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Engine Specific Info and Questions => IDI Engine => Topic started by: overdrivegear on November 28, 2007, 10:55:59 am
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I understand that the turbo cars use the pump timing of 1.05 mm and normally aspirated use 1.00 mm lift (generally speaking). I would think it'd be better to advance the NA timing to 1.05 mm to increase the peak temperatures and pressures within the cylinder with a power gain but at the expense of putting out more oxides of nitrogen.
Seems like the advanced timing would be best for HC particulates and smoke, though.
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It appears that ~4-5 degrees of advance increase NOx emissions by a factor of ~1.5-2.2, but like ya said, they also decrease particulate emissions by a factor of ~.6-.8. What's really interesting is that the most significant factor influencing peak efficiency wrt timing is the injection duration. Naturally advanced timing allows for a longer injection period assuming we have the same end. It also seems that breaking pressure alone doesn't significantly influence efficiency, we need to look at running more fuel w/ less air in order for higher breaking pressures to result in better efficiency.