Hood Ventilation Ideas
 

After a day elaborating on the topic, and with MM's help, I settled on an inexpensive, or rather completely expense FREE solution:

1. Remove the rubber seal in the back of the engine compartment.
2. Install a pair of 3/4" tall by 1/2 wide plastic blocks (I just glued them into the two off center holes on the panel where the rubber seal used to be mounted)

Close the hood. There will be a very slight resistance as you are locking the hood. That is because the rear portion of your hood cover is pushed up to enlarge the opening. If you look at the hood from inside the car you'll see now that there is about a half inch tall opening all across the width of the hood. If you look at it from the outside, you'll see no difference, and no misalignments.

This hefty little mod helps to reduce your under-hood temps by quite a bit and costs nothing.

Happy modding everyone.

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Original post
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I was looking into the vented hood ideal lately.
i really do like the looks of stock RX8, and don't want to change anything, especially the hood. I also am reluctant making permanent changes to the stock parts. (cutting holes in the hood). somewhere on the forums here i had read that people install a bunch of washers under the hood hinges, thus raising the back side of it, and creating an opening there, so the hot air could escape. But that creates a permanent opening. probably looks ugly too.

What i am thinking is to fabricate a little servo mechanism, that is tied into the my Int-X auxiliary output or just the temp sensor, and razes the hood hinges automatically based on the coolant temperature. as soon is the temp gets above a predefined threshold, the servo lifts up the rear portion of the hood, creating an opening to let the hot air out, thus increasing the airflow through the hood and the radiator.
when the engine is back to normal temp, the hood lowers itself. engine off: and the car is back to normal. no misalignments.

Basically what i am looking for as far as your guys input is concerned is the following.

Do you know of any ready to go parts, that can be used for something like this? if not, then i am open to ideas as far as what i need for a motor, and what other electronics i may want to consider using to get the thing working.

So far this is just my idea. I have not given it any more thought than what I had done to this point, so it is not a certainty that this can even be done, but on the other hand why not?

you have skills, so i won't say it'll be impossible but i'm not sure it'll be worth your time... i don't know where you're going to find lifting mechanism that'll allow the hood the open properly and flush the hood with stock fender heights. obviously something custom... imho, i think the best way would be to use two tiny airbags that's hooked up to the wastegate or bov with some sort of timer/pressure valve. for example, it'll go up only when you're boosting into 7psi+ :)

if you can do it, please make us a solid (not airbag) actuated lift to raise/lower the car a few inches. i know two things that'll happen then... you'll make tons of money, and you'll be our hero!

Man, this sounds overly complicated...

What about putting in mesh style vents - ala Lancer Evolution - where the triangle rotor shape is? Was actually discussing that about 2 months ago with another 8 owner...reason being is that when it rains all the water remains stagnant in the indentation, so maybe that would be a good place to promote airflow from the engine bay and over the hood...but I may be thinking about promoting airflow there wrong...

I already explained it. I don't want to cut the hood.

Also, regardless of where you install the vents on the hood, when moving at speeds, the ventilation will likely work, as there is positive air pressure inside the engine compartment due to the air pushed in through the front. and off course it will freely escape when the car is not moving.

Stick, what is the point of raising the car? what are you trying to accomplish? turn it into an off road? :-)

i'd love to pull into a new restaurant one evening and not worry about cracking my bumper... so would about thousands of others. +million other reasons :) but i'm afraid off-roading wasn't what i had in mind hehe

if you do make it, please make sure that it won't affect the handling.

I've seen in the past some hoods come with a vaccum controlled ram air. It might not be totaly what your looking for, but it was pretty cool cause it only popped open when you were on the throttle and when you let off it the throttle the Vac of the motor pulled it closed.

I do like the idea of using a vac or pressure actuator(s) to raise the hood.
Never thought of it that way, but it most sertanly is much more elegant than trying to fit a motor into this.

It is just that I don't want it to be tied into the TB pressure. but much rather the operating temps. My car runs hot when DD driven and not necessarily when in boost.
I mean it does not over hit, but it sometimes gets close, and that is what I am trying to eliminate.

Yeah I know, was just bringing it up. You could use something like that and over ride the system to bleed the vac off at temps but that might be alot of work.
I for along time have been looking into cutting the hood up to lower temps. I record over 160deg under hood temps all the time in 85-90deg weather after sitting for a few min. I'm still n/a I want to go forced but not till I can bleed off some of that heat.

Also as I put in the other thread.
"Get a bunch of yarn and cut it in to like 6inch pc then tape them all over your hood, tape towards the glass, yarn towards the headlights and go for a drive. Then you can really see what the air is doing over the hood of the car."

I'd really suggest that before anyone goes to buy a vented hood or add vents unless they just want looks or cooling while sitting.

