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Hood Vents VS. Hood spacers? What are you running?

Okay this might be a stupid idea, but what if you mounted one or two small fans above the intake manifold pointing down at them to push all the hot air from the exhaust down under the vehicle. You would have to have a raised hood with a vent above the fans. cabin temps would likely rise due to all the added heat under the floor
 
first of all, since you already have a raised hood or vents, you are beating your head on a wall trying to force air down. hot air rises, so already you are trying to force it the opposite direction it already goes. if you already have a vent in the hood than using the fan to force air UP would have a far greater effect. but I still don't think it would help engine coolant temps much. just compartment temps (which might help somewhat).

wrapping the header goes a LONG way to help engine bay temps.
 
1bolt said:
The long term effects of running way too cool (and 160 is WAY too cool) are Cooler oil temps which means: increased ring wear, increased cylinder wall wear, increased bearing wear on all engine bearings, lower horse power and torque, MPG will drop dramatically as your ECU will never get out of open loop mode, so you will in all likelihood carbon up your engine badly... but of course you might just stretch your rods out, egg shape a piston or bore before the carbon becomes a problem, because you are in effect driving an engine that it permanently not warmed up all the way.

In short 160 degree Thremostat = very bad idea
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You are correct to a certain degree, but keep in mind, It doen't run 160 degrees all the time, plus the 91 year model has an easier computer to work with...not that I've had any problems such as running in open loop or too fat on the fuel. We ride around all the time in 4wd, so you ARE'NT going to get any fuel economy anyhow. As far as engine longivity, you would have to ride around all the time with black smoke pouring out your exhaust for that to be a factor. Heck...it's a toy...we run the pi$$ out of them anyhow...I just like doing it with the A/C on! Lol! Maybe I look at things differently, being I've raced cars all my life with a good bit of success...but ya only live once...why not be all ya can be! :D

clic to veiw my world
 
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I am running the LeBaron hood vents, 3 row radiator and a 180 thermostat.
It runs about 185 in 90 deg weather. It will go up to about 200 seting at a stop light, but cools right back off when I start moving again. If I was going to put fans in the hood, I would go to Radio Shack and get 4 of the pam fans.
they only draw about 300 milliwatts each and move quite abit of air.
O
 
larger radiator = more coolant capacity = cooler engine. period.

anything else is pissing up a rope.

lowering the temp of your thermostat does NOTHING. having a GOOD thermostat that doesn't impede water flow when open is a good thing, but running too low is bad, for many reasons which have already been covered.

electric fans are a bandaid, and you don't get extra power, you get a slight increase in throttle response in exchange for a horrendous load on your charging system. Most stock jeep alternators can barely power the single stock fan and you'll just be changing the alternator more often.

vents help MOST when moving at slow speeds. sometimes mine made it hard to see when wheelin on hot days..

xjchop2cheapxj.jpg


but i did it the cheap way, cut an old grille in half, cut holes in the hood and screwed 'em on. they let out a TON of heat man.
 
CheapXJ said:
vents help MOST when moving at slow speeds. sometimes mine made it hard to see when wheelin on hot days..
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Why would it makeit hard to see? I have had heat pouring out of my cowl hood and I can see just fine, since its just hot air, its not like there is any color to it. :looney:
 
CheapXJ said:
electric fans are a bandaid, and you don't get extra power, you get a slight increase in throttle response in exchange for a horrendous load on your charging system.
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so what your saying is now that the load of the manual fan is gone and the work that the engine had to do to push that thing isn't needed for the fan anymore, it isn't available for the rear wheels instead? that means losing the fan actually makes you LOSE power! damn. if it werent' for the fact that I got a mpg increase out of it I'd be puttin mine right back on.

great. now I don't just have to defy the laws of man, but physics too? I'm gonna get a stern talking to when I meet the maker. :D

as an aside: I use a yellow top optima and a stock alternator for 3 years. never had a problem with available power or failure yet. don't jinx me.
 
Has anyone ever put the vents on where the louvers are pointing foward? Force some air into there. I was thinking of doing that right over the front of the intake manifold. and maybe a thin louver across the very rear of the hood.
 
1985xjlaredo said:
Has anyone ever put the vents on where the louvers are pointing foward? Force some air into there. I was thinking of doing that right over the front of the intake manifold. and maybe a thin louver across the very rear of the hood.
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it has been debated in the past in various places. I have no real data or idea if it would work better or worse.

however, the theory is that air is being forced into the engine bay thru the radiator. if the vent is facing backwards the force of the air going OVER the fins in that direction create a low pressure on the underside like an airplane wing. this is supposed to help PULL the air out of the engine bay. in theory. so it is flowing through the bay in a fluid motion. reversing the vents would have a similiar effect as having fans blowing down. there would be two points that air is being forced into the bay and the air would have to exit out the bottom, which is essentially the process that is supposed to happen without vents anyway, so not sure if it would be bad or not.

the thing to consider is driving in the rain. the water would be forced into the vents instead of blowing past them. again, in theory.
 
well to add fuel to the debate, i habe noticed a big pick up and a small mpg better with the electrics, i have run two 10" fans and am now using three 9" fans. with a 180 degree thermostat i normally run 195-210. at highway speed i run just a shade hotter(due to winch blocking airflow) at a stop the fans will actully pull it down under 195. and the heat rising is kinda cool, but it has never been so bad to make seeing difficult. also the water issue is a non issue, if your stuff cant stand a little water you should really rethink your hobby choices





 
That is a nice set up looks really good.
 
CheapXJ said:
larger radiator = more coolant capacity = cooler engine. period.
anything else is pissing up a rope.
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A bit overstated it's not nearly that cut and dried. Why do you have hood vents BTW?

lowering the temp of your thermostat does NOTHING.
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Wrong, thermostats sole reason for existence on an engine is to keep X amount of heat inside the engine so that it doesn't run too cool.
Too cool = inefficient. period.

electric fans are a bandaid, and you don't get extra power,
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Parasytic drag on an engine is a physical fact of reality, lowering drag = more power. Typically you can expect 1 to 5 HP increase just from eliminating a belt driven accessory.

you get a slight increase in throttle response in exchange for a horrendous load on your charging system. Most stock jeep alternators can barely power the single stock fan and you'll just be changing the alternator more often.
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Horrendous sounds very impressive... actual amps drawn compared to what the charging system is putting out, and what it can handle would be even more impressive.

With an auxilliary electric fan ALREADY DESIGNED IN that must run when the HVAC blower is also going; I would say that the charging system can more then handle an electric fan.

My Electric fan + Aux OEM electric fan, have been running great for 40,000 miles (give or take a few) on what apears to be the original OEM alternator, or OEM replacement... which would have 240,000 miles on it... I'm also drawing "horendous" Amps from my Sub, 500wat amp 4 speakers, CD changer, AC, 7 Autometer gauges, fog lights, etc.

vents help MOST when moving at slow speeds. sometimes mine made it hard to see when wheelin on hot days..
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Probably true of vents that are positioned towards the front of the hood. Cowl vents have the most effect at higher speeds when the low pressure at the cowl allows air to be sucked down under the vehicle, on my XJ this means the open driver side cowl (the passenger side is sealed to the air intake box) is sucking cool air down into and past the intake, header and down pipe. Dramatically lowering underhood temps (about 20 degrees) when driving 30 MPH or more.

any slower and the heat raises up out of the opening cooling things off more than the normal hood configuration (about 10 degrees average), about half as much as 30 MPH+
 
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