Individual Cyl fuel trim numbering

[banaro]

Hi,

Cyl fuel trims are referred to as CYL 1 through 8 in the software, I would like to confirm that this is normal cylinder No, not CYL No in firing order?

Thanks

[Brad Burnett]

It depends  how you have the engine wired up.  But I tend to wire it up with cyl x inj and ign going to cyl x on the engine based on position, then set firing order in ecu.  Some ecus suggest wiring cyl 1 from the ecu to the first cylinder to fire and cyl 2 to the second in the firing order.

Ecu doesn't have the ability to trim fuel based on O2 sensors for specific cylinders.

Attached is a screen grab from the fuel tab in the run time values.  The individual cylinder trims are from individual cylinder fuel trims applied by the tuner to compensate for afr imbalance from slight inconsistencies due to ITBs.

[Adamw]

1 hour ago, banaro said:

Hi,

Cyl fuel trims are referred to as CYL 1 through 8 in the software, I would like to confirm that this is normal cylinder No, not CYL No in firing order?

Thanks

Correct it refers to cylinder number. The software takes account of the of the firing order.

[banaro]

Thanks Adam,

I am coming across from an autronic ecu which has CYL No in firing order for its trims, so wanted to be sure Link was normal CYL No.

I have significant trim percentages to import due to the intake setup and would like them applied to the correct cylinders from start up, up to 25% split at an idle, and still 6% remaining between some cylinders at WOT.

Thanks Brad,

Correct me if this will not work, but I am importing all my EGT's via 0 to 5v analog inputs, converting them to Temp C via a cal table, then setting an axis of each fuel trim table to its associated cyl temp i/p, which suggests I could trim each cylinder based on its egt reading?

Thanks

Juan

[mapper]

36 minutes ago, banaro said:

Thanks Adam,

I am coming across from an autronic ecu which has CYL No in firing order for its trims, so wanted to be sure Link was normal CYL No.

I have significant trim percentages to import due to the intake setup and would like them applied to the correct cylinders from start up, up to 25% split at an idle, and still 6% remaining between some cylinders at WOT.

Thanks Brad,

Correct me if this will not work, but I am importing all my EGT's via 0 to 5v analog inputs, converting them to Temp C via a cal table, then setting an axis of each fuel trim table to its associated cyl temp i/p, which suggests I could trim each cylinder based on its egt reading?

Thanks

Juan

EGT sensor have a big lag and EGT temps are load based. If you use EGT temp as a axis, you can just use it as a overtemp protection to rich  mixture up should EGT go above normal temps. 

But this setting does not work, if you want use EGT to balance cylinders over the whole load range. In this case i would span the cyl correction table with same axis as the main fuel table. Tuning the tables is a huge work and must be done on a bearing load dyno.  Due to the lag the sensors have, you must hold steady state on each cell for several seconds until readings have stabilised. 

[banaro]

 

39 minutes ago, mapper said:

EGT sensor have a big lag and EGT temps are load based. If you use EGT temp as a axis, you can just use it as a overtemp protection to rich  mixture up should EGT go above normal temps. 

But this setting does not work, if you want use EGT to balance cylinders over the whole load range. In this case i would span the cyl correction table with same axis as the main fuel table. Tuning the tables is a huge work and must be done on a bearing load dyno.  Due to the lag the sensors have, you must hold steady state on each cell for several seconds until readings have stabilised. 

You make some good points thanks

[Brad Burnett]

8 hours ago, mapper said:

Due to the lag the sensors have, you must hold steady state on each cell for several seconds until readings have stabilised. 

This sounds terribly time consuming.

[mapper]

1 hour ago, Brad Burnett said:

This sounds terribly time consuming.

It is! I spent two full days on the last car just to get the cyl trims right. And it was just a 4cyl turbo engine. 

I upgraded my dyno after that with individual cyl lambda. This is anway much more acurrate than EGT. It's a bit faster, but it still needs one and a halfe day on a 4cyl if you want do the whole load range.