Originally Posted by
C5Shark
Hey guys,
Take a look at the stock tune for my '14 Eco... Specifically Stoich AFR, notice the values for 0% and 6.25% alcohol... Compared to a '12 those two cells are about 10% rich ('13 seems to have the same afr table as my '14).
I've leaned them out (and adjusted the other fuel tables that reference this accordingly). I've been using 93 octane since the car was new, it seems as if the result is about a 5-8% increase in fuel economy, but I need to run a few more thanks through it before I make that claim with any certainty.
I'm not sure why they would do this. Were there any major internal engine changes from '12 to '13? I didn't think there were. Even if you assume there is no fuel alcohol content compensation taking place (it is disabled) and this was done as a blanket catch all, those two cells are still rich for "up to" e10.
Slightly lower NOx emissions at the expense of fuel economy? Sabotage to artificially inflate the value of the Volt and Diesel Cruze? Cat temps were too high at stoich?
I've also noticed that the spark advance and camshaft phaser tables are greatly different compared to a '12. '13 to '14 seems to be very similar with some minor changes, I'd like to think (or hope) they're in the interest of further cal refinement...