Actual Effects of Hood Vents? - JeepForum.com
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post #1 of 36 Old 02-07-2012, 11:01 AM Thread Starter
Jeff9
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Actual Effects of Hood Vents?

I picked up a set of Lebaron hood vents for $4 yesterday from a JY. I'm debating putting them in.

I've seen many threads detailing installations of hood vents, but none that discuss whether or not they have any real effect on cooling. What have your results been?

Also, for what it's worth, I don't have a cooling problem.

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post #2 of 36 Old 02-07-2012, 11:13 AM
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You're a prime candidate for doing before and after testing...

Buy a multimeter with a thermocouple input option, and measure underhood temperatures in mixed driving situations/temps.

Install vents and test afterwards.
Would be nice to have real values.

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post #3 of 36 Old 02-07-2012, 12:58 PM
Azzy
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Some here, talks about a 70 degree reduction.

http://www.go.jeep-xj.info/HowtoBonnet.htm

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post #4 of 36 Old 02-07-2012, 01:08 PM Thread Starter
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I've seen that link before. I'm talking about coolant temps and effectiveness when idling or moving slow.
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post #5 of 36 Old 02-07-2012, 01:13 PM
chriskeenan
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coolant temps should stay the about the same, the thermostat wont let them fall below 195, even if you took the hood completely off.
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post #6 of 36 Old 02-07-2012, 01:24 PM
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Hood vents reduce the engine temperatures by about 5-10 degrees. The e-fan runs less often, and for a shorter period of time. They are effective on the road and on the 4x trails.

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post #7 of 36 Old 02-07-2012, 02:07 PM
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It worked for me. But I didn't use Lebaron vents. Definitely noticed when running the beach in 95 degree heat.

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post #8 of 36 Old 02-07-2012, 02:59 PM
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Anyone know how much of a drop in intake charge temp hood vents make as a result of lower under hood temps?

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post #9 of 36 Old 02-07-2012, 03:27 PM
chriskeenan
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Quote:
Originally Posted by kg4kzv
Anyone know how much of a drop in intake charge temp hood vents make as a result of lower under hood temps?

Chris
Probably not much, since at speed the air is forced through the radiator making it hotter, not that the jeep will know the difference since there's no IAT sensor, you'd have to rely on the o2 sensor to make fuel trim adjustments
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post #10 of 36 Old 02-07-2012, 05:16 PM
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Quote:
Originally Posted by Jeff9 View Post
I picked up a set of Lebaron hood vents for $4 yesterday from a JY. I'm debating putting them in.

I've seen many threads detailing installations of hood vents, but none that discuss whether or not they have any real effect on cooling. What have your results been?

Also, for what it's worth, I don't have a cooling problem.
Quote:
Originally Posted by Jeff9 View Post
I've seen that link before. I'm talking about coolant temps and effectiveness when idling or moving slow.

This fella has done all the hard work with proper results regarding temps and fitting location. ...

http://www.oman4x4.com/hoodvents.htm

Yessss .... its a TJ .... but its applicable to just about anything.


If however ... your XJ spends all its time in low range or at low speeds .... hack some holes anywhere you want ... as - if your fans are working properly - hot air will be blown out .... and as physics dictates ... hot air will rise out when the engines switched off.

If you spend time at highway speeds ... then the fitting location becomes a bit more critical for effective "venting".


Best locations for "vents" are in the rear, corner areas of the hood ... or even high up at the rear of the fender.

A 40series landcruiser or a jeep KK are probably, relevant examples ... unless you prefer the look of the euro XJ orvis models with fake vents ...

Easiest location to fit "vents" is the flat, unsupported areas of the hood ..

Since the XJ hood basically sits on the valve cover ... its also presumed that, thats the "hottest" spot - needing attacking with a bucktooth squirrel or a sawzall ..


I run spacers in the hood hinges since its easy. Also have a larger firewall seal to plug the gap between the hinges to stop unwanted induction air.

Did it lower underhood temps ?? ... marginally - but that wasnt the result wanted ... The goal was providing some additional underhood air movement at all vehicle speeds ... as moving air is cooling air - and static air, is insulative.

Coolant temp changes were also marginal as one would expect ... but the additional venting action does help stabilse the coolant temp somewhat ... in conjunction with a few other cooling system tweaks.

As mentioned above ... do some testing at various vehicle speeds and driving tasks.

Space up the hood hinges,
Space up the hood hinges with a larger firewall seal between the hinges,
Tape on some tell tails, especially under the hood along the rear, from corner to corner,
Do some temp tests if you can.

Dont forget the fanclutch needs certain engine bay temps to operate correctly ... and dont confuse any new underhood temps over 20mph ... with the temperature of the air being jammed in from the windscreen, disrupting the radiator air intake ..

When you think you have vehicle airflow all figgered out according to what you have been seeing .... bang in some holes and louvered thingos to duplicate the best result ... as close as possible.
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post #11 of 36 Old 02-07-2012, 08:19 PM Thread Starter
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Ahh Carves, I figured that it was only a matter of time before you joined this thread. As always, thank you for the information. I'm glad you mention that the coolant temp stabilized in your case with some more air flow under the hood. My Jeep typically "cycles" between 195-205* or so, but I'd like to keep that at 195* if I can...why not?

Seems like these things work. Looks like I'll put them in before I get my hood repainted in a month or so.
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post #12 of 36 Old 02-07-2012, 08:22 PM
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Carves, that link you posted is fantastic.
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post #13 of 36 Old 02-07-2012, 09:41 PM
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post #14 of 36 Old 02-07-2012, 10:14 PM
Carves
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Quote:
Originally Posted by Jeff9 View Post
Ahh Carves, I figured that it was only a matter of time before you joined this thread. As always, thank you for the information. I'm glad you mention that the coolant temp stabilized in your case with some more air flow under the hood. My Jeep typically "cycles" between 195-205* or so, but I'd like to keep that at 195* if I can...why not?

Seems like these things work. Looks like I'll put them in before I get my hood repainted in a month or so.

Yeah .... cant help meself ... Im just amazed that today, in a 'smarter" world ... people are still making the same mistakes, us kids were making 40 year ago when we were destroying hoods for that transam look ....


Stabilised ... in that temp variations are minimal ... ... Watching a digital temp gauge - You'll alway get constant variations depending on revs, engine load, inclines ..... yada yada ....

I'm content with 5*f ... BUT - theres a few things besides the venting Ive got happening ... that likely deserve more credit for the stable temp than the venting.

The corner venting just creams off any excess heat - thats not getting down the jampacked tranny tunnel as it should, when the vehicles moving or relying on the fans ....
... encourages a bit more radiator air intake ...
... and it lets a bit waft out after switching off.

... and theres no potential for adverse effects as with a scoop ... and it will vent better all the time compared to vents located centrally in front of the windscreen.

Its not a fix for a dodgy cooling system tho ... nor one insufficient for the driving tasks.

I'd be looking at t'stat, fans and radiator as the "cause" of your temp fluctuations .... and use any venting benefits as a bonus ... for when the going really gets tough .... or the tough go shopping ... or whatever the hell ya say over there ...
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post #15 of 36 Old 02-08-2012, 08:46 PM Thread Starter
Jeff9
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I'm not unhappy with the temp fluctuations...it's totally normal in nature. Everything is in good shape and is fairly new - as I mentioned above, my Jeep runs pretty cool. I'm just looking for a little bit extra when it comes to idling or wheeling/driving on the beach.

I wish you'd put an all-inclusive thread together of all of the cooling modifications you've done. It would be the "coolest" thread ever! <------------see what I did there?
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