[s-cars] MAF screen removal-please explain

[Kirby Smith]

This type of mass flow sensor was first applied in applications where
the flow down the body of the device was intended to be laminar.  The
usual way to make laminar flow is the wind tunnel approach -- an egg
crate or honeycomb type of screen with the hole size smaller than the
length.  Screening will make the air flow turbulent, not laminar.
However, there is no reason why the system taking data from the MAF
can't be (dare I say it) "tuned" to accomodate any type of air flow, so
long as the measurement made is repeatable with mass flow.

Does removing the screens change the flow characteristics around the
wires?  Probably at low flow levels.  Does it materially change the MAF
calibration?  I doubt it.  I suspect that at full flow, where most here
are interested, the air is turbulent in both cases, and without the
screens, more flow is possible.

kirby, still screened.


Mark Strangways wrote:
>
> Snip.
> Now for part two, does removing the screen change the way in which the hot
> wire actually measures the MASS of air (not flow or velocity) passing
> through the meter?  I don't know.  I'm inclined to believe that it would,
> but I'd defer to the more sage advice of the engineering types on the list.
> /Snip.
>
> By removing the screens, you are NOT changing the MASS of air flow that
> enters the MAF for a given amount of air flow.
> You are just making it easier to get in / out. If the motor is drawing 100
> CFM, it will draw that thru the MAF, and will give the appropriate signal
> from the MAF, regardless of screens.
>
> As Hap pointed out, it's the 'Negative Boost'. By reducing any obstruction
> to with in the inlet stream, you increase the pressure available to the
> turbo, which equals more boost. Similarly by decreasing the pressure drop
> across the filter you increase boost.
> While decreasing pressure drops, you allow more flow. If you pump can accept
> it.
>
> At least that's the way I see it .
>
> Mark S
>
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