[Shotimes] Re: 76mm MAF with 19# injector calibration

[Cohiba]

The C&L 76mm MAF is designed to mimic the stock voltage curve, by keeping
air mass and velocity passing the hot wire equal to stock, while decreasing
pressure drop and smoothing the air flow.  They are not designed to exactly
follow the voltage curve, they are designed to reduce the voltage curve by a
percentage to make the mixture a little bit leaner than stock. Using the
yellow sample tube with a 76mm C&L on a SHO will mimic the voltage curve,
but will be adjusted towards the rich side, while using the yellow tube on
its intended car (86-93 Mustang 5.0 with 19# injectors) would make the
Mustang slightly lean.  Using a clear sample tube will adjust the curve
slightly lean on the SHO, but if you were to use the clear sample tube on a
Mustang, the Mustang would be severely lean.  The sample tubes don't change
the curve, they just reposition the curve on the graph.

The voltage curves are the same, but they way the EEC uses the reported
voltages is the difference between the cars.  The EEC knows what size
injectors you are using, and what mass of air corelates to a specific
voltage.  So, when the air passing through the sample tube moves over the
hot-wire, the hot-wire reports the voltage to the EEC, then the EEC uses
it's data table to tell the injector how long to spray.  So, for example, if
you had 500 kg/hr of air coming in a stock MAF housing, the hot-wire will
tell the EEC is has 500 kg/hr of air entering, then the injectors spray the
appropriate amount of fuel.  If you add bigger injectors and bigger MAF, but
don't tell the EEC you have bigger injectors or MAF, than you want the EEC
to "think" it's getting 500 kg/hr of air still, while in reality, the car is
getting 600 kg/hr and the additional fuel from the bigger injectors create a
stoich a/f mixture.

It's not "tricking the EEC", it's just math and physics.

Hope this makes sense... it does to me...

Gary
http://users.superford.org/cohiba




----- Original Message -----
From: "Mark Nunnally" <manunnal@netheaven.com>
To: "shotimes" <shotimes@autox.team.net>
Sent: Saturday, October 19, 2002 2:10 PM
Subject: Re: [Shotimes] Re: 76mm MAF with 19# injector calibration


> >he said if programming with and LPM or EEC
> > Tuner, to use the voltage curve from a stock 86-93 Mustang 5.0, if using
> the
> > "yellow" tube, or use stock SHO voltage curve for the "clear" tube.
>
>     This is what I've never understood.  (ie different sample tubes for a
> given MAF, for the SHO and 5.0L mustang).  The 89-93 5.0L mustang and SHO
> share the same stock MAF, both EEC's are looking for the same data set.
> IOW, there is no specific mustang "curve", and no specific SHO "curve",
they
> are both the same.
>
> As for a 90mm MAF, throwing out all electronics and just talking sheer
CFM,
> unless you have a blower car, it's way overkill IMHO.
>
> mark
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