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Old 01-30-2020, 02:40 PM   #21
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I love it. This is a super cool mod, and I'll be following. May end up doing something similar myself.

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Old 02-01-2020, 06:41 AM   #22
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I have it all pop riveted together (partially). Now I need to file down and clean up the edges, take it apart, wrap the hood and then drill and rivet the rest of it together. All in all I probably have a full day wrapped up into getting to this point. A few lessons learned

1) make template after template, use lots of cardboard.
2) make panels one at a time, rivet them to the hood then recheck your templates for the remaining pieces. dimensions change as the rivets go it.
3) change your jigsaw blades often to keep cuts clean.
4) use tape to protect aluminum surface
5) don't cut aluminum big with the plans to trim. Get the template 100% right then cut
6) measure the straightness constantly, it will want to pull in different directions.


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Old 02-01-2020, 09:42 AM   #23
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I'm liking your improvements to it. How do you get under the hood now? It looks like it's riveted to the body
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Old 02-01-2020, 03:12 PM   #24
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I'm liking your improvements to it. How do you get under the hood now? It looks like it's riveted to the body
Thanks, I played around with designs that would allow the good to swing up but it would have been a mess. Now to remove the hood it needs to be lifted off. All of the aluminum you see is attached to the hood.
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Old 02-02-2020, 03:44 AM   #25
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Ok now Ive really lost. I posted this up on Grassroots and a very knowledgeable guy thats been helping me told me that due to the size of this thing what I really need is a cowl flap and to make it efficient it Really should be adjustable. What if....I used the Boxsters 70mph spoiler deployment system to automatically raise and lower the flap...and change the pitch of the rear wing. It would work in the opposite way the stock wing works though it would maximize downforce below 70mph. I wonder if just reversing the poles on the stock actuators would reverse the direction they operate, anyone know? Alright my crazy pills are wearing off.

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Old 02-02-2020, 04:45 AM   #26
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Ok Im back and with some more crazy piles. So using the stock Boxster actuator system wont work because it deploys at 70 and retracts at 45 or something. I would need a signal thats consistent at 70. I wonder how the stock system is being signaled, maybe theyre is a consistent signal I could use from it. Anyone know?
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Old 02-02-2020, 09:34 AM   #27
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If it was me, I would slap an Arduino in there as a control system.
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Old 02-02-2020, 10:30 AM   #28
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If it was me, I would slap an Arduino in there as a control system.
That's what I was thinking.... but I'm not an arduino pro... and I was afraid he'd ask me how, hahaha.

Are you a guy who can build stuff like that?

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Old 02-02-2020, 11:23 AM   #29
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That's what I was thinking.... but I'm not an arduino pro... and I was afraid he'd ask me how, hahaha.

Are you a guy who can build stuff like that?

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Yeah I do it all the time. I haven't done it on a car yet(can't be that different), but that's part of what I have planned for my '97.
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Old 02-02-2020, 12:16 PM   #30
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There's a few factory vehicles that have a similar hood extractor. Do they have adjustable flaps on them? Seems to me you're starting to over engineer it. The more complex items, the more chances of something breaking and things break a lot on race cars. Just my opinion
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Old 02-03-2020, 12:34 PM   #31
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Thumbs up

I love your guts, not anyone would attempt this.. :-)

However, Im not totally convinced regarding the benefits. If you had a middle radiator Im sure venting it via the hood is the hardcore way, better than via "the smile" and far better than the standard venting under the car. (given reasonable angles and size of outlet) As a stand alone aero-mod not needed for venting a radiator I'm afraid it will give quite a lot of drag, If I where to attemt it I believe I would go for a smaller outlet, not let the opening go so far forward.

Not that you asked for my subjective opinions.. Im certainly no expert! :-)
Love this kind of topics and creative mods, looking forward to upcoming updates!
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Old 02-11-2020, 03:41 AM   #32
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Love this project. I suggest mixing up some flowviz to see what the airflow looks like across the hood. Based on that you can adjust the angle of attack/radius to keep the airflow attached.

EDIT: if you haven’t already, you should read this: https://read.amazon.com/kp/kshare?asin=B01N25RRVT&id=7NWd7w_BSJ-sgyVpdT7aNA&reshareId=JJCPBHBDVCBEFBYGWMRF&reshareChannel=system
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Old 02-11-2020, 06:06 AM   #33
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That's what I was thinking.... but I'm not an arduino pro... and I was afraid he'd ask me how, hahaha.

Are you a guy who can build stuff like that?

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I could do it - could use a 5 or 10 HZ GPS to monitor speed and send a signal to raise or lower the flap. Right now I am running an arduino powered homemade GPS latching speedometer in my car that latches and displays my vMax on the straights and my vMins on the corners.

[Edit - tapping into the car signal instead of a GPS would probably be a lot better but I have no idea how to do that ]

Check out the digital screen in the lower left of this video. On the left is a real-time GPS speedo, and to the right is the pinned vMin or vMax speed. (The vMin is really useful, when I am trying to build speed through a corner I can peek down on the next straight and see how I did). There is a little overlap due to it being such a tiny screen - the intent was just to display the vMin/vMax but I had the current speed on there for debugging, and just left it there.



For this we could define two speeds, one at which the cowl would open and one at which it would close. Separate them by some amount (5 mph?) so that it doesn't oscillate when you are near the threshold speed. If you want to do it, I'm in. I have never controlled a motor before but we could figure it out

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Old 02-11-2020, 07:14 AM   #34
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You could easily use a voltage divider circuit from the VSS / wheel speed sensor to feed a speed reference into the arduino. From there, map an output to a relay on/off at whatever speed you want to deploy and retract. No gps lag then.
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Old 02-11-2020, 07:49 AM   #35
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I love this project!

Is there any thought to create a slight ridge on the leading edge of the vent? Most motorsport-oriented vents I have seen are slightly "proud" of the plane of the hood. I gather that this creates a small vortex which aids in extraction.

Have a look at modern cars like a McLaren P1, or more basic executions like the original racing GT40s.
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Old 02-11-2020, 11:12 AM   #36
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You could easily use a voltage divider circuit from the VSS / wheel speed sensor to feed a speed reference into the arduino. From there, map an output to a relay on/off at whatever speed you want to deploy and retract. No gps lag then.
Oh yeah that would be a lot easier/better than adding a GPS I am following this so I can learn new things. Since I only have experience with arduino GPS projects that's what everything looks like to me
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Old 02-11-2020, 02:44 PM   #37
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I love this project!

Is there any thought to create a slight ridge on the leading edge of the vent? Most motorsport-oriented vents I have seen are slightly "proud" of the plane of the hood. I gather that this creates a small vortex which aids in extraction.

Have a look at modern cars like a McLaren P1, or more basic executions like the original racing GT40s.
That would be very effective, and would lessen the need for such a large duct like truegearhead has made. The same thing on the leading edge of the front wheel wells will give you similar results.

Just those two modifications would help lessen lift, which many people call adding downforce. It isn't adding downforce, of course, but if you eliminate 200 lbs of lift, it's the same as adding 200 lbs of downforce.

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