[Diy_efi] injector advance

[Gary]

In regards to injector timing, what is the principle of bank to bank,
or batch, as compared to sequential.  At what point, does sequential
become batch?  Owners of performance engines are glad/fortunate
they have 720* to work with.

GAS


-----Original Message-----
From: diy_efi-bounces at diy-efi.org [mailto:diy_efi-bounces at diy-efi.org]On
Behalf Of Bevan Weiss
Sent: Donnerstag, 5. August 2004 14:44
To: 'A list for Do-It-Yourself EFI'
Subject: RE: [Diy_efi] injector advance


> A 4stroke cycle is still only 360degrees of the cam.  If it was 720degrees
> then you'd have the intake valve open on both intake and power... Which
I'd
> say would leave you with too much of the first, and not much of the
second.
>
> I think that you should time everything off the cam.  It makes much more
> sense.  You have a cam sensor I assume...
>
> I'd imagine the Marelli ECU will begin injecting at 300degrees of the cam.
> This allows for 30degrees of injection on a (mostly) closed intake valve
and
> then 90degrees of injection on a (mostly) open intake valve.
>
> It's best to reference everything to just before the intake valve opens.
Ie
> cylinder 1 TDC before intake.
>
> Droplets of fuel are indeed atomized when contacting the hot inlet valve,
> which allows for slightly more fuel mixture to enter the cylinder.  It's
> preferred to inject directly into the cylinder however as that guarantees
> that all you inject will enter the cylinder.  It also makes the
performance
> more proportional to the atomization of the fuel by the injector (and fuel
> pressure) than the speed of the intake charge.
>
> I'm of the opinion that a fixed injection 'advance' isn't appropriate.
> Especially if you're already running a fully sequential injection
strategy.
>
> You should inject fuel for however long is needed stopping just before the
> intake valve closes.  Ie the advance will be highly dependant on both
engine
> load, and the RPM of the engine.
> More RPM generally evolves from higher load, hence you need maximum fuel
> injection in the least time.  In this case your figure of 450degrees
before
> combustion TDC may not be enough.  On the other hand if you're just
idling,
> then your 450degrees may be way to much and you'd be injecting on an
> entirely closed valve with injection stopping before the intake valve is
> even open.
>
> Bevan
>
> >
> > -----Original Message-----
> > From: diy_efi-bounces at diy-efi.org
> > [mailto:diy_efi-bounces at diy-efi.org]On
> > Behalf Of Bevan Weiss
> > Sent: Mittwoch, 4. August 2004 23:53
> > To: 'A list for Do-It-Yourself EFI'
> > Subject: RE: [Diy_efi] injector advance
> >
> > There's only 360degrees in a full revolution.
> > If you're injecting 450degrees advanced, then you're
> > injecting 120degrees before the previous ignition event...
> > Which just doesn't make sense.
> >
> > Injection should really be timed to the closing of the intake
> > valve as opposed to any ignition event.
> > You want injection to be stopped once the valve is closed.
> > So the start time will depend on how much fuel you need
> > injected and how fast the engine is reving.
> >
> > Which injection strategy are you using? Batch or sequential
> >
> > Bevan



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