FW: MAF Upgrad

[jb24 at chrysler.com]

I am going to go out on a limb and give a simple formula that ought to
be able to allow a bypass to work.  This formula is only good for a
bypass where flow doesn't have to turn any corners, i.e. don't cut
holes either side of the MAF and plumb in a pipe with two 90 degree
elbows.

Bypass formula: A1/C1 = A2/C2
A1: MAF cross-sectional area (along flow axis)
C1: Circumference of MAF along it's ID
A2: MAF + bypass cross-sectional area (along flow axis)
C2: Circumference of total flow area (bypass + MAF)

If you stick a MAF, housing and all, in a larger tube you must work the
OD of the MAF and the ID of the tube into the calculation for the
bypass circumference.  The inlet area change is going to be roughly the
ratio of power increase, all other things being the same.  Obviously a
circular inlet has the highest flow capacity because it has the
greatest possible area to surface ratio.  A rectangular inlet of
equivalent area will flow less mostly because of an increase in surface
area.  A fluid-dynamics book will give ratios for different
cross-sections.  Be careful with the transitions as well.  If you place
a circular pipe co-axial to your MAF, radius the transitions to both.
This formula works better the greater the needed flow capacity (better
if you are going to double the power output than add 10%).

Last thing to remember is that intakes are almost always
fully-developed turbulent flow.  However this doesn't mean that it is
in the compressible flow region.  If it were, the losses to due shock
formation would be tremendous and the motor would be strangled at WOT.
---------------------- Forwarded by John R Bucknell/JTE/Chrysler on
02/27/98 09:42 AM ---------------------------

        owner-diy_efi @ efi332.eng.ohio-state.edu
        02/26/98 06:24 PM
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Subject: Re: FW: MAF Upgrad

jb24 at chrysler.com wrote:

> [snip]



>  In order for a bypass to work,
> you must have roughly the same pressure drop ratio at low flow to high
> flow as the MAF alone (as pressure ratio is related to flow).  Flow
> bench would tell you easy.  Little differences should be handled by
the
> HEGO.
> ---------------------- Forwarded by John R Bucknell/JTE/Chrysler on
> 02/26/98 03:02 PM ---------------------------
>

This is where my experience fails me.  I don't know what will make a
smaller
tube act like a bigger tube with a restriction in it.

I could make this my life's work

Joe (Soon to be World MAF Bypass Expert) Boucher
'70 RS/SS Camaro  '81 TBI Suburban