Changing injector pulse rate at idle?

[robert dingli]

I previously explained
> > 
> > This is exactly the technique that we have resorted to for high flow
> > rotary applications.  The injectors found on factory Mazda 13B efi
> > motors are huge - they flow 2-3 times the volume of 'normal' injectors.
> > Even so, this is not enough for race motors and turbo applications.
> > We use two injectors per rotor with the second bank staged so that
> > they are completly closed during idle and only start to open at higher
> > loads.

 and Craig asked :

> Is the idea to have injectors of the same size, or a small & a big one?
> 

I can't remember how Mazda do it for the six port 13B turbo.  I would
guess that the primary injector would be the smaller of the two if they 
were in fact different.

> Also, when it's in transition between single and dual injectors,how do
> you split the time each one is on for?
> 
> EG
> 1. Does the primary injector increase in time, until it is 100% on &
>    then the secondary inj progresses on from there.
> 
> OR
> 2. Does the primary injector handle light loads, then when a certain
>    on time/duty cycle is reached, the secondary injector is run in 
>    parallell with the primary (ie IDENTICAL timing)
> 
> Presumably in any situation with staged injectors the user would only
> have to adjust the fuel 'on' time & they would be oblivious to how the
> timing of multiple injectors per port is handled.
> 

Mazda uses an interesting system where the primary injector does all
of the work until it reaches 10 mS pulsewidth.  After this point the 
primary switches to something like 5 mS and the same for the secondaries.
As far as I know, the transition is undetectable.

Our system allows the user to adjust a 'stage factor' which is the
ratio of opening time between secondary and primary injector outputs
expressed as a percentage.  Since the system is purely empirical, any
non-linearity in the fuel rate as a function of set injector opening 
time is taken into account while tuning.  The two primary outputs fire
alternatively 180 degrees apart while the secondary fires twice as often
to ensure even fuelling from a single output.  Conventional injector
per port systems only use the two banks of primary outputs.  The spare
staged output could then be used for other control tasks such as NO2
or water injection.

Robert

-- 
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             Robert Dingli           r.dingli at ee.mu.oz.au

Power and Control Systems                 Thermodynamics Research Lab
Electrical Engineering                    Mechanical Engineering
   (+613) 344 7966                           (+613) 344 6728
  University of Melbourne, Parkville, 3052, Victoria, AUSTRALIA
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