injector duty cycles

[Todd King]

  <<<
  From: Mazda Ebrahimi <kleenair at ix.netcom.com> Date: Wed, 04 Dec 1996 20:22:56 
  -0500 Subject: Re: injector duty cycles
  ...
  > I find that at WOT my injectors go greater than 99% duty cycle for most of 
  the
  > Todd    Todd_King at ccm.co.intel.com
  Thanks for the info. Is this a stock engine? Are the injectors peak and hold 
  type?
  >>>
  <<<
  From: "William A. Sarkozy" <mymove at serv01.net-link.net> Date: Wed, 04 Dec 1996 
  21:44:47 -0800
  Subject: Re: injector duty cycles
  ...
  I gather that at 2000 RPM with WOT  you're pumping in the same amount of fuel 
  as you are at  6000 RPM with WOT????  100% duty cycle with (essentially) the 
  same fuel rail pressure.  Seems like we're going to run a little fat down low, 
  boys.  Help me out, here.
  >>>
  
  The engine was nearly stock. I am installing ported heads presently so will 
  report on it when it gets back on the road. These results are part of my 
  previous comments about not getting caried away with what's necessary to have 
  a useful EFI setup. The car was low 12's at about 110mph as it was; yes, the 
  O2 voltage drops during a run under these conditions so to end up safe at the 
  end of a run you must start fat at the beginning. I don't think most people 
  really consider the overall injector dynamic range problem very deeply (until 
  they are actually facing it). Consider that this engine is small (3.8L, 231"); 
  the fuel required at idle is small. The engine is also turbocharged/ 
  intercooled; the fuel required at WOT is BIG :-) , while the time to deliver 
  it shrinks with every increase in RPM. The injectors were 34 #/hr, high 
  impedance (sat type?); I have a set of 50 lb'ers waiting for the install time. 
  The inj sizing compromise must be made somewhere, unless one wants to run 
  staged injectors (ie multiple injectors per cylinder)... Glad the info has 
  stirred some thoughts out there.
  
  Todd  Todd_King at ccm.co.intel.com