Hood Vent Tech (FM Live)
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- เผยแพร่เมื่อ 7 พ.ค. 2020
- We had some good questions and interest on our Fender Vent video, and decided this week to expand on the topic with Hood Vents! This week, Keith Tanner explains the theory behind them, why you might need them, and shows us some samples on different generations of Miatas.
Verus Hood Vents:
www.flyinmiata.com/verus-nd-h...
Singular NA Vents:
www.flyinmiata.com/singular-l...
Singular NB Vents:
www.flyinmiata.com/singular-l...
Singular NC Vents:
www.flyinmiata.com/singular-l...
LLD Fender Vents:
www.flyinmiata.com/left-lane-...
Join us every Thursday at 2:00PM Mountain time on Facebook for new live content! This is a quick overview video to inform our customers of this product, and is not intended to be a guide or installation tutorial of any kind.
Flyin' Miata is the world leader in Miata performance. We offer a wide range of parts for all years of the Mazda MX-5 Miata.
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Fantastic edumacation Professor Batshit!! Great presentation, learned a ton. Loved the story about the lab coat. Really enjoying your presentations during this stupid pandemic. Can't wait to see the whole FM crew back in the shop. In a future episode, could we discuss rear spoilers and wings - when they're actually useful, how to differentiate purely aesthetic pieces from those that have genuine functional value? It might give you the opportunity to demo that super awesome magnehelic gauge again!
Dr. this was the best hoot vent education I have seen so far. Thank you !
Thanks for watching!
Another brilliant video - thank you Keith for passing on your knowledge and experience (and dispelling the myths around vents cooling turbos and cooling from lifted bonnet hinges - Mr Bernoulli would be proud!). More please.....
Great stuff, very informative and interesting session. 👍
Thanks for watching!
This is a great video, loved the air pressure grid example! It brings up a lot of interesting points. I learned something NEW today, that ambient air is drawn into the back edge of the hood. Guess I'll move my 2012 GT500 air duct a little more forward on my Dodge Magnum hood, before I install it, lol. I know when I drive my 350Z with the weather stripping removed, the heat just pours out of the back of the hood when I'm in slow moving traffic and my KOYO radiator is getting a workout. A lot of factors/ variables involved and every car, it's environment and the manner in which it is driven must be considered.
Glad you enjoyed it!
When you're moving slowly, aerodynamics don't really enter the picture so there are no relative pressures. At that point, most of the air movement is simple convection: heat rises. There's very little other airflow to affect that, so the high point of the back of the hood is a good place for the hot air to escape. If your fans are running, that's pumping air into your engine bay so it'll escape wherever it can. Get some airflow over the car and the air will start moving differently.
Thanks for another great video!
This is one of the most interesting episodes yet!
Excellent presentation, I learned a lot, thanks for your efforts!
Thank you sir, it all makes more sense now.
After watching this I believe I'm going to build an annubar to check flow and pressure behind the radiator before and after hood vent install. Thanks for tips
Very informative!
Julian Edgar has fantastic videos explaining these things in a bit more detail, he is the guy that made the cold air intake popular
I have an 04 MSM with the Little Enchilada. I used to have a problem with overheating during the Georgia summers. One thing I did was pull back the rubber insulation on the top of the firewall behind the CAI. Using my UltraGuage I saw about an 8 degree drop in intake temps. I wish I could wall off the CAI but it is so crowded in that area. I did remove my diamond grill as Keith suggested.
This was amazing!
Thanks! Keith is a wizard!
I am glad that I found this video. I don't have a race car or even a Miata but what I do have is a 1996 GMC 1-ton dually with the 6.5l turbo diesel. So at least I have a diesel!...LOL
I am planning on putting vents in at least the fender on the turbo side of the engine. Did you know that NASCAR uses NACA scoops mounted backward in the rear 1/4 window to extract air from the passenger compartment? I am going to try that on my truck's passenger-side fender. I'll let you know how that works out. Why? these engines are known to overheat in some situations especially towing up a mountain.
