this is mine, toy hdj80+intercooler. Hood scoop cames from ISUZU TROOPER 2.8 TD.
Hood scoops (1 Viewer)
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Will it make sense to install (read carefully) the scoop backwards?
Bear with me and my theory.
Air enters through the radiator and warms up (so has a tendency to go up).
Air enters from under the truck. There are no wind deflectors and other stuff to coordinate air so it bounces off the axle, wheels and other components and blows in an uncoordinated manner.
So what we have is pressure forming under the hood while driving. While stopped we have a mass of air that also resides in the upper parts of the engine bay.
If we install the scoop the usual way (as it is used for intercoolers or air intakes), we try to push all the air downwards, in spite of it trying to go up.
What if we install the scoop backwards? Won't the air over the hood create a suction effect and help air flow?
Bear with me and my theory.
Air enters through the radiator and warms up (so has a tendency to go up).
Air enters from under the truck. There are no wind deflectors and other stuff to coordinate air so it bounces off the axle, wheels and other components and blows in an uncoordinated manner.
So what we have is pressure forming under the hood while driving. While stopped we have a mass of air that also resides in the upper parts of the engine bay.
If we install the scoop the usual way (as it is used for intercoolers or air intakes), we try to push all the air downwards, in spite of it trying to go up.
What if we install the scoop backwards? Won't the air over the hood create a suction effect and help air flow?
Jason Andrews
Modaholic
That would make sense! But summer is over here in the northern hemisphere, shouldn't we be reviving the engine block heather thread instead of talking about cooling?
That was a suggestion made to me by another club member.
That would make sense! But summer is over here in the northern hemisphere, shouldn't we be reviving the engine block heather thread instead of talking about cooling?
Hmm you need to heat your block way up north (12 miles from me) in Downtown
One thing that would leave a slight doubt is that if one has a leaking exhaust manifold then some gasses could end up being sucked by the vents below the windshield.
But on the other hand one could build lateral scoops for the air vents. Air could be sucked into the cabin from the sides and also leaves and other stuff would not get so easily into the ventilation system and disintegrate there.
And the off-topic stuff... Why do you need to heat the block? What temperatures do you have in Downtown
It's not a diesel so I presume no heating is needed. Over here we have -22*F sometimes. Starting seems rough but things become normal after a minute. No heating.
But on the other hand one could build lateral scoops for the air vents. Air could be sucked into the cabin from the sides and also leaves and other stuff would not get so easily into the ventilation system and disintegrate there.
And the off-topic stuff... Why do you need to heat the block? What temperatures do you have in Downtown
It's not a diesel so I presume no heating is needed. Over here we have -22*F sometimes. Starting seems rough but things become normal after a minute. No heating.
blarsen- great work! Any chance you could post some pics of the underside of the hood?
Could the Bernoulli effect result in a higher pressure at the scoop inlet, as the air stream suddenly slows down at the aft end of the scoop? Bernoulli's principle states that for a finite volume of fluid traveling through a confined space, high velocity = low relative pressure and low velocity = high relative pressure. The air accelerates to squeeze over the bump of the scoop, resulting in a lowering of pressure as it accelerates, but as it tumbles past the end of the scoop, the same total volume of air has more space in which it may travel, which means it decelerates after the rear-opening scoop terminates, which would place the higher relative pressure air in a convenient place for it to move into the scoop, assuming that this static pressure is higher than the static pressure inside the engine compartment.
Of course, this could also be affected by the larger-picture issue of the air flowing over the hood and then moving over the incline of the windshield...
Is there anybody on here who's still familiar with their fluid dynamics?
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This had me thinking today-
Stock 80- the air moves UNDER the front axle. The nose is relatively low and creates a large, low pressure area under the vehicle. The heat and air move down and out of the engine bay into this low pressure area.
Lifted 80- the air moves OVER and UNDER the front axle. The nose is relatively high and the space underneath is huge. Does this now create a much smaller low pressure zone under the truck?
So at higher speed (above 50mph) is the cooling less effective b/c the heated air exhaust from the engine bay has a much smaller low pressure zone under the truck?
In this case, would hood venting create more efficient heat dissapation?
Really, these are wind tunnel questions but just thinking that hood vents/scoops might be more valid on a lifted truck...
Stock 80- the air moves UNDER the front axle. The nose is relatively low and creates a large, low pressure area under the vehicle. The heat and air move down and out of the engine bay into this low pressure area.
Lifted 80- the air moves OVER and UNDER the front axle. The nose is relatively high and the space underneath is huge. Does this now create a much smaller low pressure zone under the truck?
So at higher speed (above 50mph) is the cooling less effective b/c the heated air exhaust from the engine bay has a much smaller low pressure zone under the truck?
In this case, would hood venting create more efficient heat dissapation?
