Odd B4 V6 Engine Air-Filter Box Lid questions...

[Lago Blue]

Questions: Subject lids (photos below) has no apparent MAF. Listing from which the 1st 3 photos came was for a UK car (a '94 Cab) w/ what looks like an otherwise stock gasoline engine. Is there perhaps a sensor insert into the lid exit tube that is not visible in these views? Last shot confirms this type is a spark ignition engine. If not a MAF, what might it use instead, air density? Your thoughts.

Cheers.

94 Cab V6 5-Spd Eng Bay no MAF Screen Shot 2026-02-07 at 5.05.18 PM.png 94 Cab V6 5-Spd Eng Bay no MAF II Screen Shot 2026-02-07 at 5.05.49 PM.png 94 Cab V6 5-Spd Eng. Bay no MAF III Screen Shot 2026-02-07 at 5.06.10 PM.png

B4 V6 5-Spd Eng. Bay w: no MAF & no cover III Screen Shot 2026-02-01 at 10.12.39 PM.png

[Crasher]

The ABC doesn’t have an AMM.

[Lago Blue]

Thank you sir!

That is interesting. So I found a write up which says what it does have: "There is also an absolute pressure sensor + air temperature sensor instead of a flow meter,".

What I also found is this:

image_93147.png image_93148.png image_93149.png

Note the velocity stack inside. A velocity stack is what is missing from all the 7A 20v and AAH 2.8 V6 air box lids I've seen save for perhaps just this one. I do know that putting a velocity stack on my two cars of those 2 types made a seat-of-the-pants difference.
While adapting the v-stack shown may or may not be possible to our box-lids, it does reinforce the fact that Audi choose to put stacks on several of their cars (the UrQ included) but not the 7A and AAH. Not fatal but correctable.

Audi wouldn't have bothered if it wasn't useful. So why the abscence in these two cases? Why put a v-stack on others and yet leave a debilitating square-edged air-filter box lid exit right in front of these 2 MAFs? Theory: the only reason I can think of for its' absence is for performance differentiation between models. Like the necked-down MAFs and the intake port obstruction in the V6 heads, these subtle changes, these departures from empirical design (by deletion, restriction or addition) allowed the more expensive cars to be relatively faster.

I know Sauger Tuning (the German 7A site) says the big-bore MAFs don't make a difference, but that's what I did. If I lent you mine, a proper well-mated short velocity stack together with a big-bore MAF to you to put on your 7A or AAH, and you did and drove it for a while till the car adapted, you wouldn't want to give it back.

See item #8 in this thread:

https://www.audiworld.com/forums/12v...intro-2788912/

[Crasher]

Be careful messing with an ABC, they can be touchy and start idling badly.

[Lago Blue]

Good to know. That there may be issues with ABC engines, may help someone. Of the 12v engines, I'm only aware of AAH, AAH/AFC and AFC versions here in North America. My interest was just about the MAF-less air-filter box and the airflow enhancing surprise inside.