Re: VE stability

["Dave & Irina Eicher" <sailors@mwci.net>]

Hi John,

I'm new to this EFI thing. Do you know where I can find some software that
will allow my laptop (windows) computer to read the data stream from the
ALDL connector?

thanks,

dave

----- Original Message -----
From: John S. Gwynne <jsg@jsgpc.mrcday.com>
To: <gmecm@diy-efi.org>
Sent: Friday, March 10, 2000 12:50 PM
Subject: VE stability


> I've been collecting tuning data through the ALDL now for 3 1/2
> months and correcting my VE table with BLM and O2 data ('730 5L sbc,
> sc, cam, headers, axxc bin).
>
> using data only during close loop mode and testing to ensure a
> more-or-less steady state with rpm and map corresponding to the
> correct blm cell (aldl frame are not a snapshot of a given instant of
> time), I do a long term average (i.e., more than 10-20 hours of engine
> run time) to correct the VE table (letting transient errors average
> out over time). There's a little more in terms of weighting and
> smoothing, but that's the jest of it. As a result, IMHO the car runs
> better (drive-ability) and BLM cell counts are always less then +/-6
overall
> and under +/-3 for some conditions. Now the real question....
>
> I looks to me as if something is varying with operating conditions to
> prevent me from narrowing this last 4% of error (it's not that much,
> but it has my curiosity). The two conditions I see this best are 1-2 hours
of
> around-town driving versus 4 hour of highway mixed with 1-2 hours
> of around-town. It looks to me like something in the system is changing
> characteristics after a couple of hours of drive time.
>
> Has anyone else seen this?
>
> A few of my thought of what may be going on.... appreciate comment and
> suggestions....
>
> -- baro measurement screwed up because of sc
> I'm collecting data on this now. The condition does seem more
> pronounce at partial throttle conditions.
>
> -- EGR
> EGR partial pressure correction needs updated for exhaust system
>
> -- inlet air temperature reading inaccuracy
> MAT sensor may be influenced by block/manifold temp
>
> -- engine/cylinder conditions
> carbon in the cylinders changing the burn after highway driving
>
> -- sensor temperature sensitivity
> MAP sensor may be somewhat temperature sensitive (1-2%)
>
> -- limitation of the tuning procedure
> maybe, but it does look like it in the data.
>
> -- O2 sensor
> temperature/accuracy sensitivity of the O2 sensor.
>
>
>
>
>
>
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