FW: MAF Upgrad

[Joe Boucher]

Yep, this is the hole in my knowledge I was talking about.  It would have
taken a long time for me to figure the equations out.

A thought occured to me.  Believe it or not. Since all of this is in front
of the throttle plates, the pressure drop should be small compared to
throttle drop across the throttle plate.  The design I have sketched in my
head has a conical, large diameter filter into a box.  The opposite side of
the box would have two smooth exits.  One for the MAF and one for the bypass
tube.  The MAF and the bypass would smoothly attach to another box which
would then connect directly or through another tube to the throttle body.
This should fit easily under the hood of any 60's vintage Cadillac, don't ya
think?  The trick is the merger from the box to tube and tube to box.  Those
curves would be mighty tricky for a backyard hack.  Might be time to try
some of the carbon fiber technology kicked around here lately.

Joe Boucher
'70 RS/SS Camaro  '81 TBI Suburban

jb24 at chrysler.com wrote:

> 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
> Please respond to diy_efi at efi332.eng.ohio-state.edu @ SMTP
> To: diy_efi @ efi332.eng.ohio-state.edu @ SMTP
> cc:
> 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