I've noticed this quite a few times.I'll be at a stoplight and i see cars with water vapor coming out,while others don't.What causes this?
why do a lot of cars emit visible water vapor and
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The water that condensed in the exhaust system is turngin into steam. The cars you don't see steaming were either parked in a garage or have been running long enough that the water has all boiled out.
The water condenses in the exhaust because the cold wet air makes its way into the warm exhaust then everything cools off.
The water condenses in the exhaust because the cold wet air makes its way into the warm exhaust then everything cools off.
A catalytic converter changes poisonous gases to harmless carbon dioxide, nitrogen, oxygen, and water.
JHZR2
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The more metal, the more condensation surface. Longer duration before the system heats up, therefore a bigger mass of water is just in there.
Add in low-temp use, lots of idling, and relatively low flow for long times, and youre more prone to build up lots of water.
There is also the issue of combustion efficiency, fuel rates, and how much water is made. A big engine is likely to move more air/fuel at idle, and thus have more water there, then more buildup in a big system.
Condensation in the system aside, it also likely has much to do with how cold you are before coming out to the atmosphere, and then how it disperses.
Add in low-temp use, lots of idling, and relatively low flow for long times, and youre more prone to build up lots of water.
There is also the issue of combustion efficiency, fuel rates, and how much water is made. A big engine is likely to move more air/fuel at idle, and thus have more water there, then more buildup in a big system.
Condensation in the system aside, it also likely has much to do with how cold you are before coming out to the atmosphere, and then how it disperses.
JHZR2
Staff member
Originally Posted By: XCELERATIONRULES
A catalytic converter changes poisonous gases to harmless carbon dioxide, nitrogen, oxygen, and water.
over 99% of the conversion to CO2 and water occurs in the combustion in the engine.
It is only traces that get polished, compared to the bulk airflow going through the engine.
The converter is in no way the water generator...
A catalytic converter changes poisonous gases to harmless carbon dioxide, nitrogen, oxygen, and water.
over 99% of the conversion to CO2 and water occurs in the combustion in the engine.
It is only traces that get polished, compared to the bulk airflow going through the engine.
The converter is in no way the water generator...
Originally Posted By: JHZR2
Originally Posted By: XCELERATIONRULES
A catalytic converter changes poisonous gases to harmless carbon dioxide, nitrogen, oxygen, and water.
over 99% of the conversion to CO2 and water occurs in the combustion in the engine.
It is only traces that get polished, compared to the bulk airflow going through the engine.
The converter is in no way the water generator...
The converter is not a water generator because my Marauder has converters and my El Camino does not and they both emit water out of the tailpipes.
Originally Posted By: XCELERATIONRULES
A catalytic converter changes poisonous gases to harmless carbon dioxide, nitrogen, oxygen, and water.
over 99% of the conversion to CO2 and water occurs in the combustion in the engine.
It is only traces that get polished, compared to the bulk airflow going through the engine.
The converter is in no way the water generator...
The converter is not a water generator because my Marauder has converters and my El Camino does not and they both emit water out of the tailpipes.
If it's really humid out, the exhaust system in a car is just like any other surface exposed to ambient conditions. Once it cools off to the ambient temperature, and if the ambient air temperature is cool enough, atmospheric moisture will condense in the exhaust system. Probably more so because it's metal and has a fairly large surface area. Once the exhaust starts heating up, the water starts boiling off - hence steam out the tailpipe. That and the fact that one of the byproducts of combustion is water vapor.
I see the most steam when the relative humidity is high in the mornings.
I see the most steam when the relative humidity is high in the mornings.
Some mufflers may not have drain holes or they have becomed clogged - then you get even MORE vapour. Mufflers are real steam kettles! Most of the water coming out a tailpipe is the byproduct of combustion. Balance a stoichiometric oxidation of Octane and look at the H-0-H mass.
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Gasoline is about 1/7 hydrogen. Water is 1/9. You get about a gallon of water for every gallon of gas. The vapor may or may not condense enough to be seen before it gets out the tail pipe.
How about a turbo? Is the exhaust cooled more as it goes through the turbo?
How about a turbo? Is the exhaust cooled more as it goes through the turbo?
Water vapor out of the tailpipe is generally visible from a cold start for a while.
Cars that are up to temperature rarely show this, except sometimes in real cold weather.
