On the subject of Winter Gas
10-15-2014, 08:46 PM
#1
Retired Mech Design Engr
Thread Starter
iTrader: (3)
Join Date: Jan 2013
Location: Seneca, SC
Posts: 5,009
Total Cats: 856
On the subject of Winter Gas
Having seen snippets referring to crappy Winter Gas, I think I may have just put in the first tank full.
I'm seeing AFR warnings more often, and also more knock sensing, even though I have not done much to the tune lately.
Research that I have done indicates that the main performance difference between summer and winter formulations is the stoichiometric AFR, but that the octane rating is maintained.
If that is true, then it would seem to me that the best fix is to simply change the REQ_FUEL value by the proper percentage. The effect will be to decrease the AFR to the appropriate level everywhere in the tune, that is, for all open loop processes. The closed loop items will not be affected because they are really based on Lambda, though reported as AFR.
When summer gas comes back, just revert to your original REQ_FUEL setting.
Thoughts?
I'm seeing AFR warnings more often, and also more knock sensing, even though I have not done much to the tune lately.
Research that I have done indicates that the main performance difference between summer and winter formulations is the stoichiometric AFR, but that the octane rating is maintained.
If that is true, then it would seem to me that the best fix is to simply change the REQ_FUEL value by the proper percentage. The effect will be to decrease the AFR to the appropriate level everywhere in the tune, that is, for all open loop processes. The closed loop items will not be affected because they are really based on Lambda, though reported as AFR.
When summer gas comes back, just revert to your original REQ_FUEL setting.
Thoughts?
Reply
0
0
10-19-2014, 10:50 AM
#2
Retired Mech Design Engr
Thread Starter
iTrader: (3)
Join Date: Jan 2013
Location: Seneca, SC
Posts: 5,009
Total Cats: 856
I feel a little like I'm talking to myself here, but, for the record, my issue was more that the cold AIT needed more MAT correction. I went to 104% @ 50*F and now AFR's are right.
Reply
0
0
10-20-2014, 06:36 AM
#7
Retired Mech Design Engr
Thread Starter
iTrader: (3)
Join Date: Jan 2013
Location: Seneca, SC
Posts: 5,009
Total Cats: 856
See my second post. My issue was not due to winter gas, but the idea I posed can still be considered.
I'm in SC. winter gas in SC
I'm in SC. winter gas in SC
Reply
0
0
10-20-2014, 07:27 AM
#8
Elite Member
iTrader: (5)
Join Date: Oct 2011
Location: Detroit (the part with no rules or laws)
Posts: 5,677
Total Cats: 800
I've had issues with "winter grade fuel" as well. It could be a combination of both colder air and worse gas.
My AFRs are being mantained. I've found that i'm unable to run as much timing as i normally would.
My AFRs are being mantained. I've found that i'm unable to run as much timing as i normally would.
Reply
0
0
10-20-2014, 10:55 AM
#9
Retired Mech Design Engr
Thread Starter
iTrader: (3)
Join Date: Jan 2013
Location: Seneca, SC
Posts: 5,009
Total Cats: 856
Sounds like octane, not Stoichiometry
Which, if open loop, would more indicate lower octane than lower stoichiometric AFR. Hence the reason for this thread, to find out if the information I found was valid. Thanks for another data point.
Reply
0
0
Thread
Thread Starter
Forum
Replies
Last Post
