I have a 87 Town Car with a 93 Mustang GT Maf EEC. My car runs rich with the 94-95 70 mm Sensor and matching housing. I have both 55 and 70 mm sensors to try. Throughout my research and in theory a 55 mm sensor in a 70mm housing should see X amount of air, but actually be allowing more than what it thinks it's seeing because it's in a larger housing causing the engine to take in more air and run lean. Well, I threw the sensor in to try it and it's running richer than before. Make sense? Now the only explanation I can dream up is that the O2 sensors are seeing a lean condition and telling the ecu to throw more fuel. So is my thought process wrong with this MAF Swap Trick? If the O2 sensors are ultimately going to determine the fuel mixture than why does it not simply adjust it to the correct AF Ratio with either sensor?
Maf question. 55MM Sensor in 70MM Housing
- Thread starter skratpiece
- Start date
Yes. The sampling tubes are probably different. So even though the sensor is in a larger housing than it's calibrated for, the sampling tube size is also probably different causing the readings to be off.
If you really want to swap stuff out like that, get a Quarter horse or a TwEECer and reprogram the ECM.
And to answer your last question (or to try and answer it, as I"m still learning myself the whole tuning bit) the O2's are used to fine tune the A/F ratio, not to make whole sale adjustments. The car uses the rich/lean from the narrowband O2 sensors to tweak the A/F and "learn" but not to correct for a bad MAF. They work in concert, so in order for the car to run properly both sensors need to be functional.
That's my current understanding of the O2/MAF interaction with the A9L, someone please belittle me and send this man in the right direction if I'm not.
If you really want to swap stuff out like that, get a Quarter horse or a TwEECer and reprogram the ECM.
And to answer your last question (or to try and answer it, as I"m still learning myself the whole tuning bit) the O2's are used to fine tune the A/F ratio, not to make whole sale adjustments. The car uses the rich/lean from the narrowband O2 sensors to tweak the A/F and "learn" but not to correct for a bad MAF. They work in concert, so in order for the car to run properly both sensors need to be functional.
That's my current understanding of the O2/MAF interaction with the A9L, someone please belittle me and send this man in the right direction if I'm not.
Thank you. I have not swapped any sampling tube. What I am doing is leaving the appropriate 70mm housing and putting in the 55mm sensor to trick the ECU into thinking it's getting less air than it is thus less fuel. Problem is that it's blowing fuel out the tailpipe now, so it must see an extremely lean condition and be pouring on the fuel. I don't know.
Yeah I think thats whats happening. Like fish said the Oxygen Sensors just switch from back and forth from rich or lean. Your problem could be corrected by adjusting the Maf Transfer Function with a tune. When ever I start a tune the first thing I do is get the maf dialed in open loop to match the AFR the eec is commanding. I would invest in a Moats chip, Binary Editor and a Wideband. It's a bit of a learning curve but It pays off as any changes you make you can modify the tune yourself.
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Hmmm. I'd love to be able to tune this thing myself. Time to dig in.
Check out eectuning.org . Lots of good information on there.
Eh maybe. The stock sensor still thinks it's in the stock housing...so if the new 70mm sensor is flowing more air over the stock sensor at the same load as the stock housing, then the car will run rich. The only way to do this kind of thing properly is to either buy a maf that is "calibrated" for a given injector size (like a C&L or Pro-M, which have tubes that alter the airflow appropriately for the stock sensor at a given injector size) or, to tune the car. But even in order to tune it properly it really helps to have the flow numbers at given voltages for a particular MAF.
So unless someone has flow tested your setup, you'll still be guessing.
You know, the maf sensor works by trying to keep the little wire to temp and measuring the voltage needed to do so. Switching to the bigger housing would probably reduce velocity, requiring less power to heat the wire, and making it think less airflow.
Not necessarily. That wire is inside of a sampling tube, not in the larger flow chamber. Depending on how that tube was designed, the wire could actually be seeing more flow (and from the sounds of it, that's probably the case here).
Whoops, I was thinking he was lean for some reason. Multitasking fail.
Yeah he is right. Reading comprehension owns me lol. I would just pickup a calibrated maf unless you plan on modding more in the future then I think tuning is the way to go. You can find the maf transfer for just about any ford maf online.
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