F Body vs Y Body MAF Tables different, why?

[n0dih]

I just installed a Vortec/F/Y Body MAF on my LT1 in my Fleetwood and copied in the Y Body (94 and 95 are same) MAF constants.

Now I am running BLM's around 160 all the time. So I started combing over my .bin/.lt1 files and found that the F body and Y body have different constants. They share the same MAF. Why the difference? Is this because of the inlet before the MAF?

Thanks!

[Chris 96 WS6]

Probably. The WS6 has yet a different table than the other LT1s as well. My guess is it is the Y body table.

[n0dih]

Are they correcting for the ram air effect?

Can anyone please send me a copy of the tables in a gif/jpeg (or post on here) the WS6 and even LS1/LS2/LS6 tables? I would like to compare what they did.

I honestly haven't ever seen the T/A's up close enough to know how the MAF is run on the WS6 and non WS6 birds. Anyone have pictures I can look at?

Thanks!

[Chris 96 WS6]

I say scale the table until the BLMs come down. There's no exact science to it.

[vectorbundle]

maf tries to estimate total flux through intake tract cross section, indirectly via essentially effect of air velocity on the resistors at the resistor location only. total flux of course is same at any cross section in same intake tract (absent vacuum leaks), but air velocity is not uniformly distributed throughout a given cross section, and this distribution can be different at different cross sections.

this needs to be taken into consideration if a couple of sample points of velocity are to be used as proxy for entire cross section. eg, a cross section close to the tb will probably see different velocity distribution, so same velocity are a resistor means different total flux. even just turning an maf 90 deg may produce observable changes in fuel trims. so it's not surprizing that tables are different. that's my understanding of it anyway.

[n0dih]

I am still having some problems with the BLM's at idle. They seem to get upwards 146, like I have a vacuum leak, but I haven't found one. I do have a small exhaust leak at #7 port, but I can't imagine it would toss BLM's off that much. It never did before. All other ranges are reasonably tight on 124 +/- 4. My Std Deviation for BLM's is like 2.5, so it is pretty decent. When I tune with VE Master, I delete all data that isn't above 85C so I don't get anything in the warmup temps.

Thoughts?
Thanks!!

maf tries to estimate total flux through intake tract cross section, indirectly via essentially effect of air velocity on the resistors at the resistor location only. total flux of course is same at any cross section in same intake tract (absent vacuum leaks), but air velocity is not uniformly distributed throughout a given cross section, and this distribution can be different at different cross sections.

this needs to be taken into consideration if a couple of sample points of velocity are to be used as proxy for entire cross section. eg, a cross section close to the tb will probably see different velocity distribution, so same velocity are a resistor means different total flux. even just turning an maf 90 deg may produce observable changes in fuel trims. so it's not surprizing that tables are different. that's my understanding of it anyway.

[vectorbundle]

are trims asymmetric (left-right)?