Some general questions about injection

Rich M rsrich at cwcom.net
Thu Sep 28 14:14:18 GMT 2000



> -----Original Message-----
> From: owner-diy_efi at diy-efi.org [mailto:owner-diy_efi at diy-efi.org]On
> Behalf Of Nicholas Parker
> Sent: 28 September 2000 06:25
> To: diy_efi at diy-efi.org
> Subject: Some general questions about injection
>
>
> Hi List,
>                 If a 4 cylinder vehicle has 4 injectors (one per cylinder)
> wired in pairs, can I correctly assume that each pair pulse once
> per engine
> revolution ?

not neccessarily, it may be once per rev (360 degr.) or once per 2 revs (720
degr.)

>Does it matter at all that fuel will be squirted onto a closed valve?

This is intentional, the idea is that the fuel is injected onto the (hot)
inlet valve which aids evaporation before the valve opens and inlet cycle
begins.

> Is there any benefit in having a control over a single injector per
cylinder (power wise)?

Idle quality is generally better and emmissions are potentially better, but
otherwise no great benefit, power is no better.

>In  single injector control per cylinder applications, does
> each injector fire once,  per cycle?  In this case, are high flow
> injectors
> needed to put all the fuel into the cylinder through an open valve?

Generally (my experience is with Bosch and Marelli-Cosworth) the injector
will fire once per inlet cycle (720 degr.) but not into an open inlet. They
will start injecting early onto the closed inlet valve (see above) and
continue to inject into the flowing inlet, finishing before the valve shuts.
The start point will vary depending on load, the finish point remains the
same, so a longer pulse will start earlier.
There is actually a full 720 degrees of time for injection period on an
individual cylinder, so in fact larger injectors aren't neccessary.

> I have a 4 cyl  (supercharged) with 4 x 365cc injectors, and am wondering
> how to best taylor a fuel injection system for my car.  I want to
> decide the
> pulse control architecture for my FI system ie 2x2inj or 4x1inj.
>
> Thank you,  Nick Parker.
>

Hope this helps.

Rich

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