Re: Mods to '85 GM TPI ECM

[Shannen Durphey <shannen@grolen.com>]

Hello, Jim Brady.

If you can get the Broadcast code from the Eprom, I can confirm the
year/make/model your computer is from.  The BCC is a combination of
letters and numbers usually on a sticker on the chip or it's holder
inside of the ecm, and will look something like HLM 3800 or HLK 2315,
or even ARAP 4194.  Some of the recommendations will depend on what
year ecm you actually have.

If you don't have a good scantool, it's a good idea to get one.  I've
seen them for sale at Sears for cheap $$.  The scantool will allow you
to read diagnostic information from the ecm.  To read the eprom you'll
need an eprom burner, several are available from web sources.  To burn
new chips, you'll also need an eprom eraser.

Manipulating data, the heart of the issue.  To determine what can be
changed, you'll need to know what year ecm you have.  There's bunches
of info about the 86-89 TPI ecm, and also about the 90-91 MAP based
ECM.  I've seen little on the web about the 85 model. : (  You might
consider changing ecm's if it turns out that you do have an 85 model. 
The easiest way to make changes is with specially written software,
which can interpret the data from the chip and present it in more
human numbers.  There is some free stuff for 86-91 tpi's which isn't
too bad.  You can also purchase software, but you'll need to know what
year/bcc you have.  Again, lots of people are working with the 86-89
and 90-91 tpi ecm's, so using one of those computers will allow the
"been there done that" guys to help you in a jam.

Generally, the error codes can be turned on/off, fuel parameters can
be changed, and timing tables can be manipulated.  There's more, but
for "get your feet wet" tuning, it's easy to change too many things
too fast, and end up with big problems.  Some required reading:
ftp://diy-efi.org/incoming/TuneTip1.txt
ftp://diy-efi.org/incoming/GM_ECMArchives.zip
ftp://diy-efi.org/incoming/DIY_EFIArchives.zip

The DIY... archives are loaded with info, waaay too much to absorb on
the first two or three readings.  Look for programming 101 for a
heading, for a start.  TuneTip1 is a good guideline for chip tuning,
and the ECM archives will have some info in various places.  

Didja get enough to start with? : )
Shannen


Jim and Sharon Brady wrote:
> 
> Hi, my name is Jim Brady and I just joined the list a few moments ago.  My
> current project is my '87 Monte SS.  My Monte is equipped with the GM
> TPI(Tuned Port Injection) system consists of an '85 computer(I assume I have
> an '85 computer because it had a Bosch MAF burn-off box attached to it) with
> '87 hardware.  My original motor was a 305 and the system worked perfect.
> My new setup is a 383(stroked 350) with a T56 manual trans.  The only
> changes I have made to the system since I upgraded from the 305 to the 383
> is 24lb/hr injectors and a fuel pressure regulator.  Everything works great
> except full throttle.  I understand full throttle switches the ECM to open
> loop mode leaving the EPROM to feed the system pre-determined values.  Aside
> from improving my full throttle condition I would like to monitor the
> parameters of the running motor.  What do I need to approach this project?
> I assume an EPROM burner, cable for the aldl connector and software.  What
> can I manipulate with the software?  How about the EPROM.  I am new to this
> and would appreciate any help you can give on this matter.  Thanks.
> 
> Jim Brady
> '87 Monte SS 383 TPI 6 speed
> 
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