this post was submitted on 05 Dec 2023

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What happens of you use the gas from the exhaust pipe to inflate a tire? (self.nostupidquestions)

submitted 7 months ago by 0Xero0 to c/nostupidquestions

34 comments fedilink hide all child comments

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[–] dgmib 118 points 7 months ago (1 children)

The exhaust from a typical ICE wouldn’t have enough pressure to inflate a tire, so you’d need a compressor. Of course if you had a compressor you’d just use clean air.

If for some reason you used a compressor to compress exhaust gases to fill a tire, it would mostly be the same as filling with air at first.

Exhaust gas is mostly a mix of carbon dioxide and and water vapour, with small amounts of oil residue, and other organic compounds. The water vapour will condense as it cools likely leaving some liquid water in the tire, which won’t cause immediate issues but will cause vibrations which will accelerate wear not just on the tire but possibly the entire suspension.

The organic compounds will cause the rubber to break down over time and the tire will wear out sooner.

[–] [email protected] 7 points 7 months ago (1 children)

Works pretty good to fill up an air mattress, or an airbag offroad jack

[–] [email protected] 6 points 7 months ago

Much lower pressure, of course.

[–] [email protected] 52 points 7 months ago (2 children)

The exhaust won't work, but included with my grandpa's 1952 8n ford tractor came with an adaptor that you would replace a spark plug on one cylinder, and then pump up a tire using the unburned air fuel mixture into the tire, and running the enigne on the other 3 cylinders.

So the idea is very close to something that was actually done in the real world.

[–] [email protected] 33 points 7 months ago (3 children)

That's a bomb you're inflating at that point.

[–] [email protected] 8 points 7 months ago (1 children)

It isn't very likely to connect with open flame. Tires are pretty well suited for containing air.

In case your rig is on fire for long enough to melt through the very thick tires, that would be dangerous, yes.

[–] isles 3 points 7 months ago (2 children)

The inside of the Hindenburg wasn't very likely to connect with open flame.

[–] [email protected] 4 points 7 months ago

To be fair. No one puts close to a hundred men on a tractor and floats it in the sky (including a dedicated smoking lounge).

All I'm saying there's a bit of a spread to the risk evaluation.

[–] theluckyone 1 points 7 months ago

Tell me you don't understand the concept of static electricity without telling me you don't understand the concept of static electricity.

[–] [email protected] 8 points 7 months ago (1 children)

You are not the first to think of that . But I know the adaptor was somewhat common (the 8n is the most popular tractor model ever, and shared an engine with the model A) and i've never heard of issues. I'm not sure if that is because nobody talked about it though.

[–] [email protected] 3 points 7 months ago

You'd need to either already have the tractor on fire, or somehow have an ignition source for this to happen, but you've essentially made a pipe bomb.

[–] PlutoniumAcid 6 points 7 months ago

Perfect username for that comment ❤️💣

[–] CADmonkey 4 points 7 months ago (3 children)

I'm going to use this to fill my motorcycle tires. Fuel vapor bombs on both wheels. Yikes.

[–] Decoy321 2 points 7 months ago

Don't have to pay for insurance if any little crash becomes deadly!

[–] Fosheze 2 points 7 months ago

They say in a car motorcycle colision the motorcycle always loses. But that's not true; we could both lose.

[–] [email protected] 2 points 7 months ago (1 children)

Just unplug the injectors first. Or turn the fuel shutoff valve if it's carbureted.

[–] CADmonkey 1 points 7 months ago (1 children)

If you turn the fuel off on a carbureted engine, it won't run.

[–] [email protected] 1 points 7 months ago

Yes, that's the point. You don't need it to run to fill a tire: just crank it over a few times with the starter then replace the spark plug and turn the fuel back on.

If you wanted to run the engine while once cylinder is connected to a tire then you'd very quickly overinflate it. Also you'd be running the engine without a cylinder (no spark plug) which is probably always a bad idea and in many cases straight up impossible.

[–] [email protected] 41 points 7 months ago* (last edited 7 months ago) (1 children)

The pressure from an exhaust pipe is <0.17 bar or 2.5 PSI.

