Chuck:

I agree, this is all just poser stuff and there's no substitute for testing -but here's my latest idea to increase under hood air flow, specifically designed to allow for more volume of hot air to exit: (although there should be some benefit to the IC and radiator as well)

I am planning on using the NACA duct on the the passenger side fender (since it does nothing on my Touring anyway) to further ventilate the engine compartment . I'll start by drilling a series of holes along and through the top of the engine compartment/wheel well sheet metal. The holes will have rubber grommets for a finished look and to increase airflow through them. (no sharp edges means less turbulence and greater velocity) I will remove the plastic "shroud/piping" attached to the plastic fender liner and seal it off at the top with a fabricated sheet metal divider, and bottom and edges with foam backed tape. My theory is simple - that the hottest air under the hood is going to rise (positive pressure) to the bottom of the hood, (especially with the turbos on that side) exit throught my series of new holes and be drawn out between the fender and engine compartment by the negative pressure area generated by the NACA duct! Of course this will only work while the car is moving. I'm thinking about using a smoke flare and fuse inside the engine compartment at speed to see if it indeed works. All I need then is a willing passenger to stick his head out the window at 100 mph to see if the smoke comes billowing out! YEEEEHAAAWWW! Kind of like the Dukes of Hazard!!

Where do you think this fits into the fluid dynamics equation - kind of a Venturi Effect? Now THIS is a poor man's ventilated hood.........and I'll bet $20 it will work.

 

Those side ducts which are used for oil cooler air flow exits, are in a lower pressure area as you have summized. Thus if you place holes in the tubo area of the inner fender liner, it should draw hot air out the side. For this to work, the right not used oil inlet has to be blocked off.

One way to test your idea before drilling any holes is:
get a very long thin(about 1/8" id) transparent hose, have one end under the hood in the area where you want to drill the holes, have it come into the passenger area and have it make a "U" loop down and then back up, should have a little water(1/8" length to 1/4") in the bottom of this "U" loop, then route the hose back and out to the side vent with it's opening facing the rear of the car. You need a passenger/observer who will watch the water to see which way it trys to flow as speed increases as it will move towards the low pressure end.

 

I dont see so much air entering from such a small gap after the seal for the hood is removed.If anything it would mix with the incoming hot air from the radiator, remember that air entering the nose area has more velocity and ram air force.I could see a problem in a racing car at high speeds but not in this application. Plus there hasnt been any complaints of over heating yet with this seal removed .

 

My thought is to put an air dam about 4" back from the R1 splitter. This will create a low pressure zone behind it, and help the normal flow of rad air out thru the bottom of the eng bay. This method is similar to a friend's 93 z28 that I track with. worth dropping a mph or 2 at a driver-ed event for significant improvement in rad flow.

Side ducts are tempting, but actual flow channels over the wheel are very small.

 

Chuck:

Very cool, I like your "tester"! Nothing like keeping it simple before
starting to drill/cut. Should be interesting - stay tuned sportsfans!
I think the hard part of this equation is trying to balance the drill hole openings vs. the duct opening to achieve the maximum flow.
At some speed the ducting "system" I propose will probably begin to cavitate and probably quit functioning altogether. I really need a wind tunnel to work this out in a more scientific manner. Hmmm, could be a semi interesting project for an undergrad in aeronautical engineering.
Thanks for your insight! Now - about my idea of the smoke flare and fuse.............

 

KevinK2:

An interesting and elegantly simple idea to improve flow, but the question is exactly where do you place the dam, what size, shape, etc.
It goes on and on and without testing in a wind tunnel and some sort of volumetric study it's all "pi in the sky". This is why I hate winglets, vortice generators and all this stuff - it looks cool and maybe works, but it is a bitch to quantify. This is the stuff that keeps engineers occupied for an entire career. They are still trying to perfect laminar airflow for airplane wings! And THEY have supercomputers! ARGHHHHH........
I agree that the existing flow channels are small, that's why I am going to rip those suckers out since they were only meant to service the oil coolers and not move a large volume of air. I just want more hot air exhausted to lower underhood temps. If I can knock it down by 20 degrees F it will be huge.

 

I keep reading about so many people on this forum going cooling crazy, but what nobody seems to understand is that youre motor needs to see a minimum temp.Remember the ECU dosent like temps under 180F and youre water and oil t stat will be closed under 180F so overcooling isant the answer.I have just a upgraded rad and I see 175F-180F cruising in the highway .What the FD does need is better cooling at slow speeds and at Idle ,a hood with small vents might be a good compromise so hot air can be pushed out by the cooling fan when sitting in traffic yet not over cool at speed.

 

juliof,
It's not cooling while cruising on the highway we are concerned about, it's driving the car HARD on a track for 30minutes or more at a stretch. It was 17deg F here the other morning when I drove my car into work and the car had no trouble maintaining 180F water temp. And I have a MazdaComp radiator, and an R1 with the twin oil coolers, and I've also vented the fender liners and removed the washer bottle reservior to allow better airflow through the oilcoolers. Overcooling is not the problem undercoolng is.
Regards
Crispy