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Discussion Starter · #1 ·
I have an 89 5.0 LX I bought in 1989. Over the years I have done many bolt on mods. Everything from light weight drive shaft and fly wheel, to larger throttle body and MAF sensor, 3:73 gears etc... I have the original "Superchips" ECM I bought in 1989 still in the car, however, I am running out of fuel at high RPM's and could probably use more fuel all along the RPM range as of course this motor is getting much more air, but no more fuel. The ECM doesn't know I have opened things up over stock values. What I'm looking for is a setup to either replace or re-program my ECM to increase the fuel. A custom map being the epitome of what I want. Any Ideas? Thx.
 

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What other air items have you added besides a MAF and TB? Stock cylinder heads? The stock computer is able to compensate for larger TB’s as well as MAF’s as long as the ECU “gets a long” with the aftermarket MAF. Is the Superchip ECM an actual ECM or is it a chip? Either way, I’d be willing to bet that the stock tune would run better than a chip/ECM from that era.
SCT used to, maybe still does, sell chips that dyno tuners can load a tune onto. But I think that is starting to be phased out. Holley makes an ecu that allows you to tune it yourself. It’s a little expensive though. If you just have bolt-on mods I’d take the superchip out and run it stock.
How high rpm are you saying it’s running out of fuel and how do you know that it is? If it has the stock heads it won’t make all that much power above 5,500 anyway.
This is a good read. As you can see not much more air is coming in or out with bolt-ons when using stock cylinder heads.
 

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Discussion Starter · #3 ·
Yes I have the stock heads. Are you sure the stock computer can compensate for more Air? I was under the impression it's fuel table values, etc... were carved in stone. That would mean it can read the difference in air flow and add more fuel on the fly. I'm pretty sure they couldn't do that with this car back then. I don't have a really good reason why I think it's running out of fuel it just feels like it. This car revs easily past 6000 still pulling.

The Superchips computer is the entire ECM
 

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Yes I have the stock heads. Are you sure the stock computer can compensate for more Air? I was under the impression it's fuel table values, etc... were carved in stone. That would mean it can read the difference in air flow and add more fuel on the fly. I'm pretty sure they couldn't do that with this car back then. I don't have a really good reason why I think it's running out of fuel it just feels like it. This car revs easily past 6000 still pulling.

The Superchips computer is the entire ECM
Yes it can compensate on its own. That is what MAF’s do. They measure the air and add the appropriate amount of fuel. There reaches a point when more fuel is required than the stock computer can compensate for, it that case a “tune” is required. But you’re no where near that point. I’m not trying to rain on your parade, but with the mods you’ve done, (TB MAF) pretty much the same amount of air is going in as a stock one. It might rev to 6k (stock rev limit is 6,250) but the power has fallen off long before then.
Here’s a stock one that made peak power at 4,800 rpm. Here's How Much Horsepower a Fox Mustang Makes After 30 Years and 173,000 Miles
Here’s a bunch of graphs, but look at post #58. This one has a bunch of bolt-ons and it takes a nose dive not long after 4K rpm as well.
Guess My H P !!! - The Dyno & 1/4 Mile Time Thread
It’s the cylinder heads holding you back.
Here’s some info on MAF’s
This is a good read in the ecu and tuning Ford EFI System Tuning - Inside The Black Box Part 1 - Muscle Mustangs & Fast Fords
 

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Not much to add to 90lxwhite here.
I just wanted to say that as far as modern multi port fuel injection goes 1989 was the first year for 50 state MAF fuel injection. CA had MAF in 1988 but otherwise before that it was the SD(speed density) fuel injection. SD was much less flexible to any changes or mods than the MAF system that came to exist after the SD's short life(2 years? 1987/88).
The OP was probably thinking of the SD but his car is to the core very much the same as a modern fuel injection system with the exception of the huge increase in computing power, processing, and sensors that abound.
 
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