Do i need to convert to MAF?
#16
08-05-2013, 07:59 PM
No.. it's not a contradiction you just don't know the whole story. Every single Ford PCM is programmed from the factory for a specific engine displacement, injector size, and MAF meter. With those stock parts attached the computer can adjust to a wide range of engine modificatons and run it very well up to the air and fuel flow limits of those stock parts.
After that you have two choices, calibrated/scaled MAF or a tuner.
Choice 1 works OK for engines that aren't a big step away from stock but gets progressively worse the more radical the engine is, so 24's with a 75mm meter on a 5.0 will run well as long as the cam isn't too radical, but if it's a 357 with a wild cam and big heads that needs 42lb injectors then it'll be ugly to drive on the street. The reason is because the "calibrated" MAF meter thing is a trick that attempts to fool the computer into thinking it's still using 19lb injectors on a stock motor, but a larger motor with a big cam and heads has very different fueling requirements than a stock 5.0 does at all rpms, so simply scaling everything up just doesn't work very well.
With choice 2 the tuner route you will be telling the computer all the important specs about the larger parts it is expected to work with, you tell it what size the injectors are, you input the complete MAF transfer function, and you can tell it what the engine displacement is if that has changed. So now the computer has everything it needs to make accurate calculations the first time around.. it doesn't have to make continuous corrections so overall the motor just runs better.
Both options can work but tuning always works better.
After that you have two choices, calibrated/scaled MAF or a tuner.
Choice 1 works OK for engines that aren't a big step away from stock but gets progressively worse the more radical the engine is, so 24's with a 75mm meter on a 5.0 will run well as long as the cam isn't too radical, but if it's a 357 with a wild cam and big heads that needs 42lb injectors then it'll be ugly to drive on the street. The reason is because the "calibrated" MAF meter thing is a trick that attempts to fool the computer into thinking it's still using 19lb injectors on a stock motor, but a larger motor with a big cam and heads has very different fueling requirements than a stock 5.0 does at all rpms, so simply scaling everything up just doesn't work very well.
With choice 2 the tuner route you will be telling the computer all the important specs about the larger parts it is expected to work with, you tell it what size the injectors are, you input the complete MAF transfer function, and you can tell it what the engine displacement is if that has changed. So now the computer has everything it needs to make accurate calculations the first time around.. it doesn't have to make continuous corrections so overall the motor just runs better.
Both options can work but tuning always works better.
#17
08-06-2013, 02:02 PM
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Okay then my plan is to build my engine 9.0 cr, isky mile a more cam, roller rockers, port and polish the head with oversize valves, although I've heard there's are shrouding issues with the efi head? And stock manifolds with a 2.5" single exhaust. I'll get the maf with the 19lb injectors to trick the computer then buy the tuning software later. One more question: can I use a carb head instead? I've heated the efi ones are more prone to cracking, have valve shrouding issues, and are more likely to cause detonation on cheap gas.
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