Open/closed loop Jeckyl/Hyde

[Marteney, Steven J.]

>> (And this is the RIGHT way to fix it.)

Don't doubt that, but changing the injector constant has other advantages
for a modified car (which also could be accomplished another way).  Lowering
the injector constant got rid of my off-idle stumble.  At the time, and
maybe even presently, I couldn't find any info on a Pump-Shot table in $6E
code.  (Haven't looked at Dan's latest ecu though.)  The O2 in closed loop
corrects for the injector constant if necessary.  I did it because my BLM's
originally were in the 150 range.  Now they are around 128-132.  Seemed to
be what the engine wanted.  (Disclaimer: I still suspect a failing fuel pump
on my car.)
Steve

-----Original Message-----
From: romans at starstream.net [mailto:romans at starstream.net]
Sent: Friday, March 23, 2001 12:42 PM
To: gmecm at diy-efi.org
Subject: Re: Open/closed loop Jeckyl/Hyde


Don't change the injector constant from what the injectors really are.
Fuel pressure is measured at idle with the vacuum line off. (45-48 psi
usually).
If it is lean in open loop at idle, then richen the open idle afr vs temp.
This should fix the poor idle in open loop.  (And this is the RIGHT way to
fix it.)
If it doesn't then there are other issues with the chip you have done.
Mark
----- Original Message -----
From: "Marteney, Steven J." <smarteney at xlvision.com>
To: <gmecm at diy-efi.org>
Sent: Friday, March 23, 2001 7:16 AM
Subject: RE: Open/closed loop Jeckyl/Hyde


> I'm not smart enough to figure out what your injector size REALLY is (SVO
> rated at different pressure than GM, etc.) but I have two things.
>
> 1) Is the fuel pressure quoted basically as measured at idle with vacuum
> line attached?  If not, if you set it with vacuum line disconnected, then
> pressure at idle is actually high 30's probably.
>
> 2) If it truly is lean at idle in open-loop mode, start setting your
> injector constant to a lower numbers.  This makes the computer think you
> have smaller injectors and when it calculates the fuel mix it will deliver
> more fuel.  When it goes closed loop, the O2 sense is in control and will
> correct if necessary.
>
> Don't know much about IAC stuff, but lowering the constant WILL richen the
> car up at idle.
>
> Steve (89 F-body 350 similar cam)
>
> -----Original Message-----
> From: akallotte at juno.com [mailto:akallotte at juno.com]
> Sent: Thursday, March 22, 2001 6:33 PM
> To: gmecm at diy-efi.org
> Subject: Open/closed loop Jeckyl/Hyde
>
>
> Just started the motor and she's idling lean in open loop. 6E code in an
> 87 Vette, 24# SVOs at low to mid 40s PSI, 218/226 510/510 114 LSA cam,
> idling at 700-800 in Park. The only code I've changed was inj constant
> (25.9#), lower fan on, and higher tc lock.
>
> I went through the service manual idle set procedure today. Got
> everything perfect. Shut it down, restart, idled at 1400, not the idle I
> set.  In open loop, it runs poorly - lean, low vacuum, low idle, IAC wide
> open. Once it hits closed loop, IAC closes completely, vacuum picks up,
> good AFR, good idle.
>
> What is causing this? I don't know if IAC or lean condition is causing
> all the problems, although IAC would seem to cause the lean condition.
> Why is the IAC wide open in open loop and closed in closed loop? I must
> have to change something in my program, but what?  Commanded idle speed,
> maybe?
>
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