Installshield 2 said:
What a debate this is. MAF or MAP.
They both have good and bad characteristics. As they relate to engine management as a whole though, a map sensor far excedes the performance value.
Lets go thru some things here.
MAP - Manifold Absolute Pressure. Sometimes the name can be misleading. Many if not all Map sensors made today measure pressure in the intake manifold along with baro. They can compensate for altitude changes and thus fuel the motor effectively in any enviroment.
MAF - Mass Air Flow. MANY MANY kinds still exist. Mainly only two that can be useful for our conversation. Frequency and hotwire. I think the article I have linked to earlier has already cleared up some of the basic functions.
But the most important part to any of these will be air temp. When an air temp sensor is incorporated in either a MAF or MAP system it is the most important integral feature for the system. That will give you air density correction.
You see the MAP basically is an assumption of load thru preprogrammed maps in the ecu used for fueling. Its scaling and resolution are basically fixed. Some say a guessimate. Somewhat true but not really. The vehicle tuned with a map sensor will already "know" the proper fueling requirement based on its load output as it is preprogrammed specifically FOR the mods and vehicle being tuned. It "assumes" airflow by the way it was scaled in its original mapping. Usually any drastic changes made to the constant airflow thru the motor above the "bar" it recognizes goes thru undetected. Thus creating a state of fuel enrichment that is basically added by guessing. This is old though. Those days are long gone with the addition of airtemp sensors, technology, enviromental control chambers and rescaled ecu's. You can make any change you want now adays and basically have the ecu reflashed to your specific needs. Almost every manufacturer that i know that uses MAP has this offering.
Now MAF.
It directly measures the airflow "induced" into the motor. I say induce because 99 % of the vehicles out there whether FI or NA pull air thru the sensor. Very rarely will you see the MAF blown thru. It is sensitive and directional. Damage can occcur along with false output readings. This system is great for economy along with the O2 feedback to account for every molecule of air. (NOT OXYGEN) There is a difference. Even when going FI it can compensate to a point. That is where it is a little more acceptable for low boost applications. (stock unit) You can use the resolution it provides to scale your fuel map accordingly and sometimes automatically. But it like the MAP has its limitations. It is scaled for the particular application and any airflow that it cannot read accurately will go by undetected. That is to say if it doesn't create a restriction first. MAF sensors in the tract of a FI setup is a restriction to airflow. Yes you can get a new larger MAF made up and scaled for the car but so can you a MAP. One difference being that in most acses the new MAF will need to be controlled. Either by a new control module (piggy) or reflashed ECU. The difference really is that with a map you KNOW when boost comes in (or boost threshold is met). Period.
Anyone with any credible tuning experience will tell you that. A MAF sensors' resolution FALLS when increasing the capacity. You are still using a small 16 x 16 map and thus cramming in more load without dispensing the duties to more load sites for adjustment.
A map sensor will measure the amount of pressure up against the valve rather than what the engine MAY be ingesting with the MAF value. It gives you an idea of what is really going on AFTER the TB and in the runners. It allows you to tune for boost specifically. The resolution you get when using a MAP sensor for boost is unsurpassed. From 14.7 atmospheres to 30 psi of boost pressure it will allow the enduser to program the EXACT amount of fuel and ignition needed to get the engine running to peak efficiency. The correction alotted for airtemp thru the AIT sensor helps produce an accurate A/F ratio for a given density of oxygen in the mixture. MAP sensors differentiate Boost from atmospheric pressure. This allows you to tune more accurately. Now for NA any one of these sensors will work very well. Not one better than another. If both are TUNED properly you should see little difference if any. Only airflow restriction will cause a variable.
Well I tried with the limited time I had to help a little . I can go into more detail if need be later.
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i want one!
