Is this too simple?

Eric Fahlgren efahl at adams.com
Tue Apr 9 13:49:33 GMT 2002


Jeremy Harris wrote:

> are that a very simple system would suffice.  I plan on using a MAP system,
> with a single throttle body with one injector mounted to a central plenum
> feeding the inlet port runners.  I think that all I need to measure is MAP
> and inlet temperature, with the injector timer being triggered by the
> existing crank sensor (1 pulse per rev, two pulses per firing cycle).

Jeremy, you need to add RPM into your pulse width calculation, too, since
VE varies considerably across the RPM range.  You can have the same MAP
and air density, but the "gulp size" will change a bunch depending on
how fast the engine is running.

> This all seems to work OK on the bench, and I have a baseline set of
> calculated pulse widths against MAP and air temp loaded into a look up table
> in the Stamp.  The Basic Stamp is a bit slow (it takes around 100mS to run
> the loop), but I figure that this doesn't matter too much for this

Yeah, 100 ms is slow, which might cause stumbles on rapid acceleration,
but like you say, for this application, who cares?

Eric
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