If you see it, it is vapor. Steam is an invisible gas. Exhausts normally run at temps high enough so that the water/water vapor turns to steam.
And like mentioned, water is a product of burning gasoline. A LOT of water.
Cars that are up to temperature rarely show this, except sometimes in real cold weather.
If you see it, it is vapor. Steam is an invisible gas. Exhausts normally run at temps high enough so that the water/water vapor turns to steam.
And like mentioned, water is a product of burning gasoline. A LOT of water.
Originally Posted By: daves66nova
I've noticed this quite a few times.I'll be at a stoplight and i see cars with water vapor coming out,while others don't.What causes this?
Temperature of the exhaust system and the surrounding air. At temps right around freezing, most cars will emit visible steam out the tailpipe until the exhaust system gets hot, then they more or less stop. So some of the cars you're seeing are warmed up, some aren't.
When it gets a good bit colder and/or damper outside, they'll keep steaming even when fully warm. Get it cold enough and *diesels* start leaving visible vapor too. Normally they don't emit visible vapor because their exhaust is much more dilute (mostly just air) compared with a gasoline engine's exhaust. New diesels with particulate filters and catalysts emit visible vapor much more frequently than older diesels, too because:
As for the catcon argument- YES catalytic convertors do indeed put more water into the exhaust gasses because they take partially-burned fuel (hydrocarbon compounds of various forms) and react it with oxygen to form carbon dioxide and more H2O. But even without the catcon, there is a lot of water in the exhaust stream from normal combustion in the cylinders.
I've noticed this quite a few times.I'll be at a stoplight and i see cars with water vapor coming out,while others don't.What causes this?
Temperature of the exhaust system and the surrounding air. At temps right around freezing, most cars will emit visible steam out the tailpipe until the exhaust system gets hot, then they more or less stop. So some of the cars you're seeing are warmed up, some aren't.
When it gets a good bit colder and/or damper outside, they'll keep steaming even when fully warm. Get it cold enough and *diesels* start leaving visible vapor too. Normally they don't emit visible vapor because their exhaust is much more dilute (mostly just air) compared with a gasoline engine's exhaust. New diesels with particulate filters and catalysts emit visible vapor much more frequently than older diesels, too because:
As for the catcon argument- YES catalytic convertors do indeed put more water into the exhaust gasses because they take partially-burned fuel (hydrocarbon compounds of various forms) and react it with oxygen to form carbon dioxide and more H2O. But even without the catcon, there is a lot of water in the exhaust stream from normal combustion in the cylinders.
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Originally Posted By: labman
How about a turbo? Is the exhaust cooled more as it goes through the turbo?
Should be cooler since the turbo is converting mechanical energy from heat energy, but also passing a possbily 2x greater volume of fuel and air also(at 14.7lbs gauge boost).
How about a turbo? Is the exhaust cooled more as it goes through the turbo?
Should be cooler since the turbo is converting mechanical energy from heat energy, but also passing a possbily 2x greater volume of fuel and air also(at 14.7lbs gauge boost).
I'd think the exhaust coming out of a turbocharged engine is much hotter. That's why EGT gauges are important for boosted engines. The turbine section of a turbocharger gets ridiculously hot.
Blow on a camp fire and see what that does to the coals. They get HOTTER! The same thing happens to an engine that's being forced fed fuel and air at levels greater then ambient.
Blow on a camp fire and see what that does to the coals. They get HOTTER! The same thing happens to an engine that's being forced fed fuel and air at levels greater then ambient.
Originally Posted By: JHZR2
Originally Posted By: XCELERATIONRULES
A catalytic converter changes poisonous gases to harmless carbon dioxide, nitrogen, oxygen, and water.
over 99% of the conversion to CO2 and water occurs in the combustion in the engine.
It is only traces that get polished, compared to the bulk airflow going through the engine.
The converter is in no way the water generator...
+1
The combustion process generates more than a gallon of water for each gallon of gas or diesel consumed. Has essentially nothing to do with the cat.
Originally Posted By: XCELERATIONRULES
A catalytic converter changes poisonous gases to harmless carbon dioxide, nitrogen, oxygen, and water.
over 99% of the conversion to CO2 and water occurs in the combustion in the engine.
It is only traces that get polished, compared to the bulk airflow going through the engine.
The converter is in no way the water generator...
