The factory fuel injected setup with MAF is probably good even past the limits of block strength - which is somewhere north of 500 horsepower, without significant mods, or an aftermarket block. You do need to match your injectors to the expected horsepower level though, and if you're over 400 horses, you'll certainly need something besides just a stock A9L computer to handle it all.
But for a mild build that's not going to be getting over 6k, the mass air unit has some great advantages over MAP sensor setups.
MAF actually measures air flow into the engine. That means that it is better able to compensate for things like altitude changes. If all you do is toot around the block once in a while, who cares - but if you take it on road trips, or live someplace where you get vertical travel, that does matter.
For maximum horsepower, having the MAF sensor in the way just means a restriction. If you're drag racing only, then there are a lot of better setups than the factory unit. But for a daily driver, the MAF sensor means you will get better mileage, probably by 1-3 mpg better. I doubt that you would notice any power difference between MAF and MAP in most real-world driving, but it could prevent a lot of issues over time by giving proper fuel curves under a broader range of conditions.
Engine management handles not just the fuel curve, but spark as well. MAF is another tool that can help you get closer to the proper settings. Spark timing can be run closer to detonation safely without danger. Fuel curves can be set that are closer to where they need to be, without worrying about running too lean. And thanks to the fact that it actually measures the air being used, when the temperature changes dramatically, or you go to a different elevation, you're not going to be pinging or having other complications that can sometimes crop up with MAP.
The factory Ford unit also uses sequential fuel injection, instead of 'batch fire' where it squirts four injectors at a time. One squirt per cylinder. That typically improves idle quality, and very low-RPM driveability. For a throttle-body injection system it makes no difference at all, but for a port injected system, it does. A lot of the aftermarket MAP setups use batch fire.
The long runners of the factory Ford manifolds are great for making a lot of low to midrange torque, which is where our street smallblocks need a shot in the arm.
So basically, for a good-mannered street motor, or highway cruiser, the factory Ford setup is pretty dang good.
For a car that "you wouldn't want to take home to meet your mother", with a big hairy cam and serious mods, intended mostly for strip use, there are better solutions.
MAP setups can be really good. And in some ways, they are simpler to set up. But the fuel mapping is only as good as the guy that sets it up. To get it dead on takes a lot of work, and lots of testing, under lots of conditions. If you later make changes to your engine, all that hard work goes right out the window. If all you care about is WOT (wide open throttle), then you don't have to worry about how it behaves in 'all conditions', and some guys don't care about weird issues with driveability on a weekend warrior. They usually don't bother to put in all the time it takes to mess with getting the fuel and spark mapped perfectly. Few people would. They just get it 'close' and err on the side of caution to ensure that it's not going to run lean, and burn valves or pistons.
So to sum up:
If you don't expect to go over about 400 horsepower, the factory injection setup works great under a lot of conditions, and will probably get good mileage, work without fuss, and offer plenty of 'go' when you mash the skinny pedal.
For full-tilt-race applications, or highly modified combinations (including stroker kits, turbos, blowers, etc.) you might find it a lot easier to go with something like Atomic or MegaSquirt.
By the way, Megasquirt has a mod that allows use of MAF sensors, for what it's worth.
The EEC IV computers are old, yes. But they are also very rugged, very simple, and they do exactly what they were supposed to do, very well. They squirt just the right amount of fuel, and then light it with a spark at just the right time. Maybe not perfectly. But for most 5.0s, it's pretty hard to do better, especially for the money.
Last edited by Technomancer (4/24/2013 4:42 AM)
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Technomancer wrote:
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). Tuned right there's no need. As far as MPG of an aftermarket EFI vs. factory EFI I would wager that depending on the level of modification to the vehicle the aftermarket would win. Once you pass a few mild modifications all that factory work and calibration starts to go out the window and you'll need something to start making changes to the stock computer.