Tuning after injector size change.

[FDT]

I was tuning a TC 107 and found a lot of my VE tables were maxed out, using SE tuner, i changed from 3.9gms to 5.3gms and changed the constant in the tuner expecting my tune to now be running quite rich, but it is still running lean in quite a few spots, it didnt seem to change anything at all, what did i miss ?

[kd]

If you are in closed loop in those areas, I suspect the tuner is reading the O2 sensor values and changing the injector feed to be compliant with the set tune.  I am sure one of the local tuners will chime in to give a more experienced read on it.

[hrdtail78]

Changing injector size and telling the ECM the new injector size should get you into the same state of tune you had before.

[jty]

Assuming you have the SE pro super tuner, the trick to get more headroom is to increase the cylinder size, say, 10% (i.e 107 -> 118) and decrease all values in the ve tables by 10% and then add to the lean cells. This requires spreadsheet/excel. Alternatively, just increase the cylinder size and retune.

[FDT]

Assuming you have the SE pro super tuner, the trick to get more headroom is to increase the cylinder size, say, 10% (i.e 107 -> 118) and decrease all values in the ve tables by 10% and then add to the lean cells. This requires spreadsheet/excel. Alternatively, just increase the cylinder size and retune.

It is the black one, not sure what model the tuner is, i changed the injector size thinking it would do the same thing, i havent changed the CI but i will give that a go, thanks for that.

[FDT]

Changing injector size and telling the ECM the new injector size should get you into the same state of tune you had before.

That is what i thought but it didn't happen, the tune stayed the same.

[hrdtail78]

It should stay the same.  You added a bigger injector and told the ecm it was bigger.  With this info.  The ECM will recalculate pw for the new bigger injector.  So, if the bike wasn't in a good state of tune before you did this.  It will stay in that state of tune.

What needs to happen.  You need to map your VE tables for the airflow going through the engine.  Once these are mapped and the ECM knows what airflow is happening at each break point. Then the ECM can start doing accurate calculations. There are basically two sides of the equation when the ECM is trying to figure out how long to hold an injector open.  First is the air side.  The ECM calculates how much air is entering, and then it figures how long injector need to stay open to reach the target lambda for that condition.  Since your VE's were not mapped correctly in the first place.  Changing injectors is on the fuel side and has no effect on the air side.

I'll mention this.  You ran out of head room on your VE's.  Maxed out some cells at 127.5.  Adding 10% to cubic inch will allow you to take away 10% from VE tables.  This is biasing your cubic inch so the ECM will think that more airflow is going through than is actually going through the engine.  This result will take away from the VE table.  Which is the reason you get more head room.  At the same time.  You can actually lower the injector flow number in the ECM. This will also bias the ECM.  The ECM is spraying for a certain pw more than it is calculating that it is.  This will result in a richer mixture than targeted and the ECM will calculate that cylinder fill is less than it thought, and this will also lower VE and give you head room.  To help get the VE's centered again around cubic inch and injector size.  If I lower injector size.  I do it in percent and take away same percent to VE's.  At same time.  If I add to cubic inch.  I take away same percent to VE's and prefer cubic inch because that percent is also taken away from warm up enrichment and this usually is in the ballpark.  I prefer adjusting cubic inch over injector size but sometimes.  Both need to be addressed.

I would say that you didn't need bigger injectors because you ran out of headroom.  You probably only needed to add 10-15% to cubic inch and take away the same from VE's.   BUT with a 107.  3.9's probably/ hopefully won't be enough and 5.3's were needed anyway.

Bottom line.  The air flow needs to be mapped out in the VE tables in order for any speed density strategy to work properly.  Good news is that this is one of the only things all these auto tuners do.  Map VE tables.

[FDT]

It should stay the same.  You added a bigger injector and told the ecm it was bigger.  With this info.  The ECM will recalculate pw for the new bigger injector.  So, if the bike wasn't in a good state of tune before you did this.  It will stay in that state of tune.

What needs to happen.  You need to map your VE tables for the airflow going through the engine.  Once these are mapped and the ECM knows what airflow is happening at each break point. Then the ECM can start doing accurate calculations. There are basically two sides of the equation when the ECM is trying to figure out how long to hold an injector open.  First is the air side.  The ECM calculates how much air is entering, and then it figures how long injector need to stay open to reach the target lambda for that condition.  Since your VE's were not mapped correctly in the first place.  Changing injectors is on the fuel side and has no effect on the air side.

I'll mention this.  You ran out of head room on your VE's.  Maxed out some cells at 127.5.  Adding 10% to cubic inch will allow you to take away 10% from VE tables.  This is biasing your cubic inch so the ECM will think that more airflow is going through than is actually going through the engine.  This result will take away from the VE table.  Which is the reason you get more head room.  At the same time.  You can actually lower the injector flow number in the ECM. This will also bias the ECM.  The ECM is spraying for a certain pw more than it is calculating that it is.  This will result in a richer mixture than targeted and the ECM will calculate that cylinder fill is less than it thought, and this will also lower VE and give you head room.  To help get the VE's centered again around cubic inch and injector size.  If I lower injector size.  I do it in percent and take away same percent to VE's.  At same time.  If I add to cubic inch.  I take away same percent to VE's and prefer cubic inch because that percent is also taken away from warm up enrichment and this usually is in the ballpark.  I prefer adjusting cubic inch over injector size but sometimes.  Both need to be addressed.

I would say that you didn't need bigger injectors because you ran out of headroom.  You probably only needed to add 10-15% to cubic inch and take away the same from VE's.   BUT with a 107.  3.9's probably/ hopefully won't be enough and 5.3's were needed anyway.

Bottom line.  The air flow needs to be mapped out in the VE tables in order for any speed density strategy to work properly.  Good news is that this is one of the only things all these auto tuners do.  Map VE tables.

Thanks for the detailed reply, it makes sense. I will adjust and re tune today.It is pulling close to 120hp so according to the fuel moto graph 5.3's would be more suitable. Cheers