Hot air OUT! New mod sucks! (REALLY..)
 

I was sitting around yesterday thinking about my old chemistry professor mumbling something about how every 10 degree increase in temperature causes chemical reactions to double in speed. And then I realized that summer is just around the corner and had visions of my engine screaming at me for help. I've been contemplating a "vented" hood but it just did not seem to make a lot of financial sense considering the cost, shipping, painting etc. Plus, who knows how well they work? - and then there's the rain issue...... Here's what I came up with: (and true to my Scotch ancestry this is very thrifty as well)

1. The NACA side fender duct on the passenger side of
my 93 touring does absolutely - nothing. So why not
put it to work ventilating the engine compartment?
Yeah - that's the ticket! So, off comes the fender
and out comes the 3" metal cutting hole saw.
On the inside top of the inner frame you will see a
4" square that has been already been cut out -
perfect for my cut, and inside it there is really
nothing except part of a wire harness in the engine
compartment to watch out for when making the cut.
Wham - a new 3" hole now exists and looks like
this:

Damn server.......GRRRRRRRR. Anyway - on with the new thread!

I then lined the hole with strips of foil tape to create a "tunnel" to the outside:

OK -

Now we get some foil (not plastic!) clothes dryer 4" super flexible ducting and tape it to the "square", bend it, and cut out an oval section on the interior plastic liner duct to mate it to. Seal both ends with foil tape.
I sealed off the forward end of the duct, as
well as other seams to create a leakproof routing for the exiting hot air. I could have cut off some of the ducting but chose to leave it stock in case I decide to add an extra oil cooler in the future- this way I could just poke through the foil tape to make it functional again without taking the entire fender off:

And here's the view of the completed ductwork with some additional aluminum sheet to complete a sealed duct that will interface with the NACA duct. I repeated the process for the driver's side. How well does it work? I intend to do temperature measurements with a calibrated pyrometer (a $1K instrument I just happen to have laying around the shop) at different locations and speeds inside the engine compartment with/without the duct sealed and post them later. Stay tuned sports fans!:D

Pictures are taking too long to load.
Take your $10 Naca duct and shove it :D

HAHAHAHA! Would that be with KY or without?:boink:

Hmmm, you wouldn't be selling vented hoods per chance? (It's actually more like $7.50 for the foil tape..):p:

A vented hood? I drove around WITHOUT a hood :D
You know, a naca duct attached directly to the turbo manifold may prove to be interesting....

Now just take a hair dryer and mount it to that and the intake.. You will have a T-100 then and be makin mad HP.:D

To quote Dire Straits: "Money for nuttin' and my chicks for free!" I like it but it would exceed my personal budget by at least $10.00 for "cheap ghetto mods that you won't find anywhere else":allcho:

Let us know how it works out... if it works well maybe you should add some fans to push more hot air out. It might not be flashy, but hey if it gets the job done...

AHHHHH!!! you cut a 3" hole in an FD :(

edit-- seriously though... I'd imagine that Mazda put that metal on the frame there for a reason! Maybe i'm misunderstanding what you did with that holesaw...

I have a <much more common> 1990 FC, and i'd NEVER drill a hole in it anywhere...

If it works the way I envision, the suction created by the NACA ducts will provide alot more evacuation of the underhood air than could ever be provided with fans.
Only by measuring the temperatures will I find out - I'll keep everyone posted on the "science" part as it evolves. Later.

Are you gonna take temp readings in different locations of the engine compartment?

Yep, the pyrometer has teflon coated wire with a sensor tip that I can run to multiple areas under the hood. It's accurate to within 2-3 degrees F, and even better if I calibrate it with a reference standard thermometer which is total overkill . I'll also do it over a range of speeds. Also records ambient temperature. I'm also going to stick it through a hole and measure the temp INSIDE the stock airbox above my K&N to see if my "ghetto cold air intake" actually works as well. (that mod almost broke the bank at around $20 for two pieces of choke heat riser tubing and some plastic epoxy putty...but I digress...) This may the first and only ever "real time" measurements ever done on an FD3S. Now when we say are cars are hot little bastards underhood we'll have some real numbers in Farhenheit to toss around! I'm so into dense air.......it's got to be the cheapest hp out there.:zip:

Yeah, not one - but two! (But it's only sheet metal and you can't see 'em so they don't count!) I can just imagine the engine sitting in my lap one day - french frying my nuts - after a head on and me thinking, "damn, I never thought about the crumple zone enginering on this sonafabitch!":D

Re: Hot air OUT! New mod sucks! (REALLY..)
 

..uh
no flames intended but the original design/function of that vent is for the same purpose .. an exhaust for engine bay heat

Re: Re: Hot air OUT! New mod sucks! (REALLY..)
 

Actually it's to ventilate the extra passenger side oil cooler for the R models. You really need to pull the fender to see everything.

