MAF Conversion Question: What about ambient air temperature???

[bmwman91]

Ok. The AFM definitely must go for my M42 turbo project. Here is a question: What about the ambient air temperature? The AFM has a thermal resistor that puts out a signal voltage to the ECU so that the mass of incoming air can be accurately calculated when considering air temp changes. A MAF does not need/have a temp sensor since it only cares about the temperature of its wire/film, and the ambient air temp will change its temp, but it all factors together with a MAF.
People who have done MAF conversions, what did you do about this? Is there a temp-resistor in the MAF afterall? Thanks.....

[Jonathan 90 M3]

MAFs do use an intake air temp sensor, I believe one is included with the split second unit but I have also seen some people wire up the sensor that was originally in the AFM.

The temp. of the film/wire is used by the MAF to calculate the amount of air feeding the engine, not the temp. of the air.

[Racer X]

I ordered a temp sensor with my split second kit for my turbo. They list the sensor on their web site

[chesster6969]

Doesnt the DME use the Temperature Sensor and the AFM input in order to derive the Air/Fuel combinations or am I wrong?
Does the output of an MAF already have the Air Temp accounted for?

[Racer X]

I know it uses the iat for timing not sure about a/f ratio

[KC Ron Carter]

I have a split second MAF on a 85 e24 shark m30.

It has the possibility to use the added temperature sensor.

Mine is with out a temperature sensor and works just fine.

MAF


Most 80's and some early 90's BMW's used a Bosch AFM meter to measure the volume of incoming air. The AFM uses a vane (or flapper) in the flow path of the incoming air connected to a variable resistance track to give the ECU a signal. The flapper and the small rectangular port it rides in causes a huge restriction.

A Mass Air Flow (MAF) meter is a cylinder with a small heated wire element in it. The voltage required to keep it heated varies directly with the mass of air passing through the cylinder. The cylinder presents very little restriction to the air flow compared to a vane meter. This gives you the power gain. To over simplify things, an engine is essentially an air pump: more air in means more air out, which means more power.

MAF conversion (Split Second) has four trim knobs which must be set to the supplied specifications. Note mine are indexed for quick return to working mixture.

Mine:




http://www.bmpd.com/bmw/parts/catalog/engine_32.shtml

Later,