- Location
- Wasatch Range
Same experience on my 2000, without precats. Heatsoak is less of an issue with the vents open than with them covered.
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Hood Vents -Pro's and Con's
- Thread starter PSoffe
- Start date
Same experience on my 2000, without precats. Heatsoak is less of an issue with the vents open than with them covered.
Georgia Mike
NAXJA Forum User
- Location
- Flowery Branch,GA
I installed a pair of Datsun 720 hood vents on mine last year. They were fake vents save for a small oval section, so i milled between the slots to make them fully functional. My wife works for an advertising place that also makes magnetic signs for peoples' cars. She got me a couple of pieces of scrap magnetic material that I use to keep the vents covered when I don't want them open. I usually only take them off when I'm on the trail. Simple and they work great.
Einulfr
NAXJA Forum User
- Location
- Puyallup, WA
I put LeBarons on mine; the needle sits just a hair below 210 now. The engine is going to run at what it's going to run at, no changing that really. So not a huge cooling gain, but I live in the PNW where it's rare to see 90 in the summer. No drip pans and I haven't had an issue with rain at all, and it rains here a lot. It is kind of cathartic to see the air refraction from the escaping heat billowing out of the vents at a stop light, though.
sidriptide
nobody of any consequence
- Location
- western massachusetts
this wont have the same effect. the base of the windshield is a high-pressure area that is often used to feed air into the engine compartment or more correctly, into the air induction system to let the engine breathe cooler air from outside of the engine compartment.
google "cowl induction" for plenty of reading.
this is also the reason the heating system air intake is right there.
so cutting a hole in the firewall would in effect feed engine heat and fumes into the passenger compartment.
an over-all bad idea.
lowering under hood temps is never a bad idea, but it depends why you are doing it.
do it because all the cool kids are doing it, NOT because your rig over-heats.
I was thinking about doing hood vents, glad to hear the input from guys that have ran them. My concern is this: Living in Denver and the front range of the Rockies, I see a fair bit of snow, and while I'm not worried about the snow, I am worried that after driving my jeep, new falling snow would melt on the hood, possibly forming icicles into the engine bay. I'd be concerned that even with a cover or plate of some kind blocking the vents, melting snow could still form ice around important engine components. Has anyone experienced this or have any thoughts on this?
iwannadie
NAXJA Forum User
- Location
- Gilbert, Az
I get that its a high pressure area but what about hood cowls or the people who raise the rear of the hood? Would that not also put those areas in a high pressure area right at the base of the windshield?
I am by no means arguing or saying you are wrong as I know very little about all of this. It just seems to me that if a hood with a cowl setup releases heat into that high pressure area you could give the heat a place to escape in a similar way. I also thought the area under the windshield cowl(wiper motor area) was sealed off from the cabin. Obviously cutting anything that would let fumes into the cabin is a bad idea.
notamos
NAXJA Forum User
- Location
- Fort Collins, CO
I live up in Fort Collins & have never had an issue w/ what you mention (nadler234). I run the bigger Napier vents.
I think you will find that raising the back of the hood raises that high pressure area up the windshield a hair and actually gives a bit of a venturi type effect. I could be wrong but that makes sense to me
sidriptide
nobody of any consequence
- Location
- western massachusetts
my assumption has been that any kind of modification to vent heat from under the hood "probably" works best at low speeds... like wheeling. whereas cowl induction is likely useless at low speeds, but these modifications/designs are targeted for specific uses and to be passive, at best, when not actually needed.
i haven't tested any of these theories for best efficiency, hell they could even be counter-productive at times for all i know.
your results may vary......
iwannadie
NAXJA Forum User
- Location
- Gilbert, Az
Good point on speed being an issue. The high pressure zone above the cowl would not be an issue while going 20mph I'm sure.
How about the effect on air flow at high way speeds with hood vents? Does air simple flow over the hood and vents like normal, does heat escaping from the vents and push air upwards disrupting what little aerodynamics the XJ has? Does the air flow coming through the radiator see any effect from the hood vents?
For me cutting big holes in a hood is not a good idea.
MikeT4
NAXJA Forum User
- Location
- Northern California
I also went a different direction.
There is a high pressure area right at the base of the windshield but that happens at highway speeds where there isn’t a problem with air circulation under the hood.
The problem with air circulation under the hood occurs while wheeling at low speeds, say under 10 mph. Shimming the hood, vents or cowl hood allows the circulation of air to exit the engine compartment faster lowering the under the hood temperature. That in turn affects the amount of time that the e-fans need to run, therefore better circulation better cooling at the lower speeds.
There is a high pressure area right at the base of the windshield but that happens at highway speeds where there isn’t a problem with air circulation under the hood.
The problem with air circulation under the hood occurs while wheeling at low speeds, say under 10 mph. Shimming the hood, vents or cowl hood allows the circulation of air to exit the engine compartment faster lowering the under the hood temperature. That in turn affects the amount of time that the e-fans need to run, therefore better circulation better cooling at the lower speeds.
Kidd XJ
NAXJA Forum User
- Location
- Alta Loma Ca
Is that the same steel hood from Reflexxion in Arizona?
rustyjeep21
NAXJA Forum User
- Location
- pocatello
I've been running genright vents for 5 yrs. no water snow or ice problems. The fan runs less and you can definitely feel the heat coming out.
Dmondeac
NAXJA Forum User
- Location
- Midlothian, VA
Looks like a glass hood to me.
- Location
- Aberdeen, MD
I believe i've seen mid-construction pictures of that, so I think it's homemade.
Not too hard, just split the stock hood, lift the rear, and and weld side panels on. Most of the time is in bodywork
Not too hard, just split the stock hood, lift the rear, and and weld side panels on. Most of the time is in bodywork
blistovmhz
NAXJA Forum User
- Location
- Vancouver, BC
What problems Don't speed holes solve? Guessing an extra 10hp on the dyno?
Read this thread again. There are plenty of us who have specifically said no problems with any of that.
how would melting snow form an icicle? it all melts away, there's none left to freeze.. hot and dry around my vents
MikeT4
NAXJA Forum User
- Location
- Northern California
Yes it is a steel hood, I built it from a hood that I picked up in the J/Y. It really brought the under the hood temp down while wheeling on the trails.
Last edited:
- Location
- Golden, CO
Do you ever notice any fumes inside the cab?
