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hood vents: ideas...


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My plans are as follows, to direct air into the front with aluminum ducting as has been done on here. Have the cold air enter in at the naca duct front, and hot out at the rear section (idling at lights) of the naca duct/louvered inspection lids and lastly cut dimple die holes in the rear fr fenders and apply metal ducting/tunnel to the side vents. Hopefully the hot, high pressure air will flow somewhat freely out the side holes and vents, or I will resort to adding small pusher fans for added flow as Bartman has done. 

http://forums.hybridz.org/topic/95218-functional-fender-venting/?hl=fender+venting

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I like that duragg. What if you put a small little lip/angle just before the "extractor" part, that might help create a vac... Maybe...

 

And they said it couldn't be done...  behold:

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or wait,  they might have said it shouldn't be done.  I wasn't paying attention again.

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Yarn stood right up after I added the air trip device.  Heat pours out at idle.  Not sure how much it does to relieve hood pressure, but you can gain leaps and bounds there by simply blocking most of the nose grill.

 

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Edited by cygnusx1
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  • 1 month later...

Here are some pics of the hood vents I installed in my Betamotorsports hood:

 

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I placed them based on the info I had from the tests and think we "should" have decent results.  Also, when I installed these, I decided to draw the hood down tight to the seal of the cowl.  Prior to installing the hood vents I would leave it loose and let the underhood pressure push it up against the hood pins.  That would result in about 1 inch of hood rise under pressure and would allow for more air to escape from under the car thru the opening. We'll see how this works out. 

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  • 2 weeks later...

The limited testing I did at the track three weeks ago had zero negative effect on the car.  I'll be at NCCAR next Saturday with the car and hope to get more track time in.  I'll report back.

 

Mike

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Miles is nearly at the appropriate method by using electric fans to remove heat from the engine compartment by creating a low pressure area by use of fans.  I have looked at a lot of posts regarding adding vents to get rid of the engine heat.  The vents will only be effective if they are placed in a tested and verified LOW pressure area.  The effective way of creating a low pressure area is by installing an electric fan.  Let's see what kind of comments this post creates.

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  • 3 weeks later...

Blokes, vents in red riding hoods for S30's should be designed for air exit, not entry. Crap? Look at the radiator inlet size and then work out where all that engine bay air goes to. I love aero :)

You referring to Mike's cowl induction style vents? They'll pull air out if they're in clean airflow, but not as well as a regular louver style vent would do. With the typical 280 vent position I think you're likely to get air out of them. Guys with cowl induction hoods were getting yarn alternating in and out of the hole, and these are mounted a couple inches forward and more to the side from that. 

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Blokes, vents in red riding hoods for S30's should be designed for air exit, not entry. Crap? Look at the radiator inlet size and then work out where all that engine bay air goes to. I love aero :)

 

Agree.  As stated before: CFM in = CFM out

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Pressure differential drives flow.  With the "right" splitter design and side skirts you could probably get air to flow in the hood vents, past the engine, and out the bottom.  By the same logic, you could imagine that hood vents affect lift and handling at speed also. 

 

When you want the air to flow needs definition to decide what works and what doesn't. 

 

Just sayin'.  I have no race car.

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For aero goodness, air under the car is bad, air over the top is good. Air under the car creates drag and lift and can only be useful if a rear diffuser is fitted. Air over the top can be used for downforce front and rear, both when considering the shape of a S30/130 and, particularly, with the addition of appropriate front and rear aero devices . I have learnt heaps just by observing racing Z cars in action. Typically a S30, for example, with inadequate aero will lift at the front at speed, stock S130 is much better.

Edited by 260DET
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Miles has the right idea.  The front grille opening should be reduced to reduce the amount of positive air pressure going through the radiator.  Secondly, the airfoil shape of the hood creates a lift on the hood.  The two forces aid each other pushing up on the latched hood.  Part of the goal should be putting a spoiler extending above the leading edge of the hood and testing different widths and angles of such a spoiler with tufts taped behind it along the length and breadth on the hood to make certain all the tufts are lifted from the hood surface negating the hood as a lifting body.  Then the  downward air dam and splitter can provide the necessary down force at speed.

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Yeh, vents in da hood are good for several reasons. The obvious one, gets air out of the engine compartment. Not so obvious, breaks up airflow over the bonnet, err hood, to reduce lift. And, to improve vent air extraction and make a bit of downforce, mini Gurney flaps in front of the vents. All tried and proven to work on avatar car.

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Get rid of all the lift force on the hood by putting a spoiler extending upward from the leading edge of same.  Then modify the flip up inspection panels, put Gurney flaps in front of them, so they can vent out pressure under the hood.  This goes along with reducing the grille opening and ducting the smaller opening to the radiator.

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Get rid of all the lift force on the hood by putting a spoiler extending upward from the leading edge of same.  Then modify the flip up inspection panels, put Gurney flaps in front of them, so they can vent out pressure under the hood.  This goes along with reducing the grille opening and ducting the smaller opening to the radiator.

You're suggesting installing a spoiler on the leading edge of the hood? Seems like a drag and lift creation device. The area behind a spoiler is a low pressure turbulent wake. Put one on the leading edge of the hood and you're creating low(er) pressure on the hood than would have been there without it. The Gurney on the leading edge of a vent reduces the pressure behind it and helps pull air out of the vent. If there is no hole behind the lip, you're just making the situation worse.

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If anyone wants a practical demonstration of how much under bonnet pressure builds up on a standard S30/S130, just unlatch the bonnet at the rear and go for a drive, very preferably in a safe place because at quite low speeds the rear of the bonnet will lift up and obscure your vision. This happened to me accidentally when I drove out of the pits onto a race circuit with the bonnet not properly latched, from memory at just 80k's the bonnet lifted right up at the back which got me thinking. At the same time after a few laps the engine was overheating badly, all part of the same problem with the same cause. Lack of airflow through the radiator cause by air backed up behind it in the engine bay.

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This issue of hoods lifting was mentioned right after the wind tunnel test as well. I don't believe that the hoods lift ONLY because there is high pressure under the hood. There is also low pressure on top of the hood. The old experiment to show Bernoulli's principle applies: hold a piece of paper by the bottom corners and let it fold away from you. Blow over the top of it and the end of the paper will pull up towards your airstream, with no extra pressure forced under it. In the case of a Z, there is both low pressure on the top side and high pressure underneath, so to say that it lifts because there is air packed underneath misses a big portion of what is going on.

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