Hi all,
Watching the news and vw are now saying there may be a co2 scandal too. And petrol models could be affected. Does anyone have any idea on whether the mk7 will be affected by this? As I understand it the mk7 Gtd was not effected by the diesel scandal due to being an eu6 engine?
Furthermore, what can be done if the car is affected? I'm guessing if the car actually emits more co2 than claimed then the road tax goes up? Not that this causes major issues but I'd feel a bit hard done by that due to cheating I now pay more than I first thought I was signing up for.
Charlie
Pretty much impossible to fake CO2 output - CO2 and H2O are what you get when you burn fossil fuels in air, there's nowhere to hide the CO2 being produced nor prevent the car from emitting any while the car is running, if the car is combusting fuel it is also emitting CO2. Unless they passed the exhaust gases through a CO2 scrubber on their way out to absorb it - not something you could feasibly do outside a lab and very hard to hide in the presence of an official independent observer.
NOx is a byproduct of the combustion process and its formation depends greatly on temperature and pressure. You can force a diesel engine to produce less NOx by lowering the combustion temperature, but you increase soot evolution and make the car less efficient. Higher soot evolution (and increased pressure on the DPF to remove it through combustion) and higher CO2 output per mile/km at the expense of lower NOx is not something VW would want the car to be doing all the time when they're trying to maximise mpg, so you can see why the temptation was there to make the car temporarily run that way, but not all the time. Petrol engines run at much lower temps and considerably lower pressures than diesels, those conditions don't produce meaningful amounts of NOx, so it's not really a petrol problem.
The only CO2 scandal would be the use of stop-start in the EU testing cycle to reduce official CO2 output and lower mpg. For 24% of the current 11 minute EU test cycle, the car is at a standstill and if stop-start is fitted, that is 24% of the test cycle with no fuel use and therefore no emissions of CO2. All the car manufacturers are at it, but they're playing by the rules put in place. Upshot of this is that everyone got cheaper tax discs, downside is that some customers expectations of mpg were well away from reality.
It is the primary reason that with the introduction of stop-start, published mpg values went up around 20%, but real life mpg for the general public didn't really change.