NACA ducts mounted backwards are functionally just a hole. They don't extract any better due to their shape, as that shape is specifically designed to energize vortices which doesn't work in reverse. The reason they extract at all is because of the relative pressures involved and the NACA shape is not involved.
On the question of whether or not the vents cut down drag, the answer is possibly. In the 1930's or so, a Brit named Meredith did tests on airplane radiators trying to cut down the drag they cost so water-cooled engines could compete with the raw power of air-cooled radials. He found that proper ducting and exhausting the hot air from the rads could add enough thrust to almost completely offset the drag from the high pressure zone at the front of radiator. The questions are how big (or small) the hood vents have to be to optimize the Meredith Effect...
And whether or not it even matters at the speed a car goes. Cooling and handling may indeed be the only advantages in a car.
Thanks for the info. That's interesting.
Been wanting to add functional vents to my NB1...hmm 🤗
I would think that flap would break the attached flow on the hood and help lower the pressure behind it.
The pressure grid on a NC was very helpful, I'm considering getting the AD9 style hood from Carbon Miata for my NC. Some vents are in the right spot but there's 2 closer to the windshield where the pressure is high. Are those vents functional too? It's based on an aftermarket RX-7 hood so it could just be designed for a rotary.
Such a great vid. Thank you. What about fender vents? And if you’re running small over fenders as well, does such a mod serve any real purpose on an NA? It surely at least looks sort of cool:D
We did another video on fender vents. It might answer some of your questions!
I had a concept for a V6 (FWD 3.8L) mounted "behind" the rear seat of a second gen Corvair convertible with a ducted shroud for the radiator up front.
With that I had an idea of running ducts from a radiator shroud (behind the rad), past a NACA scoop, that would create a low pressure within the scoop, pulling the warm air from the shroud, past the scoop to an exhaust vent inches behind the scoop in a high pressure area (and a small fan between the scoop and exhaust vent for traffic stops).
With all that said, now the question; I'm guessing the farther away the scoop is from the radiator shroud, it would be less efficient?
Thank-you for the time. ;-)
Very useful
Thanks!
He knows what he is talking about because I can tell, and he has a white coat.
I have a 2003 and have been thinking about the singular hood vents. I also have a K&N intake on the car. My question is can there be a rain water problem with that? I know those vents seem to hangout right where the intake is. Being that I have a Florida car we get enormous amounts of rain sometimes and its a daily driver. So even just leaving my car in a parking lot doesnt sound like the best idea. I know you can get some sort of rain gutters? Or do I need to worry about that at all?
Getting a bit of water on the filter is not a problem. Submerging it so it can only suck up water, that's a problem.
Thanks, I've got a question...
The cabin in my 2009 MX5 gets hot since I put 4-1 headers on.
So a vent in a low pressure area drains high pressure air under the hood.
I like the idea of a vent (say 4" square) to drain heat. But above the headers is a high pressure area.
I'd like to cool the firewall and transmission tunnel too.
And because heat rises, a vent near the firewall seems logical.
What do u think of a vent in more of a low pressure area AND a 2nd above the headers?
Thanks, any ideas are appreciated!!
If that one above the header is in a high pressure area, it'll be counterproductive. Getting the headers ceramic coated would likely be more beneficial. We also have some heatshielding kits for the NC to cut down on heat transfer - we just did a video on them: th-cam.com/video/HM8_S6Mvoes/w-d-xo.html
Ggggggreat video !
When using the Magnahelic, did you just note the lowest reading and that is how you mapped the hood you showed the numbers on? Or did you use a different device to derive the data of the mapped hood? I have a couple Magnahelics and never thought to apply them as I THINK you did. Could you explain a bit more please? I have two vehicles I need to put vents on and want to make sure I map the hood correctly.
Basically, yes. All of the readings were lower than our reference pressure inside the cockpit, it was just a matter of how much lower. The important thing is the relative change across the hood surface, the actual values aren't that critical for what we're doing.
@@FlyinMiataVideo OK. Great. That is exactly what I thought you were doing. That was a very clever application of a Magna I have seen! I subscribed as I like your methods and see science in you (even without the Lab Coat)!
