Radiator ducting and aero...

Discussion in 'Road Racing' started by DavidBoren, Sep 10, 2014.

  1. DavidBoren

    DavidBoren Active Member

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    First off, I'm not quite sure I'm posting this in the correct section, so if this discussion is better suited somewhere else, feel free to move it.

    Now... I have been reading a lot about divergent/convergent radiator ducts. Sealed airbox for the radiator with a small opening up front, gradually tapering to the size of the radiator, with a sealed exit chute directed to a heat extraction vent in the hood, or the wheel well(s).

    Not only does this make the radiator more efficient, but it alao plays a significant role in front downforce and drag reduction.

    The theory of this type of radiator ducting has been proven on the P-51 Mustang plane. It was so effective that it actually made measurable thrust. On a car, that "thrust" would be directed upwards, producing downforce. This is evident in racecars and supercars (think McLaren P1).

    Obviously, the ductwork would be less than optimal given space restrictions such as factory bumpercover size, radiator support placement, and space between the radiator and engine pulleys. And the vent placement is dependent on hood profile.

    My question, I suppose, is if anyone on here has invested any time or thought into applying this to the SN95?

    Blocking off the grill opening and only using the opening in the bumpercover as the inlet for the radiator duct, ducting the exit of the radiator out a vent in the front of the hood, and a belly pan under the engine compartment... that is the basic system in question. Has anyone done this? Pictures? Opinions? Thoughts? Concerns?
     
  2. ttocs

    ttocs Legend

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    It sounds like the design your talking about used in airplanes uses the venture effect to get the hot air out? I dabbled for a short time in rc airplanes and cooling can be an issue with those when you live in phoenix so I did some reading up on it after burning out one motor. I remember reading that the jaguar xj220 use a similar system in its cooling but the problem it experienced was that the venture effect only really works when the car is moving and not necessarily moving slowly. I thought the 220 was known to have cooling issues on semi-long drives if you could not keep it above 85 mph or something to that effect? I think this idea could be great on a racecar but on a streetcar I think your asking for overheating issues. Sounds like fun and an interesting idea for sure though and if its not on my car GO FER IT!
     
  3. DavidBoren

    DavidBoren Active Member

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    The radiator would still have a fan(s) to ensure airflow at low speeds. The duct design is going to make use of any available air in the most efficient way possible, even if you can't achieve the optimal Chrysler/Kohler(?) dimensions.

    One of the biggest advantages of this system is that all the air entering the front of the car is ducted through the radiator and out the hood. This keeps air from just constantly cramming into the engine bay. Air entering the engine bay in a conventional system has no immediate exit. Turbulence introduced by the air hitting the irregularly shaped engine, and heat from the engine cause a high pressure zone in the engine bay. This pushes up on the bottom of the hood, and additional lift is created because the only way for this high pressure air to exit is down under the car. Air exiting under the car is also bad because it increases drag. All of this is bad, and all of this is how the car is set up in stock form.

    Simply adding a properly placed heat extraction vent(s) and a belly pan under the engine compartment will help a lot.

    It will help the radiator even without ducts because in stock form, air coming through the radiator encounters high pressure, turbulent air immediately behind the radiator, which is a problem since you want air to flow freely across the radiator without reversion or stagnation. With a belly pan and hood vents, this problem is greatly reduced.
     
  4. wmfateam

    wmfateam Active Member

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    That is project number 3 for me. I have a second hood that that I purchased specifically for this project. Was planning on making new radiator hoses so I can run the chimney from behind the radiator to the hood. Should be starting before the end of this month, once the rear control arms are done.
     
  5. ttocs

    ttocs Legend

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    with the rise on some of the cowl hoods it would not be too hard to build it into the hood as long as your motor isn't too tall.
     
  6. wmfateam

    wmfateam Active Member

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    [​IMG]
    This is kind of what I am aiming for.
     
