Sensor Questions?

[SRavet at bangate.compaq.com]

"Jim Staff"  <staffj at freenet.msp.mn.us> Wrote:
| 
| I know what the temp and o2 sensors are but I have a sensor question. 
What is 
| the difference between MAF (Mass Air Flow) sensor and a MAP (Mass Air 
Pressure?)
| sensor? It seems to me that most vehicles use a map sensor, but I would 
think 
| the MAF sensor was better. As I was instructed by an automotive engineer. 
What 
| are the pros & cons of the different systems?
| 
|           Thanks,
|              Jim Staff

The difference is that MAF is more complicated, but is more tolerant of 
engine modifications.  MAP (or SD, speed density) use a pre-calculated 
volumetric efficiency value.  Basically, rpm determines the volume of air 
moving through the engine, and the pressure determines the amount of oxygen 
in that volume.  The computer then injects the proper amount of fuel.  If 
you increase the breathing ability of this engine (headers or intake modes, 
etc), the computer doesn't know about it and will inject too little fuel.

MAF systems are really SD based, but the computer is able to modify the 
injector on time based on the reading from the MAF sensor.  It is much more 
tolerant of future engine modifications without requiring the prom to be 
updated.

Steve Ravet
sravet at bangate.compaq.com
Baby you're a genius when it comes to cooking up some chili sauce...