Low RPM problems & aftermarket intakes

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George_R

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Just wanted to share some experience

1uz-fe vvti conversion, could not run factory airbox due to space restrictions.
vvti factory airbox has a slot for MAF sensor. vvti's mass airflow sensor differs from that of earlier models, as can be seen below. That's the best intake I could fit into my engine bay. The airflow sensor is designed to be inserted in specialized slot in airbox housing.

1e99b74s-960.jpg


At higher revs it's ok , but low RPM problems do show up as rather unstable idle, bogging and hesitation when accelerating off the line. Reading some boards over the web shows the problem is often associated with custom air intakes.

a MAF sensor must see laminar airflow. That is equal flow across the entire cross-section of intake pipe and no turbulence. Any bends introduce the turbulence, and it's assumed that one must run about 3..5 diameters of intake pipe length before MAF and a couple or more diameters after.

That's not usually possible in real life, but it's ok to try and use some sort of airflow straightener. Here's my initial approach to test the concept
ff99b74s-960.jpg


Car's behavior changed significantly, so I'll come up with improved design some time later. However you got the idea.

Now to display some facts and numbers
That's the fuel trims before the honeycomb straightener mod applied
6199b74s-960.jpg


Here's what they are now
a199b74s-960.jpg


Refer to the web if you don't know much about the fuel trims; they're a powerful diagnostic tool indeed.
 


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