From: Kukukooter@aol.com@INTERNET on Tue, Nov 26, 1996 4:11 PM
>The SBEC is one very smart ignition controller, any airflow or fuel changes,
>all the sensors take notice and the air/fuel ratio is then determined. It
>will put in as much fuel and timing as the rail, pump and injectors can
>deliver. The only area it's lacking is in the way of a fat spark, which
can be >fixed by a series install of a MSD, etc.
No debating how smart the SBEC is but your statement is not exactly correct.
At Wide Open Throttle the computer is not operating closed loop. It reverts
to look-up tables to decide on injector duty cycles and timing based on a
subset of the sensors. Under these conditions it does not look at what's
coming out the tail-pipe and keep adding more timing and or fuel to there is
a mechanical limitation, it's predetermined in the programing. Under part
throttle operation when the system is operating closed loop the computer is
constantly adapting to all the sensor inputs. It is imparitive that when
making engine modifcations that dramatically improve engine breathing that
something is done to add more fuel at WOT conditions. Typically larger
injectors or adjustable fuel pressure regulators are used.
The MSD box is a favorite 2.2 turbo ungrade because it provides a hotter
spark that results in more complete burning of the fuel. General consensus
is that the biggest improvement is noticed, on these engines, in idle
quality and part throttle response.
Dave Clement
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