Category: ECU

The 2 wire sensor, is the sensor that the ECU uses as an input. It is a very important sensor. It effects startup, and running of the car.  We often see the cooling system not bled right, and an airpocket forms at the sensor. When this happens, the sensor may show 250F-300F. When this happens, the ECU thinks the car is hot, and it may not fire the injectors, based on the tune. So if you have hot start problems, that go away once you crank for a bit, the CTS is a good thing to look at, then the bleeding.  This gets back to having a Consult datascanner, so you can see what the ECU is seeing. Makes troubleshooting much easier. 

The 1 wire sensor only drives the gauge in the dash.  A cool fact, R32 and R33 are different resistances. You find these things out later, when you start a car up, and have the wrong sensor in. Then about 2 minutes in, the gauge pegs, the car is fairly cool.  NZ EFI says that the R34 is also different, need to look that one up. 

Strengths of Mass Air Flow

• Extremely accurate fueling and spark delivery across a diverse range of engine conditions (at least while in steady-states): the holy grail for engine management. A properly set-up MAF system can adapt to changes in weather and altitude with ease.
• Minor changes to engine equipment (i.e. headers, minor camshaft changes, intakes that do not significantly alter the placement of the MAF) do not require recalibration of the ECM.

Weaknesses of Mass Air Flow

• MAF systems are extremely intolerant of vacuum leaks. Any leaks between MAF sensor and engine generally cause all manner of odd problems, running lean in most cases due to un-metered air making it into the engine.
• MAF sensors can be extremely sensitive to how they are “clocked” – merely rotating the sensor at a given spot in the intake tract can be sufficient to significantly change its output.
• MAF sensors require laminar flow to read 100% accurately. True laminar fluids do not exist so this introduces some degree of inaccuracy to MAF sensor readings. Placing MAF sensors near bends, size transitions or obstructions where flow is less laminar greatly magnifies this issue.
• A MAF sensor can be a flow restriction in cases where the MAF housing is the smallest portion of the intake system.
• Hot-wire MAF elements are very fragile. Debris can destroy delicate wires easily. Dirt and oil deposits can build up on the sensor element, adversely affecting readings.
• MAF systems have a relatively poor response to transient conditions, such as sudden throttle changes. This is explained by the time it takes air to move from the MAF sensor where it is measured to the cylinder where it can be involved in combustion.
• MAF sensors are not “one-way” sensors – reversion from a camshaft with large amounts of overlap can cause air to be metered on its way in to the engine and then again on its way out resulting in an artificially high MAF reading. This can almost always be fixed by placing the MAF sensor sufficiently far from the throttle body, however doing so comes at the expense of making transient response even worse.

It may seem like there are a lot of weaknesses of MAF systems, but it is truly hard to emphasize just how amazing and important the strengths are. It is no secret that the majority of OEMs today are implementing MAF systems as the primary control strategy. There is a good reason for this, namely that engines can be controlled much more precisely (with the goal of meeting stricter and stricter emissions standards) with a MAF system than any other type of control strategy.

The 2 wire sensor, is the sensor that the ECU uses as an input. It is a very important sensor. It effects startup, and running of the car.  We often see the cooling system not bled right, and an airpocket forms at the sensor. When this happens, the sensor may show 250F-300F. When this happens, the ECU thinks the car is hot, and it may not fire the injectors, based on the tune. So if you have hot start problems, that go away once you crank for a bit, the CTS is a good thing to look at, then the bleeding.  This gets back to having a Consult datascanner, so you can see what the ECU is seeing. Makes troubleshooting much easier. 

The 1 wire sensor only drives the gauge in the dash.  A cool fact, R32 and R33 are different resistances. You find these things out later, when you start a car up, and have the wrong sensor in. Then about 2 minutes in, the gauge pegs, the car is fairly cool.  NZ EFI says that the R34 is also different, need to look that one up. 

Strengths of Mass Air Flow

• Extremely accurate fueling and spark delivery across a diverse range of engine conditions (at least while in steady-states): the holy grail for engine management. A properly set-up MAF system can adapt to changes in weather and altitude with ease.
• Minor changes to engine equipment (i.e. headers, minor camshaft changes, intakes that do not significantly alter the placement of the MAF) do not require recalibration of the ECM.

Weaknesses of Mass Air Flow

• MAF systems are extremely intolerant of vacuum leaks. Any leaks between MAF sensor and engine generally cause all manner of odd problems, running lean in most cases due to un-metered air making it into the engine.
• MAF sensors can be extremely sensitive to how they are “clocked” – merely rotating the sensor at a given spot in the intake tract can be sufficient to significantly change its output.
• MAF sensors require laminar flow to read 100% accurately. True laminar fluids do not exist so this introduces some degree of inaccuracy to MAF sensor readings. Placing MAF sensors near bends, size transitions or obstructions where flow is less laminar greatly magnifies this issue.
• A MAF sensor can be a flow restriction in cases where the MAF housing is the smallest portion of the intake system.
• Hot-wire MAF elements are very fragile. Debris can destroy delicate wires easily. Dirt and oil deposits can build up on the sensor element, adversely affecting readings.
• MAF systems have a relatively poor response to transient conditions, such as sudden throttle changes. This is explained by the time it takes air to move from the MAF sensor where it is measured to the cylinder where it can be involved in combustion.
• MAF sensors are not “one-way” sensors – reversion from a camshaft with large amounts of overlap can cause air to be metered on its way in to the engine and then again on its way out resulting in an artificially high MAF reading. This can almost always be fixed by placing the MAF sensor sufficiently far from the throttle body, however doing so comes at the expense of making transient response even worse.

It may seem like there are a lot of weaknesses of MAF systems, but it is truly hard to emphasize just how amazing and important the strengths are. It is no secret that the majority of OEMs today are implementing MAF systems as the primary control strategy. There is a good reason for this, namely that engines can be controlled much more precisely (with the goal of meeting stricter and stricter emissions standards) with a MAF system than any other type of control strategy.