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The highly lame: Hood "Risers"
Okay, so i've searched decent amount of topics here, and while I have no need to fix a current temperature problem, The science somewhat interests me, and the topic is always debatable amongst my friends.
As the topic says.. On MY Car, 1990 miata, with all a stock hood, and vented turn signals, 1. car running, say over 40mph a. air comes in thru vents? sucked in due to pressure b. would air come out and "vent" 2. car idling, 0 mph a. hot air does come from engine bay, and onto windshield u can see, but, theres no pressure then correct? some claim it vents, some claim good temp decreases, some say stupid "CR.net shit", like I said, not interested in doing it, i'm just wanting what you think about it, thanks |
Originally Posted by Blindsay
(Post 757701)
Okay, so i've searched decent amount of topics here, and while I have no need to fix a current temperature problem, The science somewhat interests me, and the topic is always debatable amongst my friends.
As the topic says.. On MY Car, 1990 miata, with all a stock hood, and vented turn signals, 1. car running, say over 40mph a. air comes in thru vents? sucked in due to pressure b. would air come out and "vent" 2. car idling, 0 mph a. hot air does come from engine bay, and onto windshield u can see, but, theres no pressure then correct? some claim it vents, some claim good temp decreases, some say stupid "CR.net shit", like I said, not interested in doing it, i'm just wanting what you think about it, thanks There is no 'highly debated' topic here. At speed, the windshield is a high pressure zone. Raising the rear of your hood simply raises the pressure in your engine bay reducing the effectiveness of your radiator. At idle, there would be no pressure, but if your car is overheating at idle, you have other issues. If you would be willing to spend time and/or money on a "performance enhancement" that would only provide a marginal effect at best, and only at idle, while actually REDUCING the performance of your car AT SPEED, then you're priorities are ass backwards. (Note: not YOU, you. The hypothetical 'you' ) |
Wtf, who debates this still? The area behind the hood is high pressure at speed, lifting the back of the hood will increase engine bay pressure and decrease cooling ability. |
Get new friends.
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GTFO
IBTL GFY FYCN DIAF EAD STFU have a nice day. |
What if you've converted your Miata to air-cooling?
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But I run a slightly elevated hood (bent), cut short rubber trim (about a foot removed from driver's side), and no splash shield on my car and my rad. fans don't turn on often.
Why? the cut rubber hood trim was an attempt to get the pressurized cowl air to the turbo area so my hood paint wouldn't turn brown, and I'm too lazy to install the splash tray, and I don't track my car, and I have a coolant reroute, and I have a slightly larger aftermarket automatic replacement radiator. My "big" intercooler is a tube/fin too so more air gets thru it. |
Various vintage V8 muscle cars use cowl induction to draw air from the high pressure region in front of the windshield.
And they knew jack about aero back then. |
wait, wait wait...
OP, you want to raise the hood to combat an overheating issue? |
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So as a cheap trick, I wonder if it would help on my car....
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A hinge-raised hood combined with halfway up headlights looks cool parked yo. To the uninformed.
But looking cool won't cool off your motor. |
LOL I know drifters fags that swear by this. They say it improves flow when the car is sideways. Did I mention they're fa66ots?
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Originally Posted by Bond
(Post 757794)
Did I mention they're fa66ots?
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Ballet, Dancing With The Starz, Figure Skating…
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don't care what you guys say. i bought some risers for $5 put them on in 4mins. and it definitely let heat out. in s. tx. traffic, while cruising, and at speed. yes that is a high pressure area in the center 12-18 inches. air does flow "in" a little in the center, stagnant near each end of those center 18", but flows "out" from under the remainder of the hood on each side. It was fine until i got a drop vent hood about a year later. only downside was i think it looks ugly, like your car was in a wreck, and everybody and their mama tells you your hood is open! it's not a vette :vash:
might not be a big deal in cali. or michigan, but in south texas it gets stupid hot. and i've had to replace a ton of my brittle underhood wiring from it. that was on my way to a pca event in the rio grand valley. i did put yarn all the way across the hood too see what it did at the track, but didn't get any video of it. like i've told other people though, ymmv. i had a splitter, and big hitler stache cutout on my bumper. not sure if that made it work better for me. |
I did the exact same test and my strings pull in at 40mph.
