How does the ECU Master EMU use VE values?
Posted: Mon Jun 29, 2015 8:55 pm
Having read parts of "Engine Management Advanced Tuning" (Greg Banish) and parts of the MegaSquirt documentation I have some questions about VE tables and how the ECU Master EMU deals with them. Please correct any mistakes in my reasoning.
Also, please tell me how to enable TeX-style equations so that my equations are more friendly, I've tried [tex], [latex] and [math]. I will then edit my post, unless a nice administrator wants to do it for me.
This is all in the context of speed density. Where is matters, assume the 3S-GTE engine is the engine we are working with.
We have that M = V_{engine} \cdot p_{air} \cdot \dfrac{\mbox{RPM}}{2}, where M is the theoretical airflow rate of the engine in its naturally aspirated form. V is the volume of the engine, p is the density of the air.
VE is defined as VE = \dfrac{\mbox{Actual instantaneous mass flow at RPM and MAP}{M}, where MAP is the intake manifold pressure.
Is this the same way VE is defined in the ECU Master EMU? Or is it defined differently?
If VE is defined in this way, then increasing the VE in some arbitrary cell does not increase the fuel directly. What it does is simply tell the ECU that the flow rate is a certain value, for a given RPM and MAP value. By increasing this value (given that everything else stays the same), the ECU would in turn calculate that more fuel is needed to meet this new volume of air. Is this how the ECU does it? Or does it use a different procedure?
Then, we have the calculation for how much fuel to deliver: Fuel F = \dfrac{\mbox{Actual mass air flow}}{AFR \cdot 120 \cdot \mbox{RPM}}
Finally when the ECU is ready to call its procedure to actually deliver fuel, it can use the equation F = \dfrac{\mbox{Injector flow rate} \cdot \mbox{Duty Cycle} \cdot 120}{\mbox{RPM}} and solve for Duty Cycle to determine how much to pulse the injector.
Is this how the ECU Master EMU does it? Even with EGO feedback turned off?
It doesn't seem to me that this is the procedure the ECU Master EMU uses. Because when I have EGO feedback turned off and change the AFR table in real-time (even increasing or decreasing the whole table at once), I don't see any change on the wideband lambda. If AFR is fixed when EGO feedback is turned off, then from where does the ECU get this constant value? The ECU doesn't know what fuel I'm using, so it cannot use a stoichiometric constant, unless it just uses a very general one.
Also, please tell me how to enable TeX-style equations so that my equations are more friendly, I've tried [tex], [latex] and [math]. I will then edit my post, unless a nice administrator wants to do it for me.
This is all in the context of speed density. Where is matters, assume the 3S-GTE engine is the engine we are working with.
We have that M = V_{engine} \cdot p_{air} \cdot \dfrac{\mbox{RPM}}{2}, where M is the theoretical airflow rate of the engine in its naturally aspirated form. V is the volume of the engine, p is the density of the air.
VE is defined as VE = \dfrac{\mbox{Actual instantaneous mass flow at RPM and MAP}{M}, where MAP is the intake manifold pressure.
Is this the same way VE is defined in the ECU Master EMU? Or is it defined differently?
If VE is defined in this way, then increasing the VE in some arbitrary cell does not increase the fuel directly. What it does is simply tell the ECU that the flow rate is a certain value, for a given RPM and MAP value. By increasing this value (given that everything else stays the same), the ECU would in turn calculate that more fuel is needed to meet this new volume of air. Is this how the ECU does it? Or does it use a different procedure?
Then, we have the calculation for how much fuel to deliver: Fuel F = \dfrac{\mbox{Actual mass air flow}}{AFR \cdot 120 \cdot \mbox{RPM}}
Finally when the ECU is ready to call its procedure to actually deliver fuel, it can use the equation F = \dfrac{\mbox{Injector flow rate} \cdot \mbox{Duty Cycle} \cdot 120}{\mbox{RPM}} and solve for Duty Cycle to determine how much to pulse the injector.
Is this how the ECU Master EMU does it? Even with EGO feedback turned off?
It doesn't seem to me that this is the procedure the ECU Master EMU uses. Because when I have EGO feedback turned off and change the AFR table in real-time (even increasing or decreasing the whole table at once), I don't see any change on the wideband lambda. If AFR is fixed when EGO feedback is turned off, then from where does the ECU get this constant value? The ECU doesn't know what fuel I'm using, so it cannot use a stoichiometric constant, unless it just uses a very general one.
for me it was good lecture before sleep for few days, in my felling all is there (how strategy works, how correction impact calculation and so on)