If you're using a differential pressure gauge wouldn't the cabin pressure not be atmospheric pressure when holding the gauge inside. Or did you run your atmospheric pressure line outside the cabin
It doesn't really matter what the reference pressure is as long as it's consistent. You're looking for the variations in pressure across the hood surface, not the absolute pressure on the hood surface.
Does it matter if the louver slats protrude above the hoodline or do they need to be under the hood into engine bay?
It does! You want them to protrude a bit as that will help generate a little more low pressure at the expense of a bit more drag.
Would Hood Spacers have the same type of effect? The ones where The Hood near the bottom of your Windshield gets Propped up??? Heat Rises so it should do wonders while Idling/Parked especially if you have a Short Ram Intake Setup right???
The base of the windshield is a high pressure area so hood risers are actually counterproductive if you are driving. A properly placed set of vents will give you the same convective airflow when parked and aerodynamic airflow when moving.
Curious if Polypropylene hood vents would be a viable option of should they be metal looking to cool down the engine of a 2015 dart
The material isn't all that important as long as it doesn't melt. The airflow is what matters.
Any recommendation on hood vents for ITBs on NC for increased intake & access to cold air? Are they necessary?
Hood vents are going to help almost any car lower the under hood temps by helping the hot air exit the engine bay faster, pulling more cool air in from the front, especially while driving. Necessary? That depends on the rest of your car and how you use it. If you are having heat issues, and don't mind the look of a vented hood, they would probably help.
would the absence of a skid plate also act as a vent from the bottom? or would it decrease performance as i can see there being extremely high pressure underneath the car
You don't want extreme high pressure under the car, otherwise it wants to fly. That's what air dams, splitters and front lips are trying to prevent. That's also why you don't really want to dump air under the car if you can avoid it.
Miatas typically develop cooling problems if you remove the engine undertray, it's a useful thing to have.
Could a scoop in a high pressure area effectively push air under the hood and onto the headers?
Then could a vent in a low pressure area (closer to the front) take the heat away?
It could, but there's no real benefit to trying to cool your headers. Better to insulate them and try to pull as much hot air out from underhood - a lot of that heat came from your heat exchangers, so you want to encourage flow through them and not just around the engine bay.
Thanks for the vid! I love the idea of remove eat from under the hood to reduce intake temperature, general engine temp etcetc. The only concern i have(and I can't find any answers) is that: could be a problem if hot air is going out from the vents instead of passing through "engine" and back under transmission tunnel? Thanks
Not really. In fact, it might actually help with transmission cooling since you're not blasting the trans with preheated air.
@@FlyinMiataVideo thanks for replying. And sorry if maybe it's a silly question, but maybe that air , even if it's hot, simply passing by let some eat exchange? It's maybe 100° celtius (i.e) , but maybe the transmission get 130°. As always thanks in advance
I have a D Max ute with a large bonnet scoop in the middle of the bonnet for the intercooler.
I'm guessing if I want to increase the airflow through this scoop I would need to place the vents behind the scoop even if that's not the lowest pressure area ?
I'm NOT driving at high speed, I would just like more cooling when towing :-)
It would probably still work best if the vents are at the lowest pressure area, the under hood air will be drawn there. It’s quite possible this will be in the “shadow” of the scoop.
Mazda ND have and I-Eloop placed under the air intake with BBR Turbo. Is it safe with water?
Anything under the hood already has a reasonable level of waterproofing.
Does adding vent on the side of the car that is ducted to the engine bay along with the hood help?
We did another video on fender vents. It can certainly help pull air through the heat exchangers but some of the other benefits are different.
going back to added downforce from hood vents, you compared the air above the hood vs in the engine bay and that makes sense because you're reducing pressure inside of engine bay which should reduce lift of the hood. Now what if you compare the air inside the engine bay vs the air underneath the car/tray cover assuming it has tray cover or flat body undertray in the front. Wouldn't this encourage a bit of lift at this point of the car due lower underhood pressures vs even lower pressure passing beneath the car or am I missing the big picture?
That's the job of your splitter and front air dam! A good front setup should give you a nice low pressure zone under the nose of the car. Remember the air is quite stagnant in the engine bay.
