Southlandmechser

Napier Precision Products Hood Vents...exclude all but heavy rain.


Screen over exhaust fans...7" holes

Fan placement. Driver side really cools off intake area.

Not as noisy inside the cab as you might think. Outside, it makes for interesting conversation.

Slackdaddy

What year is the red XJ? does it have the "pre Cats" under the intake?
More interested in the old farm house and homestead in the back ground

Southlandmechser

The red Jeep is a 1996 Cherokee Country.
The house was built in the 1840's...been in my wife's family the whole time.

NPx

Wow! Awesome install, especially with the fans!! How much clearance between the fans and the engine components?
Thanks, Doug

Southlandmechser

Doug, I positioned them both equally, the driverside being centered between the throttle body and firewall...plenty of clerance. I have them wired to my rear battery (gel battery in rear), which is isolated from my start battery. I have a control switch inside, constant power, that I leave on as I installed an adjustable 140-180 degree fan control switch, set at 180, to kick them on and off and will typically run about five minutes after engine shut-down until the underhood cools down to about 150 degrees.

JDS123

Guys are these things metal or no

BigNuge

I believe the vents are plastic.

I am considering them as well.

NPx

Hey JDS, the vents are heavy gauge ABS Plastic. We use the same plastic for the Hood Vents that we use for our Fender Flares, and a Jeep can park on the Fender Flares without breaking the flare. ABS can also be painted easily. Also, the Hood Vents come with a one year warranty against defects. Let me know if there's anything else I can help with.
www.NapierPrecisionProducts.com

JDS123

thanks, so yeah couple questions, lots of guys worry about water dripping on a particular sensor i forget which one.....not an issue with these?

And........on my 4 door 98 xj sport, to use the flat fender flares, do i have to cut the fenders?

Steve Hayes

I love these wheels! I may have to take another look at Hutchinson.

NPx

Hey JDS, we designed our Hood Vents so water would run off. The slots are in the vertical face of each rib and there is a rain gutter at the bottom of each rib that diverts rain water. Some rain water can still splash through our Vents but it is minor. Since our Flares are designed to allow larger tires and more flex it is necessary to cut sheet metal.
Let me know if there's anything else I can help with. You can always email me too: jdougn@NapierPrecisionProducts.com

JDS123

do you have to cut fenders to make your flat flares fit

NPx

Hello JDS, The purpose of our Flares is to allow for larger tires and more offroad articulation. So yes, the fenders must be cut to fit our Flares. If it helps, our Install Guides are available as free PDF downloads. Just click the title you wish to view.
Napier Precision Installation Guides
Let me know if there's anything else I can help with.
Thanks, Doug

Paul Standaert

There's a lot of talk about rain water getting into the engine bay here.

The thing that most people do not realize is that if you drive through a torrential rain or have a little too much fun going through that puddle of unknown depth, you get water all over under the hood anyway. But not many people pop their hoods right after to see how bad it got.
Hell, I have popped my hood and found frost all over the entire engine on some occasions. I also pressure wash my engine bays quite regularly and I have been doing that on my vehicles for over 20 years now. Not once did I ever have a problem unless I have faulty secondary ignition components that the moisture gets into and sends the spark straight to ground as opposed to through the spark plug. I just try to not aim the high pressure at pulley bearings and such.

Hell, lots of stuff under the hoods of vehicles in the salty states is rusty. How did it get rusty? Salt water spray. Things get wet under there. Rain water is not very conductive, nor is it very corrosive.

ELC_AMX

Sorry, off topic, but WOW, I NEED to know where you got those mesh covers for your headlights. I've looked for something like that for like two years now!



As you can see, I had to get creative to make something that would serve the same purpose, but I still want covers like those very badly.

Edit: Also, I feel obligated to note that I've never felt hood vents in the location described in this posting are useful at low speeds and in fact, might be detrimental at high speeds.

The exception is if fans are installed under them, in which case they can still be moderately useful.

Thing is, it's not ambient heat in the engine bay that gets an engine overheating - an XJ needs to run in excess of 223 degrees F to overheat when running on 50/50 water/antifreeze mix, and in order for engine bay heat to influence that in any meaningful capacity it would need to be blistering hot in there. I'm talking 300 degrees hot, hot enough to cook food. I've spent hours and hours researching how hot it gets under an engine bay and the same numbers come up again and again - 190 degrees, 200 degrees, 225 degrees. The REAL cooling comes from assisting your radiator in doing its job, that is, to help it move air more efficiently. Vents at the top of the hood, at the rear of the engine bay, don't do that well. It's like trying to cool yourself off by blowing a desk fan through a 5-gallon mesh strainer full of spaghetti and meatballs - there's just too much stuff between where the air comes in (through the grille and from underneath the jeep) and where the air would go out (in that setup, through the rear-mounted vents). It has to navigate through the whole engine bay, and in that way it doesn't really help the radiator much either, especially at low speeds.

At HIGH speeds, it actually is a bad thing.

The way engine bays are designed is to maintain an area of high pressure in the upper rear portion of the bay, therefore creating a dam of pressurized air that forces air downward and out underneath the vehicle. This actually improves airflow, because once the air is compressed into that space, what's moving into the engine bay isn't choked up on the engine and it's peripherals nearly as much, it's instead diverted more smoothly down and out. Rear-raised hoods might even be an improvement versus rear-mounted vents as well, considering that air can then exit around the edges of the engine bay where there's less getting in the way.

This is why forward mounted vents have always seemed a better option. At low speeds they actually provide an improved exit route for air pulled in by the radiator fans (therefore improving cooling, since the fans can pull air more easily and thus the radiator can cool better), and at high speeds they don't interfere with the high-pressure dam at the rear of the engine bay.

I've talked about this a lot with other people and that's the general consensus among us, but without an actual aerodynamically-educated engineer or someone of that caliber it's hard to really say. I'm eager to hear what NPx has to say (if they're interested in commenting on this), considering they produce their vents commercially. I'm not one of those kinds of guys that won't change their position once their mind has been made up!

2nd edit: I actually took a video of my hood vents in action in the past, visualizing the effect using a pinwheel. With both fans on, putting the pinwheel over a vent got it spinning pretty dang fast - this tells me that it would rather leave through the hood vents than some other means, or else I'd feel no airflow. As with any liquid, air takes the path of least resistance.

ALSO, law enforcement uses rear-mounted hood vents much in the style of what is depicted here, but the sales pitch is oriented more toward "protect electronic components from melting and keep the cabin cool by venting hot air before it has a chance to bake on the firewall." They used to/do pop the hood on very hot days to protect the electronics, but it was only done when idling for significant periods of time on hot days, which I definitely understand. So if THAT'S the purpose of the vents, this location works excellently.