its a horrible vid, but at :06 i say "40 mph" and the inner string is sucked in and never lows back out. And that was just with the gasket pulled out. anyways, who gives a flying fuck how hot it is under the hood? If i move to TX I won't change a damn thing on my setup. |
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Originally Posted by spoolin2bars
(Post 757805)
don't care what you guys say. i bought some risers for $5 put them on in 4mins. and it definitely let heat out. in s. tx. traffic, while cruising, and at speed. yes that is a high pressure area in the center 12-18 inches. air does flow "in" a little in the center, stagnant near each end of those center 18", but flows "out" from under the remainder of the hood on each side. It was fine until i got a drop vent hood about a year later. only downside was i think it looks ugly, like your car was in a wreck, and everybody and their mama tells you your hood is open! it's not a vette :vash:
might not be a big deal in cali. or michigan, but in south texas it gets stupid hot. and i've had to replace a ton of my brittle underhood wiring from it. http://www.youtube.com/watch?v=ejPk2eBnr7o that was on my way to a pca event in the rio grand valley. i did put yarn all the way across the hood too see what it did at the track, but didn't get any video of it. like i've told other people though, ymmv. i had a splitter, and big hitler stache cutout on my bumper. not sure if that made it work better for me. https://www.miataturbo.net/attachmen...ine=1312824256 |
Originally Posted by pusha
(Post 757801)
they are ballerinas, emphasis on baller
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Originally Posted by sjmarcy
(Post 757811)
Don't tell me you run those gayass "Drift Charms" on your rear toe hooks too?!!?
https://www.miataturbo.net/attachmen...ine=1312824256 |
Originally Posted by Braineack
(Post 757808)
I did the exact same test and my strings pull in at 40mph.
its a horrible vid, but at :06 i say "40 mph" and the inner string is sucked in and never lows back out. And that was just with the gasket pulled out. http://www.youtube.com/watch?v=aF-UPdfHEzU anyways, who gives a flying fuck how hot it is under the hood? If i move to TX I won't change a damn thing on my setup. i replaced my IAT wire 2yrs. ago. the wire broke inside the insulation causing my car to cut out under boost, and only after warming up. during a 15min. drive or longer, the isulation would soften/relax and the broken wire would separate. once it cooled the insulator would contract, making the wire reconnect again. this weekend, it did the same thing at the track, killing my session. extreme example, but thats one of the reasons why i care. but then again, if you don't track your car in 105*+ weather every year, it might not be that important to you. there's better ways to do this, like what i have now, but for the money and time involved it's not a bad short term solution. |
Originally Posted by Braineack
(Post 757772)
wait, wait wait...
OP, you want to raise the hood to combat an overheating issue? Nope. Simply wanted a discussion, which I feel was successful after the first few immature posts, because some people swear "by the science" that it goes both ways... and at the latter discussion of drifters.. I hang out with drifters, I don't mind them, I feel like sometimes they simply ruin nice cars with their habbits, the zipties, the barrel smashing. On otherhand, theyre ballsy, and they do what they love, and ya can't say they park their cars, for most part theyre beat. *No i don't drift my car, I just hang with some, fun nissan guys, a few rx7 guys* and I never will drift it. |
sure it'll cool the engine bay, it's easy to figure out. But at what cost? sub-par cooling system? the engineers designed all the airflow from the rad to expel under the trans tunnel at a very low pressure zone...opening up the hood disrupts the pressure system. you start to draw air from the cowl back through the tranny tunnel and this causes less airflow through the radiator. If you already have a large IC in front of the rad, the negative effects on the cooling system is worsened.
