Injector Impedence Q

Stephen Dubovsky dubovsky at vt.edu
Fri Feb 14 15:21:25 GMT 1997


At 03:16 AM 2/14/97 -0500, you wrote:
>In a message dated 97-02-13 19:02:17 EST, you write:
>
><<   If your going to go through all that trouble, simply use the EFI output
> to drive the inputs of 4 new injector drivers, or drive one BIG injector
> driver (designed for 4x the current) and run all the injectors in parallel.
>  Trivial really.  If you are replacing a TBI (non peak/hold type) injector
> w/ 4 small injectors (also non peak/hold type) the 4 injectors in parallel
> might not require much more current than the orig large injector (so use
> its output directly).  I wouldn't go to a serial/parallel arangement. >>
>
>So do you think it's possible to try and run four injectors off of the stock
>ECU? Of what impedence should those inj be? What about the current?
>
  Go measure the impedance (or more precisely the resistance) of one of
your TBI injectors.  If it is a hi-z type it will be somewhere around
10-20ohms (as opposed to 1-4 ohms for a peak/hold type).  Divide 13v/R to
get the current the old injector drew (and what the EFI could handle).  If
your new injectors have about 4x the old resistance (doubtfull now that Im
thinking about it) they will draw the same current in parallel.  You can
probably draw a little more current than before because the inj driver was
probably a little overrated. (Who ever designs w/ zero safety margin?)
Something else that just poped in my head, you might be able to crack open
the ECU and simply put in a bigger driver (or at least get the input signal
that controls it). 
SMD




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