Anti-stealth Prius camping - going large...

Idea is probably ok. I'm pretty sure it won't hurt the engine. Let's make sure it doesn't hurt you.

If you used round tubing rather than downspout, and could find a short silicone rubber tube of the right diameter, you could probably join your tubing to the exhaust with the silicone tube and have it gas-tight. You might not be limited to metal for the tube material; I don't think the car will be doing anything but idling while in this configuration, and if you've got access to a temperature probe, you might measure what's arriving at the tailpipe and find out it might be cool enough to give you more material options.

I think you want a way for condensed water to drain out separately so that it does not accumulate in the low bend there and gradually increase the back pressure. You can do that with a reducing tee out there, where the exhaust leg points up (full diameter), and the reducing leg points down, with a U bend for a trap, and then a bit beyond the trap to direct the escaping water away from your mattress.

When setting up, pour some water in the trap so it is already sealed; you don't want it being a ground-level exhaust gas outlet for as long as it takes to condense enough water to fill it.

I might also add a couple feet to the top above the roof of the tent.

 

that is so cool, well done!

 

I love it -- your setup is like a Prius Habitent, but on steroids:

I can't see any engine issues. If you wanted to insure a positive flow, you could add a 12v fan somewhere in the exhaust path. I've used this one for something different, but it works well:

Stealth is more about not making anyone uncomfortable. Think of all the places you'd like to visit or sporting events you'd like to see in person. One of the biggest expenses is hotel cost. I can park just a few blocks from the sold-out stadium the night before the game for free and roll out of bed while others fight traffic for hours. I can visit places and friends all over the country without hotel cost. It's all legal, but by being stealth, you don't make the people who actually live there uncomfortable.

Definitely!

 

Hehe. You've got the exhaust-to-coolant heat exchanger in there doing its thing, plus several feet of cold stainless steel to pass through, and not really idling long enough to take the chill off.

Were you measuring the temp of the metal tailpipe itself, or of the gas exiting the tailpipe?

 

The gas might be warmer than the metal gets.

You've reminded me of a youtube video I saw once of a guy who thought he was showing how to test a catalytic converter. He had an IR thermometer, and it was a classic case of having a fancy tool and not reading the manual:



Guy thought that because it projects a laser spot at the center of its measuring cone, he's somehow actually plucking the temperature off a sliver of exhaust pipe showing between a heat shield and a flange.

If he had taken a look at the diagram in his manual:



... he'd have known that 210.2 °F was the average of a tiny sliver of exhaust pipe, a bunch of heat shield, part of a joint flange, and some air.

 

I think you raise a good point. A catalytic converter won't even function under 400 degrees; stainless tips at end of an exhaust pipe get discolored over time from the heat of the exhaust gas, so it must be pretty darn hot. A quick Google search indicates that a foil-lined pvc vent has max temp of 230.

But the flip side is a very short idle time so my guess is that its a non-issue.

 

I believed you, but I wondered whether measuring the surface of the stainless steel tailpipe might show a lower temperature than the actual gas coming out. (The steel temperature is going to be a balance of how much heat is transferring to it from the exhaust gas and how much is radiating and convecting away.)

So I went out and compared mine, using an IR reading of the tailpipe itself, together with a thermocouple probe stuck a few inches into the tailpipe in the middle of the flow.

Still, it wasn't that bad. At idle, the thermocouple in the exhaust gas flow was seeing about 43 °C. The IR reading of the tailpipe was initially 20-something before I realized I had the emissivity set for 0.97 which is about right for water. Metals can have really low emissivity depending on how shiny they are—I could get the reading to look more like 60 °C if I lowered the emissivity setting to somewhere in the fifties. That's probably too low because the tailpipe is anything but shiny. The value given here for "Stainless steel, weathered" is 0.85, which probably would have made the reading around 40-ish and a pretty good match for the thermocouple reading.

What emissivity was yours set for?

 

An IR thermometer without an adjustment for the emissivity of the material it's pointed at can give readings quite wide of the mark depending on the material.

The good news is there are lots of materials (like good black electrical tape) that have emissivity in the high 0.90s, so if that's what the thermometer is adjusted for, you can just slap a layer of one of those on whatever you're trying to measure, and then point the IR thermometer at that.

 

Nice work! I have a similar gazebo but only half the size that I use behind the car when camping (we don't have so many bugs here) and have been thinking about an exhaust "chimney" since purchasing my Prius, glad to hear that it is possible and works well

 

Reflectix 48 in. x 125 ft. Heavy-Duty Perforated Radiant Barrier-RB4812550 - The Home Depot ?