Why Petrol Engine Emit Water through Exhaust but Not Diesel?

[zakmuh]

Hi Guys,

I always wondered why water dripping out of petrol exhaust but not in diesel cars? I tried to find in Google but no clear answer to it. All what they talk about is hyrdocarbon in both fuel type.

At traffic lights during school runs I see this in old to bradnew petorl cars.


Thanks

[Cockaigne]

Burning fuel produces water vapour.

""Hydrocarbon molecules in the fuel gas react with the oxygen molecules from the air and a lot of heat is released. The products of this combustion are carbon dioxide and water. "

[Pica-Pica]

Cockaigne said:

Burning fuel produces water vapour.

""Hydrocarbon molecules in the fuel gas react with the oxygen molecules from the air and a lot of heat is released. The products of this combustion are carbon dioxide and water. "

In a similar manner, doctors, consultants and others were asked where does the weight loss go when we diet and lose weight? The dieticians were the only ones who mostly knew. It, too, was carbon dioxide and water.

[zakmuh]

Thanks for your reply guys.

Understood, Hydrocarbon molecules thingy is the cause of this but the question here is...why not diesel ones emit water? Only happens with petrol ones

Could it be because diesel uses pure compression ignition intead of fire (spark)?

Edited by zakmuh on Wednesday 17th May 12:36

[kurokawa]

zakmuh said:

Thanks for your reply guys.

Understood, Hydrocarbon molecules thingy is the cause of this but the question here is...why not diesel ones emit water? Only happens with petrol ones

Could it be because diesel uses pure compression ignition intead of fire (spark)?

Edited by zakmuh on Wednesday 17th May 12:36

Diesel have higher energy density which lead to less hydrogen per unit of fuel
+ diesel engine run at higher pressure and temperature
Water vapour is still a product of it and it very cold climate it is possible to see condense water coming out a diesel tail pipe

[E-bmw]

kurokawa said:

zakmuh said:

Thanks for your reply guys.

Understood, Hydrocarbon molecules thingy is the cause of this but the question here is...why not diesel ones emit water? Only happens with petrol ones

Could it be because diesel uses pure compression ignition intead of fire (spark)?

Edited by zakmuh on Wednesday 17th May 12:36

Diesel have higher energy density which lead to less hydrogen per unit of fuel
+ diesel engine run at higher pressure and temperature
Water vapour is still a product of it and it very cold climate it is possible to see condense water coming out a diesel tail pipe

^^^ What 'e said.

All hydrocarbons produce water vapour/steam when burnt, just some produce different amounts.

[zakmuh]

Thanks

I found the answer as well...Diesel has larger hydrocarbon molecules with more carbon atoms and it evaporates much more slowly than petrol. Petrol is a hydrocarbon + pure water with less amount to small carbon molecules.

[GreenV8S]

E-bmw said:

All hydrocarbons produce water vapour/steam when burnt, just some produce different amounts.

The water vapour is likely to be more dilute in the exhaust of a diesel that is lightly loaded, whereas the exhaust of a petrol engine that is lightly loaded will be far more concentrated.