extraction hood
 

Inspired by http://www.rx7club.com/showpost.php?...78&postcount=9

Here are my plans. Areas outlined in black are the areas I plan to remove. Then I have to figure out the mesh. Will be used in conjunction with TSI's. Right now I have no front turn signals at all, I figure that's going to be a problem (ticket) eventually.

Comments welcome.

what do you think about this?
 

I think a vent directly over the turbo will do the best job of releasing heat in traffic.

Ben, the vent you have drawn on the passenger side of the hood looks to be right over the fusebox. I'm not sure i would do that for rain issues.

For turn signals, wire your front parking lights to flash. Should be two butt-splices per side and some heat-shrink if you're feeling daring. I've been running with no blinkers aside from those for several months now with no issues.

nice car ben why is it the real fast ones start off as silver ;) yeah don't put a vent over the fuse box man that could be bad. Are you sure there will be enough area to flow the cfm you need to cool the setup?

Good call on the fusebox. I should have thought of that. Glad I posted, I would have taken a hole saw to those areas to punch out vents for proof of concept.

One of the motivations for removing an area "inside the frame" is to assist me make the cuts. I am good at many things. Body work is not one of them. I think your concept is superior Rob. But I don't think my abilities are strong enough to make it come out looking right.

Richard, how affective they'll be, IDK. It's worth a shot. A hood was donated to me for the cause.

Looks like a good project. Let me caution you on the TSIs (no turn signals in your case) as I have said it before, but someone actually took the time to pressure test TSIs and while they make your engine bay feel cooler, it is self defeating if you are doing the hood for heat issues b/c it actually pressurizes the engine bay (obviously less so with an extraction hood) which results in less flow thru the radiator (and IC for that matter) which kinda defeats the purpose of an extraction hood in terms of cooling/overheating. You might be trading radiator flow for engine bay flow which might not be the best thing. While your engine bay may feel cooler from the airflow, it certainly may worsen coolant temps. An extraction hood works the exact opposite by decreasing engine bay pressure thus creating more flow thru the radiator and more heat exhaust from the engine bay. YMMV.

As a solution that would make more sense if you are concerned about IATs would be something more along the lines of BEGI's cold air box with a NACA duct as you would get cool air to the intake without pressurizing the engine bay.

Well Tom we will see. I have an AIT sensor and the ability to datalog it. Proof will be in the pudding. Or not.

Here's what I've learned so far early in the hot season. With default MSPNP fan control I would run between 205-211 F on the street. After boosted runs it takes a long time to cool down from 211 to 205-206. With the turn signals removed I run 203-207 and occasionally hit 211 briefly on boosted runs. The cool down from 211 to 203-205 takes a minute or so. With turn signals removed and the second fan coming on at 206 I run 203-207. Haven't seen 211 yet. My Peak IATs (130-133F) are the same after mods, but IATs return to "normal" (100-110) much more quickly with the turn signals removed.

Tells me a couple things.

• Getting air flow across the motor is a good thing
• The under hood area is definately pressurized because the cooling fan shouldn't make a difference when driving at speed, BUT IT DOES.
• My CLT and IAT are lower with the turn signals removed. Datalogs show it

As far as a cold air source for the intake. That will be addressed. But what I've noticed after getting home is that my intercooler feels cool to the touch, as does the cold side pipe going towards the throttle body. However the throttle body up pipe is HOT to the touch, like the intake manifold. Getting airflow across the intake mani should help keep IAT down.

Now my plan is to place vents in two locations. First, a vent behind the radiator to hopefully facilitate drawing air through the mouth, various mouth located heat exchangers, then out the hood's first vent. The second vent location is to facilitate drawing outside air across the engine compartment while driving. I'm hoping that the cumulative effect of all the vents will more than offset the additional pressurizing caused by TSIs. If warranted, additional vents can be created, or the originals enlarged if possible.

I have datalogging capability and use it every time I drive alone. If the plan works or fails, I will have little invested in it. I can ride with and without turnsignals to see if there is a difference after the hood is opened.

