Underhood Ventilation

tjl1388 · May 3, 2004

Underhood temps on XJ's get HOT. We all know that.... The hood vent thing has been done to death with different results based on who you talk to. What about an inline blower moter under the hood to either blow air out or in to the engine compartment. I thought maybe a vent type system with the vents facing into the wind for ram air type cooling under normal driving conditions, and for the trail, the blower would suck air through the vent onto the engine. These fans blow about 240cfm--is that enough to make a difference. I would be using two of them? Any comments on this theory would be appreciated.

If you are not familier with the blower I am refering to, look up attwood on google. They are commonly used to vent boat engine compartments.

RichP · May 3, 2004

tjl1388 said:
Underhood temps on XJ's get HOT. We all know that.... The hood vent thing has been done to death with different results based on who you talk to. What about an inline blower moter under the hood to either blow air out or in to the engine compartment. I thought maybe a vent type system with the vents facing into the wind for ram air type cooling under normal driving conditions, and for the trail, the blower would suck air through the vent onto the engine. These fans blow about 240cfm--is that enough to make a difference. I would be using two of them? Any comments on this theory would be appreciated.

If you are not familier with the blower I am refering to, look up attwood on google. They are commonly used to vent boat engine compartments.

The reason you vent a boat so well is to prevent build up of explosive gases.

The hood vents are probably the best method for an XJ. It's while off road that the underhood temps climb so much, on hiway the engine compartment stays pretty good. Just one of those things I've noticed after pulling into a gas station after cruising for an hour or so on the interstate while checking the oil... What would be nice would be if a fabber came up with a set of vents that were capable of being closed and opened. I have come up with a couple of ideas but have no clue about how to build them out of anything but cardboard and duct tape and I don't think anybody would pay for those LOL

Cottontail · May 3, 2004

I've thought about cutting a hole in the hood, and installing a fan into it with a switch in the cab to turn it on to suck the hot air out of the engine compartment.

I think it would work pretty well, I just need to do some extra research.

Any thoughts??

RichP · May 3, 2004

Why waste electricity, hot air rises, hood vents let it get out.

BrettM · May 3, 2004

isn't that what the grille and fans are for :dunno: ? they get air pushed in when you're going fast, and the fans pull air in when you're going slow... if you put some vents in the hood, or put a spacer to lift the rear of the hood then it give all that air an even easier way to escape..............

XJ91 · May 4, 2004

mad maXJ said:
isn't that what the grille and fans are for :dunno: ? they get air pushed in when you're going fast, and the fans pull air in when you're going slow... if you put some vents in the hood, or put a spacer to lift the rear of the hood then it give all that air an even easier way to escape..............

I did the hood lift in the rear. Boy what a diff in temp. It just barely passes the center line.

Funny though on the Highway it would almost red line before raising the hood. In bumper to bumper traffic it did not get as hot.

Kejtar · May 4, 2004

XJ91 said:
I did the hood lift in the rear. Boy what a diff in temp. It just barely passes the center line.

Funny though on the Highway it would almost red line before raising the hood. In bumper to bumper traffic it did not get as hot.

OK, but isn't that an indication of other problems?? My XJ never gets hot in bumper to bumper traffic, and we're talking about 105F hot air not moving, me stuck in traffic that's not moving much either......

PaulJ · May 4, 2004

With the rear of the hood lifted, you'll possibly force air in instead of helping it escape. There is a high pressure area at the cowl when cruising. That's why cowl induction was popular for awhile in the late '60s and early '70s.

BrettM · May 4, 2004

any air going in has to escape somewhere, even if it's going in there, it's still evacuating hot air that would normally build up there.

regardless, I did mine for cooling in traffic and on the trail

xj4fun · May 4, 2004

Guys,
Quick observation.

Anything done to push more air into the engine bay may reduce air flow going through the radiator. The result may be improved air flow, but reduced coolant cooling. The result may be little to no gain in reducing heat.

I would tend to think the best designs would be directed at increasing the air flow through the radiator and venting that air out of the engine bay at low pressure points.

Just like everyone else, I’ve been fighting heat for several years. Last year I figured I’d get it resolved. I dumped in a rebuilt engine, replaced the water pump, all hoses and installed a 3 core radiator. I then added hood vents. My trail temps are slightly better (still not good) and highway temps are still way to excessive.

Kent

tjl1388 · May 4, 2004

I think I am just going to install hood vents and attach the inline blower fan in a way to suck hot air out, if I put them far enough forward on the hood, this just might aid the radiator in doing its job. I will let you guys know how it works.

At the least I will have the hood vents I have been wanting.

seanyb505 · Dec 29, 2006

What about a regular house air conditioning vent? They are made so you can adjust from open to close and anywhere inbetween. They could possibly be rigged up to a mechanical lever, or some sort of electrical servo to pull the tab....Just brainstorming

87manche · Dec 29, 2006

I've considered marine deck plates.
Not nearly as slick as cable operated, but they're easy to mount, and waterproof.
Just pull the plates at the beginning of the day.

Alademuerte · Jan 2, 2007

One of the guys in the Jeep club I belong to has done the vents in his hood, I would post a pic, but the site is having domain problems right now..

But I have been meaning to ask him how his are doing for him, but I can post up when I hear from him...

But anyone else on here done this? I really am looking into it.

Underhood Ventilation

tjl1388

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RichP

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Cottontail

Three-De Off-Road

RichP

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BrettM

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XJ91

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Kejtar

PostMaster General

PaulJ

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BrettM

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xj4fun

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tjl1388

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seanyb505

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87manche

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Alademuerte

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