I posted this in another thread but felt it should have its own.
There always seems to be a lot of confusion around so called "Calibrated" MAF's. In fact I myself did not understand how it all was working till a short while ago. I still dont understand a whole lot about mustang EFI, but let me explain what little I have learned
Your MAF in your mustang is made to send a signal voltage of between 0-5v. It does not send a signal saying hey I am a 70mm MAF and this is the signal for 19# injectors. All it does is send a voltage! period no if and or buts about it. So when this voltage reaches the computer the computer sends out a pulse width to the injectors to open them for a certain amount of time. All of this is done inside the computer, but in a stock computer it thinks everything is for #19 injectors and stock MAF because that is what it has been told (programmed) to do.
Now how does it make this voltage in the MAF? It is made by a small wire that heats up when air passes over it. The more air, the more heat, the more voltage it sends to the ECU.
Ok now lets look what happens when we upgrade to a 90mm lightning MAF, which some people think is calibrated to 42# injector. ERR wrong remember all the MAF does is send a voltage. The MAF sends a voltage 0-5v and the LIGHTNING ECU is programmed to send a injector signal pulse based 42# injectors and the 90mm maf. OK so now we have the 90mm Lightning MAF in our 5.0 but being it is 90mm rather than say 50mm (i cant remember stock in 5.0) its takes a lot more air to flow through it to make the same voltage. So if all a MAF does is send voltage to the ECU, 3.5v from a 90mm is going to be tremendously more air than a 50mm at 3.5v. Now unless we have told the ecu this, it is going to give the injector the signal for the 50mm unit not the 90mm not giving it enough fuel and making it run lean.
OK now lets look at changing from 19# injectors to 24# injectors. Assume the ecu gets a 3.5v reading from the stock maf. It is then going to send a pulse with to the injectors based on that voltage because 3.5v ='s a certain amount of air to the ecu and hence it needs to give it this much gas. Now if we change the injectors from 19's to 42's and dont tell the ecu, it is going to send the same pulse width to larger 24's then it would for the 19's adding to much fuel and make the car run rich.
Now how do we fix these problems, well one way is that people get "calibrated" maf's. All these calibrated maf's do is modify the maf voltage that they send out to the computer. Lets say for example the stock maf at 3.5v is flowing 700cfm and it would send out 3.5v to a computer programmed for stock 19# injectors. But now we upgrade to 24# injectors and we go buy a 75mm maf calibrated to 24#'s. All that calibrated unit is going to do is at 700 cfm send out a lower voltage to trick the ecu into thinking it is getting less air than it is really getting. Then in turn it will send out a smaller voltage pulse to the 24# injectors to add less fuel equal to if the car had 19# injectors. Starting to ge the idea how these calibrated units work? They just modify the MAF to what will work with the stock tune. While yes they are a quick fix by "fooling" the computer, ultimately there are so many parameters in your computer that it is not the "right" way to run things.
The right way is to figure out how much air your maf flows and what voltage it gives to the computer at certain air flows. Then to tell the computer what injector pulse width it needs to send based on the voltage it receives and the size injectors it has to produce the right air/fuel mixture. This is all accomplished by having your computer reproggramed to your specific needs.
While all that i described is simplified it iss a general explanation and like everything else in cars there are 100's of if's, and's, or but's.
Now how does it make this voltage in the MAF? It is made by a small wire that heats up when air passes over it. The more air, the more heat, the more voltage it sends to the ECU.
good description except for this part is kinda backwards. the hotwire is heated by the pcm by the applied voltage. the incoming air which passes over the hotwire element cools the wire. the maf wire is programmed to stay at a certain temp, i want to say somewhere around 200*. the voltage it takes to keep that wire at 200* is how the volume of incoming air is calculated in the pcm. eg WOT, it takes 5 volts applied to it in order to keep the wire at 200*.
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Great Info Guys. Know That I Understand Maf, What Can I Use To Change The Voltage Signal Of My 73mm C&l Calibrated For 19lb For My New 60lb Siemens Deka Injectors? Will A Simple Resaistor Do The Trick?
Right on... this is exactly how it works, and ultimately its best to let your computer do the calculations for best overall driveability.
I am going to stick this since it seems to be a point of confusion for many.
I would like to add to this Post by showing the Popular 70mm SN95 Swap. The Meter can come from a 94 or 95 Mustang V6 or GT, plus the 92-94 Crown Vic, Grand Marquis, or Towncar 4.6s with the P/N F2VF-12B579-A2A or A1A. Here is a Pic of 2 of them, as you can see I cut the Flange down so that it would work with the Factory Airbox, but you can buy Adapter pieces or use a SN Style CAI Filter.
How does this work for C&L MAFs? C&L MAFs do not come with a recalibrated sensor, just a bigger MAF. Isn't the tube inside of the MAF a different size? Does this let more or less air cool the sensor? Kind of confused about the C&L now. I understand how a recalibrated sensor works now though.
The C&L meters have sample tubes that can be swapped. The different sizes allow more air to pass over the wire, cooling it. The computer compensates and uses that to correspond to the injectors.
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The C&L meters have sample tubes that can be swapped. The different sizes allow more air to pass over the wire, cooling it. The computer compensates and uses that to correspond to the injectors.
C&L has been making MAFs for years and only one series has the changeable sample tubes.
Now to address the original post.
I've never understood the need to upgrade the injectors. Even the 19lb injectors are good for at least 300HP. For that matter the stock cam is good for 350HP or more.
The Ford electronics are one of the very best systems ever devised! It is VERY adaptive and will perform well beyond most street car needs.
There are many things sold that claim all sorts of HP gains but most just try and fool the ECM into modifying the mixture. That leads to all sorts of problems and this is a formula that leads to many never solved problems.
REMEMBER THIS! No matter who or where you read the information you think you need regarding the modifications of your Mustang/Ford or indeed ANY car....THEY are trying to SELL you SOMETHING!
THEY will promise you ANYTHING to make the sale!
There are no shortcuts to a high performance automobile and upgrading your injectors and using a 'calibrated MAF' is a shortcut that will have you pulling your own teeth out trying to solve unsolvable problems!
Great Info Guys. Know That I Understand Maf, What Can I Use To Change The Voltage Signal Of My 73mm C&l Calibrated For 19lb For My New 60lb Siemens Deka Injectors? Will A Simple Resaistor Do The Trick?
Thanks
Mark
you c&l should have a sample tube you can swap out.
Very helpful made me understand whats happening.I got a question?
Got a supercharger setup sn92 paxton,Making 6psi got the anderson power pipe,been told need bigger injecors 36 ans 42lb.I got 24 now because car is a 93 cobra.Can i leave them or do I need to step up and get bigger injectors/MaFs....Honestly the main reason I got the power pipe is my original setup was not working.filter was behind headlight...
confusion around "calibrated" MAF's 
