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Thread: Modern-day Miura

  1. #131
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    I see an area that might be problematic from a cooling perspective. Obviously the radiator would've worked most efficiently if you could've oriented it perpendicular to the airflow. The fins are oriented that way, and it exposes the largest surface area for air to flow through. The problem with your packaging is that you're going to have to diffuse the incoming air from the long horizontal opening of the front grill, into the large, tall square shape of the radiator, and redirect it upward at about 60 degrees all at the same time. Your intake shroud will be an interesting shape, though could easily be formed out of a fibreglass-covered Styrofoam buck. Even then, I have a hard time imagining how you're going to prevent the duct work itself from shrouding the upper half of the radiator face. A splitter inside the duct would help somewhat, I suppose.

    Hopefully the radiator is over-sized for the engine, or you come up with an inlet design that mitigates the really low angle of the radiator because solving overheating issues once the car is complete is much more difficult.
    Last edited by Bloozberry; 11-28-2018 at 08:10 PM.

  2. #132
    Senior Member C5GTO's Avatar
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    Quote Originally Posted by Bloozberry View Post
    I see an area that might be problematic from a cooling perspective. Obviously the radiator would've worked most efficiently if you could've oriented it perpendicular to the airflow. The fins are oriented that way, and it exposes the largest surface area for air to flow through. The problem with your packaging is that you're going to have to diffuse the incoming air from the long horizontal opening of the front grill, into the large, tall square shape of the radiator, and redirect it upward at about 60 degrees all at the same time. Your intake shroud will be an interesting shape, though could easily be formed out of a fibreglass-covered Styrofoam buck. Even then, I have a hard time imagining how you're going to prevent the duct work itself from shrouding the upper half of the radiator face. A splitter inside the duct would help somewhat, I suppose.

    Hopefully the radiator is over-sized for the engine, or you come up with an inlet design that mitigates the really low angle of the radiator because solving overheating issues once the car is complete is much more difficult.
    Bloozberry: I hear what you're saying and in theory I guess it could be an issue.

    My first thought is to ask if in reality, does having the radiator mounted at an angle really cause an air flow challenge that results in overheating issues? The GT40, Cobra Daytona Coupe, Miura's, and I'm sure other cars had radiators mounted at a steep angle. Did they do something special to redirect the airflow? Did they suffer from overheating?

    I've heard that Miura's did have an overheating issue but it was caused by not bleeding all the air out of the cooling system. From what I've heard, when properly bled, no cooling issues for Miura and it didn't have anything I'm aware of to redirect the airflow for the angled radiator. It has a couple of decent sized vent holes in the panel below the grill. Maybe those let in air that in effect redirects the airflow from grill upward? I'm using a "puller" fan. It should suck whatever air that's below the radiator up through it. The radiator is a two pass design, in other words the coolant goes from inlet across top half of core and then back across the bottom half of core again before going to outlet. There's about 6 feet of aluminum tubing that carries the coolant going each way, so 12 feet between the engine and radiator. That should bleed off a decent amount of heat. From all this, I don't think I'll have a systemic overheating issue, at least it doesn't feel that way to me.

    Does anyone have enough direct experience with cars that have an angled radiator to provide some insight here?
    Joel Heinke
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  3. #133
    Hello Joel, I continue to love your build.

    I ran a 550hp 427SBC in one of my cars. It had a very low and fast sloping forward nose. I mounted the radiator in a similar manner to yours. (maybe not quite so flat). I never had an overheating problem. I road raced it with out a problem. I hope that proves to be your finding.

  4. #134
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    Joel, what angle is your radiator at, and what is the width, length, and depth of it? How many horsepower are you planning from your Coyote engine?
    Last edited by Bloozberry; 11-28-2018 at 08:12 PM.

  5. #135
    Senior Member LP700-4's Avatar
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    Joel,

    Here is a short video that goes over the math behind the effect that angling your radiator has on the surface area being cooled. https://www.youtube.com/watch?v=l3SJlGqc0P0 This assumes that air will actually enter the radiator. Do you intend to put in the hood grills on your car? They may help let air pass through the radiator easier.
    -Glenn

    "One day I had a bit of an argument with my friend Enzo Ferrari, who reckoned I wasnít able to drive a Ferrari, only tractors. Thatís when I got the idea into my head and told myself Ė Iíll make the cars myself from now on!" - Ferruccio Lamborghini

  6. #136
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    Quote Originally Posted by C5GTO View Post
    Bloozberry: I hear what you're saying and in theory I guess it could be an issue.

    My first thought is to ask if in reality, does having the radiator mounted at an angle really cause an air flow challenge that results in overheating issues? The GT40, Cobra Daytona Coupe, Miura's, and I'm sure other cars had radiators mounted at a steep angle. Did they do something special to redirect the airflow? Did they suffer from overheating?