I'm picking up the donor hood tomorrow morning. I plan on running the front vent, no matter where the rear vents end up. So I'll go ahead and take a hole saw to that area in the front and see what happens.

IMO, it's worth a shot. The worst thing that happens is I destroy a hood that was going to be thrown out anyway.

Ben

nice i look forward to this if it works i might massage mine some more and get a cold ram air intake.

There seems to be a big rush on extractor hoods.

http://clubroadster.net/forum/viewtopic.php?t=9247

http://forum.miata.net/vb/showthread.php?t=235257

http://forum.miata.net/vb/showthread.php?t=236055

http://forum.miata.net/vb/showthread...highlight=hood

http://forum.miata.net/vb/showthread...ight=hood+vent

http://forum.miata.net/vb/showthread...ight=hood+vent


Do not forget to read this thread
http://www.msprotege.com/forum/showthread.php?t=100489

I really like how this venting was done. I'll be doing similar on mine.

http://www.clubroadster.net/forum/viewtopic.php?t=9191

Or.... my photoshopped variant....
http://www.imagestation.com/picture/...b/ea2c40eb.jpg

OK, how's this? 3 small squarish vents up front, 2 wider rectangular vents near the back of the hood. Thinking I'll try to 2 blue ones first, and if needed, go for the 3 red ones too. One of my thoughts was with a basic rectangular shape, I can use some body filler to make small lips on the leading edges.

I have to keep it simple. I'm not good with body work or metal fab.

Why not just do one strip up front? instead of 3 little rectangles? Like the first picture I posted, but more towards the front and wider.

From the hunting around for ideal venting and such... I'll be doing the 3 ducts (could be one, I guess its the ricer in me wanting to do 3 in the space of one) in the hood as pictured and an undertray. Enough to develop airflow for the radiator/fmic etc.... and thats the focus.

Like this? Possible. Just afraid of cutting the "frame rails" close to the hood support. What I do like about this is again I could build up a lip on the leading edge, that would not only create a greater pressure differential, but could look pretty pimp too.

Dave, bear in mind your fab skills are far more advanced than mine. Not that I'm bad with my hands, just no experience with this (and no proper tools)...

From my hood modification browsing, I've seen a few people cut out all the webbing on the hood except for the frame around the edges. They've said it makes it flimsy while open, but no issues while closed. I had planned on no skeleton for mine... and also was thinking of the leading edge having a lip.

It should just require something like a dremel and a set of pliers and patience.
Plan was to tape it off, mark it up, cut a very wide H, with the lower side of the H being much smaller than the top. Then carefully starting to tweak the metal on both sides until its where I want. I'll be adding sides to mine, but I have a friend who can TIG... so thats kinda helpful ;)

So you're saying just cut the "H" and bend the hood at the slit to form a shape. Not just cut a big rectangle. Sounds like a plan.

I don't have a 'real' dremel. Mine is the rechargable battery kind, 12V IIRC. Not up to the task. My buddy has a JIG saw. Was going to use it with a fine metal blade, as recommended earlier.

Should I heat the metal up when I bend it? Or use something behind it to "curl" it in the shape of a vent. Hmmm...

re: tsi - rather than contending with the tsi pressure issues, put a 3" hole under the driver headlight and build a box around the headlight and airfilter. The turbo doesn't need any pressure, just a cold air source. This way you'll get what you want/need - cold air source w/o the pressure.

I think a cutting wheel is the tool for the job- saw blades/teeth are a bit too rough for the thin aluminum. I did a bunch of cutting on a hood for engine fitment and it was all with a 4" grinder (wheel gaurd removed) and metal cutting wheel.

good article on shroud engineering for the mouth
Just like a turbo setup, you can improve the system without having to go "bigger" - scroll down to "the curves have it"

On a different car with an aluminum hood, I had success using those small cutting wheels made for a handheld drill.

