[Gmecm] Saturated/P&H injection

[Robin Handley]

Many thanks again. I knew about the difference impedances but the local
solution that I'd heard of involved adding a resistor. The GMECM triumphs
yet again!

Sorry for all the questions, but here's another one! Can the 727 do both?
(I've never come across any mention of a jumper in the time I've been
researching the 727.) I have a bunch of Bosch high impedance injectors which
I'd like to use.

Thanks,

Robin

----- Original Message -----
From: <davesnothereman at netscape.net>
To: <gmecm at diy-efi.org>
Sent: 14 May 2006 20:07
Subject: Re: [Gmecm] Saturated/P&H injection


> OIther than the fact that one indicates a single driver while the other
> is plural?
>
> Peak and hold injector drivers operate low impedance injector drivers.
> They allow higher current to initially open the injector, then when
> current reaches a peak level the driver switches to "hold" mode,
> limiting current to typically 1/4 of the peak value.
>
> Saturated injector drivers are designed for high impedance injectors.
> Total current draw through these injectors is lower than the low
> impedance types, so the driver simply allows maximum current through
> the injector coil at all times.  This scheme allows the injector coil
> to become "saturated" with current.
>
> P&H drivers will operate saturated type high impedance drivers.
> Saturated drivers are not intended to be used with P & H type
> injectors, although some people (and even OEM's) will do so with the
> aid of current limiting resistors.
>
> The 7749 can operate in either saturated or P & H mode selectable by an
> external jumper.
>
> Zaphod