Mercedes Benz OVERSTATING fuel consumption

JustinR1979

uniqu3 wrote: »

I had a presentation by T.Rad recently and you'd laugh if you saw the comparison in size of their new tech EGRs to the little things you used to get on the old Vauxhalls.

Guess back then it was just a quick token effort

Joe_Horner

JustinR1979 wrote: »

I did wonder why dpf's and cats etc were fitted if they didn't lower emissions.

They lower emissions of carbon monoxide (the killer asphixiant gas), nitorus oxide (heavily implicated in acid rain and smog) and diesel particulates (very fine soot, turns buildings black and apparently clog up your lungs).

They do all theses things at the expense of producing very slightly more CO2 (non poisonous and plants love it) for a given amount of fuel burnt.

uniqu3

JustinR1979 wrote: »

Guess back then it was just a quick token effort

Yeah, you could just remove them with no worries. I recall that Vauxhall actually had an ECU patch to delete the EGR from the ECU some models because they were that troublesome.

Most new EGRs work in tandem with variable geometry turbochargers and can't be removed or deleted (i.e. without a constant MIL or poor performance) although I expect that the EU has more to do with that than anything else!

AdrianC

Joe_Horner wrote: »

EGR is a method for reducing nitrous oxide emissions by reducing burn temperatures, and has nothing at all to do with carbon compounds of any kind.

It's also worth mentioning that EGR is neither new nor limited to diesels.

My 1990 petrol Saab had EGR. My 1980 petrol Land Rover has EGR.

Joe_Horner

AdrianC wrote: »

It's also worth mentioning that EGR is neither new nor limited to diesels.

My 1990 petrol Saab had EGR. My 1980 petrol Land Rover has EGR.

EGR was introduced back in the 70s to address NOx emissions at idle. As usual with these things, it started in California as an anti-smog measure and was one of the many reasons that US cars had lower power and worse fuel consumption (so, producing more CO2 - not that anyone cared about plant food back then) than European equivalents

sh0597

I think you're confusing CO2 with other nasty emissions. DPF's don't reduce CO2 emissions, in fact they make more atmospheric CO2 by burning carbon particulates.


Catalytic converters reduce CO (Carbon monoxide) emission and also unburned fuel. They can also reduce NOx emission which I believe is also what EGR systems do.


These harmful emissions are governed by EU emission standards rather than tax. Soon cars will need to meet "euro 6" standard for example.

redux

uniqu3 wrote: »

Predominantly it's down to aftertreatment. Modern vehicles are built on a variety of carbon-reducing aftertreatments including, but not limited to, EGR systems, EGT Measurements, DPFs and Catalytic Converters. There are already massive improvements in existence in the industry for these, but they're either not cost effective or developed enough for production quite yet.

These exhaust after treatments control other emissions, not CO2.

Whilst it's not impossible that someone will one day develop carbon recapture methods, just as they might for power stations, it's total fiction to pretend this is already happening.

As others have said, if you burn a certain mass of carbon, it will produce a certain other mass of carbon dioxide. It will be 11/4ths as much.

This is inalterable basic chemistry, conservation of mass. If you convert it to a different carbon compound, then there would be less CO2, but that isn't happening.

If the fuel consumption of an engine is improved, the CO2 output will improve by the same proportion, but that is the only way to do it.

Mankysteve

mpg figures should not be used to work out the real life fuel consumption of a car but as a way to compare two different cars fuel consumption this is the mistake people are making the yes are done in a standardized fashion so that he variables are the same on two cars but in real life there are so many variables its impossible to work out what your actually fuel consumption will be.

OddballJamie

Mankysteve wrote: »

mpg figures should not be used to work out the real life fuel consumption of a car but as a way to compare two different cars fuel consumption this is the mistake people are making the yes are done in a standardized fashion so that he variables are the same on two cars but in real life there are so many variables its impossible to work out what your actually fuel consumption will be.

Doesn't always work like that as in some cases the manufacturers are the ones testing them and may or may not do certain things to skew the results.

There's no guaranteed rule of thumb for the calculation of official versus rule.

Take these as examples, hot hatch competitors.
http://www.honestjohn.co.uk/realmpg/ford/focus-st-2012
http://www.honestjohn.co.uk/realmpg/honda/civic-type-r-2007
http://www.honestjohn.co.uk/realmpg/vauxhall/astra-j-2009/vxr
http://www.honestjohn.co.uk/realmpg/renault/megane-renaultsport-2009
http://www.honestjohn.co.uk/realmpg/seat/leon-cupra-r-2010

The turbo engines are getting around 80% of official figures, yet the NA engines are much closer to the actual figures.

The reason could be down to the lab guys not using boost when conducting tests, who knows for sure?

motorguy

My golfs figure is 62.1 MPG, but i've averaged 66+ mpg brim to brim over the last 30K miles.

Depends on how the car is driven, and the length of run you're doing.

I would only use the official MPG figure relative to my current one to get an indication of what its likely to be up or down on my current car.

I certainly wouldnt be buying a car, doing mixed driving and then expecting to hit the official figure.