The two different firing orders questions

[eschaider]

The picture is nice but it doesn't say anything about the EPEC system, other than it is for a '88-'93 Mustang.

I did look through some old Ford strategy file documentation that I have and the generation of ECU you have there still has a number of tuning metrics with hard stops that will force scaling if you attempt to exceed those hard stops that Ford built in.

For n/a engines of about the same or similar displacement to the engine this was originally designed for, you would likely be OK for small improvements in torque and power. For significant power increases the scaling required for mass air flow calculations, injector sizing and a number of other metrics can distort the engine load metric which the ECU uses for pulse width calculations. The distortion becomes progressively more problematic the higher you go in the displacement or power domains.

Perhaps the most significant challenges with this generation of ECU are the lack of documentation from Ford, the absence of engine failure protections, traction control, launch control metrics etc. Very significantly the silicon that was used to power the ECU back then was typically 16 bit technology that ran at clock speeds around 10 Mhz. These ECU's were a significant step up from carbs but fall way short of what is commercially available today as a proletariat over the counter sale.

If you compare that generation of ECU to personal computers it is the equivalent of an old 4Mhz 8 bit CPM based PC compared to a modern symmetric multi-processor 3 GHz 64 bit Windows or Mac OSX based PC.

p.s. My words sound a bit harsh and they are not intended to be. The A9 ECU (A9L & A9P) were the highest performing mass air based ECU's Ford manufactured for the 88-93 5.0 Fox bodied Mustangs. In their day they were quite impressive systems. As time and technology marched on several things happened. Ford quit manufacturing new units and began selling refurb units taken in warranty exchanges. The aftermarket began to offer progressively more sophisticated and faster design ECU's based on modern silicon that ran at higher clock speeds, and used more sophisticated performance oriented tuning software and user interfaces. Eventually even A9x refurb units became scarce and the supply / demand dynamic caused any existing units to rapidly rise in price.

More significantly the commercially available over the counter aftermarket alternatives began to proliferate with more features, capabilities, performance and importantly documentation to adapt them to your particular ride. The A9x series of ECU's slowly began the fading into history process, partly because of availability, performance, adaptability and perhaps the most significant better, lower priced aftermarket alternatives.