Re: Engine swap computer & wiring question

["K.E. Towle" <karljiml@compuserve.com>]

Been read'n the mail on this project, and I can shed some light on Cimarron
Dashes
>>> >
>> > I know that the Cadillac Cimarron's digital dash does talk to the ECM,
>> > because I was going to put the Cimarron digital dash into my
Sunbird...
>> > until I found that most of the info. for the gauges goes through the
ECM
>> > before it gets to the dash.  This probably would mean that the
Cimarron
>> > wiring idea is out of consideration, right?  The only reason I thought
of it
>> > was because the dash is physically the same in it, and it has a 2.8
mpfi v6
>> > engine.

There are two different flavors of Cimarron digital dashes: 
  p/n 25081527 (white case) fits 85/86 Cimarron w/1226870 ECM  
  p/n 25083444 (blue case) fits 87/88 Cimarron w/1227730 ECM w/ARDC4468
mem-cal
One of the biggest differences between the two dashes, is the data rate
(baud) with which the ECM and dash communicate. I may get called on this,
but I believe the baud rate is determined by the ECM, so if you use a 730
ECM, you need a blue cluster.

That said, this cluster ONLY receives values for Temp, RPM, and Volts as
data from the ECM. All other displays use separate sensors, and the
Cimarron service manual states that the digital dash needs a different fuel
sender than the mechanical dash (I didn't confirm this though). I also am
reasonably sure that there is only one place you can have that dash
repaired, and that is Yazaki them self. Seems nobody else will touch it (if
anyone knows different, please tell me) and the cumulative odometer usually
reads 'error' when the dash has been out of service for a time, or 'full'
when it reaches around 250K miles. I own two myself, and one is in for
overhaul; you'll probably hear sobs from this address when I see the bill.
The remaining piece of the puzzle is the mem-cal module installed in the
730 ECM. The code for talking to the dash has to be included in the mem-cal
EPROM, and trust me, it won't talk unless you have the correct code. Then
there is the speed density variable.....
 
>> Cimarron dash would require a Cimarron ECM for the gauges to work.
>> Cimarron ECM is 2.8L only?  Getting a Cimarron dash, ECM, wiring etc.
>> would swap in nicely (assuming you can make the dash stuff fit), but now
>> you've got some calibration work probably to make it work right.  Your
>> displacement is 20% more now.
>
>Yep, I would get the whole works.  The Sunbird and Cimarron dashes have
the
>same openings, mount the same way... everything.  The '87-'88 Cimarron
>dashes are 2.8 only.  They stopped the Cimarron in '88 (thank God).
>
As a "novice veteran" of several engine swaps (two ECM/EFI engines), I can
advise that you are FAR BETTER off starting with a working combination
where you can lift (engine/trans/wires/ECM/dash) intact out of a single
car. That way you know where you are starting. Even then, a friendship with
a GM parts person who will let you spend hours pouring through factory
service manuals (and hopefully copy some), will be your second most
valuable asset. (The first is the expertise I found on this list; thanks
all!) Don't even start without exact factory schematics of the engine/ecm
combination you are installing AS WELL AS the car you are installing it
into. Hacking a mem-cal on a car that is already running is relatively low
risk, since you can always pop the stock module back in. But, creating a
hybrid project that can't work unless you are able to successfully program
a custom EPROM could be a recipe for months of frustration (unless you're
an old hand at it, in which case, disregard most of this last paragraph).
Proceed with caution, and please share what you learn.

Karl

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