Pulsewidths & injectors & coils ;-)

[Moofaloof at aol.com]

In a message dated 9/12/00 2:47:15 AM Atlantic Daylight Time, 
nrparker at ihug.co.nz writes:

> Hello List,
>  What are ballpark figures for the resolution (in time) you need for
>  effective injector control?  What have people discovered empirically?  Is
>  8us stupidly small? Is 64us too course? 

Depends on how fine a control you want to get. An engine will do fine  with 
pulsewidths accurate to the tenths of ms.  Many calibrations are not accurate 
to within that level of precision.  

My injectors are 365cc/min rating
>  (not sure if that 100% duty for 1 minute?) What is the usually way of
>  specifying flow capacity?

cc/min, or more commonly on these lists lbs/hr.

>  More questions I have regarding coils.
>  What is the normal method for coil control..I understand turning it off
>  makes a spark, it is essentially like an inductor to control.  Can the coil
>  run say all the time, (with a current limit method - say resistor ballast)
>  and only be turned off for say a couple of ms whenever you want a spark?

Inductive coils are normally energized for a specified dwell period (1-8 ms 
typically for an efi application) prior to being discharged through the spark 
plug.  The dwell time depends on the characteristic of the coil and driver 
circuit.  Charging the coil all the time will typically overheat the driver 
circuitry and the coil and result in premature failure.  Its also pretty 
wasteful of power since the coil will look like alot like a short circuit 
once fully saturated.
jc





>  
>  Thank you, Nick Parker.
>  
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