DIY-WB Output Voltage Scaling

[Richard Wakeling]

daklein at netzero.net wrote:

> Here's an Idea!!  hook it up to an extra PCM input, and have the pcm
> table lookup the AFR(like it does volts to whatever for MAP, temps, etc),
> put it in the aldl datastream and have your palm
> pilot display it for ya.
>
> Doa!! if only I could get successfully started on the serial communication part
> of a palm program.

Hi All,
    Some of you will know that we are already logging and displaying the WB output
on our soon to be available for the American market DST (diagnostic scan tool).
    Led displays are useful but you have to face the facts that the NTK WB is
probably the most important sensor that we are all going to use for tuning and it
is for this reason that it must be hooked into an unused A/D input on our ECM/PCM's

    We are doing this at present with the 749 code (Sunbird, Typhoon, Cyclone) and
plan to include other codes as the need arises. We have successively removed the
heartbeat from the ALDL and are no longer requesting data to be transmitted like
all other scan tools. Now a continuous stream of data which the OPERATOR can now
decide, is transmitted in the ALDL. An example would be RPM, MAP, WB. and if only
these three items are continuously output we can achieve very reasonable rates of
better than 100 frames per second. Unheard of before but now possible with Delco.

Rates (frames per second) are dependant upon the amount of data requested.

Baud Rate = 8192
Number of Bits per Byte = 10 (don't forget the stop and start bits)

Aprox 819.2 bytes per second. Theoretically, if you were ONLY sending out 1 byte,
you would get 819.2 Hz... however we cannot forget the formatting of the Delco ALDL
stream which includes 4 other bytes, (Message ID, Message Length, Message Mode, and
KSUM). So, the formula goes like this:
Since we are now not even requesting information, and the format has been decided
before we start to log

rate = (8192 / 10) / (number of bytes requested + 4)

e.g. Say we want to look at RPM, MAP and WB. Given that all are 1 byte in length,
RPM *25 format, and MAP is 5V range, and WB s 5V range as well.

rate = (8192 / 10) / (3 + 4)
rate = 819.2 / 7
rate = 117  Hz (117 frames per second)     Compared to the standard GM which is
approx 11-12 fps.

The beauty of data logging is you have recorded data to COMPARE, thus you know the
exact RPM and MAP readings, so you're not blindly approximating where you are
making important A/F changes.
    Our DST will also have a built in Editor so ALDL fields can be changed as well
as all known fuel and spark maps. It also caters for different map sensors. keying
in '1' for a 1 BAR, 2 for a 2 BAR and 3 for a 3 BAR. Making it very easy to
accurately make changes on a 2 BAR program using a 3 BAR map sensor. We know the
SYTY group are using 3 BAR sensors.

Cheers Richard and Andrew.
http://dickselectronics.cjb.net
Sorry we have not had time to update this page.

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