Fuel pressure reg/EGO Qs

[Mary or Stephen Burgess]

At 05:47 PM 2/11/00 +1100, you wrote:
>Hey y'all
>
>Could someone please explain to me:
>
>1. Why do they have fuel pressure regulators manifold pressure referenced?
>Why don't they just take this into account in the fuel map? Is it so that
>the injectors are open longer at idle, improving trimmability and hence idle
>quality?
>
>2. Has anyone tried to use a standard EGO sensor to tune an engine? I'm
>currently trying it, but it has so much hysteresis that it isn't working.
>How do factory ECUs do closed loop control, esp at idle?


Hi-

I may not be totally correct in this (manufacturers may have other reasons),
but I've tried manifold reference of the fuel pressure regulator to do two
things - 1. alter fuel pressure and increase dynamic range of fuel injectors
on high rpm engines without the need for multiple injectors and large memory
ECU maps (injectors sized for idle don't usually perform well at 12000 rpm)
, 2. mechanically compensate for engine loading (suddenly snapping the
throttle open raises the fuel pressure and helps eliminate bog and surging
problems)


Tuning with just the ego sensor can be done roughly, but I suggest you also
use exhaust temperature sensors to "fine tune" the mixture. Lean mixtures
burn hotter giving hotter exhaust, rich mixtures give cooler exhausts, and
ideal mixture will be somewhere in the middle. Using both the EGO sensor and
an exhaust temperature reading should allow you to "dial in" the fuel and
ignition tuning.

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