howfueltableajustmentsareapplied
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howfueltableajustmentsareapplied [2008/01/23 10:58] 76.100.119.159 created |
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| - | ====== Overview ====== | + | ====== ECMLink RPM-based Fuel Adjustments ====== |
| When you change the RPM-based fuel sliders, the ECU doesn't **always** use the adjustments you entered. RPM-based adjustments are only made during certain modes of open loop operation in the ECU, primarily the WOT open loop mode. And even at WOT, the full entered value may not always be used. The RPM-based fuel sliders can be thought of as adjustments to the A/F mixture only when you're running beyond the highest airflow curve in the ECU. This curve corresponds to roughly 2.1 g/rev (AirflowPerRev) or about 16-17psi. When you're running wide open throttle with less airflow than that, DSMLink will interpolate according to the fuel curves defined from the factory. | When you change the RPM-based fuel sliders, the ECU doesn't **always** use the adjustments you entered. RPM-based adjustments are only made during certain modes of open loop operation in the ECU, primarily the WOT open loop mode. And even at WOT, the full entered value may not always be used. The RPM-based fuel sliders can be thought of as adjustments to the A/F mixture only when you're running beyond the highest airflow curve in the ECU. This curve corresponds to roughly 2.1 g/rev (AirflowPerRev) or about 16-17psi. When you're running wide open throttle with less airflow than that, DSMLink will interpolate according to the fuel curves defined from the factory. | ||
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| + | **V3 NOTE**: V3 changes this even further to take into account the extended load indices provided by V3 functionality. If you view LoadFactor from your logs, you'll see the value used to cap and extrapolate these fuel slider values. In V3, you get no adjustment at all below a LoadFactor of 0.8 (roughly atmospheric pressure) and you get full adjustment above 1.6 (roughly 11psi). Between these two points, the ECU will interpolate your RPM-based fuel settings for you. | ||
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| Now if you run the math, you'll notice that -9% on the mid airflow curve actually results in 12:1 A/F ratio instead of the 11:1 that would have resulted from the original -14% adjustment on the highest airflow curve. The reasoning behind that is that the factory defined a leaner mixture at that airflow curve for a reason. They did all sorts of tests and measurements and such to decide that at those low airflow values, the engine could tolerate a leaner mixture. They defined almost 11:1 at that airflow versus 9.5:1 at the highest airflow. So instead of our trying to maintain the original 11:1 ratio the user entered by plugging -14% into the fuel slider, we allow the mixture to run a little leaner according to the ratio established by the factory. | Now if you run the math, you'll notice that -9% on the mid airflow curve actually results in 12:1 A/F ratio instead of the 11:1 that would have resulted from the original -14% adjustment on the highest airflow curve. The reasoning behind that is that the factory defined a leaner mixture at that airflow curve for a reason. They did all sorts of tests and measurements and such to decide that at those low airflow values, the engine could tolerate a leaner mixture. They defined almost 11:1 at that airflow versus 9.5:1 at the highest airflow. So instead of our trying to maintain the original 11:1 ratio the user entered by plugging -14% into the fuel slider, we allow the mixture to run a little leaner according to the ratio established by the factory. | ||
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howfueltableajustmentsareapplied.1201103914.txt.gz ยท Last modified: 2008/01/23 10:58 by 76.100.119.159
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