@@FlyinMiataVideo what about that MGB-GT in the background. I’m looking for a louver solution for my car.
@@jamesw.prescott2834 The MG is not exactly stock. It just looks like a B.
But if you wanted to louver the hood on that car, modeling the work after the E-type would look pretty darn good and probably work well. The trick is to find an old hotrodder who can punch louvers for you in that case.
I know this video is old and don’t know if I’ll get response but would your hi/low pressures be in relative same location on all vehicles? I’m doing vents on a Silverado hd, I’ve noticed thru research that sports cars (vets, bmw, mustang etc.) have them towards the front factory but on trucks it seems the factory puts them towards the back?
It could be that the big flat grille of trucks has an effect on the ideal location. We’ve never tested the pressures on one so we can’t say if what you’re seeing is driven by function or fashion.
@@FlyinMiataVideo I’m looking on Amazon for the gauge and going to find out next week 🤙 I was assuming something similar as you were describing what happens with the pointer noise of the car in video. Thank you for quick response.
Will the hood vents impact transmission temperatures by changing the airflow inside the engine bay?
They should mean there's less hot air passing through the tunnel. In my experience, there's still a fair bit of air going through there and it's hot air thanks to all the heat exchangers in the nose.
We have not done instrumented testing on transmission fluid temps before and after hood vents, though.
@@FlyinMiataVideo so it will coolthe transmission a bit?
@@ken1279 Honestly, I'm not sure. Less airflow through the tunnel, but it's such hot air I'm not sure there was much heat transfer going on anyhow.
@@FlyinMiataVideo thank you!
What els can I test the pressure as I cant find them tester here in aus with out being crazy expensive
Try googling "DIY Manometer". It won't be as easy to use as the gauges we show here, but you can make one for very little money. All you really need to know is relative pressures at various points across the bonnet, so units aren't important.
@Flyin' Miata Does the NACA duct affect the flow of the left vent? Thanks
Maybe. It depends on what’s being done with the air brought under hood by the inlet. If it’s going into a box with the engine intake in it, it won’t affect local pressures on the bottom of the vent. If it’s just dumping air under hood, it will probably decrease flow through that vent as well as the radiator inlet due to the decrease in relative pressure. In the case of the white Miata here, the NACA duct is a styling leftover from a previous incarnation of the car and is blocked off :)
Either way, it’s unlikely to make any significant difference to the pressure on the top of the hood vent.
@@FlyinMiataVideo Thanks for confirming that it was from a previous incarnation of the car! Appreciate the tech videos you have, very good stuff!
May not work on a slow moving off road vehicle in the Desert?
Right, most of what we're talking about here requires active airflow over the hood. For slow moving like rock crawling, you just want a lot of holes in the hood and good fans.
My clutch overheated once. Would these vents help with cooling the clutch ?
No, there is no cooling airflow through the bellhousing. An overheated clutch is one that's being slipped too much.
We have seen water spray used to cool an abused clutch, but it was an emergency pit repair in the middle of a competition - the crew rerouted the windshield washer sprayer into the bellhousing. Not something we'd recommend as a normal setup!
@@FlyinMiataVideo Thank you. It happened on my first day at the track . I'd never driven a standard transmission on a track before and I think I was using the clutch to slow the car going into turns.
I've learned not to do that anymore.
What differential pressure range gauge would you suggest to use for pressure "sniffer" testing like you demonstrated in the video? It looks like you showed both a 0-1.0 inH20 and a 0-3.0 inH20 gauge in the video.
It's pretty rare to need the 3.0 range when dealing with aero forces.
@FlyinMiataVideo thank you. In that case would you suggest 0-1.0 inH20?
@@metalmandoman It's probably the best choice for this sort of use.
@FlyinMiataVideo thank you for the advice! I appreciate it. The pressure "sniffer" implement you made places the "foot" fairly close to the sensing tube. Do you find that this close proximity disturbs the airflow and affects the pressure reading; or, due to the fact that absolute pressure measurements are not really important here, negate any disturbance effects?
Consistency is more important than the absolute numbers in the sort of testing we’re doing. We definitely wanted to get the tube into the local airflow for the surface and not into any separated air further away.
