1.8T K..White smoke/damp full flooring
 

Hi guys

Noticed some white exost/damp/smoke/ fumes in my rear view mirror tonight having a test drive..
Nothing while regular driving and everything is sound and working,nice temp,good power,etc.. but when I cane It I see white clouds dissppering..any cause for concern?

Thanks

Is it smoke or steam? The difference is very important. Smoke persists/slowly disperses whatever theweather, steam evaporates/vanishes fast or slow depending on weather conditions.

TC

Steam is invisible. What you may be seeing is water vapour.

Indeed. But most people use the term in the context at hand. We all know what I mean.

TC

I guess my Steam Iron is not well then.----:p:



Having a touch of the vapours.---

Water is a normal waste product of the combustion process. When the engine is warming up, the cold exhaust is enough to condense some water out and cause the remainder to appear as vapour clouds.
This then causes liquid water to build up in the low points of the exhaust - mainly the rear silencer. As the whole system heats up, this then starts to boil off (or just run out), meaning that it can be some time after the engine is fully warm before the steam disappears.

Because the metal of the exhaust systems is so much colder this time of year the metal pinches all of the heat out of the vapour. Leaving behind lots of condensed liquid.

Eventually the pipe will get hot enough to dry itself out but can take Ages to do so.

The combustion of petrol (let's call that octane C8H18) in an engine with an adequate air supply (only the oxygen O2 is involved) goes like this.

2.C8H18 + 25.O2 ----------> 16.CO2 + 18.H2O + lots of heat energy

On the left is petrol and oxygen (as air) and on the right are the combustion products, Carbon Dioxide (CO2) and Water (H2O). The numbers (2, 25, 16 and 18) give the molecular proportions needed for a perfect chemical reaction (the combustion, also called oxidation). So, the numbers of atoms of each element (Carbon C, Oxygen O, Hydrogen H) on the left match exactly with their number on the right. Simplistically, what element goes in comes out - but in a different form. Chemists call it a balanced equation. This is why we have electronically controlled/measured systems on the engine for fuel and air input. You can check all this out on Wikipedia here: https://en.wikipedia.org/wiki/Gasoline

If you read that article, you'll see the amounts of water and carbon dioxide produced when a litre of petrol is burned. It's a lot more water than most people realise. In fact a litre of petrol generates more than a litre of water. Of course this comes out of the engine as super-heated steam and is ejected out of the tail pipe. By that stage, it's cooled down a lot and may well be visible as a vapour cloud in cold weather.

The amount of steam ejected from the exhaust pipe is surprisingly large. Assuming it's cooled to normal ambient (20°C), the volume of steam from each litre of fuel is over 1,300 litres. This is calculated from a physical constant called the Molar Volume, which is 22.4 litres at normal temp/pressure. That's the volume of steam from just 18 grams of water (H2O = 18) etc.

TC

my car has been showing "Steam" (which to my understanding - IS water vapour ;) ) lately due to the weather conditions :)

as i don't drive above 2.5k rpm until up to temp (thermostat open) it won't fully clear until up to temp and the exhaust is hot enough to evaporate any remaining moisture - when my car reaches running temp, if i floor it through the rev range i'll get some Steam - this clears quickly tho as the exhaust heats :}

Paul.

Where are you VikingMG?
We need to know if it's smoke, steam or water vapour!

TC