Re: Tuning in Open Loop for Newby

[rr <RRauscher@nni.com>]

Dennis Zacek wrote:

> 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.

I have seen the same thing in a pfi '730 v6. Moderate accel puts the int right
at max,
quickly, for only a short period of time. Needs more fuel, maybe to add some
accel enrichment.

BobR.

>
> 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@nni.com>
> To: <gmecm@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@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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