Howard Coleman

iTrader: (6)

i feel strongly that the fd needs a vented hood and since i couldn't find anything i liked did my own in 05. i thought others would be interested and offered a group buy but there was no interest. (most people saw it as hacking up their car.)

i still love my Cool Loovers after almost 3 years the aluminum looks exactly like the day it was installed. if i repaint the car at some point i may paint it... or not.

here is the initial post in my thread slightly edited to remove the group buy stuff...



a DOWNPIPE for your engine compartment: COOL LOOVERS and other heat fixes

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As everyone knows the FD is a rolling oven.

Sure, it outrolls most other sportscars but it is busy baking everything in the engine compartment. I learned that real fast when I stopped at a wayside in Florida and made the mistake of leaning on hood of my newly purchased FD without an asbestos glove.

I have been re-engineering my FD during the last 6 years and have finally gotten around to addressing the heat in the engine compartment from an exit perspective. So you bought the 2 inch radiator and a big intercooler… due to the lack of exhaust flow out of the engine compartment you might just as well weld a plate over the backsides of both heat exchangers.

Plainly stated: you’ll get no flow if there’s no place to go.

Care to take a guess as to the exhaust speed of the air thru the intercooler?

I asked a bunch of people what they thought the exit speed of the air through the intercooler was at 60 mph. Guesses averaged 30 mph. My opinion was less than 10 mph. I rigged a digital windspeed gauge to the back of my ASP/M2 large intercooler and found my guess was a bit optimistic.

Actual measured intercooler exhaust velocity was 1.5 to 3 mph at 60 mph!

If there is that much constriction in the engine compartment (and I run no air conditioner, power steering or air pump to further impede airflow) is it not surprising that our FDs really are rolling ovens?

Combine the lack of airflow with the 300 degrees hotter exhaust you get from a rotary versus piston engine and the fact that the stock OEM turbo manifold is 22 pounds of cast iron which is just about the most heat retentive material on our planet and you have the recipe for lots of cooked everything.

As you know, fortunately, there are a number of fixes available to promote underhood coolness and powerplant longevity…

I am happy to add to the list.

Before getting in to Cool Loovers lets consider the FD hood.

It is aluminum and gorgeous but…

Mazda wrapped our thermally challenged powerplant/system in a BLANKET!

Open your hood, and what do you see on the underside? Yikes, how could they do that… here they build this beautiful light aluminum hood. Aluminum. The opposite of cast iron. Aluminum conducts heat like crazy. Away from the engine compartment! But not with the blanket shielding it. Get rid of the blanket… Let your aluminum hood radiate heat. And no, you won’t burn your paint by removing it.

The other problem with the hood is that there are no HOLES in it.

Unless you are going to drill holes in your firewall to let the heat out (which will allow you to remove your heater) you better either remove your hood or put some holes in it. Of course some of us have bought aftermarket hoods made from fiberglass or carbon fiber that do have holes. Unfortunately carbon fiber and fiberglass are close to cast iron as far as heat retention. Think the opposite of aluminum… but they do have holes which exhaust heat.

They also cost $500 plus and many look, er, homebuilt.

The aluminum hood is just too nice to ditch so it just needs some holes… 74 to be exact and they’d be louvers, Cool Loovers of course.

While I get lots of nice comments as to the “look” the purpose is to produce an additional absence of heat.

Of course I instrumented everything… and learned some things. Properly designed louvered/ducted hoods generally don’t reduce underhood temperature while driving down the road. The reason is that they promote more heat transfer from the coolant and the intake charge. That’s because they raise the speed through the exchanger. The speed through my intercooler more than doubled as it now has more exhaust area through the Cool Loovers. Sort of like a 3 inch exhaust pipe versus the OEM setup. I note a drop in charge air temperature of approximately 10%.

The other major benefit is after you turn off the motor. Normal underhood air temperature measured near the front of the throttle body on a 78 degree day is about 91 degrees. 4 minutes after shutdown that temperature is 195 degrees. 20 minutes after shutdown the temperature is 160 degrees!

And that’s without the insulating blanket!

Most of us pop the hood after a drive to promote cool-down. That works at home but there are many places (work?) where it isn’t possible. That’s where the Cool Loovers earn their keep. With Cool Loovers the temperature only goes to 140 and is 128 after 20 minutes.

Cool Loovers are made from aluminum and are the exact thickness so as to conform to the hood yet are substantial. They retain the supporting hood ribs and are attached with pop rivets. You can leave them as is or paint them if you wish. A friend of mine has a white FD and is going to paint his hood flat black and leave the Cool Loovers aluminum.

Cool Loovers are nicely finished as to the edges, the louvers are cleanly cut, and the rivet holes are drilled. Rivets and clear comprehensive instructions are included. You’ll need a drill, an 1/8th inch bit, some of that 3M Blue Painters tape, a rivet tool and something to cut the hood. I experimented and found using a 3 inch electric cutting disc with a file to dress it up worked nicely. An approximate 2 hour easy job ideally with 2 people so hood removal/replacement and the Cool Loover hood placement is uneventful.

2007

2005


howard coleman

recon fd

Man that guy did a great job with the s2k. I think that is pretty cool with the one side.

nice!

Old Slow Coach

You don't need a raised lip before hood vents for them to work!!! Might they work better with a raised lip? Probably, but they absolutely work well enough without a lip. Air entering through the intercooler opening pressurizes the engine bay and is relieved through top vents. Even if this theory is bunk, heat still pours out when you're stopped at a light. The best proof I have that my vents work at speed is that my engine temps are lower at speed than they are standing still.

ptrhahn

iTrader: (9)

This does not work. Folks tested it years ago... the pressure in that area will not allow air to exit the engine bay.

