so i have read a bunch of random threads to try and see what is out hear on the wed and one thing that I am not sure of is the difference between MAF and SD I have read two pages of people talking about there egr valves header and smog pumps and it all tied back to whether or not you a SD or MAF WHATS THE DIFFERENCE some one please tell I too am a VERY proud owner of older model f-250 4x4 and i would really like to know any help would great thanks

 

SD= speed density
MAF= Mass air flow

Simple version:

Speed density only reads the air leaving the engine(O2 sensor), so it is not too happy with modifications.

MAF reads air IN(MAF sensor in th air filter tube) and OUT(O2 sensor) and will compensate for changes(to a degree). Thus you can put a cam, headers, etc and the computer will adjust fuel(again to a degree).


My '89 is SD and I removed the cats, installed headers and true duals, removed smog pump and the truck runs FINE! I live in a NON Echeck area, so visual checks are an issue.

 

In a nutshell;

Speed density measures vacuum in the intake manifold. This is a frequency signal that is sent back to the ECU which is used to help determine load, which is used to help fuel the engine. On trucks, these systems are also considered batch fire which fires the injectors in groups of 4 at a time.

Mass air measures the the amount of air (mass) going into the engine. This is a voltage signal that the ECU reads (0-5 volt range) which is also used to determine load and fuel the engine. This type of system fires the injectors sequentially; one at a time.

 

ok so i am reading this right you truck can only be one or the other right and being that my truck only has one o2 sensor which is before the cat and it has the maf sensor then it most be maf. out of the two sd or maf which one do you guys think is better to have and way? i'm not trying ask a bunch of stupid questions im just trying to lean a little something here oh and by the way thanks for answering my first question guys both of you helped me out.

 

Follow the fresh air pluming from your air filter to the aluminum manifold. If along the way there is a short piece of the plumbing that has a wired connector to it, that is the MAF sensor. The speed density will not have it.

 

Speed density trucks have two air hoses all the way to the airbox. MAF trucks have two hoses that go into a "Y", and then one big hose going to the airbox.

- 94-95 F-150/Bronco 302 and 351 California-Emissions trucks were MAF + OBD1
- All 96 F-150/Bronco regardless of engine were MAF + OBD II
- 96-97 F-250/350 California-emissions trucks were MAF + OBD II
- 96-97 F-250/350 Non-California were SD and OBD-1
- 94-95 F150/Bronco Non-California were SD and OBD-1
- All 93 and earlier trucks were SD + OBD1.

 

sweet thanks