The implement in the video was not one used in testing, but was a mock-up quickly assembled for the video. Some dimensions may have been a little different.
What's wrong with putting vent behind the hood so hot air can escape through the back?
It's all about pressures. There's a region of higher pressure at the base of the windshield/back of the hood so it's not as effective at extracting air. In fact, we've seen "vents" back there act as intakes, pushing air under the hood instead of pulling it out.
Do you have any brand recommendations? I don't want to experiment with the stuff on ebay
Recommendations for Hood vents? Check our website. We sell quite a few louvers at the moment, and it really comes down to what generation you have and how clean you want them to look. The Singular kit for NA/NB miatas are very popular functional, but we also sell Spiked Performance hood vents and a smaller "knifed" louver set as well. We also have Verus louvers for ND Miatas that can be equipped with rain rails and are a very clean install due to the hidden rivets that can be retrofitted to earlier Miatas. Need more info? Feel free to reach out to our customer support team directly via phone or email. They'll be happy to help and answer any questions you might have!
Would putting vents on only one side create more downforce/less lift on one side compared to the other?
Not that we've tried, but probably.
I spy a Flyin’ MG in the background
Can you guys do a a grid-like pressure test across the underside and top of Each gen miata hood to determine best vent placement for each particular gen?.
I presume optimal locations would be based on the biggest difference in pressure but the amount of hoods needed to test all options makes that far to expensive to ask for as a test. At least we would all have the data to act on ourselves.
We have published gridded pressure tests across the top of the hood for the first three generations and Verus has released CFD analysis of the ND - you can see it all on our website in the hood vent instructions and/or listings. Underhood, things are fairly static so the variation is much lower.
@@FlyinMiataVideo maybe I should have looked harder. Thanks for the reply!!!!
Can I just glue them on or do I have to rivet them in
With the right adhesive, you could glue them on. We don't have specific suggestions.
How about a 72 corvette with an l88 hood? Where is a good spot for vents or vent?
You'll want to find the lowest pressure on the top of the hood, and the best way to do that is measure with a magnehelic gauge. It's going to depend on the shape of the car, so maybe someone in the Corvette community has already done this.
It will likely end up being similar to the areas identified on the Miata, as shown around 7:00 or so.
Flyin' Miata thanks very good information
So another words it’s to reduce heat lol From under the hood and keep lower temperatures? Lol even though you said it’s not for that that’s basically what you said in different phrase
Where do I get those louvers?
Which ones? We sell Verus AND Singular hood vents, as well as LLD fender vents on our web site!
Is he actually a car doctor?
More like mad scientist :)
Dear Flyin’ Miata, thank you for the informative video but please answer my email about the actual order I placed thank you
Aaron, we are sorry if there has been any delay in replying to your email. Our tech department has been swamped with an increased volume of e-mail recently since our phone lines have been off. Please be patient with us, some one will definitely be returning your email as soon as possible. Thank you for your patience and understanding!
oh i'm not sure , watch the WRC cars where they have an outlet .
th-cam.com/video/jvFdoTwjvvw/w-d-xo.html
Get rid of the camera person. Get a tripod.
great video! i have a question, is it making any sense to make air inlet into turbo? to keep it cooler? just air going on the exterior of turbo.
@MrMen98989 Thanks! It is ideal to provide cooler fresh air to a turbocharged car, which is why our turbo kits come with a divider to help keep the air filter separated from the ambient engine bay heat as much as possible. Fresh air comes in through the front bumper and is drawn in through the filter.
@@FlyinMiataVideo maybe i said it wrong, sorry, inlet on turbo, not in* not like air intake for engine to be sucked in. Air intake at the back of the hood going straight on turbo, only to manage turbo temperatures a tiny bit.
@@MrMen98989 The turbocharger should have no trouble dealing with the temperatures involved - it's built to do so. However, there are things around the turbo that might benefit from some protection from heat. Since you can't always depend on cooling airflow as it's dependent on vehicle airspeed and not load, it's usually best to add heat shielding instead.
@@FlyinMiataVideo perfect, thank you!