injection timing

[Robert Harris]

Gasoline is an excellent solvent.  Dissolves oil and grease
from everything - including valves, rings, cylinder walls and
nicely dilutes the oil - especially when the metal is cold. All
that nasty oil coated metal is stripped clean and shiny - a 
good recommendation for running extra rich at cold idle.:)

"When some one gets something for nothing -
             some one else gets nothing for something "

If the first ingredient ain't Habanero, then the rest don't matter.
Robert Harris <bob at bobthecomputerguy.com>


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> From: Stephen Dubovsky <dubovsky at vt.edu>
> To: diy_efi at coulomb.eng.ohio-state.edu
> Subject: Re: injection timing
> Date: Tuesday, August 26, 1997 4:11 PM
> 
> At 04:57 PM 8/26/97 -0400, you wrote:
> >
> >How come a Bosch CIS ( continuous injection ( mechanical)) on a Porsche
> >924 ( or any audi /VW for  that matter of the late 70's ) tends to have a
> >MUCH smoother idle than many newer sequential efi systems. ??  The spray
> >is always sprayed constantly, at the intake valve, and to mee that would
> >cause puddling, and rough idle, but ironically runs smoother and better
> >than most efi systems.  My car with a stock ( but soon to be modified CIS
> >(K-Jetronic)) is capable of idling STEADILY at under 300 RPM. A stab at
> >the gas peadle gives immmediate response. ( nearly impossible to stall it
> >even at the low idle when just jabbing at the accelerator.)
> >
> >Anyone ever consider adding a feedback system to CIS other than
> >KE-jetronic's (frequency valve ) ???  (trick is to modulate "control
> >pressure", (formerly from the warm up regulator,  why not put in a
> >variable valve to control pressure in the circuit to give  closed loop
> >fuel delivery ?
> >
> >
> >Just some thoughts for chewing..
> >
> >Dave
> >
> >
> 
> Actually the CIS (K-jetronic) is closed loop.  The system pressure is set
> up to run rich (good for WOT) and leans the system out to stoic by letting
> some air 'leak' around the metering flap (or is this the 'freq valve' you
> refer to in the KE-jetronic?)  Anyway, the only real difference in leaning
> the mixture and lowering the fuel pressure is that you could probably
> reduce the idle speed a little bit more in the fuel-P system.  My 83 3.0L
> 911 (last year w/ CIS) used to idle at 800-1000 rpm, but now w/ a K&N air
> filt idles at 1500.  Something about improved flow;)  BTW, it still idles
> at 800-1000 at startup, but runs rich until the O2 sensor heats and puts
> the system in closed loop;)  I SHOULD go in and set the idle speed better
> by adjusting the flap or throttle body, but what's wrong w/ running a
> little rich at startup;) (BTW, I also have the air-intake pop off valve to
> keep the rare backfire on VERY cold mornings from blowing up my airbox).
> 
> Just a few, but sometimes worthless, thoughts...
> Stephen Dubovsky