Ideas for 165 hood vents

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Re: Ideas for 165 hood vents

Postby UtahSleeper » Tue Jul 17, 2012 3:20 am

So, zero, have you gotten any numbers?

On a side note, I am going to try and make a center hood vent, similiar to some of the carbon ebay ones for subies. Trying to go center ish, but a little further away from the turbo with a vent low enough to get the hot air out.
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Re: Ideas for 165 hood vents

Postby ZeroDrift » Tue Jul 17, 2012 5:56 pm

UtahSleeper wrote:So, zero, have you gotten any numbers?

On a side note, I am going to try and make a center hood vent, similiar to some of the carbon ebay ones for subies. Trying to go center ish, but a little further away from the turbo with a vent low enough to get the hot air out.



I've been too busy to take actual data as of late. The plus side is that the car hasn't had any cooling issues with the vents, radiator ducting and splitter. Have yet to encounter stop and go traffic in 105 degree weather yet, but did fine with 90 degree stop and go a few weeks ago.
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Re: Ideas for 165 hood vents

Postby 206st165 » Sun Aug 18, 2013 7:02 pm

I've actually been mocking up a design using 2 vents. The man center vent is off of a 06-07 Subaru STI, it's actually not the hood scoop but just the mesh that I see STI owners use when they swap to fmic. But in winter/rain season you can swap out to the hood scoop fairly easily. Then the second vent would be right over the intake box and that would be the turbo vent off of a 85/86 Nissan 300ZX Turbo Z31. Running this one would work with aftermarket intake cones or stock intake boxes. If using the stock intake box just the lid would have to be removed or cut and a thick rubber seal installed to seal the box the to bottom of the hood. As soon as I get a second st16* hood I will be cutting and adding my vents and definitely making a DIY
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Re: Ideas for 165 hood vents

Postby monkey8oi » Tue Aug 20, 2013 3:07 am

ZeroDrift wrote:After much searching and reviewing of aero information I have settled on a vent. Its stainless and I will rivet it underneath the hood so only the vents are exposed. Should add approximately 80+ square inches of ventilation and will be placed behind the headlights.

Reasoning for the place is several fold and will be tested both before and after the installation. Firstly I don't want to have the heat from the engine bay enter the cabin through the vents at the base of the windshield. Secondly, air should spill off the side of the car better when there is a side draft and placed further back will allow air to better travel from the front to the rear. Concerns about the headlights being up are put to rest as they will be down for the hottest parts of the day and this is primarily when heat is at its peak, so its a bit of a compromise but a practical one for both placement and overall efficiency.

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these look great!!! where did you find these?
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Re: Ideas for 165 hood vents

Postby ___Scott___ » Tue Aug 20, 2013 3:25 am

They look like engine compartment vents for boats. A quick search turned up these:

http://www.go2marine.com/product/27108F ... nless.html
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Re: Ideas for 165 hood vents

Postby ZeroDrift » Tue Aug 20, 2013 5:14 pm

___Scott___ wrote:They look like engine compartment vents for boats. A quick search turned up these:

http://www.go2marine.com/product/27108F ... nless.html


They are marine vents and are not bad for the price. Honestly I am considering of the other style of vents that don't have peaks, but rather a more simplified shape. Should be better suited for the application.
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Re: Ideas for 165 hood vents

Postby monkey8oi » Tue Aug 20, 2013 7:14 pm

I like the way these look a lot!! I will be looking into picking some of these up in the near future.. Thanks..
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Re: Ideas for 165 hood vents

Postby Eurus » Mon Oct 07, 2013 7:46 am

Any more information on Vent placement?
I picked up this from ebay and am planning on integrating it, but dont know how far back/ forward it should be on a st165 to vent heat from the turbo and Intercooler.

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I am also trying to figure out what to use the round hole for, is it ducted to to something in particular on the 185?

If no one has spent time checking where the pressure differences, in a st165 engine bay, are I wouldn't mind, but don't know how to go about this.

