# MAF vs. MAP



## dreadsword (Dec 2, 2002)

Could someone please explain the distinction between the two and the relative merits of each? Or, if this already exists some where, drop me a link. I've switched from a 98 civic to a 92 1600 NX, and I'm curious to know about the differences in air metering and how they impact performance.

Regards,
--Rod.


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## LittlebittaContact (Oct 12, 2002)

A MAF, or Mass Air Flow Sensor measures the amount of air flowing through the Air Intake and relays this information to the vehicles computer.

A MAP, or Manifold Absoulute Pressure Sensor Measures the pressure in the manifold, this is also sometimes called a barometric pressure sensor.

I Hope this helps. 
No i didnt look this up it was off the top of my head so it may not be the exact definition, but you get the idea.


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## Twomissanman (Dec 19, 2002)

Hey does anyone have a MAF for my 92 ser


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## javierb14 (Jul 9, 2002)

MAF's are easier to tune but are more restrictive.
MAP's are less restrictive but more difficult to tune than a MAF car.


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## bahearn (Jul 15, 2002)

Your car has a MAF. Honda is the big MAP user.


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## dreadsword (Dec 2, 2002)

Yes - I am becoming more aquainted witht the MAF all of the time. I had to take the thing off this past weekend to do an intake install... very nervous as I've heard plenty of stories of people killing them and then having their car down for weeks trying to find a cheap replacement on eBay. Anyway, it certainly is delicate and restrictive... what a bizarre design. I would love to know more about the physics behind the two designs (MAP/MAF) - I know our maf's involve air flowing over a hot wire generating some voltage level or something.... but could some one explain more? And what sort of tuning potential is there with it?

Regards,
--R


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## hpro123 (Apr 30, 2002)

MAF cons: 

1. DELICATE: True, you should also be carefull with air filters that need oiling. Any more than prescribed and you might end up with a useless MAF from the oil deposits. Still, I would think no more than 1/500-1000 actually fail.

2. RESTRICTIVE: True, but not an issue for naturally aspirated engines since usually MAFS outflow whatever you can do to a n/a engine. SR20 MAF flow enough for over 250hp.

3. PLACEMENT: you need to put it where the air flow is smooth, turbulence may through the reading off. MAPs on the other hand can be placed anywhere, even inside the ECU casing!

4. EXPENSIVE: TRUE! Especially compared to MAPs which are dirt cheap.

5. Not very friendly to Turbo applications and avid DIYers.

MAF PROS:

1. Auto-Adjust to ANY mod up to the limit of their flow. Cannot be stressed enough!!!! Anything you may do that will increase the air "needs" of your engine (headers, cams, porting, etc) does not need ANY ECU reprogramming! MAPs on the other hand need ECU reprogramming always!

2. Lets the ECU work on fuel and ignition instead of trying to compute what exactly the pressure read from the MAP actually means in terms of air flow!

3. Auto-adjusts to barometric differences (as in high altitudes) where the MAP based systems only guess/approximate what actually happens.

4. Again, if you stick to N/A engines, TUNE your heart out. In all probability your MAF supports anything you can get from the engine.

Finally, you can just search in google.com with "maf, map, technical" and get several places where they discuus the tech side of both. As for the MAFs, the hot-wire is "kept" by the ECU to a Constant temperature. The more air that passes through the MAF orifice, the more voltage is needed to heat the wire so it remains at this Constant temperature. 


Chris


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## bahearn (Jul 15, 2002)

To properly meter fuel, you need to know how many molecules of oxygen have been ingested into the engine.

The MAF system is better at this because it directly measures the number of oxygen molecules by determining the MASS of air moving into the engine. Mass is a directly measured property. The MAF wires are heated to a certain temperature. As intake air moves past the wires and absorbs heat from them, electronics alter voltage to the wires in an attempt to maintain that certain temperature. The voltage change is what the ECU uses to determine the MASS of air ingested.

MAP system measures intake manifold pressure. Pressure of a gas is dependent upon its temperature, so pressure is not a direct measure of the number of oxygen molecules present. MAP systems require a temperture probe in the intake to make the calculation neccessary to approximate the mass. I don't know anything about the computer maps in a MAP system to guess why they can't store enough data points to cover the alterations in airflow caused by changing intake and exhaust restrictions. A MAP system really behaves just like a carburetor in this regard. Reduce intake or exhaust restriction and you have to rejet. Carbs meter fuel by using differential pressure of static air against the fuel reservoir vs that sensed at the high velocity region at the venturi (as fluid velocity rises, pressure falls). If it were easy to apply feedback from the O2 sensor, Honda would stll be using carburetors, I'm sure.


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