Engine loses power when starting off.

[XfireZ51]

Dyno,

The O2s modify the fueling by R/L bank but only in Closed Loop. The VE table is used no matter, but fueling will be the same for both banks in the case of Open Loop. This is true IF there's been no LEARN prior to use. Otherwise the learned BLM will be used, just not modified. In Closed Loop, the PW will be calc'd for the individual bank of cylinders dynamically using O2 sensor input.
One reason I like using C/L. In the case of the secondaries operating, remember the cal effectively divides the calc'd PW between the 2 injectors.

[Dynomite]

Thank you.......the information is much appreciated

Originally Posted by XfireZ51

Dyno,

The O2s modify the fueling by R/L bank but only in Closed Loop. The VE table is used no matter, but fueling will be the same for both banks in the case of Open Loop. This is true IF there's been no LEARN prior to use. Otherwise the learned BLM will be used, just not modified. In Closed Loop, the PW will be calc'd for the individual bank of cylinders dynamically using O2 sensor input.
One reason I like using C/L. In the case of the secondaries operating, remember the cal effectively divides the calc'd PW between the 2 injectors.

[Schrade]

Sounds like an 'exacerbation' of the 'hesitation' that I'm trying to resolve.

Backfire? Maybe lean gases lighting up in the out-pipes, when fuel delivery catches up.

I think mine would probably do the same, except that everything is burning pretty cleanly, and the hardware is clean. My MILD lope, just above idle, leads me to believe that fuel delivery coming off of idle, isn't in sync with the air increase, again, JUST COMING OFF idle.

Idle @ 0% TO is PERFECT rock steady, no codes. Above 2.4% TO is smooth again too. I still have the secondary-blocking TB gasket installed as well, which eliminates secondarys' leaking air for the diags...

I found my bolt (screenshot stuck in 'seeing eye' tool's LED - will post tomorrow), and will resume DataMaster with incremental idle increase with modded throttle stop screw tomorrow or Monday. SOMEone will be able to make something of it, I'm sure.

I think this is gonna' be real interesting here...

[Schrade]

Originally Posted by XfireZ51

Dyno,

The O2s modify the fueling by R/L bank but only in Closed Loop.

Got that.

The VE table is used no matter, but fueling will be the same for both banks in the case of Open Loop.

Got that.

This is true IF there's been no LEARN prior to use. Otherwise the learned BLM will be used, just not modified. In Closed Loop, the PW will be calc'd for the individual bank of cylinders dynamically using O2 sensor input.
One reason I like using C/L. In the case of the secondaries operating, remember the cal effectively divides the calc'd PW between the 2 injectors.

Is this OEM operation? (division of PW?)

Or is it Marc's over-write operation?

In other words, does his NEW coding do this duty operation, whereas it did NOT divide PW between 1' and 2', in original configuration?

[Dynomite]

Originally Posted by XfireZ51

Dyno,

The O2s modify the fueling by R/L bank but only in Closed Loop. The VE table is used no matter, but fueling will be the same for both banks in the case of Open Loop. This is true IF there's been no LEARN prior to use. Otherwise the learned BLM will be used, just not modified. In Closed Loop, the PW will be calc'd for the individual bank of cylinders dynamically using O2 sensor input.
One reason I like using C/L. In the case of the secondaries operating, remember the cal effectively divides the calc'd PW between the 2 injectors.

Would you summarize the coolant temperatures and other circumstances that will switch the ECM from Open Loop to Closed Loop?

When in Closed Loop, what are the learning input sources (I know o2s).
And since o2s, there is definitely a difference in the location of the o2s in regard to stock exhaust manifolds vrs Headers......what might be the difference in ECM learning?

If running Marc's CHIP.....I assume the fuel trim is learned in Closed Loop beyond that baseline fueling set by Marc? Or maybe Marc keeps it in Open Loop

Or maybe I should stick to my Open End Flex Head Ratchet Metric Wrenches

My two ZR1s (90' and 91') run like rockets and I am not sure why......I blame it on Marc's CHIPS

[XfireZ51]

Chuck,

There is a constant in the calibration for the secondary injector. When they are turned ON, the ECM splits the PW. Part of the OEM software.




Dyno,

Originally Posted by Dynomite

Would you summarize the coolant temperatures and other circumstances that will switch the ECM from Open Loop to Closed Loop?