Kento

Virtually everyone with a stock hood can say the same thing.

This isn't to say that additional venting to the engine bay isn't helpful.

Old Slow Coach

True. But the obvious point being made is that, at speed, a vented hood is more helpful than non-vented hood at reducing temps.

Kento

Thus the reason for my second sentence in that post...

DomFD3S

Agreed.

This is also the reason why...(if you're like me and have trees near where I park...) if you get leaves or bugs that sit near the base of the window/wipers...when driving they don't really move anywhere.

Monkman33

iTrader: (28)

There is a thread about this. Take off the strip and tape some pieces of yarn to the back edge of your hood. apparently it will actually suck the yarn into the engine bay. Which means that it doesnt help.

Old Slow Coach

If the yarn just hung and didn't move, that would be an indication that it doesn't help. If the yarn gets sucked in, then that means air is moving through the gap. In this case, colder outside air is displacing hot inside air. If air is moving through the gap, then it must be flushing through the engine compartment and out the underside of the car.

Ottoman

I have an oem hood with one of those Fiberglass reverse Vents blended into it...

although more "agressive" than just cutting vents

i feel the raised front "lip" of the vent helps to increase the low pressure area behind it and futher improve the heat dissipation

jkstill

iTrader: (11)

That is acutally a high pressure area, ala cowl induction.

AHarada

iTrader: (25)

Thanks guys, there's some great info in this thread!

I've read through David Hayes vented hood thread, and I've actually just been waiting for an update, and when the hood is complete, I'm sure he'll have some very helpful insight. Did you place the vents in any strategic area to aid in venting, or is it a hit and miss kind of thing?


I've also read through Howard Coleman's cool louvers thread. I think your hood is excellent from a functionality point of view, and the fact that it releases heat from throughout the engine bay instead of focusing on just the radiator/IC area is the best. The only problem is that I'd like to keep the sleek look of the stock hood, and those louvers are just too aggressive looking for me.

AHarada

iTrader: (25)

Everytime I drive the car, I pop the hood and let the fans run for like 10 minutes after shutdown to get a head start against heat soak. With the hood open, you can literally see the heat waves pouring out of the engine bay. It's very easy to see why our cars heat soak so bad when you do this because the stock hood basicaly insulates all of the heat. I'm sure Howard can attest to the benefits of letting heat escape after shutdown.

Kento

Negative. It's not "colder outside air displacing hot inside air"; it's the fact that the area in front of the windshield is a higher pressure area than the engine bay.

When airflow speeds up over a surface, it creates a lower pressure than an adjacent surface where airflow is slower. In order to flow up over the hood surface, airflow has to speed up to match the airflow speed going underneath the car, which is basically flowing straight. However, once that airflow hits the base of the windshield, it immediately gets slowed down and builds up in front of it, creating a high pressure zone. This is the reason that NASCAR racecars made use of that high pressure zone by positioning ducts to feed the intake from that area. Once the airflow starts flowing over the top of the windshield and over the roof, it begins to speed up again.

Old Slow Coach

I didn't say the reason that it's displaced has anything to do with temperature. What I said was "In this case, colder outside air is displacing hot inside air." This is an indisputable fact, which does not state the reason for the displacement. It's the pressure difference that causes the air to move through the gap, sucking the yarn inside. At stand still. when pressure is not a factor, the hot air will rise through the gap and air flow direction will be reversed.

Kento

Read your post again, please.
Um...what did I just mention in my post?
Then why are you mentioning it in the first place?

Old Slow Coach

Look, ******, you made an assumption that I was saying that temperature is the reason for the displacement. Suppose I originally stated that the colder high-pressure air displaces the hotter low-pressure air, would that get through your skull?

Kento

Well, I'd say it was a reasonable "assumption" based on your post.

Just FYI, air temperature has little to do with pressure zones in an aerodynamic sense.

AHarada

iTrader: (25)

LOL, lets keep it civil.

This thread was for people to express thoughts and opinions, as well as technical knowledge and information, and each person can interpret what's discussed in this thread however they want.

jkstill

iTrader: (11)

Are these available somewhere?

Or was the group buy for custom louvers?

I've been on the verge of buying a hood. Some are downright ugly and most don't fit properly.

It seems there may be enough interest here to resurrect the group buy.

Kento

Thoughts and opinions are no big deal. But if you're going to offer technical knowledge, it needs to be written succintly so that it can't be misinterpreted, otherwise you're spreading false information.

Tygern8r

So can you aerodynamic engineers agree on something before my head explodes? How about a recap, without the name calling.

1) Venting hood: survey says - Good

2) Removing weatherstipping - good or bad? Pressure vortices, yarn vectors, vaccuum differentials-I kind of care why, but not really. I just want to know if it's going to help or not.

If you really want to figure it out, do the math http://www.princeton.edu/~asmits/Bic...Bernoulli.html

AHarada

iTrader: (25)

You need to read through Howard Coleman's louver thread.

https://www.rx7club.com/3rd-generation-specific-1993-2002-16/downpipe-your-engine-compartment-cool-loovers-other-heat-fixes-448589/

People have tested the idea of removing the weather stripping from the back of the hood, and I thought it would be a good idea, but it's been tested and the results are always detrimental to cooling efficiency.

Check out the IC exit speeds test in the thread I just posted, basically to sum it up, his vented hood doubled the exit speeds behind the IC.

Kento

Bad IMO, because all you're doing is inserting airflow into the back of the engine bay, and any and all road debris that gets kicked up will find its way into that area as well. You're a lot better off using the low pressure above the hood to evacuate heated engine bay air out because you'll actually be helping airflow through the radiator and IC.