Serious cooling ducts and hood vents (think gt40) Now with pics - Page 2 - Miata Turbo Forum - Boost cars, acquire cats.

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Old 05-19-2011, 05:12 PM   #21
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Quote:
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Your ducting idea to get air from the radiator up to the hood vent is great, yes, I'm just saying that when you don't have that ducting, air that comes out of the back of the radiator circulates through the engine bay and then the air is evacuated out below/behind the engine. This helps to keep the air temp in the engine bay down, especially if there is a turbo. Ducting all the air leaving the radiator out the hood means that all the rest of the engine bay will essentially be static air, which is going to get superheated by the turbo and downpipe very quickly, which means some of the temperature sensitive things like the brake fluid and the air the intake is getting, might get much hotter.
how do you figure? did i miss the part where the op mentioned he has paneled underneath to make a flat bottom? all it takes is a little heat control wrap or wall blocking off that area. and thats regardless of wether or not he makes that duct to the hood.
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Old 05-19-2011, 05:33 PM   #22
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One of the benefits of ducting is evacuation of general engine bay pressure - if you don't evacuate it, it pushes up on the hood and creates lift.

Sealing the radiator to the hood is a cool idea in theory, but in practice there are other benefits that you're negating that don't justify the gains IMO.

Seal the front, vent the hood right behind the radiator, but don't let the rest of the engine bay miss out on the party.
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Old 05-19-2011, 05:42 PM   #23
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You might want to check out the Georgia Tech Wreck Racing car. They have something similar on their V8 lexus motor miata. They might be able to give some additional advice.
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Old 05-19-2011, 06:26 PM   #24
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It is hard to tell from your pics, but it almost seems like you will be creating a high pressure zone right behind the radiator, which would make it more difficult for air to pass through there.

On the other hand, if the airflow guide works well, and air flows right through the radiator and out of the bonnet, then you could easily end up running too cool, which would be problem.

I have a small extractor on my hood and do not use any ducting to/from it. My car often runs too cool on track, which requires me to block off a large portion of the radiator. Sometimes I struggle to hit 150F! Even with the front blocked, and on a moderate/cool day, coolant takes a while to hit 180F.

I think you may be fixing a problem you do not have. There is such a thing as "too cool".
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Old 05-19-2011, 08:16 PM   #25
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Hopefully this will help people imagine whats going on here.



Quote:
Originally Posted by Savington View Post
One of the benefits of ducting is evacuation of general engine bay pressure - if you don't evacuate it, it pushes up on the hood and creates lift.
Im not sure how there can be engine bay pressure due to the fact that the high pressure area would be totally sealed off. The high pressure area at the bottom of the windshield is also sealed by the rubber seal on top of the firewall.



In the above sketch, its the front of an na facing left, green is airflow, red in front of the radiator is ducting already there, the regular ducting most people have, and red behind it is what im building, and the maroon is the pipe tat I will set into the rear duct to let air pass straight through the radiator, straight through it and onto the turbo.

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Old 05-19-2011, 08:21 PM   #26
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Quote:
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It is hard to tell from your pics, but it almost seems like you will be creating a high pressure zone right behind the radiator, which would make it more difficult for air to pass through there.
People forget that the total area that the radiator covers is NOT the total flow area, the factory opening represents the size of the hole necessary for maximum flow through the radiator, this is because a lot of the frontal area on a radiator is the radiator fins and tubes, therefore the actual airflow gaps total the same size as the radiator opening or less. My design has at least the square area of the factory opening the whole way through the duct.

This is a pic of georgia techs angled setup, and for the noobs a sketch as to how theirs is different than mine.





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Old 05-19-2011, 08:36 PM   #27
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Duct the front, use a hood vent, win at life.
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Old 05-19-2011, 08:38 PM   #28
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Post edited due to general useless of hustlers post

Dann

Last edited by nitrodann; 05-19-2011 at 09:20 PM.
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Old 05-20-2011, 12:39 AM   #29
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He speaks the truth though.
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Old 05-20-2011, 01:44 AM   #30
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Come now curly, now your following hustlers lead.

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Old 05-20-2011, 02:16 AM   #31
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Where would your intercooler play into all of this? I like sav's split ducting. Similar to how I am doing mine.
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Old 05-20-2011, 03:49 AM   #32
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Intercooler is mouth sized and half the height of the rad, so half of the mouth air will be split into it.

Update morepics of build











This is not all final, Im considering this a mock up.

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Old 05-20-2011, 03:50 AM   #33
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Double post sorry

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Old 05-20-2011, 11:55 AM   #34
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Quote:
Originally Posted by wildo View Post
It is hard to tell from your pics, but it almost seems like you will be creating a high pressure zone right behind the radiator, which would make it more difficult for air to pass through there.

On the other hand, if the airflow guide works well, and air flows right through the radiator and out of the bonnet, then you could easily end up running too cool, which would be problem.

I have a small extractor on my hood and do not use any ducting to/from it. My car often runs too cool on track, which requires me to block off a large portion of the radiator. Sometimes I struggle to hit 150F! Even with the front blocked, and on a moderate/cool day, coolant takes a while to hit 180F.

I think you may be fixing a problem you do not have. There is such a thing as "too cool".
Hey newb, ever heard of a "thermostat"?

@ OP: I was having overheating problems in the summer with the A/C on during freeway driving - I know it's not racetrack driving, but hear me out - I put a vented hood on the car and it completely cured my problem. Even more surprising: after installing the vented hood, I would turn my A/C on going down the freeway, (which turned the radiator fans on) and the radiator fans were now able to increase airflow so much because of the low pressure engine bay that my coolant temps actually went DOWN with the A/C on - all the way down to thermostat temp - which means the hood vents were working so well that my thermostat actually had to close on a 90+ degree day with A/C on full blast with nothing more than a simple extraction hoood...

Just sayin'
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Old 05-20-2011, 02:11 PM   #35
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Just to repeat some concerns, you really need some air flow through the engine bay. You might think about some way to direct cool outside air to help with that that won't increase pressures too much. Something like brake ducting but for your intake and exhaust to help keep underhood temps from building up.
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Old 05-20-2011, 02:17 PM   #36
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These wheels. Want. Now.
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Old 05-20-2011, 04:10 PM   #37
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Quote:
Originally Posted by Savington View Post
One of the benefits of ducting is evacuation of general engine bay pressure - if you don't evacuate it, it pushes up on the hood and creates lift.

Sealing the radiator to the hood is a cool idea in theory, but in practice there are other benefits that you're negating that don't justify the gains IMO.

Seal the front, vent the hood right behind the radiator, but don't let the rest of the engine bay miss out on the party.
Exactly.
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Old 05-20-2011, 07:54 PM   #38
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I like it! As long as it works that is. Fast work.
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Old 05-20-2011, 08:45 PM   #39
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I've been looking at this for a while trying to figure out the ideal design. The best example I have come across is the BMW ALMS car:




Good luck making something like that work though.
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Old 05-20-2011, 09:16 PM   #40
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now that **** is awesome. Where do the two smaller ducts go?
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