I've attached a jpeg of 3 tables used for C/L operation. One shows the parameters for the ECM to consider if it was a HOT start, COLD Start or WARM start. Then there is an accompanying TIMER telling the ECM how long to wait before C/L based on the start-up temp. So anything under 29C will use 5 minutes as an example. However, in addition there is an O2 WINDOW.
So it could go out of C/L depending on whether its too rich or too lean with reference to the voltage being generated by the O2.
You also see a table for what the target AFR is when in O/L and that is referenced to CTS. So colder the coolant temp, the richer the mixture. The number in the table is how much additional fuel from the baseline. Changes in the baseline will affect this table then.

Originally Posted by Dynomite

When in Closed Loop, what are the learning input sources (I know o2s).
And since o2s, there is definitely a difference in the location of the o2s in regard to stock exhaust manifolds vrs Headers......what might be the difference in ECM learning?

The O2 is the final word for C/L. Whatever the ECM is doing ends up as a signal from the O2. The feedback loop to the ECM causes it to modify the fueling accordingly. SA is being affected based on the RPM/MAP along w modifiers like DECEL, startup, CTS.
There is a table that defines for the ECM the amount of delay, based on airflow, before allowing the INT to change. Its an O2 INT Delay. This way the ECM correlates the effect of changes it has made w the results coming from the O2. Otherwise it would be out of sync and "chase its tail". In general, the use of headers and moving of the O2 further back has not demonstrated a need for changing the values in this table.

Originally Posted by Dynomite

If running Marc's CHIP.....I assume the fuel trim is learned in Closed Loop beyond that baseline fueling set by Marc? Or maybe Marc keeps it in Open Loop

Haven't really looked at one of Marc's cals recently. I know he has stated that the LT-5 came with a bit of a rich fuel table and that headers pretty much bring it into line. So my impression is that he doesn't do much tweaking on fuel there. Most tuners will resort to O/L when larger cams are introduced into the equation.
All "LEARN" happens in C/L. However, LEARN is not always ON with C/L. Several other parameters define when LEARN is active. If LEARN is not active, the ECM uses whatever fuel trims have been stored for those cells.
The overall goal is to get the VE tables to be as close to optimum as possible requiring little intervention by the ECM.

Originally Posted by Dynomite

Or maybe I should stick to my Open End Flex Head Ratchet Metric Wrenches

My two ZR1s (90' and 91') run like rockets and I am not sure why......I blame it on Marc's CHIPS

[Dynomite]

Thanks for the tables and explanations

Originally Posted by XfireZ51

I've attached a jpeg of 3 tables used for C/L operation. One shows the parameters for the ECM to consider if it was a HOT start, COLD Start or WARM start. Then there is an accompanying TIMER telling the ECM how long to wait before C/L based on the start-up temp. So anything under 29C will use 5 minutes as an example. However, in addition there is an O2 WINDOW.

So it could go out of C/L depending on whether its too rich or too lean with reference to the voltage being generated by the O2.
You also see a table for what the target AFR is when in O/L and that is referenced to CTS. So colder the coolant temp, the richer the mixture. The number in the table is how much additional fuel from the baseline. Changes in the baseline will affect this table then.

The O2 is the final word for C/L. Whatever the ECM is doing ends up as a signal from the O2. The feedback loop to the ECM causes it to modify the fueling accordingly. SA is being affected based on the RPM/MAP along w modifiers like DECEL, startup, CTS.
There is a table that defines for the ECM the amount of delay, based on airflow, before allowing the INT to change. Its an O2 INT Delay. This way the ECM correlates the effect of changes it has made w the results coming from the O2. Otherwise it would be out of sync and "chase its tail". In general, the use of headers and moving of the O2 further back has not demonstrated a need for changing the values in this table.

Most tuners will resort to O/L when larger cams are introduced into the equation. All "LEARN" happens in C/L. However, LEARN is not always ON with C/L. Several other parameters define when LEARN is active. If LEARN is not active, the ECM uses whatever fuel trims have been stored for those cells. The overall goal is to get the VE tables to be as close to optimum as possible requiring little intervention by the ECM.

The values in these tables are not necessarily stock.

[XfireZ51]

Cliff,

As an FYI, the values in these tables are not necessarily stock.

[Dynomite]

Originally Posted by XfireZ51

Cliff,

As an FYI, the values in these tables are not necessarily stock.

Copied this technical information in one spot so I can get back to it with note added if that is OK with you

Fuel Trim and Closed/Open Loop Operation

[XfireZ51]

Originally Posted by Dynomite

Copied this technical information in one spot so I can get back to it with note added if that is OK with you

Fuel Trim and Closed/Open Loop Operation

My pleasure. Glad to contribute. The issue of using the correct injector bias may be another topic you would be interested in. I am in the process of discovering just how important it is but won't be done until car is back on the road.