RomRaider

you're assuming that my target for ALL closed loop operation would be stoich, or close to it (i actually target 15.5:1 for closed loop).

in actuality, what i am curious about is whether or not the ecu will target richer than stoich in closed loop. the only question at this point is whether or not the table i mentioned has enough authority to offset 2.5 afr points so that i can run say 13:1. i also don't know whether or not the ecu will remain in closed loop if the table is "in effect" (although i am fairly sure it will, since the other factors mentioned by bill that trigger open loop fueling would not be satisfied). finally, i do not know whether or not the offset error introduced by greater levels of exhaust gas backpressure will skew the front o2 sensor's readings too much to be of use for closed loop operation at higher engine loads.

however, IF it works, there are some substantial benefits to this, especially if one runs a utec on top. if the afrs at the point of handoff are actually closed loop controlled they will be extremely repeatable, and all one has to do is align the utec's fuel map to those afrs.

the utec in SD mode on top of an oem reflash is absolutely killer. an added bonus is that when in SD mode the utec does NOT offset the MAFV in any way, so you see the true mass air flow and engine loads. i am shocked at how stable the SD afrs are despite having NO IAT corrections programmed in the utec at this point. i've been laptopless for 3 months now and the temperatures have changed drastically, yet i am only running about 0.7afr richer. but i digress....

in actuality, what i am curious about is whether or not the ecu will target richer than stoich in closed loop. the only question at this point is whether or not the table i mentioned has enough authority to offset 2.5 afr points so that i can run say 13:1. i also don't know whether or not the ecu will remain in closed loop if the table is "in effect"

Basically ltft is a fueling pattern that the ecu learns from the frequency and magnitude of short term fueling behaviour i.e. the % of fuel the ecu either adds or removes to achieve a closed loop afr of 14.7.

This is fine for closed loop however the ecu also applies ltft to open loop which creates problems for tuners as it will also change the afr in open loop.

Most people on this forum try and achieve a stable ltft of +/- 5% before changing open loop settings so that they know they have a stable platform to work with.

It's normally only an issue for those who have changed either injector scaler or maf settings.

Is the LT Fuel Trim used in Open Loop fueling?

i'm dying to try this out but i'm getting the dreaded programming voltage too low (4.2v) so that's the next action item.

i'm not going to screw around trying to figure out why it's happening... i've already been on my back in my footwell in the rain checking the flashblock connector (which is fine). i'm just going to jumper some IGN power to pin 6 (blue) on the obd2 port.

as soon as i get flashing again i will keep this thread updated with my closed loop afr offset testing progress.

ken

sweet.

now a flipside question. can the car be made to run in OL mode 100% of the time by making sure all cells in the "3d load/rpm/lamba manual enrichment" map is above 0% enrichment (aka richer than 14.7afr)? i assume this would also completely disable LTFT learning? how would this affect STFT correction?

if LTFT and STFT are disabled and the car is in open loop 100% of the time, it would make it a lot easier to tune an intake and/or injectors. then once OL afrs are close to what the "AFR" target map says, enable CL and have an extremely smooth driving car with minimal learning and correction.