Also, how would one go about keeping water/ snow out with a huge hole in the hood, while still moving air?

Edit: New Info.
http://gtfour.supras.org.nz/ST185RC%20description.htm

So the above link answers a couple of my questions. The hole vents to the cam gear cover. It seems, with a little thought, one could just measure how far from the front the vent is placed on a 185, and match it on the 165; or is the body shape too much different?
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Re: Ideas for 165 hood vents

Postby GT4_DRED » Mon Oct 07, 2013 12:44 pm

There are a few guys on the board with that setup on their 165s; they used the original CS hood. I wouldn't rely on the same measurements from the 185 chassis for the 165, but the large opening sits over the manifold.
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Re: Ideas for 165 hood vents

Postby Eurus » Tue Oct 08, 2013 7:57 am

GT4_DRED wrote:There are a few guys on the board with that setup on their 165s; they used the original CS hood. I wouldn't rely on the same measurements from the 185 chassis for the 165, but the large opening sits over the manifold.

I have seen a few guys, on the board, run them. Im not sure what you mean by the original hood, I thought it was a 18 and 20 fitment only? Ninja edit: I guess you mean including the rear vents too?

Is there a way to go about measuring the pressures/ air movement, and how the vent would affect it, without cutting and multiple hoods or expensive software that I could only find at Lockheed Martin? I will do some more research, so expect a few edits again tonight (morning).

Also,if those who do run these vents could chime in, what do you do about the massive hole? Do you have a sheet underneath with louvers cut, similar to Evolutions 6-9?

Edit: I forgot to mention, I do have access to a Manometer, but dont know how to use it. Currently looking up that info now.


Edit 2: Sorry for rambiling on, and taking over this thread, but I want to do this correctly, though I guess Im not really starting the best way.

However, I noticed in the drawings on page 3 by Zerodrift, his hood is flat, but the Cs vent has a curve or hump at the front of it. Now Im not an engineer, but that hump leads me to believe that the vent actually has a way of sucking air out, same principle as a wings curvature? Im sure my wording is way off, but I cant be totally wrong about this.
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Re: Ideas for 165 hood vents

Postby UtahSleeper » Mon Nov 04, 2013 5:15 pm

I believe those vents suck air out of the bay from just the air passing over the bump right before the opening.

I don't know much about those vents, but if you look at some of the links Zero has posted it could help with figuring out placement.
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Re: Ideas for 165 hood vents

Postby ZeroDrift » Sat Nov 09, 2013 3:27 pm

I'm not sure which picture you were referencing Eurus. In the image where I have some lines drawn over the Rx7, the last version I put in place an upper air guide. Unfortunately I did not think of taking a picture of it at the time, but the upper guide did bulge slightly above the surface of the hood. Internally the guide was fitted closely to the fins on the radiator, and had sides to ensure all air exiting the upper half of the radiator exited upwards. The exit area was approximately 2/3rds the size of the area of the radiator (just the section that was guided upwards.)

This was a basic rendition of a concept that I saw on an old P-51 Mustang which had a large cooling unit underneath the main fuselage. The exit of this has an adjustable duct, which actually provides thrust from heat expansion of the three heat exchangers. By the way, if you really want to see aero work that is useful, look at slow moving aircraft and how they design ducting, transitions between surfaces, and of course control surfaces. There are many forums in which aero work is often hashed and discussed in great detail.

Image

As far as the purpose of a bulge before the vent is to create a low pressure zone which allows airflow from below to exit. Without the bulge airflow will become quite turbulent as the two air streams converge.

Edit: Look into tuft testing: Here is a quick video I did with the 'Trac: https://www.youtube.com/watch?v=lBx9PyYooUE

Also, just wanted to say thank you for contributing to this thread. Keep us posted on your findings!
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Re: Ideas for 165 hood vents

Postby Rick89GTS » Sat Nov 09, 2013 7:21 pm

Eurus wrote:Any more information on Vent placement?
I picked up this from ebay and am planning on integrating it, but dont know how far back/ forward it should be on a st165 to vent heat from the turbo and Intercooler....

