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What would cause my maf to be unstable at wot like this? I am trying to dial in my wot and it is OK but I think my maf is causing it to fluctuate more than it should. I run a 85mm truck maf connected to the filter of my hurricane intake. Is it because the big cam/fast 102 or because it's to close to the filter? Do you thing it would help moving it more towards the throttle body?
Do you have a screen in front of it? You can try clocking it differently in the intake tube if possible or like you said, move it a few inches further from the filter. Are there any bends in the tubing close by?
I would check for a screen, amke sure the air is straight, clean the sensor, maybe rotate the MAF if you can, and if none of that works, try swapping it out.
ok thanks. any other reason my wot afrs would fluctuate +/-.4?
What you need to do is, log the injector on-time and duty, then examine it to see if it fluctuates also. If it does, you find out why (maf signal or wahtever). If it doesn't, you have either a wishy-washy wideband, or an internal engine problem with combustion (partial misfires and so forth) Or could be clogged injectors or fluctuating fuel pressure (anything you can think of that might change fuel flow)
Perfectly normal. Here are two examples from two different engines. I messed with the graph settings to exaggerate the MAF instability.
On this one it's N/A 375" car running low 11s at 122mph.
This one is a head/cam LQ4 on a 100 shot running high 10s at 130mph.
Remember, the computer is sampling the MAF at a higher frequency than the scanner is able to. This will result in outlier deviations that aren't far percentage wise from the average. Makes your graph look ugly but it doesn't screw up your tune. As long as your MAF trends higher while RPMs rise during acceleration and the deviations are small in percentage, then you're good.
I don't see the wideband on your log. I don't see anything inherently wrong with your o2 milivolts. Your wideband will also be wavy like the MAF for many of the same reasons. Remember that the engine runs in pulses, and even with 8 cylinders, it isn't going to be constant and linear. It will always be a waveform on intake airflow and exhaust gasses. +/- .4 AFR is only about 3% error point to point. Average error is more important.
09-17-2016, 07:18 AM
maf unstable at wot 
