Anyone have a link or can tell me what it is and why some done use it?

Thanks

 

MAF- mass air flow sensor
It measures that mass of air flowing into your engine, that way fuel injector based cars can squirt the right amount of fuel with the air.
Carburator based cars don't have them I think ...

 

Then why do some have it and some dont on the Evo?

 

All stock evos have it. Some have upgraded to stand alone ecu and so can bypass the MAF. They are using speed density.

 

BTW, where is the HKS store in Taiwan?

 

MAF sensors tend to be fragile. Many of them are 'hot wire' anemometers and they measure the amount of airflow by the cooling effect on a heated wire.

The problem is that the wire is normally very small and therefore subject to mechanical damage.

The other problem with them is that they can get contaminated by things like oil mist in the air and will read low. Several Subarus that I've seen have had engines go POP because the MAF sensor was dirty and the cars were run HARD

 

The MAF sensor on the Evo is the Karmann Vortex type.... there are other kinds as well e.g. flapper door.

 

Its outside of Taipei in a city called Tzong He. www.hks.com.tw if you can read chinese check it out. The store has a upgraded Evo 8 with HKS 3037 turbo and they only made 396whp Maybe trying to keep it safe I dont know but some say those guys dont know what the hell they are doing. They are suppose to be the sole distributor of HKS in Taiwan.

 

the MAF sensor is a measuring/metering device.. It uses different methods to measure the quantity of air (air volume) air temp, and in some cases atmospheric pressure to calculate the density of the air (Quantity or air molecules in a given space) with that information the cars ECU can calculate the correct amount of fuel to add to the engine regardless of load.. There are 4 types of MAF sensors, Hot Wire, Flapper door, Karmann, and and older style that had a rotating "propeller" honestly I've never seen one of those in use though..

There are cars that do not use a MAF sensor, but use speed density or even simpler open loop systems that operate on throttle position only, the air density in a speed density setup is calculated by reading air temp, air pressure/vacuum, and RPM (and throttle position on some setups) to calculate the air mass, speed density has the advantage of responding quickly to changes, but has a few disadvantages that can affect drivability.

There are different reasons for why some types are used, restriction, durability, flexibility, accuracy, cost, each type has its advantages and disadvantages in each of those qualifications...

BTW, airflow sensors are called MAS, MAF, VAF, etc.. The correct term for our sensor is a Von Karmann Vortex Airflow Meter, it works by reading the vorticies (small swirls of air created by passing air over a small aerodynamic survace) The Karmann sensor is considered to be one of the more accurate sensors, however its sensitive to concussion pressure, and intake and filter restrictions, also there's a minimum airflow that is required in order for it to produce a signal and therefore can have trouble if you alter those characteristics that lower restrictions, larger diameter pipes can lower air velocity even though its flowing the same amount of air, lowered restriction filters or cone filters can disturb the direction of the airflow into the sensor, etc..

Hope this answers your question..

 

My reply is pretty generic.. But applies to the choices that some make for upgrading their stock Airflow sensor to another system in an attempt to accomodate perceived shortcomings of the stock system.

 

some of it is a bit confusing but now I know what it basically is. thanks

 

If you want to understand Von Karmann vortex theory, its covered in aerospace engineering in the 4th year. Don't ask why I know this.....

 

hey jack you are so knowledgable as usual. yeah i definetly noticed the sensitivity to concussion pressure when i close my hood and sometimes i hear a slight RPM change for a few seconds hehe

 

Pull up next to a big diesel truck at a stop light......see how sensitive they are

 

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