[Diy_efi] Newbie with a simplified Motronic project

[arnie]

The MAF system will self compensate for changing in engine VE as the
mileage/wear take it's toll.  As engine wear would occur, a SD setup would
need to be 'retuned' to compensate for changes in engine efficiency.

GAS

----- Original Message -----
From: "Eric D Byrd" <klox at juno.com>
To: <diy_efi at diy-efi.org>
Sent: Saturday, October 26, 2002 11:13 PM
Subject: Re: [Diy_efi] Newbie with a simplified Motronic project


> I think all you need for basic fuel and ignition control is MAP, IAT and
> RPM.  The reason MAF is good is that it accounts for both pressure and
> temperature.  An accurate MAF signal, interpreted by an accurately tuned
> ECU table, is just as good as MAP + IAT interpreted by an accurately
> tuned ECU table.  Consider the equation of state, that it has three
> variables, pressure, temperature and density.  Fix pressure and temp, and
> you have density.  What an ECU really wants is an accurate measure of
> density, because that's how you set fuel mixture.  And to set timing, you
> need to know density and water temp, because the fireball burns at a rate
> dependent on density and temp in the chamber at TDC.  Essentially
> dependent on what is known as the "second speed of sound", a term
> applicable usually only to heat transfer issues in engineering.  With
> those in mind, I still wonder why they bothered with making an MAF
> sensor.  It isn't more accurate, simply because all your accuracy rests
> on the accuracy of your tune in your ECU.

> --Eric Byrd



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