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I really think that a vacuum actuator is going to be the best choice here. Small and light, inherently resistant to heat and moisture, and practically free.
You'll need a reservoir tank with a check valve in order to keep it open after engine shut-down, but it's possible that the time-delay could be solved with nothing more than a tiny pinhole somewhere in the system. In other words, no electronics needed at all. Start the engine, vacuum happens, and the louvers open. Stop the engine, and the louvers close at a rate determined by the leakage of the system.
I really think that a vacuum actuator is going to be the best choice here. Small and light, inherently resistant to heat and moisture, and practically free.
You'll need a reservoir tank with a check valve in order to keep it open after engine shut-down, but it's possible that the time-delay could be solved with nothing more than a tiny pinhole somewhere in the system. In other words, no electronics needed at all. Start the engine, vacuum happens, and the louvers open. Stop the engine, and the louvers close at a rate determined by the leakage of the system.
This is what I was planning on using for delay.
It has quite the range, and can be tucked somewhere inside the car.
I already have a 4.2 liter vacuum reservoir, and a bunch of check valves sitting in a box for this project.
Said reservoir was a pair of 20 cm stainless steel Ikea salad bowls in an earlier life, and now resides ahead of the left front wheel well, inside the bumper opening.
When I was a child, my uncle Diego used to tell us "When in doubt, weld salad bowls together."
Nobody really understood what he meant by this at the time. My father thought he was a bit crazy. Turns out that now I understand what tio Diego was onto.
Truthfully, I still feel like this project is crying out for an all-mechanical solution, with the louvers gently drifting closed after shutdown as the pressure in the bowls slowly equalizes with atmospheric.
I started working on a home automation controller. Raspberry Pi 3B+ with POE hat and 7" touchscreen. Plan to add a gesture/proximity sensor so it acts similar to the smart thermostats and I can throw stuff at it to make it do things. Right now it runs in kiosk mode connected to Home Assistant Dashboard, but I plan to PXE boot it once I get the build nice and tuned.
You could maybe find a small solenoid to put in line with the vacuum hose and connect that to your timer circuit. Have the solenoid operate a small valve.
Just also had an idea... a motor for an electric exhaust cutout. They are water proof and temperature resistant to a degree. They are kinda large though. I have one not installed yet and have been playing with it. You can control how far it opens and they don't operate instantaneously like a solenoid. the brand I bought was under $100 for the "kit" and I think they sell replacement motors separate. I can share link it or give more info if you want...
The louvers need to stay open for a couple minutes to let heat escape and cool down.
Understood. Hence, a one-way valve between the engine and sputnik. Stick a vacuum gauge on it, and see how long vacuum lasts after shutdown. Unless you have a leak somewhere, it should hold up for a while.
Worst-case, a smaller reservoir, with a check valve, inline with the feed to the vacuum actuator. If it does a good job, you might even need to put a bleed hole into it to prevent the louvers from staying open forever.
Either way, this is easily going to be the lightest weight, most reliable, and, IMO, most elegant solution vs anything electronic. Probably lowest-cost as well.
IIRC my mercerdes does something cool with the grill in winter vs summer temps. my prelude has vacuum actuators, just like the NB has one for VICS or VTCS.
I used to be a photographer, in the sense that I got paid to take pictures of things. These days, I'm just a guy with a cell phone that would have made past-me green with envy, and who happens to be surrounded by things which are made of food and emit poop and noise.
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