I went to HomeDepot and picked up 36 TPI very smooth cut, thin metal jigsaw blades. I also got some 3" metal cut-off blades and a mandrell to use them with my cordless drill. I can give it a shot, and hopefully clean up the edge easily with a grinding point on the drill. :x:

I'm going to try Splitime's "H" concept and bend the leading edge up a bit, and the trailing edge down a bit. If I screw it up, I'll just cut a big rectangle out.

cut the leading rectangle and form the rest of the hood up to make a cowl this will create a low pressure region after the hood and keep alot more water out. that is just what i can see though could be wrong. it might take a little heat/hammering to get it to look right but this would be a simple solution

This thread makes me want to hack my CF hood... just don't know what and how to do it

I think I get what you're saying, and if I do it's the opposite of what needs to happen. The front edge will be slightly raised which will help increase the pressure differential over and under the hood at the opening. Then the rear edge will be pushed down towards the motor a bit to create a scoop to help direct the air through the opening.

no so long as there is abit of overlap to the edges the increased velocity should create a low pressure system. This would be like running a scoop to funnel air in but in reverse you beat the hood up in the triangle and stretch the metal to a point of about 2-3 inches above the highest point. you might tig on abit of an extension or part the hood and add abit more aluminum to stretch it easier. This should siphon air though. forgive the paint work Not all of us are as artistic as scot and Adam

I understand what you mean. Would look cool to replace the power buldge with something like that. It would be like the Simpson hood.

c h a r a c t e r s

Ok, did the H thing. Best tool to cut with was the jig saw with fine metal blade. Only problem was the drill holes to get the blade in. After that, the saw cut smooth and clean. Too bad I didn't figure out the "scroll" function of the saw, or I would have only had 1 drill hole instead of 3. The worst part cosmetically is how I tried to grind out the drill holes. I should have left them and gone over with filler. Cut the H, bent the rear flap down, bent the small front flap up. It would look super bad ass once cleaned up.

Obviously I didn't do any prep work to the hood for cosmetics. And it looks 10x worse in the pics than it does in person. I am going to try it out some more, and after I make final adjustments--IF I deam the idea sound (more on that coming)--I will prep it up and try to make it look purdy. I was too eager to try it to clean up the edges.

So on the car it went, and I went off for a drive. I have a typical drive I take after making changes. I always do the same thing. 5 minute warm up, take the same route starting like a granny, go to this end of a dead street, turn around and come out WOT 1-4. Then I drive around a lake... The whole thing is about 15 miles.

Here's my take from watching the laptop as driving, and also going over the datalogs.
My peak IAT after 4 gears at WOT was 4 def F less than yesterday's run from the exact same drive. But what was really interesting was typical IAT. About 10-15 deg F lower. In fact, cruising IAT was appx the same as IAT before driving anywhere. It was 92F before I drove away, and it was 96F when I got back into my driveway. It's usually 110F or so.
Coolant temps were about the same. 203F going to 207F in boost. Hit 211F once briefly. The peak numbers were the same, but it spent much more time at 203F than before. The car seems to like to hold itself at 203F. It has a factory thermostat in it still. Next coolant flush, I have a new thermostat for it.

Next experiment is replacing the turnsignals and seeing what that does. After that, I am going to vent the area over the turbo. I'll do it symmetrically with a matching vent over the intake mani.

Hood installation is easy. So if anyone else in the area wants to try it out, you're welcome to.

thanks for experimenting, I may do something similar.

When I was finishing my turbo stuff, I ran over my hood after I set it down in the yard so it's kinda ugly anyway.

Damn that sucks about the hood al, hack that beast up.
That drop in IAT is awesome though.
What's next on the venting project?

Looks cool man, I might do the same thing on my hood, going to mock it up and see tomorrow.

nice i look forward to more results

ben- were you running the stock undertray?

yes, though it's been "modified" for IC pipes.
I am also going to cut out the hood per your location idea, however I'm only going to remove a smaller area, inside the frame rails only.

So Ben, you going to mass produce these if they work? ;)

you must be looking at pics of a different hood :gay:

but seriously, if I had another hood I know I would do better. I wouldn't mess with the cut-off disk, and I would use the scroll function on the saw. I would also have placed the vent another 1" towards the back.

you should keep the cut out pieces, reattach with a hinge at one end and then connect the other end to a cable (old hood release?). Then we'll have some real time data comparisons. :gay:

Actually Rob I was thinking about something more like a big magnet sheet.

