I have read many posts that use the terms MAF and SD. What do they stand for? I know they have something to do with fuel injection but that's about all I've been able to determine thus far. How can one tell which is installed on their vehicle? Why is one considered better than the other? Or are they?

Dave

 

Its the computer system MAF is mass air flow SD is speed density. MAF allows you to do more modifications to the motor. Like bigger cams, heads etc. The computer can adjust for it where SD can't. There are SD compatible mods though.

The way I tell is an SD truck will have the map sensor on the passenger firewall towards the tops with a vacuum line and a small wire harness going to it. MAF will have the MAF sensor on the intake hose.

 

MAF incorporates an air mass measureing device(the MAF meter) into the intake tract so the computer knows how much air the engine is consuming and can adjust to it in real time. This also allows the system to better adapt to engine performance mods like aftermarket camshafts, heads, and exhaust systems. SD or speed density as it is called has no such device and instead relies on preprogrammed tables and engine vacuum to determine fueling requirements, obviously you could have 2 very different engines that produce nearly identical vacuum signals so the programming is everything. It too can compensate for some engine mods with feedback from the O2 sensor but it takes a lot more time for the computer to learn and it's pretty easy to go beyond the computer adjustment capacity where the motor won't run very well at all.

 

SD, is that simply an atmospheric pressure sensor? Sort of like a barometer? My truck is the SD type ( thank you, Redrivergorge) for the description on how to tell. Can one change to MAF 'cause from Conanski's description the engine would respond more quickly to changes such as load, speed, up or down hills etc. Thus one should get more accurate fuel metering and more useable power.

 

Yes, and there is quight a few threads here about it. Do a search and you will find Conanski holding many guys hands as they do this.

 

You can change to speed density, but unless you have made major mods to the airflow characteristics of the motor, there is no need to change. Even SD is somewhat tolerant to small changes. Ford Motorsports sells a MAF conversion kit or you can piece together kits from donor vehicles. Tranny type also comes into play if you have an EEC controlled tranny.

 

This^^ If your not planning on crazy mods or a big cam I wouldn't bother. There are quite a few Lightning guys running 500hp on stock SD.

 

Thank you everyone for all the replies. It allows me to make an informed decision. For the present I am going to remain with my SD system.

Dave