Effects of humidity on MAF transfer/function

[zenboy99]

I've never really thought about this, but I thought it would be worthy of discussion. I just drove around for an hour in the rain and got a good data log, I'm curious to see how it compares to the datalog on a cool dry winter day.

My co-workers husband is an atmospheric scientist and I'm going to ask him a few questions. I believe a given volume of air will have the same oxygen content no matter what the humidity of that air is? Same with altitude, a given volume of air will have the same oxygen content at low pressure and high pressure, however pressure will effect how air is being pumped in and out of the engine. So how would a higher moisture content effect the voltage of my MAF? Water has a better specific heat (heat transfer ability) than air so I would think the voltage should change faster. But if the oxygen content is the same for a given volume of air being introduced the MAF shouldn't be effected.

The scientist in me is thinking that with a higher humidity an extra amount of moisture/water is being introduced into the combustion chamber. Wouldn't this lower combustion temps and effect the exhaust leaving the chamber?

It would be interesting to take two new mustangs, one driven in a cool winter desert and the other driven in Seattle and see how the EEC adapts to those conditions.

Just some thoughts, any opinions or comments are welcome.

 

[blksn955.o]

The maf takes into account those things.

There are tables I believe that deal with humidity...I have the names but I dont remember off the top of my head.

I asked the same question or one related to it when I first started using the tweecer.

 

[final5-0]

People will say moisture or temp will not effect things cause the maf has the ability to compensate.

Once upon a time I would have agreed.
Still do, for the most part.

however

Two years ago at the end of Summer I had been working with my final WOT fuel ratio.

Had lots of data from a time period that the temps were usually about the same. These dlogs were from the afternoons after I got off work.

Early one Sat morning I made a couple dlogs back to back with driving conditions no different from all the others. The only change I had made to the file for both of those test passes was a slight change to only one maf point.

Much to my suprise when I looked at those two dlogs
The ratio for the entire OL or WOT part of the curve had dropped about .25 of 1 point.

Nothing but the temps had changed. In the earlier dlogs taken from the afternoons the temps had been in the high 80. That Sat morning the temps had dropped to the mid 60's.

Makes one think a bit .................. don't it
then again
Hard Data Don't Lie

Grady