Tuning in Open Loop for Newby

[Dennis Zacek]

Thanks I have been programming the 7730 for a few months now( i converted
from the 870 slow ecm)  Car runs great in open loop and WOT is right on as
well( running high 11's) but drivablity needs work.  I have just learned as
well to set the blm's to 128 and tune from the int.  actually still in the
process but should be a mjor tuning aid.  just for info I kept on having a
proble that when at idle I was at 120blm then accellerate . the int would go
way lean like 150 the the blm would catch up to 128 and the int would steady
out in the 120's ...The setting of the blm's at 128 should help me dial the
ve maps in.
On another note . most ofthe time one should not have to adj the rpm vs
coolant or any of the open loop parameters.... Right???
- ---- Original Message -----
From: "rr" <RRauscher at nni.com>
To: <gmecm at diy-efi.org>
Sent: Wednesday, August 23, 2000 5:08 PM
Subject: Re: Tuning in Open Loop for Newby


>
> The open loop AFR correction vs. MAP and AFR correction vs. coolant temp
> tables are only used in open-loop (no O2 sensor feedback). These
'corrections'
> are used until the engine and O2 warm up enough to go closed loop.
>
> Once in closed-loop, the desired afr is set to 14.7 (this is used in the
bpw
> calc).
>
> If starting to tune in open-loop (no O2), then set the afr vs. map table
to the
> 14.7 value. You can then look at the O2 sensor and make the gross
adjustments
> required. Once close, go to closed-loop (O2 feedback), set the blm min/max
> to 128, and use the int to tune.
>
> Open-loop tuning is only needed when you are starting with an engine that
> is radically different from anything gm has produced. I've used it on
> occasion in a couple of areas of the ve table.
>
> BobR.
>
> WEG1192 at aol.com wrote:
>
> > After reviewing a bunch of EPROM bins, I have a question about tuning.
My
> > understanding is that the tuning is for closed loop operation. But to
tune,
> > you set the closed loop enable temp way high to keep the ECM from
entering
> > closed loop. So now, are you tuning in open loop or closed loop? If open
loop
> > is nothing more than the closed loop tables without O2 feedback, what
are all
> > the open loop AFR correction vs. MAP and AFR correction vs. coolant temp
> > tables for? Seems to me that these tables would interfere with proper
tuning
> > for closed loop operation. If you tune with those corrections applied,
and
> > then you drive in closed loop, seems that your tuning would be
inaccurate?
> >
> > Also, it was mentioned a while back that setting ignition timing advance
to
> > just before knock occurs at all RPMs is not always the best setting. If
> > that's the case, what criteria is used as your tuning goal? Best
acceleration
> > under WOT? Best mileage? Etc.
> >
> > Thanks
>
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