[Diy_efi] idle control strategy for SD systems w/o bypass air

[Mike R Brown]

Tom,
	That is the only thing they do and it is done in the calibration
portion of the code (maps, tables, and constants).  The basic algorithms
have never changed from Edelbrock (same code as Weber wrote it) and the
richening has had only limited success.  Most installations it doesn't
help that much.  The stability of the control loop still causes 'blower
roll'.

Mike


Tom Sharpe wrote:
> 
> BobD, Edelbrock has a new chip that sets the air temp to 55 at tps < 14
> which stops the blower roll by richening idle a bunch.  Maybe the code
> changed as well.  TomS
> On Tue, 27 Aug 2002 11:28:13 -0500, pjr at teknology.net wrote :
> 
> > I had the same difficulty controlling a random, 100 RPM idle roll with a
> > BDS blown, 355 SBC equipped w/ Accel DFI and 16, 25lb. injectors in the
> hat
> > at 40 PSI F/P. I found that giving the engine as much idle spark as it
> > would tolerate and then dialing back the fuel and spark alternately, gave
> > me a pretty stable idle w/ only a random 25 RPM roll now. Kinda tuff
> > controlling fuel on one of those monkeys.......long distance from injector
> > tip to intake valve, large plenum volume, huge valve overlap and spinning
> > rotors in the way....etc!   ;-)
> >
> >
> > Cheers!
> > PJR
> > ----------------------------------------
> > ----- Original Message -----
> > From: <socrace at ameritech.net>
> > To: <diy_efi at diy-efi.org>
> > Sent: Tuesday, August 27, 2002 12:02 AM
> > Subject: Re: [Diy_efi] idle control strategy for SD systems w/o bypass air
> > control?
> >
> >
> > >     There's another method that I've been using for awhile that
> > stabilizes
> > > idle rpm pretty well with or without an air motor.
> > >     The method can be simply stated as follows: as idle rpm drops,
> richen
> > > the mixture in direct proportion to the rpm drop. As rpm rises, lean the
> > > mixture by the same rule.
> > >     This works because an idling motor is (usually) pulling air at Mach
> 1
> > > through the throttle system. This means that air mass entering the
> > manifold
> > > per unit of time cannot change, so the mixture changes with rpm.
> > >     I believe this is the main reason that an idling engine will stall
> so
> > > easily with a sudden load change, as the rpm drops it just runs leaner
> > and
> > > leaner.
> > >     I used this method to stabilize the idle on my Edelbrock Pro-Flo, a
> > > typical heat soak "blower roll" idler.
> > > Bob D
> > >
> > > On Mon, 26 Aug 2002 07:45:41, you wrote:
> > >  >Vary the ignition timing.
> > >  >If man built it, man can crack it.
> > >  >BobR.
> > >
> > >
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> > >
> >
> >
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> 
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