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 below.

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 later.

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)

EPROM Programmer
(11/12/01 update: XELTEK ROMMASTER/2 @ $179 died! The following is faster
and cheaper anyway...)
Intronics Pocket Programmer $150
UV Eraser 
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
raised windows.
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 glossary.

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 EPROM, 0xfff.

Other References

Anything under Automotive in my bookmarks.
'7783 tidbits
Jason Weir's TBI Installation Page
Delco 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)
E-Mail me.


This information is made available for personal use only and may not be reproduced without written consent of the author(s). Any attempt to sell or use this information for personal gain or business purposes is expressly forbidden.
E-Mail me.