Lambda target overlay limitation

[Julien]

Hi guys,

my loom is almost finished, we should power up next Saturday..

I’m working on my base map.

My tuner is more used to race engines than road cars. So he’s not very confident with the modeled fuel equation and would like to use the traditional mode. (He’s already troubled to work with %of the master fuel than actual opening time)

Since I want to use E85 I’d like to make the configuration as much compliant as practical.

We’ll do a first dyno session to map on SP98 and once all will be fine another one for E85.

I’m not looking for more power on E85 so I’ll probably simply use a simple 4D table with %ethanol 5-85 with the output 0-33 or a dual table with interpolation (as it will be used for the ignition since it need to be more refined)

I don’t see any problem doing it.

Where I see one problem is on the closed loop lambda that I also like to implement.

The stoichiometric ratio in the fuel main is on AFR it would be interesting to use it as lambda with a table that we could configure with %Ethanol (or another reference for other fuels)

The lambda target overlay feature could also have done that but you can’t make a correction over 2. Since the difference between gasoline and ethanol is 4.9 it’s a dead end for me at the moment.

Another point that make me not wanting to go with the modeled equation is that it need the lambda sensor all the time and on my car (Porsche 911 tt) the sensors are really close to the turbos and even if I installed them on coolers I’m worry they won’t last long.
They would also be needed for the CLL to work you would answer… but I could live without CCL where I’ll be in trouble in modeled mode

 

[Adamw]

2 hours ago, Julien said:

The lambda target overlay feature could also have done that but you can’t make a correction over 2. Since the difference between gasoline and ethanol is 4.9 it’s a dead end for me at the moment.

Im not sure I understand the problem.  The ECU uses Lambda, not AFR for all calculations.  Lambda 1 = stoichiometric no mater what fuel is used.  In traditional fuel equation the Stoichiometric Ratio setting in the software is only used to convert lambda into AFR for those who are more familiar with working in AFR units.  You can use the "U" key to swap between AFR and lambda units in the target table.  

 

2 hours ago, Julien said:

Another point that make me not wanting to go with the modeled equation is that it need the lambda sensor all the time and on my car (Porsche 911 tt) the sensors are really close to the turbos and even if I installed them on coolers I’m worry they won’t last long.

A lambda sensor is not a requirement for Modelled mode.  

[Julien]

13 hours ago, Adamw said:

Im not sure I understand the problem.  The ECU uses Lambda, not AFR for all calculations.  Lambda 1 = stoichiometric no mater what fuel is used.  In traditional fuel equation the Stoichiometric Ratio setting in the software is only used to convert lambda into AFR for those who are more familiar with working in AFR units.  You can use the "U" key to swap between AFR and lambda units in the target table.  

 

A lambda sensor is not a requirement for Modelled mode.  

On the main fuel page, you enter the stoichiometric value of the fuel to define the lambda =1 so without the possibility of linking this to an external table such as %eth if you change the fuel your AFR target will remain the same, no?

Ok for the sensor, the algorithm will use the lambda target table to define the fuel mass (not the actual value) my bad

 

[Brad Burnett]

I would highly recommend the modelled multifuel equation over traditional for a flex fuel setup.

Are you planning on running an ethanol content sensor?

2 sensors that are immensely valuable with these ecus in flex fuel operation are ethanol content and fuel pressure.

Ive been blown away at the modelled equation with pressure baked in.  Ive had fuel pumps fail and have been able to drive my car back home on about 10-15psi with no ill effects.

[Julien]

Yes both of these sensors are installed.

But I could use traditional equation with interpolation using the %eth as transition.

My only problem is on CLL that won’t work

[Adamw]

11 hours ago, Julien said:

On the main fuel page, you enter the stoichiometric value of the fuel to define the lambda =1 so without the possibility of linking this to an external table such as %eth if you change the fuel your AFR target will remain the same, no?

As I already mentioned, in traditional equation the stoichiometric ratio setting has no influence on fuel control or CLL.  The only thing it effects is the conversion from lambda to AFR units for display on the gauges etc.  Stick to using lambda instead of AFR will cause you less confusion.  Or if you must use always AFR then use 14.7: stoich ratio setting and always aim for gasoline AFR target numbers regardless of fuel.  

 

4 hours ago, Julien said:

My only problem is on CLL that won’t work

CLL will work the same using either equation.

[Julien]

Ok, I understand my mistake with the fixed value of AFR and the way the lambda sensor works… it will output 2,5v for the stoichiometric point whatever the fuel used because it’ll sens the O2 value and nothing else..