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Weird mid trims wtf??

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AL92

15+ Year Contributor
933
4
Dec 12, 2003
regina, SK, Canada
For awhile I think I had big leak on my cheapo dejon intake pipe coupler.I think it was letting air in behind my gm maf. I fixed it as my trims were low 140,mid 140 and high 105.
I have maft and base set to my 650 injectors.
Now I have my ltrim at 85 can actually dial it leaner a bit now and high is sitting at 104 but mid is at 140.Car seems to run fine .Does this mid at 140 indicate any particular condition?
If I raise up my base to raise my mid trims I would think my high trims will jump up.I can of course compensate on the ltrim with the idle knob.
So should I worry about the 140 mid trim??
 
The change in deadtime of your 650's will effect fuel trims as well, dont expect to get them perfect unless there is a change. Have you leak tested your system? If you have, then there isnt much that you'll be able to do aside from just playing with the settings to get them reasonably close. I dont know how long you've been driving around on these new settings also, but Id suggest looking at not only the trim but also the STFT, and combine the numbers to get your instantaneous fueling changes, as the cruise LTFT takes a good while for it to change. The idle LTFT will reflect changes very quickly. Id say go for a 10 minute cruise with each change you make to fueling and like I said watch the STFT in addition to the LTFT's, in order to get a true idea of the fueling changes taking place at the request of the closed loop condition. Its not a quick task to dial them in correctly, and I doubt its an issue necessarily caused by the MAFT mid range, however you must understand that the MAFT will not read exactly like the 2g MAS, it will have different values at different airflow velocities, which will also cause skewed results in your LTFT's, so it could also be based on the calibration that should be done to the MAFT anyway, and not even a fueling issue. I hope what I said makes sense. Basically to sum this up, the larger injectors have larger solenoids inside them, causing a delayed fueling reaction compared to the stock injectors so a deadtime change is needed to get perfect fueling, the cruise LTFT's take a good amount of time to react, and the MAFT doesnt read perfectly at all airflow ranges due to individual tolerances of the meters as well as the angle/clocking at which the meter is installed.
 
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