[Jtab]

Looking for a MAF transfer function for an OEM Ford slot mass air sensor in a PMAS 80mm (flanged) housing.

Here's a link to the housing:
https://www.pmas-maf.com/product/hb80f- ... per-black/

I'm VERY disappointed with PMAS customer service: They have disabled their phone line and only take emails, and they stopped replying to my emails after I ordered their housing.

[cgrey8]

Converting between transfers when all that's changed is the diameter of the housing is just an algebra exercise. I believe there's probably an excel spreadsheet out there to even handle this for you somewhere. If not, anybody with some excel savvy can make one.

But the jist of how to do this is take the transfer of a slot style meter from a known diameter, then multiply each value in the transfer by the percentage difference in cross-sectional area of the new enclosure.

Cross-sectional area formula is π r^2 OR π (d/2)^2

So just for instance lets say that stock slot meter enclosures use a 76mm enclosure and you are going to an 80mm enclosure.
cross-sectional area of a 76mm diameter -> π (76/2)^2 = 4536 mm2
cross-sectional area of an 80mm diameter -> π (80/2)^2 = 5027 mm2

The ratio between the two is:
5027/4536 = 1.108

So you'd multiply every flow value in the transfer by 1.108 so that for any given voltage, the corresponding value is 1.108 times higher with the 80mm curve than with the stock 76mm curve.

Now this isn't going to account for differences in airflow track and flow efficiencies which can affect the actual MAF curve, but this will certainly get you close enough to enter into your tune as a starting place to tweak from.

Now in full disclosure, I don't remember what the actual stock diameter is that slot meters used. You'll need to do some searching for that. I also don't remember what the stock flow curve for those meters is. Although I do remember it wasn't difficult to come by. Back when I converted from a C&L meter to a stock slot meter installed in a piece of PVC pipe, I was able to find the values without too much trouble. So I know the numbers can be found.

[jsa]

This might/not be relevant.

[Jtab]

@cgrey8 that is how I calculated the maf transfer I am running now. I figured out the calculation using decipha's listed maf transfers and applied them to an 80mm housing. I suspect something is wrong because my pickup performs worse at lower rpm than it did with the previous meter (from a 1995 Explorer), which was mounted identically to the new meter. My new PMAS housing is advertised as 3"-3.5" taper, rather than a single diameter, so I think that might be part of the issue.

From my research, having the flanged meter connected directly to the air cleaner may be to blame, but it's all factory Ford configuration and hardware with the exception of the maf meter, and (again) it worked great with the last meter.

There are multiple factors at play, but I think an accurate transfer function is a good starting point.

[Jtab]

This might/not be relevant.

jsa -
How do I use that table without knowing the original pipe ID and airflow values? The only variable in that spreadsheet is meter housing diameter. What if the original values are wrong?

[Jtab]

Another thought: pmas lists their housing as "HB80F 80mm Draw Through MAF Housing w/Flange 3″ – 3.5″ Taper", so that throws all algebraic conversions out the window! Is it 3", 3.5", or 80mm?

Should I just guess until I find the value that runs best?

My engine feels like it misses at low-speed, high-load conditions, and I think it runs rich all the time.

[cgrey8]

I would start by measuring the actual diameter right where the sensor is located and for now, ignore the neck-down immediately after it. While airflows after the MAF do have an affect on the flow before it, there's only so much you can do with a static analysis, which is what we are doing to convert flowrates of a known MAF curve to what we believe the flowrate should be for the new enclosure. This is why if you want to eliminate the guesswork, you flow-test the meter on a flow bench. But since that's easier said than done, we play the cards we have.

So yes, start with a calculation based on the measured diameter where the sensor is in the housing. Run that and tweak from there. The tweaks you determine are necessary based on datalogs of the MAF running in place are your dynamic analysis.

The good news is none of the numbers need to be accurate to real-life as would be measured by laboratory equipment. They just need to be accurate relative to each other in order to get the tune to control the engine correctly. It certainly makes life easier for the tuner when the numbers are that accurate, but it's not an absolute requirement.

[Jtab]

PMAS eventually got back to me. Better late than never, I suppose. I've attached the data from their flow test; it opens with notepad. My pickup runs much better with accurate flow data... who would've thought! I think I need to add some sort of straightener to the intake, and relocate my ACT sensor to the intake, though.

On another note, does loading a tune with a different MAF transfer reset adaptive learning?

[cgrey8]

...does loading a tune with a different MAF transfer reset adaptive learning?

No. The adaptives, if not cleared manually, will just have to relearn from wherever they are to where they need to be (not ideal when they all aren't starting at 1).