Fuel Figures EuroIII and EuroIV - Whats the logic??

[Goldfish11]

I have just been looking at the fuel consumption figures for the new EuroIV figures. These are meant to be more environmentally friendly, but it seems they have worse MPG figures. It is now better to drive a E270CDI Euro3 than a E220CDI Euro4 in terms of emmissions. I thought this was all about CO2. According to my OLevel physics if you burn something you generate a given amount of CO2 so if you are now doing less MPG does that not mean we are generating more CO2 per mile. I guess it also has something to do with particulates.

This also is discussed in the following What Car article

http://www.whatcar.com/News_SpecialReport.asp?NA_ID=213179


Is this just an other Euro Con or am I missing something?

 

[Thmsshaun]

Seems it bit backward if you ask me.

 

[Dieselman]

I've not bothered reading the article but here goes.

It all depends on what emmissions are flavour of the month. Depending on what you are trying to reduce and by what methods there will be an impact on other emmissions and efficiency.

There are two emmissions from diesels under the spotlight, NoX and particulates. A fairly simple method of reducing particulates is to fit a particulate trap and a method of reducing Nox is to untroduce exhauset gas into the airstream, EGR, or to retard the injection timing.

Particulate traps do trap the particulated but due to the small pore size also create exhaust back pressure so reduce efficiency.
Using EGR as a method of reducing Nox reduces the amount of oxygen in the intake air so reduces combustion temperature but also efficiency.
Retarding the timing also reduces combustion temperature but not surprisingly also reduces efficiency.

My opinion is to run any engine at it's most efficient to reduce the amount of fuel consumed and the total emmissions will be lower as a result.

 

[RichardM]

My opinion is to run any engine at it's most efficient to reduce the amount of fuel consumed and the total emmissions will be lower as a result.

But wouldn't that offer the lowest performance?

 

[Dieselman]

But wouldn't that offer the lowest performance?

You've lost me.??

Surely if an engine is run at it's most efficient setup it will produce more power and torque due to converting more of the fuel energy into motion.

The problem is that some local polutants MAY rise, but overall there would be a reduction due to less fuel being consumed.