Quote:
Originally Posted by MetroMPG
- between model years 2009 to 2015, the percentage of new vehicles sold with GDI engines jumped from 5% to 46%
- GDI engines emit lower levels of CO2, but they emit more black carbon
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Your ordinary gasoline engine sucks in an air-fuel mix with fuel droplets that tend to vaporize due to the temperature rise created as each cylinder adiabatically compresses the air-fuel mix.
I suspect that this does not occur with a GDI engine. Rather, the fuel is injected at or near the top of the compression stroke, and the fuel does not have time to vaporize before it is ignited. This will lead to soot formation, since the fuel droplets themselves do not have sufficient surface area to combust completely.