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    Aero Testing

    I’ve been planning a big cooling and aero related modification for awhile now. Before I did anything, I want to get some reference data to know whether I've achieved my objective of reducing drag, improving cooling and saving a couple of lbs.

    The plan is to use a non-M manual radiator and a large oil cooler mounted on the back. Ideally I'd use a fullface oil cooler. Unfortunately, nothing off the shelf exists at this point. Fabricate a vent on the back of the radiator to vent out of the hood. The idea here is to minimize air coming into the engine bay to reduce drag, improve downforce and be able to use a flimsier hood which can be 2-3 lbs lighter. I currently have a bunch of gaps and openings so I'm guessing I have a big ol' high pressure region under the hood which is made worse with the front splitter.

    The complication is having enough room on the backside of the radiator to make a vent that promotes flow attachment up and over the engine then out of the hood without screwing up the flow up the windshield which could affect flow across the rear wing.

    Back to the radiator/oil cooler. I think most people go the wrong direction by adding thicker radiators, more radiators, and more fluid. One thing that has had a huge impact is reducing my coolant volume to about 1.75 gallons. I might have a radiator with a fullface oil cooler custom made, need to get off my butt and get pricing.

    First, I want to take a pressure differential across the radiator. I installed an air probe before and after the radiator connected to a meter mounted on the dash.

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    Second, want to check for flow detachment across the hood and windshield. I’ll record this with a GoPro mounted above the windshield.

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    Attached Files
    Last edited by bigjae46; 11-07-2024, 10:24 AM.

    #2
    Hell yeah, looking forward to seeing the results.
    2002 Topasblau M3 - Coupe - 6MT - Karbonius CSL Airbox - MSS54HP Conversion - Kassel MAP - SSV1 - HJS - PCS Tune - Beisan - MK60 Swap - ZCP Rack - Nogaros - AutoSolutions - 996 Brembos - Slon - CMP - VinceBar - Koni - Eibach - BlueBus - Journal

    2012 Alpinweiss 128i - Coupe - 6AT - Slicktop - Manual Seats - Daily - Journal

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      #3
      Third picture has me convinced this car is held together by gaffer tape lol

      Jae is doing some race team aero sh!t by himself. Very impressive, looking forward to updates.

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        #4
        Some learnings - if you delete the cabin air filter housing, you need to seal up the hole. You get a lot of air being sucked through the opening into the engine bay. I think this reduced the differential pressure across the radiator, I have to watch the in-car which has the manometer readings.

        Had some issues with the pressure probe tubes - need to secure them better. They would move and get jammed between the hood and fender which caused a pinch point.

        When I towing the car to the track, all of the tufts were straight. On track, the tufts behind the side vent showed some turbulent air so there is some air extraction from the vent.

        Here is the baseline with the cabin air filter opening covered.



        ***VIDEO with cabin air filter opening uncovered coming***

        I signed up for a PCA event in Dec to do some more testing. Here's the plan

        - I'm going to get better air pressure readings.
        - Tape down my floppy hood and windshield cowl, cover the cabin air filter opening
        - Cover the kidney grills
        - Rip off all of the duct tape around the radiator ducting check the differential across the radiator
        - Uncover the kidney grills
        - Un seal the windshield cowl


        Originally posted by Slideways View Post
        Third picture has me convinced this car is held together by gaffer tape lol

        Jae is doing some race team aero sh!t by himself. Very impressive, looking forward to updates.
        Lol...thanks! Had to seal all of the gaps in the ducting. We'll see what comes of this.

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          #5
          The trailing edge of the hood bounces around more than I would have guessed. Just me - I'd find that kind of distracting at speed.

          Full props on the experiment and lessons learned.

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            #6
            Originally posted by Estoril View Post
            The trailing edge of the hood bounces around more than I would have guessed. Just me - I'd find that kind of distracting at speed.

            Full props on the experiment and lessons learned.
            I made the carbon hood. I made it light...too light at 6lbs...and the underside is two small plates for the hinge mounting. As a result, it tends to flutter. I consider my hood to be more of an engine bay covering than an actual hood...lol

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              #7
              Here is the video with the cabin air opening uncovered. The hood tends to lift up at a slightly lower speed

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                #8
                I have some plans to dig into cooling this winter. Saw your post on professional awesome Facebook page. Excited to see this is your car and a more detailed breakdown of your findings!

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