#makemegofast

What is an airflow meter (AFM); how would you recognize it and what does it do?

Did you know that as you press the accelerator to go faster in your car so you allow more air and fuel into the engine by Siemens Injectors.

All this takes place under the bonnet or hood but how is it controlled? Well, the airflow meter is an important component in regulating the amount of fuel siemens injectors into the engine of a modern car so all modern petrol and diesel engines have an AFM.

As you go faster the AFM senses that more air is flowing and tells the engine’s brain (ECU) which then instructs the siemens injectors to pump more fuel.

It’s a bit like running faster or up a hill; your brain senses your muscles need more oxygen; your heart rate rises and you breathe faster.

Engines with carburetors (remember them?) do not need an AFM because the carb itself regulates the amount of fuel and air going into the engine. So when your engine management panel indicates a fault in the AFM you’ll need to find it and replace it.

This can often be done without specialist tools and using a bit of common sense and a workshop manual..

Look for the air intake manifold opening to the engine. This is usually plastic, shaped a bit like a small trumpet. Follow it to the air manifold filter and usually, you will find the AFM either in the filter box or clipped into the pipework going to the engine.

Most AFMs have a 12 volt (not dangerous) electrical plug into them which is easily disconnected.

What are the different types of Siemens Injectors used in modern cars and how do they work?

The earlier type of AFM (siemens injector) used a vane or flap inside the meter body; as air passed by it opened the flap. A spring then returned the flap towards a closed position when the engine speed slowed down.

These vane types are cumbersome and expensive to make. Later types of AFM are often called Air Flow Sensors and work on a hot wire system; airflow (over the wires) is measured by how much current is required to keep one of the wires at a predetermined temperature.

Look inside and you can usually see two filaments; these have to be thin to measure accurately the speed at which air is flowing into the engine.

Which companies make air flow meters? Are there pattern copies on the market? Original equipment fitted to European cars is made by companies like Bosch, Siemens injector, yes there are a lot of pattern copies on the market. Depending on your budget you may prefer to fit a genuine replacement.