I've also been looking into the idea of getting something like those e-turbos and using them to force air out of the bay.

if you lift the hood at speed, air will go in (because of the high pressure area at the base of the windshield with leads to things historically like "cowl industion" intake systems) rather then air go out of the engine compartment... which would probably hurt things more then help


...not to mention if it would work somehow, you'll be venting engine comparment air into your HVAC system

Anyone have any ideas how high the pressure gets at the base of the windshield?
I will do the experiment today. i will disconnect my boost gauge from the throttle body, and leave the hose loose in the engine compartment, and monitor the air pressure inside there while driving home.
If anyone could do the same but affix the boost gage hose at the base of the windshield and drive 80 mph and report, I'd appreciate that. if not, I'll do that myself on another day.
Basically I want to compare the pressure on the outside (at the base of the windshield, and on the inside) with the idea, that if the inside pressure is higher, I've got myself a project, otherwise there is no point in trying that.

Meanwhile, I looked at the hinges, and how they are setup on the car, and i think given the amount of space there, I could possibly get away with two little hydrolic actuators, and a solenoid.

The idea is to use the engine oil pressure to lift the hood, while controlling it with the solenoid.

I am also considering to make it a Kit, if there is enough interest off course.

So what.....
 

The pressure won't even MOVE a boost gauge!

You would need a much more sensitive gauge like a magnehelic, it will be in the "millimeters of water" area.....

The "high" pressure area is only at the center of the hood, once you get outside the wipers, it is a low pressure again, so lifting the rear of the hood would allow air out at the edges, but air would flow in around the middle.....

S

If that is the case then then concept of RAM AIR is completely reduces itself to completely useless, nevertheless it is quite widely implemented.

I am pretty sure that at 80 MPH, I'll see that arrow move a little. Think of all that air being pushed into your engine compartment with nowhere to get out...

Besides, i don't have a gauge like that anyway, but I would appreciate the input from anyone who does.

No problem, I have 3, I'll try the pressure inside and out, when I get a chance.

Ram air IS mostly hype, you won't gain even 1/2 a psi.....

The air being rammed thru the rad has LOADS of space to get out, thru the bottom, past the tranny. The only advantage to a vented hood would be in slow traffic or at a stop, to prevent the exhaust heat coming up to the top of the compartment and just soaking there.

S

Yeah Stealth is right, ram air is mostly BS, the gain from it being colder than underhood air is what most people notice.

It's hard to even hit 1 psi blowing into a pipe hooked to the boost gague and thats giving the air no other place to go.
If you look at Nascars they all (unless they changed it) get the air for the motors intake right off the the center of the windsheild, but thats at alot higher speeds.

Cool.
I'd appreciate the results of that.
well yes this is actually the main thing that bothers me. at idles, in FL sun and hit, it just gets too hot. Once I start moving the temps reduce. When i turn up the AC, the temps also stay at bay, as the AC on the position 2 and 3 will activate the cooling vents with it. But I don't want to run my AC on high speed all the time. it is annoying.

Plus just want to build something cool :-)

Trekk
You might be right. Cant argue with you as i just don't have the facts.
We won't know for sure until we do. Won't we? :-)

What about venting/ducting the base of the hood where the wipers seat? Instead of raising the hood just provide some ducting out at the back. You can locate it based on your pressure readings and where the stagnation pressure is lowest. You may have to do some cutting in your firewall and fab up some ducting or just mesh screens to keep the leaves and rodents out.

My second thought is you can buy a vented hood for around 600-700 from the forum vendors and swap it out and measure the differences to see if the straight venting helps any vs. stock. That way you can keep your pretty stock hood.

Please read post 1^.

Honeywell makes several damper motors and a modulation motors. Check a boiler supply company or building controls supplier. Some of the torqes go to 300psi. There are all types of input drivers for them also. Get a Honeywell tradeline cat. and look in there. Please post your results.

The low pressure zone is not at the center of the windshield.

"The "high" pressure area is only at the center of the hood"

I dont know what you have been smoking Mac11!

wtf are you talking about? Where is that quoted from?

Lots of big ideas. Here is a little one that actually works:

Remove the rubber seal from the cowl.

I think he's quoting me, but hasn't taken his meds yet....

S

You suck :)
But it's a good idea.

I'll try it.

I did it on mine and ran around with a laser thermometer for a few days.
When you are stopped, the heat pours out from that opening - which is not nice if you use the "fresh air" option on your A/C controls (I never do because I like to recirculate the new-car smell!). Temps there can be up to 160°F.
When you are moving, it "splatters" at a frequency that I suspect is regulated by some resonant effect tied to speed. I saw oscillations from ambient (around 104°F) up to 140°F.
Most importantly, it moved up my "break-over" ambient temp up from 107°F or so.
I can rage along at that ambient temp now, whereas before, I'd start to overheat with the A/C on and over 4000 RPM.

if that space between the hood and wind shield is a escape route for hot air, than wouldn't cutting the triangle dip in the center of our hoods help more hot air get out of the engine bay?

I know the OP counted out cutting into the hood, and his idea sounds better/easier than mine. Although I would rather like too just control the height of the hood with a #'ed switch.

When your are moving the back of the hood becomes a high pressure area, and air would move IN, exactly what you don't need.....

When standing still it would let hot air out, but cripple your a/c inlet, so it would be for hard core racers only. First prove your "hardness" by removing the a/c to save weight. Then the open-at-the-rear hood means something.