    I've heard that Miura's did have an overheating issue but it was caused by not bleeding all the air out of the cooling system. From what I've heard, when properly bled, no cooling issues for Miura and it didn't have anything I'm aware of to redirect the airflow for the angled radiator. It has a couple of decent sized vent holes in the panel below the grill. Maybe those let in air that in effect redirects the airflow from grill upward? I'm using a "puller" fan. It should suck whatever air that's below the radiator up through it. The radiator is a two pass design, in other words the coolant goes from inlet across top half of core and then back across the bottom half of core again before going to outlet. There's about 6 feet of aluminum tubing that carries the coolant going each way, so 12 feet between the engine and radiator. That should bleed off a decent amount of heat. From all this, I don't think I'll have a systemic overheating issue, at least it doesn't feel that way to me.

    Does anyone have enough direct experience with cars that have an angled radiator to provide some insight here?
    Joel, I think we talked about this before, but for the benefit of the rest of the Forum, I did a fair amount of research before committing to front radiators on the chassis style which you purchased as well as the Chupacabra chassis. The best info came from my bud Fran Hall, owner of Race Car Replicas. I started with him figuring that he had vast first hand experience with this configuration in everything from a GT40 to a Lola. He assured me that if the rest of the system was properly done, and that is a big if, then radically leaning the radiator was not an issue and a typical automotive water pump would irrigate a field if you let it, and that 20+ feet of aluminum hose properly done would double the dissipation of the cooling system. I have since found all of that to be true. The key to it is a properly done and coordinated entire system. Of all the transfer methods (fluid to air, fluid to fluid, etc.), fluid to air is the absolute worst but still the most sensible for automotive use, so you are starting with a built in disadvantage. Ever considered a typical transmission cooler that is built into the bottom of a radiator? It is done that way because it is way more efficient to make the fluid to fluid transfer of transmission fluid heat into the still very hot radiator water than it is to transfer it to the much cooler air. As a side note, there are two things that I have asked many experts and cannot get an answer. Why are radiator inlets typically 1-1//2" and their outlets 1-3/4"? Is more water coming out than going in? The second thing, why are there 5/8" and 3/4" heater hoses? What difference does it make, especially when the coil in the heater is a standard 3/8"?

  7. #137
    Senior Member C5GTO's Avatar
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    Quote Originally Posted by jm14 View Post
    Hello Joel, I continue to love your build.

    I ran a 550hp 427SBC in one of my cars. It had a very low and fast sloping forward nose. I mounted the radiator in a similar manner to yours. (maybe not quite so flat). I never had an overheating problem. I road raced it with out a problem. I hope that proves to be your finding.
    jm14: thanks for the data point!
    Joel Heinke
    Be original; don't be afraid of being bold!

  8. #138
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    Quote Originally Posted by Bloozberry View Post
    Joel, what angle is your radiator at, and what is the width, length, and depth of it? How many horsepower are you planning from your Coyote engine?
    Bloozberry: it's an aluminum 2 core (2 - 1" cores) mounted at 30 degrees. The core is 18" high, 22" wide, and 2" thick. The Coyote is advertised at 435 HP but I'm told they can run at 450 HP if properly tuned. The only mod I'm planning is to use an 8 stack EFI. I don't know if this will increase or decrease the HP.
    Joel Heinke
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  9. #139
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    76mx, on traditional radiators, the larger, lower hose runs to the water pumpís suction port. By making the lower hose larger in diameter than the upper hose, the vacuum pressure in the hose at the pump inlet is reduced. By reducing the vacuum pressure (raising the positive pressure), the coolant's boiling point also raises, reducing the chance of localized steam bubbles forming and being sucked in to the pump, causing cavitation, loss of efficiency, and potentially erosion of the pump.
    Last edited by Bloozberry; 11-28-2018 at 08:38 PM.

  10. #140
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    To compare jm14's experience with what you can expect, you'd need to know more about his set up. His climate may be very different than yours, his car may not have had a mid-mounted engine (which are notoriously harder to cool), and he may or may not have had ducting that redirected his airflow properly through the radiator... which is all I've suggested.

    For your own configuration, a 30 degree slope from horizontal results in halving the frontal area of the rad... so it reduces it from 18"x22"=396 in2 to sine30x18"x22"=198 in2. You can't regain the area unless you redirect the airflow so it arrives perpendicular to the face of the radiator. If you don't, every fin and every cooling tube will act as a deflector... if you can't see through the rad at the angle the airflow will hit it, then you've reduced the effectiveness.

    To help visualize whether you'll have heating problems or not, take a look at the size of radiators in other cars that run 400+ HP. My guess is that their effective cooling area will be greater than 200 in2. Also, 76mx mentioned that it may be possible to double your cooling capacity by having tubes that run from the rear to the front and back again. That may be the case, but it may not. According to Gary Witzenburg, Pontiac thought they could do without a radiator for the same reasons with the 98 HP Fiero during the initial design. They ended up having to put in a 300 in2 rad.

    Anyway, all I'm saying is that to achieve the full efficiency of your radiator, you'll need an inlet shroud that converts as much of your long narrow front grill area into a 60 degree upward sweeping shroud that fits the front face of the rad. Or you can wing it and see how it works without one.
    Last edited by Bloozberry; 11-28-2018 at 09:10 PM.

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