All it's doing now (in stock form) is ventilating the inside of the fender cavity next to the bumper, there's no way for engine bay heat to escape and enter the duct, except for maybe a few small gaps far forward near the air cleaner. There is no real dedicated flow "path". I also removed the plastic dummy plate on the bumper to allow any additional fresh ram air (positive pressure) to enter the engine bay through the gaps. It's all about creating differential pressures and thereby flow. By far the hottest part of the engine bay is the passenger side above the turbos and exhaust toward the back near the firewall, and that's where my exit "tunnel" that I created is. Since hot air rises (positive pressure) it will accelerate to the bottom of the hood, enter the tunnel and be literally sucked out by the low pressure area created by the NACA duct and the cooler, denser (low pressure again) air on the outside of the fender. The same tunnel and duct I fabricated on the driver's side does the same thing, and the interior fender intake for the oil cooler is now blocked off inside the fender well also to increase the pressure differential and "sucking". Exhaust for my oil cooler now exits two grills that are in the front of the wheel well that I riveted in place flush with the liner. Of couse this all doesn't do a thing for you while sitting in traffic, and I'm sure at some really high speed it will start cavitating and reach maximum volume, but at that point you have so much fresh air ramming the front of the car it becomes academic. Only by measuring the real time temps at different locations at speed with an extremely accurate pyrometer like I have can I prove any of this works! And, it may not do a darned thing, but it sure is an interesting project and costs next to nothing to do, and my bet is that it works as well as spending 2 Large or more on a quality "vented" hood! (although I think the vented hood would obviously do a much better job for the intercooler and is absolutely neccessary with a larger intercooler to allow it to function at maximum capacity) I also like the challenge of doing everything I can stealth - I prefer the stock look and will bet that my car will be worth more in the future than highly modded ones with non OEM stuff bolted on. Don't get me wrong, I like some of the "fancy" exterior stuff - just not on my personal car. All I wanna do is go fast, save money and stay cool - literally.

Amen to cheap asses like me and Ron.
Nick

(does this count tho? i mean it isn't like there is a kit for something like this... and we're to cheap to buy it. and i'm sure it works.)

HAHAHHA! The kit is a feakin' roll of metal duct tape, a metal cutting hole saw and some metallic dryer vent duct! And you can buy it from my website for only - lemme' see - how's about $300.00 or so?

Well, that's what you get when you cross an old 2 stroke motorcycle racer fart like me with an FD3S! I did a preliminary run today with one fender on and one off just to get a feel. (kind of like dating a virgin!) The freakin' duct that was uncovered was damn hot -even after being exposed to fresh air - so I know that it is working - and - the top of my hood felt alot cooler than it usually does when I park it. Sheeeiit - it works! Now I need to develop the methodology for testing.......to make a valid scientific statement. On to the pyrometer....;) Jeez, now I'm getting in really deep:eek:

Ron: can you post pictures that are not sooo cropped. I am having a hard time visualizing what you are doing. sounds promising.

thesaint

Ron
Suggestion: upgrade those plastic fastener clips with new ones (redesigned) I have a friend who lost his while driving...now that you have increased the flow through those vents, its better to be safe...i was told that mazda does not sell the part separate from the fender...

Me thinks hot air moves vertically, not horizontally. Put the 4" holes in the hood. That'd be nice and ghetto.

Yep - good thinking. I was able to take mine out without breaking them, but they are cheesy. I also replaced the plastic "mesh" insert in the NACA ducts with stainless steel 1/4 screen secured with QuikPlastik brand plastic epoxy putty. When I reinstalled the ducts I put a 1/4" strip of 3M "grey" outdoor double sided foam tape around the entire border of the duct - it's not going anywhere. The stainless mesh also looks better IMO.
You can purchase the duct by itself separate from the fender - it is around $140.00- crazy.. but not the individual fastners.

Let's see if this helps:

AND this:

And this:

And this view on the driver's side, from the front looking toward the rear:

Thanks.

Looks like it will work. I am just hesitant to cut into the car like you did.

thesaint

Yep - I would not do any cutting until I have had a chance to measure the temps to see if it works as good as I think. I'm keeping the plugs that I cut out since they could easily be welded back in if need be. I gave that a lot of thought because you can often get into structural issues without even knowing it. It does not APPEAR to have any impact since it is just stamped sheet metal but you never know....

An additional caution on this mod: You may need to shop around to find the "super flexible" dryer heat duct which is a METAL FOIL. Regular metal dryer duct will not make the tight radius bends required in order to easily fit inside the space between the engine compartment and interior of the fender. DO NOT USE PLASTIC as it will melt and/or degrade rapidly. Do not use regular duct tape to seal everything - use METAL only. I would still recommend everyone to wait until I have posted temperature readings to see how well this works before cutting. It could be just a huge waste of your time.
(Although my test drive the other day WAS impressive, it offers no proof that it will be effective beyond all doubt)

SO WHAT HAPPPENED???

DID YOU DO THE TEST?????

DID THE VENTS MAKE A DIFF IN TEMPS??

First your ghetto intake and now this? Where will it end! ;)

I can't wait till you post that you took a saw to your hood to "vent" it. It'll be hilarious!

I love ghetto mods...cheap and effective. Hope this works. If so I'm buying a circular saw.

Ron, what are the other ghetto mods?

