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QUOTE (stephen_lee @ Oct 2, 2011 - 10:11 AM)

>its gonna make ur car run rich
smaller diameter = greater air flow per unit area. since the maf only reads a small area it will get a false "higher airflow" reading
The laws of fluid mechanics state that Q(flow)=V(centerline velocity)*A(cross sectional). The A of his current set up with the small D = 3564.7mm^2 . The A of the desired set up is 3959.2 mm^2 . it's 90% of the area. Assuming for instance the engine needs .5 m^3 of volume and we use the standard diameter for reference, it looks like
.5 m^3 = Vc * .003959m^2 where Vc = 126.288 m/s
What we find from fluid mechanics as well is that the velocity of the center of a pipe is faster in the center than it is at the edge. In fact at an incrementally small (.01mm) the velocity is effectively 0. This then means that if you take the radius/2 aka D/4, the velocity would be about 63.144 m/s. The relationship is nearly linear from the center to NEARLY the edge as seen here
graph of velocityIn the current setup with the maf in the middle with our hypothetical Q of .5, our Vc is .5=Vc(.003564) meaning Vc(actual) = 140.264 m/s with this linear relationship in mind we know that in a right triangle with the x being the radius, 33.685 and the y being the Vc at 140.265, we find a hypothetical angle of 76.496 degrees. Taking this same angle and applying a new y of the the desired 126.288 we get 126.288/tan(63.152) = 30.328 mm.
This all means that in his CURRENT set up, the appropriate location of his maf in that apparatus is 33.685-30.328 = 3.356mm closer to the edge of his tube.
That would THEORETICALLY be the location for his maf such that his motor would not run rich.
I'm just trying to provide a little bit of SOLUTION instead of more problems
So if you want to use that configuration you should get a about a 3.3-3.5 mm shim to shim your maf sensor holder out a little bit more.
Hope this helps you
Just a little bit of engineering to help solve a problem.