MSefi.com read only forum (Jan.15,2018)

Hi,
My engine is a research engine which installed the megasquirt-II controller and coupled with dyno, also an AFR analyser has already installed. I have two question to ask.
1) If I just want to change the amount of the fuel injection for exooeriment, should I tune the AFR table or the VE table? How can I make sure that the close-loop AFR control is disabled?
By reading the manual, I already disable the EGO sensor, but the result is hard to seperate with the case when the EGO sensor is on.

2)Is there is a possibility to control the fuel injection as a square wave at the steady state? The engine RPM is fixed , I want to see the wideband EGR sensor responce signal under the control of the square wave fuel injection command.
Is there anybody can give me a solusion of this experiment?

Tks

leo wrote:Hi,
My engine is a research engine which installed the megasquirt-II controller and coupled with dyno, also an AFR analyser has already installed. I have two question to ask.
1) If I just want to change the amount of the fuel injection for exooeriment, should I tune the AFR table or the VE table?

VE table, if you're on B&G code. (MS2/Extra can be set up so you could do this with the AFR table, but it's covered at MSExtra.com so I will assume this is not what you are running.

How can I make sure that the close-loop AFR control is disabled?
By reading the manual, I already disable the EGO sensor, but the result is hard to seperate with the case when the EGO sensor is on.

Set controller authority to zero.

2)Is there is a possibility to control the fuel injection as a square wave at the steady state? The engine RPM is fixed , I want to see the wideband EGR sensor responce signal under the control of the square wave fuel injection command.
Is there anybody can give me a solusion of this experiment?

Tks

I'm not sure I understand the question. At a steady state, the fuel injection output should be a square wave with a constant duty cycle, assuming you are not using PWM current limiting.

Matt Cramer wrote:

leo wrote:Hi,
My engine is a research engine which installed the megasquirt-II controller and coupled with dyno, also an AFR analyser has already installed. I have two question to ask.
1) If I just want to change the amount of the fuel injection for exooeriment, should I tune the AFR table or the VE table?

VE table, if you're on B&G code. (MS2/Extra can be set up so you could do this with the AFR table, but it's covered at MSExtra.com so I will assume this is not what you are running.

How can I make sure that the close-loop AFR control is disabled?
By reading the manual, I already disable the EGO sensor, but the result is hard to seperate with the case when the EGO sensor is on.

Set controller authority to zero.

2)Is there is a possibility to control the fuel injection as a square wave at the steady state? The engine RPM is fixed , I want to see the wideband EGR sensor responce signal under the control of the square wave fuel injection command.
Is there anybody can give me a solusion of this experiment?

Tks

I'm not sure I understand the question. At a steady state, the fuel injection output should be a square wave with a constant duty cycle, assuming you are not using PWM current limiting.

Thank you Matt,

For the last question, I am sorry I did not describe it clearly.
What I mean is that , during the experiment , the AFR control is open loop and the injection is calibrated by the VE table so that the EGO out is at the stoichiometric value, now the engine is running at steady state because I have DYNO to keep the speed at constant. Then I want to change the fuel injection under a square wave disturbance, so that the widband EGO signal should be like a square wave too. By doing this , I can estimate the delay in the combustion process. But I want the disturbance added each time is the same, so I want to realize this by the code. What can I do base the megatune software to realize this object? One method in my mind now is to change the value of the VE table at this state by the code, but I did not find a way to implement this. Or can you give me some suggestion to do this ?

leo,

You might be looking for the 'Additional Fuel' settings under 'Fuel Set-Up -> Other Fuel Settings' in the 2.920 code. See 'Fuel Response Time' at:

http://www.megamanual.com/mt29.htm#so

The code itself is here: http://www.megamanual.com/ms2/code.htm

Lance.