[Diy_efi] Fixed frequency PWM batch mode FI

[Bruce]

Are you going to use 1-2-4 injectors?.
If more then one, where exactly do you want to place them?.
Bruce


----- Original Message ----- 
From: "Les Dittert" <lesd at earthlink.net>
> Mine is also air cooled  Volkswagen, turbocharged.
> My only concern is having a beat frequency between the engine RPM
> and the pulse rate.  In thinking about it more I just need to guarantee
> the pulse rate is higher than the RPM. I want to use a small
> microcontroller
> for this engine.  While it is possible to control the rate of the PWM,
> it would then
> perhaps require a crank sensor which is added complexity.
> I figured since some General Motors engines do batch fire of all
> injectors
> simultaneously, they would run into the same problems of uneven fuel
> distribution
> if I'm not mistaken.  The other limitation might be getting low enough
> fuel rate
> for idle, because of multiple injections happening with very short pulse
> width.
> I want to keep the system very simple, so I am using a mass airflow
> sensor to
> avoid having fancy multidimensional lookups. A couple of lookup tables
> should do it.
> I'm not delegating a mission to this either. I'm using a crane hi 6 with
> boost retard
> and that should work fine for this simple engine. Anything is better
> than the two carburetors that are on there now!
> 
> -Les 
> -----Original Message-----
> From: diy_efi-admin at diy-efi.org [mailto:diy_efi-admin at diy-efi.org] On
> Behalf Of Bruce
> Sent: Sunday, August 20, 1995 5:26 AM
> To: diy_efi at diy-efi.org
> Subject: Re: [Diy_efi] Fixed frequency PWM batch mode FI
> 
> 
> 
> There was a VW guy that did an ecm that way.  I think he was firing them
> every 12.5msec. For racing/off road why not?.
> So long as it's clean enough to idle, who cares?.   I think the other
> guy
> took some heat about it not being able to work, but he said it did. Some
> GMs default to that under some conditions Bruce
> 
> 
> ----- Original Message -----
> From: "Les Dittert" <lesd at earthlink.net>
> To: <diy_efi at diy-efi.org>
> Sent: Monday, August 19, 2002 8:42 PM
> Subject: [Diy_efi] Fixed frequency PWM batch mode FI
> 
> 
> > I have searched high and low and haven't found the answer to this
> > question:
> > are there any disadvantages to running the injectors at a fixed 
> > frequency of injection that isn't related to RPM? I realize that doing
> 
> > this in batch mode will result in some injections hitting a close 
> > valve sometimes and then sometimes hitting an open valve.
> > Since some OEM fuel systems run batch mode where they fire all
> injectors
> > at the same time
> > I figured they have the same situation anyway.
> > Another question:
> > If using a fixed frequency you what should that frequency be?
> > I'm assuming it should be something equivalent to running a sequential
> > injection system at about 4000 RPM.
> >
> > -Les



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