+1
The combustion process generates more than a gallon of water for each gallon of gas or diesel consumed. Has essentially nothing to do with the cat.
Hahaha. Some of this stuff gets funny sometimes.
Yes, some of the energy LOST in a turbo is heat. Heat adds energy but it's a volume of air that does the work. I could run compressed nitrogen across a turbine wheel and make a turbo work, and ABSORB heat all the way! We actually used nitrous to boost the wheels in a twin turbo V8 in the eighties.
I guess it depends where you guys are getting your temp reading. At the exhaust port=hotter. At the tailpipe=cooler.
I'm thinking a turbo would have slightly cooler air at no boost, and hotter at high boost levels of course.
Yes, some of the energy LOST in a turbo is heat. Heat adds energy but it's a volume of air that does the work. I could run compressed nitrogen across a turbine wheel and make a turbo work, and ABSORB heat all the way! We actually used nitrous to boost the wheels in a twin turbo V8 in the eighties.
I guess it depends where you guys are getting your temp reading. At the exhaust port=hotter. At the tailpipe=cooler.
I'm thinking a turbo would have slightly cooler air at no boost, and hotter at high boost levels of course.
Basic thermo. The MAJOR energy component spinning a turbo is rapidly expanding exhaust gases due to heat of combustion. What do you think moves a piston: heat ENERGY. There is a small contribution due to mechanical pumping of compressed air. This is why a turbo spools up when you roll in WOT at a specific RPM and why its just "idling" (20K rpm) at light throttle stasis.
Energy is conserved so it has to be converted. So the conversion is Heat > Mechanical. IN this conversion heat is REMOVED from the exhaust.
-Class dismissed - its Harpoon ALe time ... Darn it's Monday!
Energy is conserved so it has to be converted. So the conversion is Heat > Mechanical. IN this conversion heat is REMOVED from the exhaust.
-Class dismissed - its Harpoon ALe time ... Darn it's Monday!
Originally Posted By: SteveSRT8
Hahaha. Some of this stuff gets funny sometimes.
Yes, some of the energy LOST in a turbo is heat. Heat adds energy but it's a volume of air that does the work. I could run compressed nitrogen across a turbine wheel and make a turbo work, and ABSORB heat all the way!
Lets see you spin it to 100K rpm and also have it flow 700 CFM at 14PSIG. You would need to INPUT more energy than you get out. Your compressor did the work to pressurise the tank gasses which are being released into the turbo as kinetic energy.
Hahaha. Some of this stuff gets funny sometimes.
Yes, some of the energy LOST in a turbo is heat. Heat adds energy but it's a volume of air that does the work. I could run compressed nitrogen across a turbine wheel and make a turbo work, and ABSORB heat all the way!
Lets see you spin it to 100K rpm and also have it flow 700 CFM at 14PSIG. You would need to INPUT more energy than you get out. Your compressor did the work to pressurise the tank gasses which are being released into the turbo as kinetic energy.
Originally Posted By: Drew99GT
If it's really humid out, the exhaust system in a car is just like any other surface exposed to ambient conditions. Once it cools off to the ambient temperature, and if the ambient air temperature is cool enough, atmospheric moisture will condense in the exhaust system. Probably more so because it's metal and has a fairly large surface area. Once the exhaust starts heating up, the water starts boiling off - hence steam out the tailpipe. That and the fact that one of the byproducts of combustion is water vapor.
I see the most steam when the relative humidity is high in the mornings.
Down here in the jungle humid heat I see water all the time coming out of car's tail pipes...I was behind a patrol car yesterday that had a good deal of water coming out of it...I was always told that was a good thing.
If it's really humid out, the exhaust system in a car is just like any other surface exposed to ambient conditions. Once it cools off to the ambient temperature, and if the ambient air temperature is cool enough, atmospheric moisture will condense in the exhaust system. Probably more so because it's metal and has a fairly large surface area. Once the exhaust starts heating up, the water starts boiling off - hence steam out the tailpipe. That and the fact that one of the byproducts of combustion is water vapor.
I see the most steam when the relative humidity is high in the mornings.
Down here in the jungle humid heat I see water all the time coming out of car's tail pipes...I was behind a patrol car yesterday that had a good deal of water coming out of it...I was always told that was a good thing.
Better that the water goes out the tailpipie instead of puddling in the mufflers - especially resonators with glass-fibre packing.
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