  7. RichV

    RichV Well-Known Member

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    I see the benefit if you actually race, but for the street its a lot of effort and money for nothing.

    American Iron Mustangs and other makes have been doing it for years. It doesn't have to be quite this radical. Even 03 Cobra style hoods or Saleen style heat extractor hoods work. Not as well as the above tho.
     
  8. D3VST8R96GT

    D3VST8R96GT Well-Known Member

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    I am preparing a car for the Texas mile and have pondered a lot about this topic...

    The best concept I have is box the radiator and get a well vented hood to take advantage of the venturi effect. There isn't much room to work with
     
  9. DavidBoren

    DavidBoren Active Member

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    Yes, this theory makes most sense put into practice on a racecar. But it is not without its benefits on a daily driver. Having a boxed radiator, with a properly designed small opening inlet, allows you to block off your grill. This reduces drag, and is a very popular "eco-mod" to increase gas mileage.

    These mods will be beneficial regardless of intended use. But I am talking about a road racing vehicle in a racing and performance section, so it's safe to assume that I am not saying that this is for everyone, or that we should all do this to our daily driver cars.

    WMFATEAM, that car is sweet. Wher did you find that picture? Is there any information that goes with it? Maybe a build up article, or even a company name that makes some of the things shown in the picture?
     
  10. D3VST8R96GT

    D3VST8R96GT Well-Known Member

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    That's the c6r racecar
     
  11. D3VST8R96GT

    D3VST8R96GT Well-Known Member

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    Over all the hardest part will be effectively evacuating the air. Without ducting the air will turbulent. But blocking off the grill isn't hard they make fiber glass bumpers without the cut out
     
  12. DavidBoren

    DavidBoren Active Member

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    I saw that it was a 'vette, just didn't know who made the parts. Anyways, thank you.

    I don't think that you can block off the grill without using ducts. Or at least, I wouldn't.

    If the vent(s) in the hood are placed properly in a low pressure zone (on the break line), then air should be sucked out of the engine bay by the air moving over the hood.

    With a belly pan under the engine compartment, the air being sucked out the vents would pull air in through the grill opening, across the radiator.

    This would happen even without ducts to and from the radiator. And, all things considered, a properly placed heat extraction vent and a belly pan under the engine compartment would be a smart investment for any vehicle, even your daily driver.
     
  13. DavidBoren

    DavidBoren Active Member

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    But, yes, you are right. Without ducts, the air being extracted from the engine bay would be turbulent. And you would be introducing turbulence to the slipstream over the car.

    This is why a good heat extraction hood usually has two vents with a tapering shape to each vent. These vents direct the hot, turbulent air from the engine bay out to the sides of the car, rather than straight over the top.
     
  14. D3VST8R96GT

    D3VST8R96GT Well-Known Member

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    I need my own wind tunnel already
     
  15. DavidBoren

    DavidBoren Active Member

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    Get one or two large fans and a handheld wind speed measuring device. Cover your car in the little strings and park it in the garage with the fans in front of it. Turn on the fans, measure the speed, record the flow pattern shown by the strings. It's not perfect, but it should give you an idea of how the air is traveling over/around your car.

    Just a thought.
     
  16. D3VST8R96GT

    D3VST8R96GT Well-Known Member

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    I plan on trial and error.... Lol fans are expensive
     
  17. badsheep5.0

    badsheep5.0 Member

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    So this is were you got all that shit you wanna do to NY car
     
  18. CC'S95GT

    CC'S95GT Legend

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    You don't want the fans in front of the car either. The blades from the fan create a turbulance and would show a false reading on your strings. Sucking is better than blowing.
     
  19. RichV

    RichV Well-Known Member

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    A lot of race cars don't run fans at all since they are always moving. So that's no-bueno on the street.

    Again, this is all way too much for the street. But then again there are cars with $10,000 suspensions that only get driven to Dairy Queen.
     
  20. D3VST8R96GT

    D3VST8R96GT Well-Known Member

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    ok......