Quote:
Originally Posted by jamesm
i'm not sure what your mechanical setup is, so i can't really say for sure why your MAF required adjustment, but i know that even on stock cars some have found it to be necessary.
there are a few major components to fueling calculations that effect what you see in fuel trims or fueling error charts if you use them. MAF scaling, port injector scaling, injector battery offset (or dead time, or latency, whatever), and also direct injector flow rate. generally speaking you adjust what you change, so if you install an intake, you look to make maf corrections. if you install larger injectors, you're adjustments should be to the scaler and latency, not touching the other areas. the only time in which you'd have to mess with direct injector flow rate is when you change fuel density (use e85).
when you find yourself applying a flat correction to the whole maf scale, that is a smell. it tells you there is something else wrong, unless of course you've just changed the diameter of your maf tube.
it's very important when trying to calculate or correct fueling error that you maintain process separation between the involved components. i've found logging port and direct injection independently (through port/di ratio adjustments and logging injection mode) to be absolutely crucial in getting everything correct once e85 was introduced. if aftermarket port injectors are involved, you'll want to isolate them as well and eliminate noise introduced by the direct injection system when tuning them.
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Only modification that would require adjustment in the fueling I have is a cat delete on the front pipe and a drop in filter with trimmed intake snorkel. I switched back to the factory air filter and the high LTFT remained the same as with the aFe panel filter. The snorkel and drop in filter were accounted for in the tune, according to Shiv's posts. The rest of the intake is completely stock, including the sound tube. Not sure how the exhaust mod can change the MAF sensor readings.
With no vacuum or exhaust leaks to skew the O2 readings. The fuel trims were running pretty high but not high enough to trigger CEL with Vishnu's STG 1 tune. Was the same when I replace the air filter with the factory unit. How would you adjust for more fuel enrichment in this instance. Unfortunately, I do not have any way to log port to DI ratios effect on AFR. Also, what do you think about the 11.25 AFR at high load. I understand that O2 sensors are not 100% accurate, but does it read so rich that we have to run the AFRs that low?
After the adjustment I made and the LTFT at 0%, car runs smoother and IAM is pinned at 1.0 and not budging at all. Although, it is running a tad rich according to the STFT at low load, part throttle conditions.