Looking at my datalog, my cruise coolant temp hit 200F in a few places. Not constantly or sustained, but I've never seen less than 203F before--though it does like to sustain 203F.

I gotta say that coolant temps have never concerned me like oil temps. Even running 203f coolant temp is fine IMO- after all the OE fan thermoswitch doesn't even trigger on until 207f. My reason to vent the hood is primarily for traffic driving (since I don't see elevated temps at speed anyway). If the turbine generated heat is allowed to escape when the car comes to a stop, rather than waiting for the fan to come and starting forcing underhood hot air out, I believe a lot of heat soak can be avoided.

My A/C is cold now. I mean *cold*. Boosting around town I felt like Satan frozen in the 7th layer of hell.

are you converted to 134a? Did you make any other cuts?
Just wondering how this changed the heat (rise) in traffic? and if it's sufficient to bleed of heat from the turbo too while stopped?

most likely a result of the increased airflow through the condensor.

I'm glad you cut it like you did, that's how I would have suggested.

a little expensive, but the hood vents on the bottom of this page would look cool: http://www.carbontrix.com/vents.htm

No it's R12 that's been topped off with Freeze12. I topped it off around a year ago, a couple of ounces was all. Haven't put the gauges on it since, either, but it's cold. I'll put a thermometer in a vent next time I take it out.

Haven't cut the other vents in yet. Not had time. I did get to help Ben w/ his turbo project, and I got to hang some shelves in the garage though. So at least I have been productive.

The difference is absolutely the extra airflow through the condensor. Neat stuff. If I got another crack at it, I would just have cut 3 sides (the sides and the rear) instead of doing the H. I think it would have been easier for me to build up a little lip in the front with some filler (liquid steel?) than for me to do the extra body work required in making my cuts look right.

Your PS/AC+ alternator belts wont like the easy acces to rain much.

Rain? In Atlanta? :rofl:

I ain't scurred.

I bet at highway speeds there wouldn't be any rain problems. When it rains you could carry that magnet around and cover it up.

In Atlanta? :gay: Ben? :gay:

Am I missing something? Does it not rain in ATL?

It's just hot there all the time and they don't get much rain. There is also only like 3 hours of non-heavy traffic through the interstate highways through and around atlanta. I think they say traffic starts at 3 am and ends at about midnight or something (humorously).

Ok, i bet at 45 mph with enough lip action on the hood he wouldn't have any rain problems but what do I know.

hey if if makes the AC colder, I wouldnt be either

Out where Ben lives? No sweat going highway speeds. Now where I live, first gear is still very useful, even now that I'm boosted ;)

Hard to get to the speed limit in town, and I can hardly imagine Ben driving at or under hwy speeds where he lives. Not with that power - more like race track speeds. Though I will say that after 10pm during the week, traffic is pretty much dead in town. That's when I make my logged runs- small stretch of major hwy that comes inside the perimeter interstate that remains four lanes (for commuter traffic). I can check for speed traps driving out, and then make the run on return.

Yes- 75% percent of GA is in a severe drought right now. It's the kind of drought that's going to kill some big trees around here. We had one almost 20 years ago and it killed a 150yr old oak tree off my back porch.

yeah I'd love to use that one day....just a pretty vent. Cut out the shape and bondo it from underneath....boom extraction hood heaven. and keeps with my red/black theme :greddy:

Though it seems pricey- there's something to be said for cutting a hole, sticking on event and driving away. I'd go for the fiberglass variant... if there was one.

that vent is also pretty big (10" front to back). might be cool on a larger car, but I think it may be too deep and too tall to look right on the miata.

is that where you got your CF naca duct from?

believe me, all the fiberglass in my garage is makin me itch (pun not intended) to build a vent.

no here: https://secure.mckinneycorp.com/

not always the best...one time when i was a kid i burned a hole in my carpet cause i thought crayons smelled good.

mmmmm..... crayons....:p

I was always one to play with electricity myself nothing like abit of selfimposed electroshock to get the juices flowing. :rofl: singed crayons and carpet is a delicacy, in Virginia is it hmm.