View Full Version : AFR drift-e38

May 17th, 2008, 02:49 AM
I am experiencing a considerable amount of drift in afr between day and night in my car. I have injector flow IAT table dialed in so that it increases fuel by 2% every 10 degrees C. The problem is I believe we require more deg increments in the IAT-injector flow table so we can adjust fueling every 5 degrees in air temp.

The other night I had 13.0:1 WOT afrs in 21 deg air, Today my WOT mixtures were 13.5:1 in 28 deg ambient temps. That is 4% leaner over a 7 degree difference in temperature. That is a lot but it is something I have found on a consistant basis over the last few months. Some would argue my w/b(innovate) is inaccurate but my sensor is new and my findings have been consistant as already mentioned. On a hot day I get more KR(which is normal) but this is from lean mixture not spark. Plus If I have the car in closed loop my w/b readings have always been consistant with the narrowband settings. Something I could do is use the open loop table B0141 to correct discrepancies in afrs in different climates in conjuction with the injector flow modifier. I have to sort through some logs to see the differences between IVT and IAT(and ECT) between day and night. On a warm 28deg day, ECT and more likely IVT could be much hotter than a 20 deg night where IVT(intake valve temp) could be much cooler. Exaggerating a little...there may be a difference of 15deg in IVT between a cool night(not many cars on the road) and a hot day in traffic. Even though there would be say only 8 deg difference in IAT. We can't do much with injector flow modifier table in this regard so some fine tuning to B0141 could result in more consistant afrs across the board. This will result in a SD tune that will be accurate year round in all conditions. I have started tracking some results and as of yet have not enough data to commence to many changes but I believe swingtan and a few others have been logging IVT compared to ect and IAT, so please feel free to post your data here as I believe this will help a lot.



May 18th, 2008, 08:04 AM
You might want to read some of redhardsupra's work on iat blow bias.
He is always looking for guys to help him log data and crunch numbers. Take a read of his blog and send him a PM.

May 31st, 2008, 12:33 PM
afr drift was a problem with the early stuff too, the COS with IAT correction fixed that.

with the e38 stuff, for now, im playing with B1213, still not perfect, but ten times better, though when i get my head around the charge temperature all will be good.