Injector control

[Ludis Langens]

bearbvd at sni.net (Greg Hermann) wrote:
> First--has anybody figured out how small an incremental adjustment to
> injector pulse width time the OEM ecm's are capable of making (GM, Bosch,
> etc.???)?? If so, is it posted anywhere??

GM is 1/65536 or 1/65517 of a second.  So, about 15 microseconds.

> Second, a few months ago, I talked with Lance Ward, the FP tech guy, on the
> phone. He said (among other things) that they program their ecu so as not
> to allow injector pulse widths shorter than 1 MILLI second.

One particular ECM and calibration increases narrow pulse widths using
this table (1 unit is 1/65517 seconds):

  1 unit -> 16 units
  16     -> 31
  32     -> 47
  48     -> 58
  64     -> 72
  80     -> 86
  96     -> 101
  112    -> 115
  128    -> 130
  144    -> 144

Thus, any pulse width less than about 2.2 milliseconds gets stretched. 
When used with an automatic transmission, this same ECM doubles up
injector pulses when they would have been less than 1 millisecond.  That
is, it gives one twice as long pulse instead of two short pulses.

-- 
Ludis Langens                               ludis (at) cruzers (dot) com
Mac, Fiero, & engine controller goodies:  http://www.cruzers.com/~ludis/