I had the same problem on my 165, but it's just a case of trial and error. I made a paper template and tried to figure out the best placement in that gap approximately between the turbo and radiator. I marked it with masking tape before I made the cut-out on a spare hood. Some guys use a bent plate angled like the letter "Z" to keep rain out while still allowing heat to escape.

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Re: Ideas for 165 hood vents

Postby Eurus » Sun Nov 10, 2013 8:16 am

At ZeroDrift:
I did not notice the buldge on the last picture, so I wasnt sure if due to the CS vents curvature/ buldge i would need the same ducting as in your images, since it would create that low pressure zone. However, in my mind that low pressure zone would create a vacuum, not just keep the air from being turbulent. If that's the case, its only keeping air flow smooth, then I would need ducting to go along with it; though i am afraid to do so with the turbo towards the front of the car, as is seen in the last two images, you had ducting would be needed in front of the motor/ turbo.

At Rick89gts
I would be interested in a top down image of where the hole is above the engine bay.

Ive recently made the decision to start in SCCA rallycross with the celica, and therefore cant use this vent in my class. However, I still plan on doing it with an extra hood, once I have my garage back. Since its more about fun, than it is about rules I might see if I can just run the hood anyway.
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Re: Ideas for 165 hood vents

Postby ZeroDrift » Sun Nov 10, 2013 5:01 pm

I never did get a picture of the finished product. However you can see the vertical lip that was leading the opening. That flap was used to rivet the upper air guide in the final version. Also, a flap such as this is better than a smooth bulge from what I recall.

Image

The image below, the last image has the additional air guide I have been mentioning, which is crudely drawn. Note the changes from the middle picture and the lower. The upper air guide protruded above the hood roughly 3/4". It also reduced the overall vent area, which increases air speed (The closer velocity from different air streams that merge, the less turbulence).

Image

Food for thought. An opening on a flat surface, with high velocity airflow; will create a reduction in down force. Hoods of cars experience higher velocity airflow and a poorly designed vent will cause air to either go into the vent, or ruin good airflow characteristics that already exist. I've experienced this first hand with the Rx7. The first two open vents (picture above: no guide, and lower guide) caused the front of the car to feel very light (vague feeling) compared to a normal hood. The addition of the upper and lower air guide provided a smoother transition for the two air streams to merge, which increased down force (reduced lift from turbulence). However, the vent I was using is considerably larger than what most can even do on an Alltrac, so this won't be as much of an issue. The largest concern is ensuring air flows out of the vent, and not into it. Should air flow into it, you are increasing pressure behind the radiator which will reduce it's efficiency (counter productive).


Decided to make a quick paint sketch...

Image

Crude paint drawings of how air flows over a hood with a duct or vent of various designs. A and B are the same vent, but different scenarios of how air may interact with the vent.
A: This is counterproductive when moving as air flows into the vent. This increases air pressure behind the radiator, and reduces overall cooling ability. This is very detrimental for cooling, and will cause a lower pressure zone above the vent (increased lift). Vent design, and angle of the hood will have a great impact upon this.
B: Small amount of air may flow out while moving. Chances of air flowing outwards at speed greatly depends upon under hood pressure forcing its way up. Since under hood air is slow moving, this would cause drag/turbulence in all likelihood.
C: Forward leading edge causes eddy currents in the airflow. High pressure before, and low afterwards. Low pressure will assist/encourage air to flow outwards. The lower duct which guides air out increases the speed of air exiting to an extent. Airflow exiting will still be significantly lower compared to velocity of the main airstream.
D: Upper and lower air guides increase airspeed significantly. Vent area is reduced, but efficiency increases drastically. Air streams are more closely matched with velocities and minimal drag occurs. This is an ideal vent when ducted to to radiator directly. With proper ducting before and after the radiator, cooling efficiency should increase, and front end lift minimized. Should proper ducting be used, it should be possible to increase down force.
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