Injectors and fuses

[dn]

> In the 2.5 ohm systems i have checked they don't take more than 1-
> 1.5amp/injector. Around 2 amp should bee a good choise since the most


A little judicious application of Ohm's Law will reveal that at
12V, a 2.5 ohm load will draw almost 5 Amps!.  Considering that
the standard battery voltage is closer to 14V, the current draw
becomes even larger. Mind, you, the inductance of the injector
will self limit the current until the inductor "charges" up, the
above calculation would be worst case if the injector was on 100%
of the time.  Most injector drivers are also current limited, but
this only protects the injector, not the driver circuit.

The 1-1.5 A figure you quote is most likely the average current,
not the peak.  Fuses would have to be rated to handle peak
currents, with a safety factor of about 25% added on for good
measure.  I would use an 8-10 A, standard automotive fuse, this
will protect the driver from catastrophic failure, but should
never blow under normal conditions.  I would think that most auto
makers use some fuse in the circuit, whether it is replaceable
(read visible) or not is another issue.  May be just a fusible
link in the wiring somewhere.

regards
dn




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 Darrell A. Norquay                   Internet: dn at dlogtech.cuc.ab.ca     
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