The latest gasoline and AFR

[Oxford]

I have a very curious question.

All gasoline in Canada has at least 10% ethanol in it and as of January this year the government has Okay-ed the mixed blend to increase to 15%.

Now regular unblended gasoline has a Stoich/Lambda of 14.75 - 1 and a blended 10% gasoline/ethanol has a Stoich/Lambda of 14.3 - 1

How would someone adjust a global setting to accommodate for this change?
 Simply changing/dialing the fuel trims or adjusting the PE fueling is not going to cut it, some say go 4points richer on all fueling adjustments... obviously that's a lot of work and will not come close to proper adjustment.

[Maxrpm]

What is the end result your looking for? Power or mileage, as each requires a different afr. While
the newest systems are pretty good one is always going to lack to achieve the other. That being said remember mass air systems are first an emissions system designed to keep unburnt fuel to a minimum.
O2 samples exhaust,mass air sensor measures volume of air and the computer uses the info to make the necessary changes in timing and fuel pressure or PW based on the parameters loaded to keep them in check.  The 14.7 stoich or 1.00 lambda  number is used/based on perfect combustion based on a pure fuel octane/isooctane.
While we can achieve 14.7/1.00 or even higher under very light loads, naturally aspirated engines make the most power in the 12.5 to 13.5 /.850 to .910 lambda range. Unless someone has done extensive mods to their engine the factory tuning is going to deal with the blends as they are of now. If you really want to play with it you would need EFI live or HP tuner and time on a dyno. With these programmers  you can log runs and then grab a specific portion or the whole fuel or timing map and make adjustments based on what you've seen. You can tell it to do it by a specific number like the 4 you mentioned or by a percentage and it will do it to the area you want or the whole map.

[Mike]

Thanks for your input Mike! Much appreciated!

What is the end result your looking for? Power or mileage, as each requires a different afr. While
the newest systems are pretty good one is always going to lack to achieve the other. That being said remember mass air systems are first an emissions system designed to keep unburnt fuel to a minimum.
O2 samples exhaust,mass air sensor measures volume of air and the computer uses the info to make the necessary changes in timing and fuel pressure or PW based on the parameters loaded to keep them in check.  The 14.7 stoich or 1.00 lambda  number is used/based on perfect combustion based on a pure fuel octane/isooctane.
While we can achieve 14.7/1.00 or even higher under very light loads, naturally aspirated engines make the most power in the 12.5 to 13.5 /.850 to .910 lambda range. Unless someone has done extensive mods to their engine the factory tuning is going to deal with the blends as they are of now. If you really want to play with it you would need EFI live or HP tuner and time on a dyno. With these programmers  you can log runs and then grab a specific portion or the whole fuel or timing map and make adjustments based on what you've seen. You can tell it to do it by a specific number like the 4 you mentioned or by a percentage and it will do it to the area you want or the whole map.

[Oxford]

Thank you gentlemen, I have extensive knowledge and access to the mentioned (or like software) and I do understand quiet well. What I am getting at is, the new closed loop fueling requirements using the blended fuels is 14.3/1 and maybe 14/1 with certain blended fuels, also the WOT (wide open throttle) requirements of 12.8/1 - 12.4/1 would also reach 12/1 -12.4/1 in using the blended fuels now sold at the consumer end.
Our fantastic GM`s computer systems can and do adjust very well but the AFR in closed loop is defined and held to the 14.75/1. During WOT it is the PE (power enrichment)(open loop) and I can and have adjusted it without problem.My main concern is, I can and have went to 1 step colder Iridium spark plugs to assist with the fuel blends and has helped considerably (many hours of data logging and such) But the main AFR (global) should be fixed at 14.3/1 for closed loop operation due to the natural raised oxygen content of the blended fuel. So my persuit of information is, is there a global setting I can adjust that will allow the manipulation of the fixed 14.75/1 for closed loop operation?

Cheers