DAPSUPRSLO

iTrader: (14)

I don't understand how the maf can account for any kind of chaging atmospheric conditions without feedback from the oxygen sensors. I understand that it is an accurate way to measure the incomming air but how does it correct for anything. Does it get feedback from the map sensor and use that? If it doesn't correct for anything wouldn't it just be better to turn it off.

txhorns281

iTrader: (12)

you might want to tune Open Loop, SD operation if you are primarily trying to align your VE table. That way none of your sensors are biasing AFR production. It's fundamentally the request and production of AFR without any confusion.

Steve Bryant

iTrader: (1)

The MAF is actually extremely accurate in measuring air flow rate while compensating for density due to atmospheric pressure and temperature to give the dynamic mass or moving "weight" of the incoming air. This allows the PCM to accurately inject the correct mass of fuel needed for the commanded AFR which is a ratio of the air mass to the fuel mass. If the PCM is commanding an equalivalency ration (ER) of 1.0 that is stochometric or about 14.68:1 AFR if everything is calibrated correctly. I have a PLX WB and I'm currently running Open Loop all the time until I get everything tweaked the way I want it. However, back about a month ago when I had my MAF disabled via my bin file, and I was running Speed Density (SD) it was amazingly accurate once the VE values were proper. When I re-enabled the MAF everything was smoother and more accurate yet. Later, when I re-enable closed loop and the NBO2 can relearn the LTFT values, it should be very dead on. I've rambled here, but I hope that this explanation helps some.

All my best,

Steve

DAPSUPRSLO

iTrader: (14)

I understand what the maf does but I don't understand it's use without the 02 sensors. I will be running a cam that will not like 02 sensors and am curious to what the benefit of continuing to use the maf is? Once you dial your ve in for a certain weather conditions does the maf correct for varying weather conditions? If not I see no point to run it unless you are running closed loop.

txhorns281

iTrader: (12)

In whatever weather the MAF is calibrated in, it will act like an anchor to not let fuel trims get too far off. As far as the benefit of running a MAF, if you are good enough a tuner then you become your computer's correction factor. You could run SD Open Loop but then you'd constantly have to update your tune for weather conditions. The key is to find a way where you have some control to update your tune, but also have the PCM be adaptive enough to where your sensor don't completely take over and confuse your fueling. Cams and sensor don't seem to get along...

SmokingWS6

iTrader: (1)

A4's use the maf to caculate load unless you have a have a vaccume modulated transmission.

slow

iTrader: (7)

since the factory uses the maf for open loop fueling from the factory, i do not see a problem with doing the same thing.

Ryan

GrannySShifting

iTrader: (10)

cooler air is denser. same temp but high pressure air is denser obviously. both situations will result in higher maf readings and more fuel.

Cooler air will cool the MAF "thermistors"? off faster. Denser air will do the same

DAPSUPRSLO

iTrader: (14)

Ah, this makes things a little clearer. So the maf does infact still adjust your normal driving a/f as long as the calibration is correct. No I'm starting to see. If the calibration is off then you will be constantly lean or rich or switch between the two. If the 02s were plugged in they would compensate for this by adjusting your ltrms to correct for whatever condition. But if they are not plugged in then whatever calibration is plugged in the maf will take over.

DAPSUPRSLO

iTrader: (14)

I understand the principal of the operation of the maf and its sensor wires (the cooler they get the more air the maf is actually seeing). It is a good point to point out as you state Jeff that the cooler air would cause the maf to constantly think more air is comming through the motor. However this works out sense cooler air is more dense and more fuel is needed to burn it.

DAPSUPRSLO

iTrader: (14)

No problem with that, m6 here.

Bink

Steve Bryant is absolutely correct. I run open loop, through the maf, year round. Ambient temps from 98*F to 0*F.
O2 sensors have nothing to do with temps or pressure ...just 14.7 AFR.
We have MAF, MAP (referenced Barometric pressure) and Intake Air Temp for weather conditions.

O2 sensors and closed loop are nice simply because they are using the PCM's calibration to it's fullest advantage. Closed loop adds another level of refinement.
The key is getting the O2s working with Overlap. I shall see soon.

DAPSUPRSLO

iTrader: (14)

This is a good thread. Thanks for the info guys. It sounds to me like the maf is good at holding a constant a/f ratio more so then just SD tuning.

Another_User

Soooo...how's that goin for ya? I hope you have found something I haven't.