Author Topic: pump advancement for 1.6 na  (Read 1965 times)

November 28, 2007, 10:55:59 am

overdrivegear

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pump advancement for 1.6 na
« on: November 28, 2007, 10:55:59 am »
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.
1985 Westy Golf 1.6 NA
1987 Cabriolet (soon to be 1.6 NA)

Reply #1November 28, 2007, 01:51:52 pm

lyeinyoureye

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pump advancement for 1.6 na
« Reply #1 on: November 28, 2007, 01:51:52 pm »
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.