LOAD SENSORS

Perfect Power Articles.

 

The engine load needs to be determined in order to compute the fuel quantity (and mixture) of an engine. Traditionally it was the throttle position. This was easy, but not very successful. The problem comes from the fact that at very low butterfly openings the mechanical tolerances play havoc with the airflow.

A much better way is airflow. Measuring the airflow into an engine gives a good understanding of the load. Sensing the airflow directly is a little tricky, but it is done successfully in many engines. It can be done in two different ways:

  1. With ‘vane’ type arrangement, where the airflow pushes open a flap and the flap movement is measured.
  2. With a ‘hot wire’ placed in the airflow, where the moving air cools the wire, and this cooling is converted to an airflow value.


BOTH HAVE ONE OTHER ADVANTAGE:

They measure the AIR-MASS. Since the air density changes with temperature this helps to calculate the exact fuel requirements. Otherwise the air temperature must be determined by other means. However, both of these airflow devices have their problems. The mechanical flap has overshoot and unreliability problems, to mention a few. The hot wire reacts very badly to moisture, vibration, and dust coating. All of these shortfalls have been addressed, and some very good hot wire sensors are available.

 

Then there is the manifold pressure sensing. This is a roundabout way of determining the airflow. Because it is solid state, the sensor is very easy and fast. For a given butterfly (and air flow duct) the manifold pressure is a true measurement of the airflow. This gets a little tricky with different atmospheric pressures like high altitude, but this is easily overcome. This type of sensor gives one other measurement: Valve overlap or pulsating manifold pressure. The manifold pressure pulsates anyhow, even without valve overlap. So – the engine engineers put a ‘damping’ container in the way when the pulsating is not important.

 

SUMMARY

The manifold pressure sensing as a way of determining the airflow is very popular because it is fast and easy. The ‘hot wire’ method is second best, but has still some followers.

The manifold pressure sensor is called MAP (Manifold Absolute Pressure) or AMP (Absolute Manifold Pressure). We prefer AMP, because most of our products have two tuning maps.

 

2.5 Bar AMP MAP Sensor 3 Bar AMP MAP Sensor

 


TUNING DEVICES WHICH USE AMP OR MAP:

SMT8 Piggy-Back Unit
SMT8L Piggy-Back Unit
SMT8T Piggy-Back Unit
SMT8-FT Fuel Tuner Unit
TF10 Turbo Fueller Unit

 

VISIT THE FOLLOWING LINKS FOR MORE INFORMATION ON LOAD SENSORS (AMP)

Product Manuals
Application Notes
FAQ’s