Engine air intake locations |
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Engine air intake locations |
Charles Freeborn |
May 22 2021, 05:02 PM
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#1
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Member Group: Members Posts: 250 Joined: 21-May 14 From: United States Member No.: 17,377 Region Association: Pacific Northwest |
My car has a downdraft fan and lowered roofline that AJRS was building in the 9o's.
When I installed a CHT I realized that it needed more airflow to the cooling fan. Methinks I'll add some scoop(s) to the equation to see if I can get the head temps down. So, location, location, location. Three images below. Where will the optimum pickup location be? I've seen a webpage done by a professor who used his AX 914 as a model and did some computer and water tank tests, but I can't read the squiggly lines well enough to tell where the best place to locate scoop(s) is. What I've come up with so far: Store bought scoops - of the kind one sees on hoods. Kinda cute, fiberglasss, would punch 4" holes through the sail panels, move other stuff out of the way and plumb to a plenum that seals to the top of the fan housing. Build a lexan scoop / plenum (clear so I can see through it with rearview) and catch the airflow at the trailing edge of the roof. Opening would be roughly 2.5" x 12" to match fan opening (11" round fan) Build a lexan scoop / plenum that catches air at the leading edge of the roof, would probably run through the interior of the car and out through the rear window opening. This seems the most obtrusive to the driver ergonomics, distraction, etc. I suppose one more option would be to do a sort of hybrid of the two roof top collectors and have it punch down through the roof just in front of the rear hoop. I've seen one (also an AJRS car) done that way. It too had the raked windshield and lowered roofline as mine does. What say ye? where is the optimal pressure on a 914? BTW, I've worked with plenty of Lexan, have all the tools, so fab isn't an issue. Thanks. |
URY914 |
May 22 2021, 07:07 PM
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#2
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I built the lightest 914 in the history of mankind. Group: Members Posts: 120,967 Joined: 3-February 03 From: Jacksonville, FL Member No.: 222 Region Association: None |
You can see the scope here.
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stownsen914 |
May 23 2021, 08:04 AM
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#3
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Senior Member Group: Members Posts: 913 Joined: 3-October 06 From: Ossining, NY Member No.: 6,985 Region Association: None |
The farther forward on the car you put a scoop, the better. Especially on a no-so-aerodynamic car like a 914, air gets dirtier as it passes over the car and gets harder to capture unless the scoop protrudes above the car (to poke through the air boundary layer).
Another idea - headlight bucket to a tube that runs through the cockpit. More work, but may be more likely to be vintage legal (SCCA allowed this from the 1980s or so I believe). I have a front hood NACA similar to the above on my 914, but I stuck it right in the middle of the hood. Very effective. I run at CHT and can quickly see a 50-75 degree temp increase on cool down laps once I slow from cooldown laps speed to paddock speed. I assume due to the scoop. (On a 911 motor.) Pic below. Note the intake scoop over the engine bay area. I don't have a good way to measure the effectiveness of that one, but I have to imagine it gets cool air to the engine. None of this is likely vintage legal though. |
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