Patrick G
April 20th, 2011, 01:31 AM
In the US, our gas is getting worse. We are seeing 10% ethanol at most pumps and 15% is coming soon. As I log commanded AFR, I see it drop from 14.68:1 to more like 14.3 or 14.1 with the ethanol blended fuel. It seems that this is a result of the B3671 table (E38). Fuel economy drops with the ethanol blended fuel, partially because the engine is commanding a richer stoich. Trying a little experiment, I added .8 to the stoich table across the board. Now with pure gasoline, the commanded AFR is 15.48 and with the blended ethanol fuel, my commanded AFR is 15.1-15.3:1. I added .5 to the EQ ratio on my PE multiplier and the commanded AFR at WOT is still 12.44 like it was before.
I have not verified if the AFR is actually leaner with the wideband, but on a GM vehicle with a flex fuel capability, why wouldn't this approach work to achieve a leaner cruising AFR and improve economy?
I have not verified if the AFR is actually leaner with the wideband, but on a GM vehicle with a flex fuel capability, why wouldn't this approach work to achieve a leaner cruising AFR and improve economy?