idleair
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idleair [2011/07/28 16:01] dmertz |
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| The purpose of this function is to work around various airflow setup issues that tend to cause stalling or bogging of the engine when pushing the clutch in or simply free rev'ing. This problem is usually the result of an inflated airflow signal reported to the ECU on throttle lift conditions. This might be caused by an aftermarket intake snorkel or a vented BOV, for example. | The purpose of this function is to work around various airflow setup issues that tend to cause stalling or bogging of the engine when pushing the clutch in or simply free rev'ing. This problem is usually the result of an inflated airflow signal reported to the ECU on throttle lift conditions. This might be caused by an aftermarket intake snorkel or a vented BOV, for example. | ||
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| ===== Stalling Engine Example ===== | ===== Stalling Engine Example ===== | ||
| The following clip from a customer's log file shows this problem very clearly. | The following clip from a customer's log file shows this problem very clearly. | ||
| - | {{ http://ecmtuning.com/images/forums/wikipics/badsamplelog.png }} | + | {{ https://www.ecmtuning.com/images/forums/wikipics/badsamplelog.png }} |
| - | You can see that as the throttle was quickly closed, the idle switch went active and engine speed (RPM) started to fall, as it's supposed to. But airflow per rev actually ROSE! If engine speed and engine load is falling, airflow per rev should fall as well. | + | You can see that as the throttle was quickly closed, the idle switch went active and engine speed (RPM) started to fall, as it's supposed to. But airflow per rev actually ROSE! If engine speed and engine load are falling, airflow per rev should fall as well. |
| The problem here is that the MAF sensor is being disrupted in some way under these conditions and the ECU is injecting far more fuel than it should. The ECU "sees" more airflow and believes the engine needs more fuel as a result. But the engine does not need more fuel...it needs less. The ECU just has no way to know that. This excess fuel can basically flood the engine and cause it to bog (as seen in this example) or even die entirely. | The problem here is that the MAF sensor is being disrupted in some way under these conditions and the ECU is injecting far more fuel than it should. The ECU "sees" more airflow and believes the engine needs more fuel as a result. But the engine does not need more fuel...it needs less. The ECU just has no way to know that. This excess fuel can basically flood the engine and cause it to bog (as seen in this example) or even die entirely. | ||
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| ===== Idle Air Clamp ===== | ===== Idle Air Clamp ===== | ||
| - | {{ http://ecmtuning.com/images/forums/wikipics/idleairclamp.png}} | + | {{ https://www.ecmtuning.com/images/forums/wikipics/idleairclamp.png}} |
| What you basically do is to tell the ECU to clamp airflow under these conditions to some value that you know is more reasonable. If the throttle is closed (idle switch is active), you can assume airflow demand is minimal and you can clamp any abnormally high airflow reading accordingly. | What you basically do is to tell the ECU to clamp airflow under these conditions to some value that you know is more reasonable. If the throttle is closed (idle switch is active), you can assume airflow demand is minimal and you can clamp any abnormally high airflow reading accordingly. | ||
idleair.1311883300.txt.gz ยท Last modified: 2011/07/28 16:01 by dmertz
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