S

You could but the inside of this hood is a bit different then a standard hood on the inside because its aluminum.

yeah, I removed the rubber stripe from the back of my hood as well and I can see the heat waves poor out it now. And my oil temps are about 5-degrees cooler, and water temps about 6-7 degrees cooler at speed and around 3-4 degrees cooler while in traffic, confirmed with a sCANalyser.

It takes 2 seconds to pull off the stripe, and you can put it back quite easily if you want to. And it doesn't make anything look different.

Vents in the triangle is what the Veilside hood does.

Fabricate a vent that channels air through the little square holes in the frame (located just behind and above the tires) and out the fender vents. That will satisfy your desire for cooler engine temps, and ½ this board's desire to have functional fender vents :)

the optimal place for a vent is somewhere before or in the front of the triangle in the hood. Its where the flow seperates from the body (just wash your car and take it for a spin....) and can provide the best flow from the engine bay being in the area between the airbox/battery/ecu area and engine

I found a solution, and it works simply fantastic!
I even tried to switch back an forth to make sure the difference is there and I am not imagining things, and hell yes. It works great whether at high speed or stand still.
As MM suggested I removed the rubber stripe, and on top of it to increase the opening, glued in two plastick blocks about 3/4" tall, so whe the hood closes, the blocks push thecurve of it up a little, making the opening much larger.

That is it. Solved the problem of overheating right up. No more need for the 800 hood.
Costs $0.00 :-) and looks great.

I may post a coule of pics just to show where I had added the plastick pieces, if anyone really needs it.

Thanks everyone for your help.

Oh yeh, I don't care about drawing air from outside. Alwys recirculate. If I want outside air, I'll open the window. :)

Yeah, I forgot to mention the adhesive foam "chocks" I put along the edge of the cowl plastic to keep the opening at maximum.

I'm guessing the aerodynamics of the car create a low pressure zone under the car so when you are moving and drawing air in your cowl is it moving over and past the engine then down under the car and out. It would also create downforce if that theory is true. Too bad its beyond the equiptment I have to test this theory. Anybody want to loan me a windtunnel?


I think you wouldn't have to be a hardcore racer to appreciate more air cooling. I bet anyone that runs the oil temps upwards of the 260s would find this useful.

Dude, I don't know about the down-force, but whatever it is it works like a charm.

Here in South FL the FL turnpike it is very common to see people do 100 MPH and more during the rush hour. when you are going 80, it just feels slow, and cars are catching on to you and begin to pass.
At this speeds, usually if I go into boost (which is happening instantly, as soon as I open the throttle), the coolant temps would get close to a 100C in a matter of seconds. So I had to be real careful not to overdo it.

Today I tried it with the new mode...
I just couldn't get it there.

I was trying really hard to get the engine to go hot.
only driving it in 2nd gear at 8K+ rpm and around -15 - 20 HG with AF around 15.3-15.7 for probably a minute or more it finally got hot.
(By the way, I fixed that, and added fuel to get the AF to 14 in that area :) )

And in Idles, it just doesn't get hot anymore.

Oh by the way, I would like to say a special thanks to MM.
If it wasn't for him, I would have probably dropped at least a 100 bucks getting the parts to get it to automatically open (if not more).
Yes it would have worked, and it would be a cool thing to watch your hood rise while you drive, but I don't care. All I wanted was to get it to run cooler, so thanks MM.

Glad it worked for you!

Can we get pics?

or you can do what I did to mine

still a work in progress and needs the holes cut out and painted etc


https://www.rx8club.com/attachment.p...0&d=1186043578
https://www.rx8club.com/attachment.p...2&d=1186043578

A picture is worth a thousand words.

that would be a votex in a turbulent high pressure zone...

... which is also why the rain collects in the hood rotor symbol and dances around gently - there is no air movement :uhh:

I disagree that there is no air movement.

good for you...

now look at what an average aerodynamic profile looks like and see the flow boundary leave the hood around the 1/3 of the way and learn the reason for that departure from the hood is a high pressure vortex at the cowl area...
http://a332.g.akamai.net/f/332/936/1...z.misc.500.jpg

and then look at a functional cowl induction hood and how it directs air from the cowl directly into the carberator... wouldn't make sense to put an intake in an area where air is drawing away now whould it?
http://www.glasstek.com/Gallery/6566impala2CIHD2.jpg

That shit is not designed in the same way the RX-8 hood/cowl is. The center of the hood draws in very little/no air as compared to the outer edges. There is also plenty of airflow over the rotor shaped area and the "gutters" around the rotor.

I'd give a damn if it didn't work, and made things worse, but it works, whether by pulling cold air into the hood, or sucking hot air it out. Who cares? As long as it works and it keeps the engine cooler it is all that matter to me.

Amemiya make a $2-300 solution depending on carbon or fro. You can see from the bottom pic it vents out the back as well.

http://www.re-amemiya.co.jp/commodit...59858&scd=9295

http://www.re-amemiya.co.jp/commodit...bonbon_all.jpg

Would work, but would require cutting.