Really, these are wind tunnel questions but just thinking that hood vents/scoops might be more valid on a lifted truck...
I finally got around to doing the Yarn test. The video is in two phases. In the first part, the Yarn is about 5" long. Got concerned the Yarn itself might be too heavy so I cut it in half to 2.5". The yarn on the far right isn't moving much because it is stuck to the tape. The hood scoop (If I go with it) would go like shown in the below picture. Another alternative is to put it on back wards facing the windshield to pull hot air out.
Here is the link to the video with the string tests. I went higher res so you could see the yarn
http://www.risingsun4x4club.org/uploads/Romer/Yarn.wmv
Seems like the flow is pretty good infront of the windshield washer dimples.
Thoughts?
The goal is not to reduce intake temp, but reduce under hood temps.
Here is the link to the video with the string tests. I went higher res so you could see the yarn
http://www.risingsun4x4club.org/uploads/Romer/Yarn.wmv
Seems like the flow is pretty good infront of the windshield washer dimples.
Thoughts?
The goal is not to reduce intake temp, but reduce under hood temps.
aren't the pieces of string supposed to stand up or something from being in a low pressure a zone. All I saw was them flapping in the breeze.
James, Had the same problem. If your running Vista here is the fix. Otherwise go into IE and change your default player to Windows Media Player
Open IE7 > Tools > Internet Options
Click on the "Programs" tab
Click on the "Set Programs" button
Click the "Set program access and computer defaults" link
Click the "Custom" option
Go down to the "Choose a default media player:" option and select "Windows Media Player"
Click the "Ok" button
Close "Default Programs" window
Click the "Ok" button on the "Internet Options" window
Rick - I was told by several people I needed to do this test as the pressure areas above the hood may not be a straight shot. Based on the video I think it is a lends to a scoop doing some good reducing the underhood temps. Now I know someone well say this doesn't take into account what will happen under the hood and they are right.
No comments on the video?
Looks like you had pretty beven air flow all over the hood.
Put that scoop were you have it mocked up.
ken,
sounds like you and the wife were having a good time being silly! hehe
you need more yarn, closer together
i can see that the middle of the hood is a big low pressure area. I bet if you stuck a raisin on the middle of the hood, it would not fly off.
the high pressure at the base of the windshield too (as when your wife says 75-80) I can see the yarn pushing away as the high pressure increases- it becomes more apparent the faster you go.
you have a high pressure zone at the front of the truck (given).
Air seperation from the surface = turbulence=slower movement= low pressure zone created.
I'm sure the ARB bullbar hoops are generating a lot of turbulence as well.
If the pressure from the engine bay is more than the air pressure above the hood (at speed) than the vent will always exhaust engine heat, at idle or at speed.
I think you will still capture a lot of debris, as it is still a scoop facing forward. maybe you have ideas on solving that tho...
sounds like you and the wife were having a good time being silly! hehe
you need more yarn, closer together
i can see that the middle of the hood is a big low pressure area. I bet if you stuck a raisin on the middle of the hood, it would not fly off.
the high pressure at the base of the windshield too (as when your wife says 75-80) I can see the yarn pushing away as the high pressure increases- it becomes more apparent the faster you go.
you have a high pressure zone at the front of the truck (given).
Air seperation from the surface = turbulence=slower movement= low pressure zone created.
I'm sure the ARB bullbar hoops are generating a lot of turbulence as well.
If the pressure from the engine bay is more than the air pressure above the hood (at speed) than the vent will always exhaust engine heat, at idle or at speed.
I think you will still capture a lot of debris, as it is still a scoop facing forward. maybe you have ideas on solving that tho...
alia176
SILVER Star
Romer,
The yarn test is showing me (nice video BTW) that if you install the hood scoop backwards (facing the windshield), the under hood hot air will be extracted. Unless an inter cooler is placed under the scoop (like the other two fellas), it seems illogical to me to face the scoop forward as you're simply over pressurizing a chamber that we know for a fact doesn't evacuate efficiently. Furthermore, water and snow won't be ingested by the hood if facing rear ward. Just my .02 cents.
Someday, I hope to have my daughter appease me with my vehicular whims such as conducting yarn tests!!
The yarn test is showing me (nice video BTW) that if you install the hood scoop backwards (facing the windshield), the under hood hot air will be extracted. Unless an inter cooler is placed under the scoop (like the other two fellas), it seems illogical to me to face the scoop forward as you're simply over pressurizing a chamber that we know for a fact doesn't evacuate efficiently. Furthermore, water and snow won't be ingested by the hood if facing rear ward. Just my .02 cents.
Someday, I hope to have my daughter appease me with my vehicular whims such as conducting yarn tests!!
wildsmith
SILVER Star
My rear facing Kenlowe scoop definately improved cooling. No numbers to back that up, just a lot less electric fan usage.
