Non Distructive testing (letting the smoke out)

[Sandy]

If the drivers are peak and hold style and the work as advertised, they
will do the peak, essentially until the trigger current is reached, the
hold at the hold current. So if you have 50 injectors you will only have
the hold current that the drive supports, so adding injectors is a waste O
time unless they are saturated types. I missed the start of the thread so
didn't get the reason for paralleling injectors, but you can't parallel
peak and hold style injectors, will not work as you think. Saturated
(15ohm) injectors will, and it just depends on the current capability of
the driver, and as you are trying to find out, how hot they will run. The
other thing to watch out for is that as you parallel the injector you also
increase the amount of current back into the flyback/clamp diode that is in
the circuit, so that is also another source of heat or problem.  Just some
food for thougth. 

Sandy

At 03:34 PM 1/12/99 +0200, you wrote:
>Hi
>
>I am not a expert on this, but if the ECU uses a current controlled driver
>then it would force a constant current through a injector. This current is
>the independant of the resistance and inductance of the injector. So if this
>is the case then you can put as many injectors in series as possible ?! That
>is if the turn-on current can be achieved by the voltage accross each
>injector.
>
>So the question is, what kind of driver are the ECU using, is it quasi
>current controlled, open loop or square voltage driven?
>
>Cheers
>Carlo
>
>> -----Original Message-----
>> From:	Roland Johansson [SMTP:scirocco at mail.bip.net]
>> Sent:	Tuesday, January 12, 1999 12:02 PM
>> To:	diy_efi at efi332.eng.ohio-state.edu
>> Subject:	SV: Non Distructive testing (letting the smoke out)
>> 
>> If you place a finger on the drive transistor/or several and
>> start it with normal number of injektors, simulate full throttle
>> for longest on times. The transistor/s should get wam but not
>> burn your finger in about 10-15 minutes time, try with bigger
>> number of injektors, if you burn your finger you will be closer
>> to the limit, probobly over if out temp are high
>> 
>> This is not scientific but could give you a good estimation if
>> it will work. If the drivers get what you think is to hot, try
>> add a old computer fan and test again.
>> 
>> 
>> Roland Johansson
>> Scirocco 1,6l TIC -82
>> 
>> 
>> 
>> > Nother thing, what would be a "safe test" for how long
>> overloading
>> > a driver would take.  If I wanted to see if something was
>> going to
>> > work on injector drivers, how long in running them would it
>> take to
>> > see if they fail?.
>> >   I have two items to test, running 16 injectors off of a 8
>> cyl TPI ecm
>> >   Running 4 P+H injectors where 2 are normally fittted.
>> > I would figure if the ecm gets only warm to the touch that
>> would be one
>> > clue.
>> > Cheers
>> > Bruce
>