[Gmecm] Back to square one

[Robin Handley]

> $58 for the 7749 will work in an NA application.  It's going to expect the
2 BAR MAP sensor.  To use the 1 BAR sensor you'll need to re-scale some of
the tables.

Doesn't %KAFOPT3% bit 5 tell the code whether a 1 or 2 bar MAP sensor is
connected? Does this not cause everything to be scaled automatically?

> The turbo Sunbird was the first to use the $58 code.  The Syclone and
Typhoon were second.  It's better to start with a calibration for a 4
cylinder car.

Agreed. So, could I take the AYBN commented hack for a 6cyl 4.3 Turbo Sy/Ty
and overwrite the lookup values with those from a genuine 4cyl Sunbird .BIN?
Are they a direct map?

> The $58 calibration does not have tables which extend to 7000 rpm,
although it does provide a means to adjust fuel and spark after rpm exceeds
the maximum tables entries.  It probably won't be an issue.  At that engine
speed you're not usually looking for high resolution tuning.

Agreed.

> Other people have used the 7749 calibration in a 7727 / 7730.  I believe
there's a page on the thirdgen.org site which details the correct pinout,
but I might be wrong.

This is where I found my pinout conversion info:
http://www.thirdgen.org/techboard/diy-prom/213539-58-frequently-asked-questi
ons.html

Is this the one you meant? I guess it just needs mapping from 730 to 727
pinout for my ECM. I was just looking for confirmation that I hadn't missed
anything subtle, since the above (and other) discussions just talk about $58
code on a 730 (not a 727).

> The turbo Sunbird calibration is 16k large.  It will fit on a 32k eprom
and work.  You will need to move it to the "top" of the chip.  Look for
instructions on "bin stacking" for one method to do this.  The memcal must
match the calibration in the number of cylinders it's designed for or else
there will be a "cylinder select" error set.

No problems there. I've now looked at the AYBN hack and its associated .BIN.
The hack is 16k and the .BIN has the first 16k padded with $FF - so already
in the right format for my 32k EPROM.

> To make the "special secret super duper code modification" you'll probably
need to learn the $58 code.  There may not be an equivalent function in the
$58 as you worked with in the $8D.

The 'not actually a quote from my Email' code modification allows OTF map
changes from a laptop, so I'm pretty keen to be able to reproduce it! :-) I
just wondered if there was a Sunbird specific hack that I've missed - that
might make code changes easier. If not, am I right in thinking that AYBN is
the best/most commented $58 hack to use? The comments with the AYBN code are
a LOT sparser than ANHT :-( although the description of the lookup tables
seems better - and the Sunbird document that I've seen is a massive help.
:-)

BTW: Is the Sunbird code/bin unique? Does it have a 4 letter name, like
ANHT?

Thanks,

Robin

> -----Original Message-----
> From: Robin Handley <Robin at FuryWorld.fsnet.co.uk>
> To: gmecm at diy-efi.org
> Sent: Wed, 10 May 2006 10:04:42 +0100
> Subject: [Gmecm] Back to square one
>
>
> After a couple of years of researching and playing with GMECM, I thought I
> was getting my head around it but, having started thinking about changing
> the code in my 16149396 (1227727 with SRAM) from $8D/ANHT to something
> possibly better hacked and easier for me to understand all the
arrays/tables
> required in applying it to a 2 litre 4 cylinder naturally aspirated engine
> that will rev to 7000+RPM, I am now confused and need help/advice.
>
> I've read quite a lot recently about Turbo Sunbird code and it being
> identical to Sy/Ty code. What I've read tells me that both originally ran
on
> 1227749 hardware, that they are part of the $58 family, and that the EPROM
> size fitted to this hardware was 16k, whereas 1227727 & 1227730 hardware
> came with 32k EPROMs fitted (what I have). Also, that it is possible to
run
> $58 code on a 1227730/1227727 if a few ECM pins are wired differently. I
> don't have or want IAC or EGR or any transmission connections, so I think
> the only one that might matter here is the wire to connect to my
injectors.
> Have I got the above correct? :-)
>
> So, if I am to do the switch from $8D/ANHT to $58/Sunbird code, and get
back
> up to where I am now, I need a .BIN (I have something called Sunbird.bin,
> but no idea what 4 letter designation this relates to) and I need a
> commented hack - for ALDL monitoring, reference, and code modification
(I've
> done a nifty change to ANHT that I really need to recreate with any new
> code). A .ECU would be nice, but I am capable and happy to generate one
from
> the hack.
>
> I've looked at the .BINs and hacks on www.moates.net (which seems to be a
> copy of the www.diy-efi.org equivalent, but with hacks) and found 4
1227749
> $58 4.3 Turbo .BINs (1576BBZA58, 1618BBZB58, 4175AYBN58, BBZB1580 - all
16k)
> and one $58 hack (AYBN - which is configured for 6cyl but mentions Turbo
> Sunbird in the header, and the accompanying .BIN is 32k !!! - This
confused
> me, can anyone explain?)
>
> Could somebody with a good overview of GMECM put me straight, please. :-)
Is
> the Turbo Sunbird code the best start point for a 2.0 4cyl NA engine? Is
it
> the exact same code as the 6cyl 4.3 Turbos, but with different lookup
> values? Will Sunbird code run on 16149396/1227727 hardware (I'm in the UK,
> so getting new ECM hardware is not trivial) with a dizzy reluctor trigger
> feeding an 8 pin GM HEI? (I don't have/want EGR, IAC, or any transmission
> related stuff - just something that will run my NA engine's ignition and
> injection - after tuning (obviously) - but with clear visibility about
what
> needs to be set, and what it actually does.) BTW: I have a WBO2 for
tuning,
> and a MAP sensor with the following ID: 460 7236 (which I believe to be a
1
> bar sensor, but this number does not match that on a web site of GM
> sensors!)
>
> If so, please advise which .BIN should I start with, and which hack? And
can
> I reuse my MAP sensor (I believe the $58 code has an option for a 1 bar
> sensor)?
>
> Help! (Sorry for all the questions.)
>
> Robin