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this effects every vehicle quite differently though, wouldn't it?
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You should try driving with your hood open.
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Originally Posted by Blindsay
(Post 758023)
this effects every vehicle quite differently though, wouldn't it?
You have a high pressure zone at the inlet to your radiator. You also have a high pressure zone at the spot where your windshield meets your hood. You have a low pressure zone back and underneath the car. Nearly (if not all) cars are like this. It's why you don't see radiators in the hood of a car (don't get me started on top-mount interwarmers) SO: You run an undertray and seal the rad inlet to ensure that you get maximum pressure at the inlet to your radiator with minimal seepage while avoiding higher pressure in the engine bay. You seal the hood off so that no other high pressure zones cause higher pressure in the engine bay**. Then you make sure that that undertray you are running exits towards the rear of the motor since the underside of a car is generally a low pressure zone. In the end, the high pressure at the radiator inlet is forced through the radiator into an area of lower pressure. The lower the pressure, the more efficient this process will be. I think the logic that most people would cite would be along the lines of "heat rises, therefore giving it a spot to escape at the back of the hood is good, since air enters in through the front, and therefore can exit from the back." Much like a turbo though, it is a combination of pressure AND flow. ** You CAN run a hood vent just behind the radiator as long as it is in a lower pressure zone on the hood. |
This thread makes me sad.
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This shit will not shit up the race section, fwi for those of you with any other "brilliant" ideas.
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If you want to reduce underhood temperatures, remove the heat source, the engine.
Per this discussion on CR and the fact that someone said Import Tuner did a test about hood risers on a Miata.
Originally Posted by Doppelganger
Yeah, read that article and it was rather really inconclusive. Randomly measured underhood temps. are no indication of airflow across the radiator. They also didn't say if it's venting or pulling heat out (given the physics of airflow, it would be pulling air into the engine bay). Lower underhood temps don't mean shit in all honesty...all engines care about is if the cooling system can properly transfer heat away. So intake temps in their test with their intake next to the hot manifold and near the firewall were reduced because air was coming into the engine bay at the firewall. Guess what? That is all air that could have passed over the radiator instead...which is slightly more important. Intake temps high? Try isolating the intake away from the damn header. Years ago, on my NA, I moved the intake ina box behind a TSI, put some extra shielding over the manifold, removed the coolant lines from the TB and I could put my hand on the IM at any time because intake temps were that cool (ambient).
So where did Import Tuner state any power gains or drop in coolant temperatures? Clearly that is what matters...not just underhood temps and slightly lower intake temps. Clearly the chickenheads running that "test" aren't to be trusted. "And keep in mind that these benefits were found by propping the hood of our naturally aspirated 1.6L Miata-we can only imaging how doing so (or adding a properly engineered, vented hood, for that matter) would benefit a more powerful turbocharged car, or an engine that runs hotter altogether, like a turbo rotary.".....really? So take a car that is now challenged at getting air across the radiator because there is now an intercooler blocking it and reduce the low pressure behind the heat exchangers by adding a lower path of resistance at the back of the firewall and I'm sure coolant temps will love you.....but hey, the useless AIR under the hood will be cooler!!!! You're not getting many serious replies because we've been through this discussion 72.5 times already. |
Yo dawg, i heard your underhood temps were high. So we installed an a/c unit in your engine bay!
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Let's see some more yarns and tall tale videos...
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If i can find string here at work, ill glady do a better video at lunch.
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I'd like to remind everyone that my Professional Datalogging Set already contains a convenient string dispenser. No need to buy this low-quality yarn, instead use pre-waxed, high-strength woven datalogging thread that is easily dispensed from a convenient carrying case.
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Originally Posted by Savington
(Post 758032)
This thread makes me sad.
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Originally Posted by SJPatMarcy90RMcCartin
(Post 758115)
I'd like to remind everyone that my Professional Datalogging Set already contains a convenient string dispenser. No need to buy this low-quality yarn, instead use pre-waxed, high-strength woven datalogging thread that is easily dispensed from a convenient carrying case.
