fuel mileage, because they don't, but they sure as heck reduce heat-soaking everything under the hood. This especially benefits such things as the battery, alternator, sensors, and rubber hoses, belts and gaskets. etc subject to the heat. It also helps prevent vapor-lock in the fuel rail, which can result in hard starts.

By the way, I also installed a couple of the triangular-shaped Hyline louvers in the hood of my Mazda3 to keep things cooler under there. I did this after losing a battery prematurely, which I think was due to the heat. I even installed a six-inch radiator fan to blow the hot engine bay air out of the louvers while in stop-and-go traffic and after engine shutdown in hot weather. Again, it didn't do anything for or against my fuel mileage, but the engine bay sure runs cooler, according to the ambient temperature gauge I've got to keep tract of things there.