|
||
|
21st January 2017, 22:27 | #1 |
Avid contributor
MG ZT-T, R75 1.8T Tourer,R75 2,5 V6 Join Date: Sep 2016
Location: Bergen
Posts: 170
Thanks: 77
Thanked 21 Times in 18 Posts
|
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 |
22nd January 2017, 09:51 | #2 |
This is my second home
Rover75 and Mreg Corsa. Join Date: Nov 2006
Location: Sumweer onat mote o'dust (Sagin)
Posts: 21,753
Thanks: 341
Thanked 3,660 Times in 2,924 Posts
|
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 |
22nd January 2017, 13:40 | #3 |
Avid contributor
MG ZT/T Join Date: Dec 2015
Location: Thurrock
Posts: 244
Thanks: 37
Thanked 39 Times in 34 Posts
|
Steam is invisible. What you may be seeing is water vapour.
|
22nd January 2017, 13:50 | #4 |
This is my second home
Rover75 and Mreg Corsa. Join Date: Nov 2006
Location: Sumweer onat mote o'dust (Sagin)
Posts: 21,753
Thanks: 341
Thanked 3,660 Times in 2,924 Posts
|
|
22nd January 2017, 15:15 | #5 |
This is my second home
R75 Saloon. Join Date: Feb 2009
Location: France/or Devon.
Posts: 14,003
Thanks: 3,851
Thanked 2,167 Times in 1,816 Posts
|
|
22nd January 2017, 17:24 | #6 |
Gets stuck in
Connoisseur SE 1.8 Auto Saloon Join Date: Jul 2015
Location: Kendal
Posts: 633
Thanks: 129
Thanked 176 Times in 147 Posts
|
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. |
22nd January 2017, 17:50 | #7 |
This is my second home
R75 Saloon. Join Date: Feb 2009
Location: France/or Devon.
Posts: 14,003
Thanks: 3,851
Thanked 2,167 Times in 1,816 Posts
|
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. |
22nd January 2017, 18:18 | #8 |
This is my second home
Rover75 and Mreg Corsa. Join Date: Nov 2006
Location: Sumweer onat mote o'dust (Sagin)
Posts: 21,753
Thanks: 341
Thanked 3,660 Times in 2,924 Posts
|
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 |
23rd January 2017, 00:20 | #9 |
Posted a thing or two
Rover 75 1.8t Join Date: Oct 2015
Location: Edinburgh
Posts: 1,377
Thanks: 384
Thanked 409 Times in 267 Posts
|
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. |
23rd January 2017, 10:01 | #10 |
This is my second home
Rover75 and Mreg Corsa. Join Date: Nov 2006
Location: Sumweer onat mote o'dust (Sagin)
Posts: 21,753
Thanks: 341
Thanked 3,660 Times in 2,924 Posts
|
Where are you VikingMG?
We need to know if it's smoke, steam or water vapour! TC |
|
|