My car tires have to be pressurized to 2.3 bar or 33 PSI.

So what happens is you get a flat tire that smells funny. And if you are doing that in a garage, you'll probably get carbon monoxide poisoning.

[–] XeroxCool 7 points 7 months ago (1 children)

Factor error: 33psi is about a typical car tire pressure. Race bicycles are like 120. Please keep 330 away from rubber

[–] [email protected] 13 points 7 months ago* (last edited 7 months ago) (1 children)

Looks like google helpfully stripped away the "." in 2.3 bar because my locale wants me to use a "," instead.

2.3 bar != 330 psi

But the point still stands. 0.17 bar / 2.5 PSI is not enough to inflate a tire.

[–] [email protected] 15 points 7 months ago

You get tired.

[–] [email protected] 11 points 7 months ago* (last edited 7 months ago) (2 children)

There's going to be a limit to how much pressure before stalling and/or damaging the engine, but it would inflate, and as the gases cooled, it would deflate somewhat.

Exhaust jacks are used in 4x4 recovery, so an engine can lift a car, but they seem pretty limited and dangerous and I've only seen one used once in my ~25yrs off road.

[–] 0Xero0 1 points 7 months ago (3 children)

Okay hear me out, I know this is funking stupid but what if: We only use a portion of the exhaust and make some sort of system that can feed the gas to when wheels are spinning and monitor the pressure at the same time, then add a lining on the inside of the tires to protect the rubber.

[–] aelwero 9 points 7 months ago

These systems exist already, they just use a belt driven air compressor because it's ridiculously more practical/efficient.

[–] [email protected] 6 points 7 months ago

I have an air compressor which is powered by the 12V DC outlet in a car. They are quite cost effective and easy to buy. I use it all the time to refill my tires. Much better than some odd exhaust pressure solution.

[–] [email protected] 3 points 7 months ago (1 children)

and make some sort of system that can feed the gas to when wheels are spinning

Rotating seals are always a pain in the ass.

[–] [email protected] 3 points 7 months ago* (last edited 7 months ago)

Yeah, these guys suck.

[–] XeroxCool 1 points 7 months ago

so an engine can lift a car

Force = pressure x area

It's not that big of a feat. Using the very low estimate of 2.5psi from another comment about exhaust pressure, that means it can sustain 2.5 pounds(force) per square inch. To lift half a 5000lb suv the force needed would be 2500lbs. Rearrange the equation to [area = force/pressure] and it becomes [area = 2500lbs/2.5 lbs per square inch] so 1,000 square inches. Divide by 144square inches per square foot (12x12) and you get 6.94 square feet gives you 2500lbs of force from 2.5psi. Then to find that area from a circle, divide by pi and square root the result (rearranging area=pi*r^2 ) and you find that 2.5psi will lift the side of an SUV with a little less than a 3 foot diameter circle. That's about the size of the lift bags I've seen.

And all that while I'm thinking 2.5psi sounds low. Regardless, I doubt an exhaust system would handle anything close to tire pressure before popping off fittings. Plus mufflers have weep holes and fittings tend to leak anyway. They rely on the direction and speed of exhaust gas a fair amount.

[–] [email protected] 11 points 7 months ago

You'd fill a tire with pretty low pressure, dirty, mostly co2, I'd assume. It probably wouldn't be drivable and even if it was the small amount of oil and fuel residue would likely damage the inside of the tire after a while.

There are some cool gadgets that you screw into a spark plug socket in the engine and crank it over with the starter to inflate a tire. You'd want to unplug the fuel injector(s) or you'd be turning the tire into a bomb.

[–] [email protected] 10 points 7 months ago (1 children)

The sherp vehicle does just that.

[–] [email protected] 1 points 7 months ago

Much lower tyre pressure than almost any other vehicle, I'd imagine.

[–] [email protected] 6 points 7 months ago

The tire works fine, the air your using is hot, so as it cools down the tire will lose pressure a bit

[–] [email protected] 6 points 7 months ago

I'm not so sure you can get enough pressure from the exhaust