I've always read that you can mount the airflow meter in any position and it will still work. This can be done when the stock air filter box is removed and a cone filter installed in its place. I found this information to be correct, but also found that different positions change the computer's air / fuel curve slightly.

I just finished testing three positions of mounting the meter, first being with the flap arc facing downward, then with it up, and then in the stock (horizontal) position.

With the downward position, I observed a slight low end bog followed by a midrange 'ramping up' of power up to 4000 rpm and black spark plugs.

With it up, the bog went away and off-idle response was very good. The ramping up of power also went away and the car didn't feel as fast.

Tonight I installed it in its stock position and observed the same great off-idle throttle response and torque, but with no ramping up of power through midrange like in the first position. The power just climbed smoothly. I thought the car might be slower this way so I tried some 1-2 gear runs from a stop to 4000 rpm in each gear and the car still felt plenty fast.

In conclusion, I have found that the flapper valve in the air flow meter reacts to gravitational pull because it is unbalanced and held in position by a spring. I surmise that positioning it such that it opens downward richens up the midrange and low end mixture, while doing the opposite gives a slightly lean condition. Stock configuration gave the best drivability by far and plenty of power, probably 1-2% off the first position or maybe more (seat of pants dyno is inaccurate).

I am still undecided on whether or not the stock position is as powerful as with the flapper going down, but my future forays into S-AFC land will show if any power can be gained by riching up the midrange over stock settings. The car drives so well now with the meter installed horizontally that I won't change it. It still pulls plenty hard for my taste and has excellent low end torque and off-idle throttle response. It feels like a good V6 right now and is pretty fun to drive.

 

I hadmine all crooked for the longest time, flapper up I think. Then I started thinking and made it flat, that helped. Then I started thinking more and just took it off, that works better

 

put a voltmeter on the ecu pin and you can actually get #'s to validate your seat of the pants. hmm actually if you do that you could prolly have a good handle on the afc settings before you even get it, or god forbid just modify the afm and not use the afc all together

mike

 

I'll be really interested to see your actual results.

I like the idea of actual voltage #'s too!

Conventional wisdom tells us that putting it upside down or right side up would be the same, but mounting it on it's side would have an effect.

I'd imagine that either way would have a positive and negative effect - dependding on the rev-range. ie one is better down low, and one is better up high.

Keep us up to date!

 

The '89+ AFM can be mounted in any position as long as it is basically on a horizontal plane. The '86-'88 AFM can only be mounted in it's original conifguration, or rotated 180 degrees so that it is upside down. As you said, any other orientation and the flapper will be effected by gravity.

 

If you searched the thread you would've found the answer.
I tried every position for installing a front mount (many hours cutting, welding and re-positioning) to make the piping easier. The flapper door type cannot be mounted any other position than rib side upor down meaning level". In any other position, gravity will have a effect on the flapper door and cause all sorts of weird problems when floored.
Also, door type AFM will not work if you mount it between the turbo and throttle body. It has to go before the turbo. The latter can be mounted anywhere and any position.

 

http://my.engr.ucdavis.edu/~pko/OldSetup.html

notice where the afm is

 

You should post your link about the Bonez adapter "flip" this helped me out alot. I noticed a gain (no dyno proof) from turning the AFM back the right way up. Smart idea!

-Mike

 

There's another problem with mounting the AFM vertically. Because the flap can now be affected by gravity, it's also affected by the car's vertical movement. So any rapid up and down movement (bumps in the road) will cause the flap to wobble up and down on it's spring. This can cause the engine to stumble, and you may not even realise why.

There are very good reasons why no manufacturer has ever mounted flap AFM's any way other than perfectly horizontal.