Exhaust differences.

[Kaie]

So I've always wondered this and sort of made my own halfass reasoning which may or not make sense to anyone else.

Its a nice chilly morning.... you go turn on your car and you can see your exhaust. No big deal, this is just how it is. You take off down the road on your way to work. With nothing better to do while waiting at a stop light, you look around. You watch the cars drive by, the cars waiting with you, and the cars at the gas station. But then you notice, some of the cars have a visible steamy exhaust and some don't.

Whats the all about? How come some cars even after they warm up still produce exhaust. But once you hit the freeway and drive around a bunch. You step out of your car and your exhaust isnt visible...

 

[Hokiefyd]

There was just a thread about this a few weeks ago. It all has to do with exhaust pipe temperatures as I recall. The hotter the exhaust system becomes, the quicker the "steam" disappears. Those vehicles with larger systems with more capacity, or multiple mufflers and/or dual outlets, tend to steam the exhaust for a long time.

For example both of the previous Cadillacs I owned, and my current Acura, will pretty much steam all the time around town when the air is cold, even after some use. They all had/have dual mufflers that probably take longer to warm up. On the other hand, most vehicles I've had with a single outlet exhaust (like my Dodge Dakota and Toyota Camry) will clear the steam pretty quickly after running for a short while.

 

[javacontour]

Yep, water vapor is a natural product of combustion, so there will be steam in the exhaust stream. If your exhaust system is still cold, there will be some condensation along the pipe similar to that ice tea glass that sweats in the summer time.

I believe those two factors contribute to the steam you see. As soon as the engine and exhaust system warm, you'll see less steam.

You may also notice you don't see steam when a car is under load, but once it stops at a light, you'll notice more steam as the system cools down a bit at the light.

As you said, it's just how it is.

 

[Kaie]

Oh interesting. I was thinking it had to do with all the internal workings being at operating temp. Or something about moisture from the car being parked.

I would've searched, but i didn't even know what to type in order to search haha.

Thanks!

 

[javacontour]

One thing to keep in mind is that roughly one gallon of water is produced as a combustion by product when one gallon of gasoline is burnt. So when it's cold, you'll see that water as the condensed steam leaving the tail pipe.

 

[DreamerGT]

Both my cars steam like a steam engine

 

[Hokiefyd]

Originally Posted By: DreamerGT
Both my cars steam like a steam engine


That makes sense, as both probably have pretty large capacity dual-muffler, dual-outlet exhaust systems. Those types generally take longer to warm up, so I would expect a lot of steam from your cars.

 

[Kestas]

Exhaust system temperatures are one factor. The other is that the engine runs rich during warmup. A rich fuel mixture = more water vapor from the tailpipe. More water vapor = higher tendency for condensation of steam into visible vapor. True steam is invisible.

 

[hardcore302]

Yeah, I posted this a month or so back. I have 2.5 inch dual exhaust all the way through, so I colletcs more moisture.

 

[mechtech2]

Cold cars dump liquid water or water vapor out the exhaust.
Some more than others.
It heats up to become steam, which is invisible.
In very cold weather, you can see the vapor much more and much longer.
Where does the water come from? It's OK! It is a natural chemical byproduct of burning gasoline.

 

[JTK]

Originally Posted By: javacontour
One thing to keep in mind is that roughly one gallon of water is produced as a combustion by product when one gallon of gasoline is burnt. So when it's cold, you'll see that water as the condensed steam leaving the tail pipe.


I forget the exact number, but I think it's more like 7 gal of gasoline to 1 gal of liquid water.

 

[SteveSRT8]

does everyone forget that cats produce water?

It's all about temp and velocity, any modern car is pumping out water vapor constantly during operation.

 

[mechtech2]

You could have easily set up a 7-11 drink dispenser with the huge amounts of liquid water produced on many old large V8 Chryslers.

They looked like a rhino relieving himself at the zoo!