What does "badly tuned" mean? I feel like there is a need for a lot more clarity. Anyone have the source study (or know what it is). I'd like to know more.
Edit: more links!
Naomi Zimmerman's webpage: http://naomizimmerman.com/publications/
Abstract of the relevant paper: http://atmos-meas-tech-discuss.net/8/2881/2015/amtd-8-2881-2...
This PDF is labelled "supplemental" but it looks like the full text of the paper. http://atmos-meas-tech-discuss.net/8/2881/2015/amtd-8-2881-2...
I wonder how much could be attributed to old cars instead. That's something that would be easily measured by identifying the cars. But that may open a different can of worms if they determine people with the oldest cars are the biggest polluters* because it could be seen as an attack on the poor.
* Odds are the old cars are the biggest polluters.. less efficient to start with, more likely to be out of tune, more worn parts, etc. But I don't have any data to state that as a conclusion.
The SOCAAR facility has operated at this roadside location since 2006 and is one of the largest air quality research lab in Canada.
Over the years, we have routinely seen peaks in CO2 as vehicles pass our monitoring station. However, when some vehicles pass, we also see NOx, black carbon or ultrafine particle peak(s).
While we have video footage of the road, it can be extremely difficult to link the measurements to a single passing vehicle. Identifying these vehicles and why their emissions are different from the rest of the vehicle fleet is where the research our heading.
Bad air-fuel ratios also cause lots of pollution due to unburned fuel being sent out the tailpipe. I would think that this is less common with fuel-injected vehicles, but there are still plenty of old carburated vehicles on the road, especially where road salt isn't used.
On some high performance cars you can even go as far as using the fuel's injection to cool combustion and decrease knock in the combustion cycle of the engine...sometimes this can lead to a richer AFR (more fuel in exhaust gases) which causes pollution.
GDI cars have the capability of going extremely lean under highway speeds to drastically increase mpg and decrease emissions. This is the beauty of GDI.
"The most surprising thing we found was how broad the range of emissions was," says Evans. "As we looked at the exhaust coming out of individual vehicles, we saw so many variations. How you drive, hard acceleration, age of the vehicle, how the car is maintained – these are things we can influence that can all have an effect on pollution."
Not sure how they can tell "how a car is maintained" or "how you drive" from spot checking 100K with a roadside probe... anyone have thoughts?
Modern cars don't need routine "tune-ups." Yes, if a sensor fails or something like that it can cause an emissions problem, but a properly working engine computer tunes itself, and if it detects anything isn't what it should be, it activates the "check engine" light on the dashboard.