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I get it, Danny, but why not? It's a way to pump (and pull*) modestly heated air into the place where the fan will suck it in. Probably not as good as stock but maybe better than doing nothing?

Cardboard tells me it could work as planned, mechanically speaking. Whether it would make any difference to the engine, good or bad, is another matter.

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*my theory is the flap, pulled just beyond horizontal, will cause the fan air to Bernoulli the rising, exhaust tube-heated air up and into the engine bay as well, effectively (or not-very effectively?) transforming the 3-4 exhaust pipes into a cheap and cheesy heat exchanger. 

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edsnova posted:

I get it, Danny, but why not? It's a way to pump (and pull*) modestly heated air into the place where the fan will suck it in. Probably not as good as stock but maybe better than doing nothing?

*my theory is the flap, pulled just beyond horizontal, will cause the fan air to Bernoulli the rising, exhaust tube-heated air up and into the engine bay as well, effectively (or not-very effectively?) transforming the 3-4 exhaust pipes into a cheap and cheesy heat exchanger. 

I'm not seeing how the air would be even modestly heated when the engine is cold.

If the engine is cold enough for any of this to matter, it'll be cold enough for the oil to be bypassing the cooler. The cooler won't have hot oil circulating through it, so the air would be pretty much the same temperature coming out as it was going in.

As for the Bernoulli effect on the exhaust, I suppose that's possible, but I would also suppose the effect to be really, really minimal.

I'm wondering (in a Spyder, especially) why any of this matters. If you are operating the car, it's warm outside. If it's warm outside, and the engine is even modestly hopped up, it'll make more than enough heat eventually. If you are trying to prolong the life of an engine that will certainly see less than 4000 mi/yr of action, then you are worrying that the engine might need to be rebuilt in 2040 instead of 2045 (and that is being generous).

If you want to do it because you want to do it-- then I completely understand that.

Carry on.

Well, Stan, 30 seconds after startup those headers are waaay too hot to touch. Hot air wants to rise. But...

You guys are right: It's a bridge too far and at least a misdemeanor violation of the KISS principle. It's long past time I wrapped this project up. I'll just duct it down and out and let the N.O. worry about not having thermostatic control during warm-up. 

Thanks for your kind and experience-inflected advice. 

Riveting the pieces together. Getting the edges flat. Trimming the sheet aluminum. 

I'll share with you all that someone whose knowledge and opinion I respect deeply has advised me that this underpan ain't gonna cut it. He says I should just tear it off and carry on, and I frankly think he may be right.

But I also feel like, since I'm this far into it, I might as well carry on to completion, just to see how good (or bad) it turns out, and even if I do end up crumpling it up for the recycling guys.

Here's the rearmost bit fit up under the car again. As you can see, I still have to make a little plate to connect the broad, flat area in the back to the piece in the middle, which also still needs the louvres to be finally fitted.  

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There are also "doors" on each side to allow for access to the upper outside exhaust flange bolts. It would probably be best to weld both top bolts in as studs, facing backward, to make R&R of the mufflers easy.

And there's a little gap up front where it slides over the pipe shroud. I'll CAD that piece this AM I think.

After those things there's some more riv-nuts to make all the pieces fast. And some insulation for the ceilings of the pipe and muffler shroud bits. 

It's actually getting there.

 

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Thanks, @DannyP, I think if I were half as savvy as you at assessing the amount of time jobs will take I'd never have gotten started on this. Last night after dinner I hammered out a piece to shroud the cutout for the gate shifter cable anchor. 

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I got back after it for two hours this am:IMG_5009IMG_5010IMG_5011IMG_5012IMG_5014

This piece will get rivets tonight or tomorrow. The trick to doing this, apparently, is you have to assemble it with all the fasteners before trying to shape or fasten anything else to it, or else everything that's not what your working on will change shape. 

With this little bulb thing on it I made the (much simpler) close-off plate for the back and started on the last two bits of flat bar reinforcement. 

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Last edited by edsnova

Louvres test-fitted.

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Mufflers test fitted...

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This is an enormous PIA, by the way. The mufflers would not slot in until I removed that stiffening plate I just made in the back. The shrouds kind of curve around the mufflers and so you have to leave the pan loose and jiggle the exhaust in. 

Just a few more little pieces to make and then some final thread-certs and rivets, clean up, tapping, etc. 

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Last edited by edsnova

Thanks all.

It's quite far from perfect and, as proud as I am of it, I'm still not sure it's going to make the final cut. 

Sort of like a first draft of a very long, complex article. You write and write and, if you're in a good groove, you feel really good about it—and it IS really good!—but it still needs an editor. 

And the editor might ask a question you can't answer, and that might be a fatal thing that causes the story to be killed, and you might even get mad but, in the end you'll be glad they asked that question and saved you from embarrassment or an even worse disaster.

In terms of my current skills, this piece is like a rough draft of the second long magazine article I ever wrote. 

The good news is it can all be taken off the car in under an hour (putting it back on is closer to two) so it's an option either way.

And I am learning a lot.

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