Basically everything ends up being application specific in the cheapest way possible because....EPA. That's automotive in a nutshell lol.

That's interesting that crowd uses a 'lag' from the MAF as justification to switch to SD...physically, that way of thinking is backwards. The air must pass through the MAF first, before it ever reaches the intake manifold to begin increasing MAP and fill the intake manifold. Every time you snap the throttle open on a MAF and SD (blended) setup, the MAF will always report airflow before the VE/dynamic airflow does. In the Subaru case, with more volume between the MAF and intake via larger IC or plumbing, the MAF would overestimate air delivery rather than underestimate because of flow lag. Coincidentally, this is why GM MAF only stuff can run so well...and how Ford gets away with exclusively MAF in plenty of vehicles. In reality however, each application has specific compensation for airflow discrepancies due to transients like a throttle stab. Things are smoothed and filtered and predicted to make sure none of the measurement noise has too much effect on the fueling control. That said...the subie guys might have another issue entirely with the MAF, like flow restriction or caps on flow measurement.

 

Definitely helps. Thanks!

 

What about big CID NA...I am in the process of gathering parts for a 434 LS build

 

Big inch big cam stuff can be particularly nasty for any typical controller to fully handle. Depends on how extreme the build is. A MAF can wind up totally useless on an engine that size when revs are below around 3000 because of the intake reversion that happens with a late IVC camshaft, especially with larger intake tube diameter. Naturally you'd want to hop over to speed density, but even that is limited in capability with rowdy high overlap camshaft setups. The scavenging that takes place dragging uncombusted air and fuel through the chamber and out the exhaust makes the typical fuel trim approach more complicated. A typical speed density model doesn't compensate for that kind of scavenging because its terrible for emissions - OEMs would never put that into production, so the software doesn't really exist. Aftermarket controllers like Holley offer some combined SD/Alpha-N capability for more extreme combinations that can't be accurately managed by a MAF or explicit SD models that the OEMs use. It isn't too dissimilar from EFI controls on high revving motorcycle engines - those are a blend of SD and Alpha-N as well.

I'm of the mindset that if you have an NA combo that needs a vacuum pump at idle to give your brake booster an assist...you probably want to start looking at some Alpha-N options.

 

My cam is going to me on the smaller side

 

Reversion is the enemy of the MAF. As long as you don't run out of maf frequency or hit an airflow limit, I like having a MAF.

 

A lot of Subarus, including mine, have a "rich dip" while boost is building. With big turbos it gets bad enough that you can feel and hear the engine sputtering while it happens. Half of that problem turned out to be the wall-wetting compensation in the factory tune - you could watch it add fuel while the rich dip was happening. But even after that compensation is fixed you can still see the rich dip in the WBO2 channel of a data log, it's just small enough that you rarely notice it from the driver's seat.