|Older boys just have more expensive toys. I'm currently
working to retrofit a modified GM EFI controller and Crossfire Fuel Injection
manifold to my 1971 Camaro. The installation has begun...
First and foremost, THANKS to the folks on the DIY_EFI
mailing list and Dr Bruce Plecan, who convinced me that my old CFI manifold
may not be ready for scrap just yet. He's running just such a manifold
on his system, which is described in the general background information
I picked up the Crossfire Injection manifold several years ago from
an individual who had replaced it with a regular intake and carb. The 1227747
ECM and matching distributor (from a Chevy P/U -- 1991 TGMC 1500 8-350
2500 series) were mail-ordered from Peer's Used Auto Parts in WV (some
more fine folks I found on the Internet). I'm sure it voids the warranty,
but the first thing any engineer does is look
inside to see what you've got to work with.
Next I visited a local junkyard to get a wiring harness. Unable to locate
a suitable harness from a truck, I settled for one from a 1988 Oldsmobile.
The Olds was a Sequential Port Injection system with MAF and DIS but the
harness turned out to be remarkably similar. Practically all of the EFI
portion of the harness was separated from other wires in the car. Several
did return to the dash area, which I didn't care to disassemble. In retrospect,
maybe I should have. You'll at least need the ALDL connector and the VSS
unit from under the driver's side of the dash. Rotsa ruck, Raggy. I snipped
the ALDL wires and got only the connector. If you skip getting the VSS here, you'll pay
With the harness back at home and a GM EFI manual in hand I traced the
wires and wired the system back
together. With a bit
of work I managed to spin the distributor with a drill and get comfortable
with the system. I had just about figured out how to
simulate a "run" on the bench when I decided it was time to go live.
Installing the Crossfire Manifold
The original CFI system was available on 1982-83
Chevy Corvettes and Z28s. It used twin throttle bodies on a manifold that
*looked* much like the old 2x4 crossram intakes from 1969. It does NOT
share the limelight as being a desirable item. I've made a few
minor modifications to help bring back that performance heritage. The
actual installation went fairly smoothly,
with the bulk of the
work being the plumbing of fuel lines. The return line to the tank
had been removed long ago, so I bought a new fuel line
and used one for the pressure side and one for the return. I
used an external pump from a Ford pickup (Airtex part # E2000
from Autozone). It maxes at ~50psi but you only need 11psi for a TBI
installation. It is mounted directly to the frame
with 2 large hose clamps and a rubber cushion. A protective plate will
cover the pump for safety's sake and noise reduction.
See the installation page for more about the other parts required.
Several special tools were needed. I doubt I got any special treatment,
so I'll include my costs for reference.
MSPI Pro-Link $150
Linder Technical Services (317-487-1868 or http://www.lindertech.com)
(11/12/01 update: XELTEK ROMMASTER/2 @ $179 died! The following is faster
and cheaper anyway...)
Intronics Pocket Programmer $150
Datarase II $39
General Device Instruments (916-393-1655 or http://www.generaldevice.com)
bulk used EPROMS $50 (50 @ $1ea)
EPROMS for the '7747 are 2732A. No AMD (too wide) and no
Astro Marketing (407-727-8817)
(don't forget the age of these things...everything's got to die sometime)
There's a special plastic carrier for the EPROMs:
Robinson-Nugent PROM carriers part # PRC-246-E3
Used to hold the 24 pin PROMS. Min order need is 250.
About 25 cents/part. A gracious list member (Thanks Mike!)
organized a group buy.
The "delco_edit" software aka "promedit" (by Wayne Blair) is a dandy piece of
software for editing tables in a binary file. Editing the tables is much easier
when you've got an appropriate configuration file (.ecu) for promedit. Here's
how to use promedit and here's our work-in-progress .ecu file.
NOTICE: There have been some incompatibility problems between the .ecu
files and promedit. Until we can get that worked out, here's a zip
file with promedit and the .ecu file I'm currently using.
If you've got one of the older versions of promedit, here's an older version of the ecu file. There's also a more
extensive one at the DIY_EFI website under GM systems but I make
no guarantee about the compatibility thing again.
General Background Info
I started with Bruce's
setup and tips he has for tuning, since he has already done this. Other
info on the controller is there
too. Then I ran across this gem,
which describes the operation of the GM ECM in terms that I could understand.
With that knowledge and the Chilton's manual for EFI I followed the DIY_EFI
mailing list and noted a few things that
should be in a FAQ (which the DIY_EFI list is sorely lacking) or a
Tuning My Setup
If you didn't read it already, scan Bruce's tuning tips.
I disconnected the "Set Timing" wire on the distributor and set the timing
to 6 degrees BTDC.
I adjusted the fuel pressure to achieve an idle.
Connect the MPSI scanner and made a road trip.
With the "proof-of-concept" out of the way, I'm going to try this by the
book. First, one needs to set the fuel pressure to @14psi. Since there's
not a straightforward method for hooking up a gauge to the TBI system, I've
added one. I set the fuel constant in the EPROM and
we're ready to start tuning all over again.
'7747 CPU Details
The family of ECMs manufactured by GM in the late '80s is known as "C3".
They have a special Motorola CPU which bears close functional resemblance
to the MC6801 with a pinout similar to that of a 6800. As used in this
application, the CPU is set for mode 5, a mode with both internal and external
RAM and ROM (with a socketed/removable 2732 EPROM). Basic fuel and timing
parameters are stored in the EPROM. The EPROM has tables and some program
code. It maps into processor space from 0xd000 to 0xdfff. The ROM appears
in the processor space from 0xe000 to 0xffff. Data space in the EPROM is
from 0x000 to 0x616. Code starts at 0x617 and continues to the end of the
Anything under Automotive in my bookmarks.
Weir's TBI Installation Page
Info from DIY_EFI folks
A collection of mostly
Ford EEC-IV related info.
Converting a carbed Ford to EFI
- another work in progress
Reference document for a 1988 GM 2.0 Turbo PFI System. (in PDF format--ie, you'll need the Adobe Acrobat Reader)
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