rusefi.com

Hi Guys,
to introduce myself first, my name is Toni, I am 35 and come from Germany. As already mentioned in the subject, I own a Chevrolet Corvette C3 built in 1982. My profession is an industrial mechanic from which I trained to become a state-certified technician for mechanical engineering in the field of construction. I trust myself to be able to do almost anything imaginable on my vehicle.

My Corvette C3 is equipped with the Crossfire Injection System. More precisely, it is the L83 5.7L Small Block V8. Starting this year the Corvette was equipped with the Computer Command Control ECM and with the Model 400 Throttle Body Injection System. 1982 was the last year of the C3, followed by 1984 with the C4. 1982 and 1984 were the only years for the Corvette with Crossfire Injection. However, the system was still used in other models of the GM group, each with its own specific ECM, which somewhat restricts their compatibility but does not completely exclude them.

What am I going to do:
I am planning a complete restoration of my car. Complete means really complete in my case. As far as the frame and the chassis are concerned, it remains to be seen what their respective states are once they are separated. However, initial inspections of the substance were quite satisfactory, but the existing wiring is not. Over the years the previous owners (I assume 2-3) made a few modifications and accessories and removed them again, which left clear traces on the cabling. In addition, in my country it is necessary to make various adjustments to the lighting of the vehicle in order to comply with the road traffic regulations.
The spare parts market for my vehicle is still pretty well stocked. Many parts are still or again produced. Unfortunately, the ECM falls under the few exceptions. Here and there a few modules appear again, but there are fewer and fewer, even those that have been repaired are very rare.
It is entirely possible to use an ECM from other CFIs, but these require adjustments to the cable harnesses, connectors or the board and chips with an uncertain outcome.
And these alternative ECMs are not exactly cheap either, for similarly old conductor tracks and chips.
With the restoration, I would ultimately like to have a tailor-made wiring harness for my vehicle and my ideas and, if possible, with a new ECM, preferably from RusEfi.
As I am not too deeply rooted in the electronics segment, I am sure that I will need your support with this plan. I have a detailed circuit diagram for my vehicle, which I am currently emulating with a 2D CAD system in order to integrate my necessary changes. It would make no sense for me to carry out a restoration with new mechanical paint and trimmings and then to reinstall a 40 year old cable harness with a 40 year old "computer".

What kind of support do I need:
- Which RusEfi would be the most suitable for my case?
- What else has to be adjusted for my vehicle with the naked RusEfi?

Here are the I / Os from my ECM:
Connector 1:
- 1 - Crank Discrete
- 2 - Distributor Ref High
- 3 - Distributor Ref Low
- 4 - Coolant Temperature
- 5 - Throttle Position Sensor
- 6 - Third Gear Discrete (no input)
- 7 - Load Temp Function 2
- 8 - O2 sensor high
- 9 - Canister Purge Solenoid
- 10 - HEI bypass
- 11 - + 5V return
- 12 - Stepper Coil B High
- 13 - Stepper Coil B Low
- 14 - Air Switch Solenoid
- 15 - O2 sensor low
- 16 - Air Divert Solenoid
- 17 - Stepper Coil A High
- 18 - Stepper Coil A Low
- 19 - HEI Spark Timing
- 20 - Manifold Absolute Pressure
- 21 - Manifold Temperature (no input)
- 22 - Load Temp Function 1
Connector 2:
- 1 - Scaling Resistor Lead B (no input)
- 2 - speed sensor
- 3 - Assembly Line Diagnostic Link
- 4 - Spark Retard Control
- 5 - Park / Neutral Switch
- 6 - Single / Dual Injector Select
- 7 - Serial Data
- 8 - Injector # 1 Drive
- 9 - Injector # 2 Drive
- 10 - + 12V battery
- 11 - + 5V Sensor Reference
- 12 - System Return
- 13 - System Return
- 14 - Fuel Pump Relay Return
- 15 - 12V battery
- 16 - + 12V Ignition Switched
- 17 - + 12V Relay Switched
- 18 - Fuel Punp Relay Drive
- 19 - Torque Convertor Clutch
- 20 - System Check Lamp
- 21 - Air Conditioner Clutch
- 22 - Fourth Gear Discrete
- 23 - Vehicle Elapsed Time
- 24 - Scaling Resistor Lead A (no input)

I probably don't know what is important and what kind of questions to ask in order to get the right answers.
Surely, with your help, this thread will develop to a satisfactory solution and maybe we can help other C3 CFI owners a little.

I look forward to a lively discussion, try to answer every question for details as best I can and of course I will report on my progress.

Best regards
Toni

PS: I hope the Google translation is easy to understand, probably better than my own.

Being 1982 it probably has a lot of weirdness

Please clarify your goals. Is your goal to keep distributor or are you open to upgrade ignition system? How many injectors are currently on the car? What is the resistance in ohms of that/those injectors?

Being old American iron I bet there is a huge aftermarket support. I simply know nothing about old American iron.

The Corvette got little less iron in her than other cars of her age, because the chassis is made of fiberglass reinforced plastic.
But there's enough of it to rust apart in front of your eyes.

My Goals would be to hold as much original hardware as possible that catch the eye at first sight because of the state as an "historic vehicle" of my car here in Germany.

The Crossfire Injection is an 2 x 1 Throttle Body Injection. It includes a pair, front and rear, each controlled by the ECM.
Here is maybe a good source of information about the CFI:
https://www.restore-an-old-car.com/corvette-crossfire-engine.html
I actually don't know the resistance of the injectors. Nothing found in the net so far.
Have to measure myself when back to the car.

What would be an upgrade to my ignition system?
The ignition system in the original configuration is controlled by the ECM. It got Electronic Spark Timing, a HEI Distributor and an Electronic Spark Control. Could supply a schematic if that helps.

The aftermarket situation is really good until now for nearly everything on my car, except the ECM as mentioned in my first post.

Those could be low-resistance injectors which we do not support. Timing advance could be controlled by funny custom PWM signal. There is a lot of custom weirdness this might have. A lot of drama for a one-time application I would only have limited resources to be involved and you said "As I am not too deeply rooted in the electronics segment, I am sure that I will need your support with this plan." This could be hard

So it would be more possible with higher resistance injectors?
What range would you support?
Would it be possible with the origninal injector with an additional resistor in line?
Even with the ECM I would support you with as much information as I can get about it.
My shop manual is until now the best source of information yet.
There is also a PROM Chip on the ECM that was called the brain of the ECM.
Maybe i can get the data stored on that.

Ok tha Data Sheet of the EPROM Chip isn't easy to obtain.
I found nothing satisfactory yet.
There are aftermarket chips like Hypertech out there with different timing curves.
Without an proper Chip Reading Device I think it is not possible do read the Data.
Maybe through the ALDL(OBD1) Connector?
I wouldn't say it will be a one-time application, because many Corvette 82 C3 (25407 were built with CFI) and 84 C4 (51547 were built with CFI) owners, not to mention the owners of the other CFI equipped models, have the same problem as I with the ECM with no sight for an real alternativ.

my first reaction would be throw the CFI/TBI out and fit a TPI system from a later model. if you use something from the late 80s or early 90s even the TÜV may accept that for a historic vehicle. with that you can decide if you what to keep the batch/bank fire injection or to go all in with a fully sequential injection, or everything between. especially with a new wiring loom.

i'm sure you could make it work with the CFI, but if i understand the factory system well enough from my quick google search, you will fight the same devils they fought back than like poor manifold design, two idle controll valves, etc