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Originally Posted by SJPatMarcy90RMcCartin
(Post 758115)
I'd like to remind everyone that my Professional Datalogging Set already contains a convenient string dispenser. No need to buy this low-quality yarn, instead use pre-waxed, high-strength woven datalogging thread that is easily dispensed from a convenient carrying case.
It sounds like there may be some brainy video data soon enough. Make sure you dismiss it immediately! |
Originally Posted by spoolin2bars
(Post 758168)
where can we purchase this dataloggin you speak of? is there an aero version of it?
Originally Posted by sjmarcy
(Post 758176)
Information derived from data is how you resolve questions such as hood riser mods.
It sounds like there may be some brainy video data soon enough. Make sure you dismiss it immediately! Identify, Quantify, and Modify, that's my motto. |
I feel like under certain circumstances a decrease in airflow over the radiator is not necessarily a bad thing, while reduction in underhood temperatures could prove to have a marginal benefit. My last 2 dynos saw a 20whp gain on my car almost exclusively resulting from lower ambient temperatures. Isn't it reasonable to think that a street driven miata that has no cooling issues may actually see a power gain from installing hood risers and thus lowering intake temps?
I'm half tempted to go take my hood off and drive around to prove (or disprove) that, in some instances, less airflow across the radiator is not necessarily going to send coolant temps out of control. Not saying we should all go install hood risers, but I'm not entirely convinced that these things are actually the devil either. *Please don't ban me, lol* |
I would question whether one can apply results from a dyno run directly to real-world situations, particularly the (in)ability of even the biggest floor fans to replicate airflow over the car at speed.
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and heatsoaked ICers.
my AITs are crazy high on most dyno pulls. I always let the IC cool off on my last run on the dyno and get crazy elevated results. I give two shits about my underhood temps. My intake sources fairly ambient air, and my IC sheds 80-90% of all the heat the turbo adds. My cooling system keeps my coolant betwen 180-190°F in almost all situations, so I have nothing to gain from a reduction of 20 degrees at my fuse box and wiper blade motor. |
Then you've clearly never experienced fusebox heatsoak. Terrible thing that is.
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Originally Posted by mgeoffriau
(Post 758202)
I would question whether one can apply results from a dyno run directly to real-world situations, particularly the (in)ability of even the biggest floor fans to replicate airflow over the car at speed.
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Originally Posted by mgeoffriau
(Post 758202)
I would question whether one can apply results from a dyno run directly to real-world situations, particularly the (in)ability of even the biggest floor fans to replicate airflow over the car at speed.
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Originally Posted by sjmarcy
(Post 758225)
Which is why you should datalog on the roll. It's more real world than a dyno with a fan.
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Originally Posted by mgeoffriau
(Post 758231)
That's weird, I thought I just pointed that out.
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Originally Posted by FRT_Fun
(Post 758207)
Then you've clearly never experienced fusebox heatsoak. Terrible thing that is.
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Originally Posted by Braineack
(Post 758204)
My cooling system keeps my coolant betwen 180-190°F in almost all situations, so I have nothing to gain from a reduction of 20 degrees at my fuse box and wiper blade motor.
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my wiring harness is a boss.
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Impossible.
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Cconducting electricity.... Like a boss.
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Originally Posted by Reverant
(Post 758445)
Impossible.
I dunno, it's put me in my place. I'm bowing before it. I keep prodding it with my DMM and it's like "TROLLED BITCH." |
it doesnt matter it raises your oil temps so i would rather have lower oil temps. reguardless it looks stupid. give up trying to justify it.
this topis is so worn out and old. |
Originally Posted by turbotyla
(Post 758657)
it doesnt matter it raises your oil temps so i would rather have lower oil temps. reguardless it looks stupid. give up trying to justify it.
this topis is so worn out and old. |
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