HD Racing (AKA:Homedepot): Manual Boost Controller
HD Racing: Cold RAM Air intakes
HD Racing: tourque brace[My favorite] two big ass(10" & 12") eye bolts...

Well, there are probably a few others out there, but my #1 cardinal rule is that a ghetto mod can't easily be seen or show on the outside of the car, cause I'm pretty much a diehard fan of the stock look. So, I never did get around to actually measuring the temperatures because I did not need to. The "hot air out" mod works extremely well....after a drive you can feel how hot the naca scoops are vs. the temperature of the fender right next to them. One of the biggest problems that all auto manufacturers are up against is having enough airflow through the engine compartment, with all the stuff they cram in there. While larger radiators like the Fluidyne and the Koyo are a help, they really are only more efficient than the stock at higher speeds and with highly modded engines. Intercoolers other than the stock (which is a total joke) are excellent as well, but they are damned expensive. I don't think you can find better fans other than the stockers, and the fan mod is worthwhile as long as they don't run all the time. A dp is an absolute must. All these items add up to decreased underhood and engine temps. I don't think I've ever seen ANY engine as inherently hot as the rotary - it's just the nature of the beast.

The reason the "hot air out" mod works so well is that you are actually helping to improve the efficiency of the radiator and intercooler by providing more airflow volume. A vented hood does the same thing. I think it would be ludicrous to make any quantitative statement about increasing power, but there is no question that this will help under hood components (and hopefully the engine) last longer.

I still plan on measuring how well it works - I just need to get motivated enough to spend the better part of a day doing this in a scientific method.

Damn, I get my FD next week and there are so many things I want to do to it since it's been in the shop. Keep us updated on new ideas.

Not important, but i was the 1000th view

Did you ever measure the temps. :D

This is a pretty interesting idea. The idea of cutting the FD makes me nervous, but I might get over it if this works really well. Do you think this would be too ambitious for a novice to try? Have you measured the temps or are you still satisfied that it is working well from your observations?
Sorry if that's too many questions.

Doesn't hot air rise? So a vented hood, in theory, should allow more hot air out whereas a 2" hole that has piping going downward would upset this flow. :confused:

Wow, talk about resurrecting a thread from the past.........:D

Anyway, yes of course - hot air rises - to the bottom of the hood, which is then literally sucked out the upper rear corners of the engine room by the low pressure area created by the NACA ducts at speed. And we are talking about TWO, 21/2" holes - one on each side. That's a pretty decent amount of air flow. The faster you go, the more it "sucks", until cavitation sets in and you have reached a maximum flow. What speed that happens at is anyone's guess.

It won't do a thing sitting at a stoplight - nor will a vented hood. That is why the Miata thermosensor mod is such a great idea also to help kick the fans on high at 205 instead of 217 while idling.*

(*I think that's the right temp differrence.)

water thermoswitch listed as switching on at 226F in manual. Yikes!

Wanna play with ducting, but gotta get new engine first, then brakes, then suspension then.... well you know :)

I STILL think it's cool you did this! My idol...

Nah, too lazy to go to the trouble. All I know is that it works VERY well, and what I was after from the very beginning was to improve the airflow through the engine compartment. (which hopefull improves airflow the radiator, intercooler, yadda yadda)

Like I said before, this was Mr. Chin's idea from the beginning, I just found kind of a funky and inexpensive way to implement it.

If he doesn't, I will... one of these days. I'd like to do a *good* job, it'd probably have to be split vents to go around the hood reinforcemens, but for a SMIC it should help, along with saving me a fucking thousand dollars. Hey, my car's already been totalled and put back together once, where's the harm =)

I did that (sig) I know it works cause I see the heatwave rising sitting @ the light.

ok i am kinda lost as of whre evrything is. where i marked it in green that is the engine bay and that i have it over the 4"square. and the blue is the bottome that wodl go to the vent. am i rigth if not i need this explainde d a bit more and pics form more of a distance.
joel

How hard is it remove the fenders?

jupiter....do you have any better pics of what you did? It looks pretty nice and clean from your pic

I hate to be a member of the ghetto club, but the last time I had my fender off I did this to my car too. There are some pics (a little higher-res and less cropped) HERE . They may not be the quickest to load, so be patient.

Can't say that I've driven it enough yet to notice anything significant, but I respected the theory behind it. Maybe I'll play with the digital kitchen thermometer if I get bored this weekend.

..dave

Yep, the green area is where you make the foil lined duct. You need to cut the hole in the interior side of the frame by putting your hole saw inside the exterior square to cut. BE VERY CAREFULL not to let the saw blade nick anything on the inside or you'll be paying big bucks to fix it......... The red area is where you cut the oval in the plastic duct to attach your 4" dryer hose.

Somewhere in this thread you mentioned that your passenger side vent did nothing originally, but I think now you're using them both for engine compartment airflow, right? I think you mentioned briefly that you changed the ducting for the oil cooler on the driver's side? But I'm not clear about that, given that I think it is supposed to use the driver's side fender vent.

I wonder if doing this mod only to the passenger side would cause any anomalies in airflow?

jds