Hey guys,

I'm confused as to what the difference between SD and MAF are. I have gathered that SD is either older or inferior technology, but it's hard when I'm just getting bits and pieces from a bunch of seasoned engineers like you all
Could someone break down SD and MAF for me? Also, I was wondering which type my engine is. It's a 351W from a '93 F-150. Thanks

 

You probably have a speed density, mass air cam out in all trucks in 96 unless you have a california truck. You can mod the crap outta your motor but if you want it to run right you will need a 112 or 114 lobe seperation cam. to put it in simple terms the speed denstiy is a closed minded system that only sees what it is told. The chip in the computer has certain boundaries and should your motor take the air fuel mixture requirements out of those boundaries or should I say ask for more of a certain mixture the computer gets confused and doesn't know how to adjust the fuel to the air coming in so your engine in turn runs like crap. Mass air monitors things as they go so you can do a lot of modifications and throw in a cam and it can compensate for the increase in air flow by adding more fuel. If you get to a certain point you still have to program it but that is usually if your trying to add forced induction and wanting to tune it to perfection. Keep in mind should you want to go with a radical lobe seperation cam 112 and down then you can call a chip manufactuer and tell them all your specs down to the cam and anything else you have done (you have to get specific or at least tell them everything) and they can provide you a chip that will provide the speed density with the ability to operate where you want it to in relation to your modifications. They figure up a certain boundary that your motor should work in as far as air fuel requirments and put the appropriate info into the chip.
depending on how far your taking it you will also have to use larger injectors and you will have to adjust the fuel psi accordingly. this is my take on it, so it is probably still clear as mud huh? Later

speed density===dumb not flexible but works if you tell it what to do and how
mass air=======smart flexible and takes what you throw at it

 

oh okay, i think i get it now. So it's just the computer technology?

 

Yes. It is just different ways that the computer measures the airflow into the engine.

 

I found this it makes more sense than I did however it is what I said just worded better, check it out



http://www.fordsunlimited.com/tech/maf.htm

 

SD uses a map(manifold absolute pressure) sensor. It tells the ecm the amount of vacumn in intake manifold. Using this input from map and other sensors the ecm uses a mathmatical formula to figure out how long to open the injectors . MAF (mass air flow) tells the ecm how much air is entering the intake.

 

jwtaylor, my truck is a 95' ( not california ) and it has MAF. I thought that 94's had it too. Are you sure about the 96' and newer?

 

96 newer are OBD-II. Some of the earlier 5.0's and 5.8's were MAF OBD-I

 

I think in 96 they all had it now as gamehunter mentioned some had it previously so if you have it then your have saved yourself some money and trouble. Good luck with your engine

 

Somewhere I heard that in 95 they had both on 351w.. two tubes from the air filter is NOT MAF.... and that is what mine is. but I can neither confirm nor deny the presence of a MAF!

 

If it is MAF then you will have a sensor housing just after the filter box, usually aluminum unit about 3-4" long.