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Hood vents, scoops etc. Heat extraction

Just going to throw this out there, on an 89 4.0 AW4 I had the issue. I'm at 2500' and when going up to the pass at 7500' I would have to turn off the a/c and sometimes stop & open the hood with conditions of 110*+ with a tailwind. Used the LaBaron louvers and they defiantly helped but a/c would go a bit warm and temps would still be close to the red. I ended up cutting out a bit larger section of the hood and made "covers" that can be removed when needed by removing 4 sheet metal screw per side. I just painted them black as the paint is badly faded so looking pretty wasn't a consideration.

Now when cooling is needed I take them off and toss 'em in the back or just leave 'em at the house. Biggest benny is the a/c, stays much, much colder and my temps now stay just above the middle line between 100 & 210 with the later model elec fan and good stock cooling system converted to the later also. I do run a 195 stat and my sensor is in the back of the head.


The other issue I had, kinda, with the louvers was when it snows I generally am getting snow off of lower hanging, weighted down branches and this snow would fall onto the louvers and melt. Never had any problems but didn't like it all the same.


Mine is used for trails, running my dobie and around town mostly so it doesn't get driven but once a week so keeping the sun out of the engine compartment was also a consideration for me. Unless it is going to get really windy I don't even put the screws in from April 'till Nov.
From what I've seen on here, if you guys having the issue with the incredibly beautiful rigs can make, modify and keep everything looking the way ya do, making something like this look nice and be easily removable wouldn't be to much of an issue I don't believe.


And while I don't have much to contribute here (and happy that maybe this time I can!), I really appreciate all the info and ideas from everyone and love seeing what you guys do. My hat is definitely off to ya's. I try to do mods and actually get a few done but age and incurable, but very treatable cancer have made it somewhat difficult to get things done. Still work and for you Vegas guys, if you can't get around town on the surface streets in the PM rush, that be my fault...but I got nothin' what-so-ever to do with the construction, they don't let me play with the signal timings for that anymore unless it goes political.


Thanks again to all, please keep the build threads coming and everyone have a safe and Happy 4th of July!!


Chuck
 
Systems tend to want to equalize.

And the sky is blue.

That still doesn't mean there's low pressure on the back because there's high pressure on the front. You could have a 40'+ long vehicle with a front like a city bus and the rear like a tear drop. There would be no low pressure/near zero relative wind velocity zone on the back, but the front would be a mess of turbulence and high pressure.

Again: there's a low pressure wake on the back of the XJ because it's shaped like a brick and airflow detaches (in a not clean manner to boot). That's why a lot of semis run these:

WERNER_TRAILERTAILX-300x200.jpg
 
Those look pretty sweet!!! How was installation? Any pics of them from the bottom side of the hood?

From ehall's build thread:

Engine bay temperatures have proven to be a problem. The coolant temperature hasn't hit critical temperature yet, but the hood itself has gotten extremely hot a few times, even to the point where rain water evaporates off within a couple of seconds. I looked around at various options for a while but couldn't really find anything I liked, then I found the Rugged Ridge vents for TJ and JK for $50 and decided to try them. They fit pretty well and seem to do the job. Not great quality (OMIX-ADA) but they seem to work alright for now.

The plan was to put one hole on the driver side of the hood over the exhaust manifold to let hot air out, and keep the passenger side closed to protect the ignition components. I also wanted to avoid putting the hole over the brake booster to avoid rust, while also avoiding the truss that runs through the middle of the hood metal. Several measurements later and I had the vents positioned in a spot that looked safe so I drilled for the screw holes, and then measured and marked a spot for the hole.

Hood_Vent_Hole.sized.jpg


The hole could have been a little more to the drivers side. The manifold air temperature sensor is exposed, as is the warning switch on the brake distribution block. I will probably move the distribution block soon, and worst case I can probably move the air temperature sensor too. At some point I would also like to rig up a solenoid or vacuum diaphragm with a flap to close the hole when the temperature is low, but there's a fair bit of engineering involved in that.

Hood_Vent_Exposed_Electronics.sized.jpg


Hood_Vent_Hole_Inside.sized.jpg


The final product looks pretty good.

Rugged_Ridge_Hood_Vents_Installed.jpg


I've taken some measurements with an infrared thermometer and already noticed a dramatic amount of heat shedding. I drove around for an hour to get everything hot and the passenger side decorative vent only measured at 88 degrees, while the driver side vent with the hole measured 133 degrees. I was also able to put my hand on the hood and keep it there--warm but not hot like before. It really draws the heat out of the hood. Quality of the parts is kind of iffy, so I'm not sure how long it will hold up, but for now it seems to work alright.
 
With being unibody we are missing something most cars have. Venting in the wheelwell. The front of the xj is more frame like than any other part of the rig. And many of us are plated as well. Has anyone tried drilling like 1” holes in less structural area to help give that air some place to go? Most cars have air come in the front and escape by going down and sucked out the gaps on the wheelwell.
 
With being unibody we are missing something most cars have. Venting in the wheelwell. The front of the xj is more frame like than any other part of the rig. And many of us are plated as well. Has anyone tried drilling like 1” holes in less structural area to help give that air some place to go? Most cars have air come in the front and escape by going down and sucked out the gaps on the wheelwell.

Yeah, I would recommend against that. The radiator air flow (the only air flow that matters) of most cars is designed to duct into the low pressure zone under the car.

What car have you seen that vents the engine bay into the wheel well? That would be a first for me. The air in the wheel well is very turbulent and wouldn't exhaust well at all.
 
My thoughts are, the vents in the wheel well were to facilitate brake cooling but I could be wrong. :dunno: I usually see them only on performance vehicles.
There are some vehicles with what I would assume are engine room vents but they are above the wheel well.
 
Yeah, I would recommend against that. The radiator air flow (the only air flow that matters) of most cars is designed to duct into the low pressure zone under the car.

What car have you seen that vents the engine bay into the wheel well? That would be a first for me. The air in the wheel well is very turbulent and wouldn't exhaust well at all.

“Vent” is maybe the wrong word makes it sound like it has duct work. Really its just a gap between the inner fender and the frame that allows air from the engine bay and well to exchange in some way. Just remember when working on the YJ the heat coming up from the wheelwell was well hot. On the XJ this seems to be greatly reduced.
 
I have them. I have long fought with high temperatures, and the Hyline vents are one of the things that have helped.


The kit included a full size metal template that was quite accurate. Their instructions are complete, and they do not take any any of the internal support for the hood.


David Bricker / SYR
 
I've seen a lot of good ideas for vents to pull the heat but I'm thinking of adding the timed relay first. This year with more wheeling I'm getting the soak more often.
 
Just spent Saturday wheeling at 4,000+' and 100* temps. New stock cooling, ZJ clutch fan, RodLovers.com 16x7 vents, coolant temps stayed around 215* with the AC cranked. Still warm, but never overheated liked it used to without the vents. Was also able to pop the hood without gloves on. Granted, it wasn't exactly pleasant, but this used to be something that was impossible in these conditions.
 
I thought I already commented this but I don't see it. BleepinJeep.com has a set of vents for sale for $49.99. I ordered a set and will post pics once they come in.
 
I had my exhaust "manifold" off to weld up all the cracks.
While it was off I put a ton of header wrap and also fabricated a sheet metal heat shield
Then I made a hood hinge spacer kit with longer bolts
I assume this has prevented any underhood temp problems
 
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