Nissan Injectors....what gives ??

[A.Clampitt]

diy_efi at coulomb.eng.ohio-state.edu wrote:
> 
> I've just spent the last few days doing a complete wire trace (several
> times !!) for the newly installed aftermarket injection system on my
> Datsun.  The reason ??.......even though the computer says it is getting an
> RPM signal (via a crank trigger indicating TDC) there was nary a peep out
> of the injectors.   I thought maybe the injector drivers had died.
> 
> Now, almost by accident, I've found the likely cause of the problem.  I'd
> been advised to use 'ballast' resistors in series with these injectors as
> they are from an early 80's Nissan L28 engine and that's what Nissan did in
> those days.  I was told  the injectors wouldn't work properly without them.
> In a last desperate act to get the engine running, I  bypassed the
> resistors to power the injectors direct - lo and behold,  the engine starts
> and runs beautifully !!
> 
> Can anyone shed any light on this ??.  The injectors show a resistance of
> 2.5 Ohm in each case, which I'm told means that they need to run with the
> ballast resistors, but are there exceptions to this rule ?? (it seems that
> I have one !!).   Am I risking damage to my computer, injectors or anything
> else by doing this ?? (ie running without the resistors).  BTW, the
> resistors are off an engine of the same period and checkout OK.
> 
> 
> Stephen Lamb

>From Gregory's EFI and Engine Management it seems that Nissan used 
Injectors of around 2,35 Ohm resistance both with ( R30 Skyline range) 
and without injector resistors (R31 Skyline range) 

As I understand , there are two conflicting requirements when actuating 
an injector :-
	High current to give a fast opening of the injector at cycle 
start.
	Low current to minimise static dissipation and ensure fast 
closing of the injector at cycle end.  

	The purpose of the resistor was to ensure full voltage across the 
injector at the start of injection to ensure that the injector opened 
quickly , once the current flow built up ,the drop across the resistor 
limited the current to a "holding" level just to keep the injector open 
without excess dissipation in the injector ( and possibly the switching 
transistor in the ECU) And also allowing faster injector close times from 
the lower holding current 

	I think that many (or most )modern ECUs do this electronically 
(without the use of limiting resistors) by the use of integrated injector 
drivers which allow the current to ramp up to a relatively high level 
2-4A) ( to open the injectors quickly ) when this high current is 
reached, the  injector driver automatically drops the current to a lower 
( .5A - 1A) holding or sustain current for the remainder of the injectors 
open time .

	Following from this , it may be a good idea to contact the 
MANUFACTURER of the control unit you have ( not some oily oick from the 
retailer ! ) and question them on the type of driver used in the system. 
 	Sounds very much as if your controller was designed for no 
resistor !

	If I've got this totally arse about face , please do not hesitate 
to flame or send large checks to help educate me properly ! <:->