Originally Posted by
AccordULEV
Hi there - first post. I've read through the thread. I just installed a Magnuson S/C on my 2017 Tundra FFV a week ago. It wasn't until recently that I cared to know anything about the ethanol calculation the ECU does (due to the Tundra's lack of an actual ethanol sensor). Magnuson's instruction manual says that with the provided calibration, after the first start the ethanol density should decrement to 0%, but it doesn't and hangs around 14 to 25%. After refueling, I understand it takes the first few minutes of drive time to calculate the ethanol %. I've been in touch with Magnuson tech support, who has been amazing, and they assure me that up to 30% is okay and there is only a problem if the number starts ramping way up, as there is no way to simply turn the ethanol sensor off. Maybe this has been the way they've attempted to "tune out" the ethanol density - by lowering the MAF tables so that the ECU sees a richer mixture after refueling and zeroes the ethanol (??) I am curious of one thing.
In closed-loop operation, the AFR(commanded and measured) is consistently reported as 14.7:1, no matter what the ethanol density is reported (14.9% to 25%). If I were running E85, the optimal AFR is 9.8:1. Would the ECU indeed report a commanded (and in following) a measured AFR of 9.8:1 (in theory)?? It seems like the ethanol density % is just a modifier to the base fuel injection maps, or no? Higher ethanol % will cause richer AFR, lower will cause leaner, but ultimately it relies on the AFR sensor to determine that after refueling?
Any help in understanding this is appreciated. I have not taken a dive into VCM editor and have no plans to, but want to understand what's going on, what I should be seeing and the logic.
Many thanks!