Detuning for lower octane

[Compelica]

With fuel prices rising I have opted to pump RON95 for the time being instead of my usual RON97. For a liter of RON97 I can get 2.3 liters of RON95, hence the circumstances.

I have my self-developed tune based on Wayne's ROM which I have targeted for RON97, which I have increased ignition advance on the Base Timing B table, and the KCA table flattened out at 6 degs.Now I don't have my Tactrix plugged all the time so I depend on monitoring the KCA OBD2 PID to get a gauge of IAM and knock that I am seeing. Most of the time I see it at around 4 degs, which equates to an IAM of roughly 0.6.

However on high RPM high loads I see the KCA values drop tremendously, down to 1 deg (sometimes even less than 0) which I am assuming at this point that IAM/FLKC/FBKC is pulling almost the entire KCA table in response to knock. So the likely answer is to simply remove 3-4 degs off Base Timing B at those areas, but then I would expect my IAM to increase since I am now running less timing, which would then compensate for the overall total timing.

Instead, what I think would be a better way for the tune to adapt both to RON95/RON97 would be to remove a fixed amount of degs from the high RPM high loads areas from Base Timing B and add it into the KCA table instead? I don't see a problem with it, apart from the ECU taking potentially longer for IAM to adapt and less consistent power output.

[Wayno]

If you want more range, then reduce base timing and increase KCA, as you said. You could do 4 deg on entire both tables, including the cells that are 0 in KCA.

[steve99]

If you a pre facelift you can use the flex fuel roms and disable the fueling compensations but keep the riming adjustments. If you put a toggle switch to earth on the evap, you can actually switch between two timing maps instantly, you could evem add a little richer fueling if needed on the lower octane fuel


put your 95 fueling in E0 and 97 oin the E85

[steve99]

Alternativly do what wayne said and shift more timing into the KCA map so the iam has more scope to drop timng, also set your iam initial to say 0.7 instead of 1

[Compelica]

Originally Posted by Wayno

If you want more range, then reduce base timing and increase KCA, as you said. You could do 4 deg on entire both tables, including the cells that are 0 in KCA.

Originally Posted by steve99

Alternativly do what wayne said and shift more timing into the KCA map so the iam has more scope to drop timng, also set your iam initial to say 0.7 instead of 1

Thanks, looks like shifting more timing to the KCA table would work well for now. Am not intending to tune for RON95 at the moment, but to just get more safety assurance.

Originally Posted by steve99

If you a pre facelift you can use the flex fuel roms and disable the fueling compensations but keep the riming adjustments. If you put a toggle switch to earth on the evap, you can actually switch between two timing maps instantly, you could evem add a little richer fueling if needed on the lower octane fuel


put your 95 fueling in E0 and 97 oin the E85

This is interesting. I've never taken a look at flex fuel ROMs / hardware implementations as they were generally catered for E85 which we don't have here, but the fact that it can be used to 'switch' between two states is particularly compelling - I'll take a further look.

I suppose it could also be used for multiple timing maps, with a switch to deliver fixed voltages (0V, 3V, 5V for example), but if I understand the implementation correctly the second setting would only reside between the E0 and E85 value range?

[steve99]

Originally Posted by Compelica

Thanks, looks like shifting more timing to the KCA table would work well for now. Am not intending to tune for RON95 at the moment, but to just get more safety assurance.


This is interesting. I've never taken a look at flex fuel ROMs / hardware implementations as they were generally catered for E85 which we don't have here, but the fact that it can be used to 'switch' between two states is particularly compelling - I'll take a further look.

I suppose it could also be used for multiple timing maps, with a switch to deliver fixed voltages (0V, 3V, 5V for example), but if I understand the implementation correctly the second setting would only reside between the E0 and E85 value range?

yes it you input a voltage to the evap to simulate a flex kit you can have multiple maps

[Compelica]

Originally Posted by steve99

yes it you input a voltage to the evap to simulate a flex kit you can have multiple maps

Mine is a JDM model, which apparently has the EVAP pin installed. As it's on A01G I'd assume that the purge function is no longer working, since Australian models don't have that pin; in the same way it likely means the tune also does not have the evaporative purge function.

To install the switch, do I just unpin the existing pin and repin from my own connector?

[steve99]

Originally Posted by Compelica

Mine is a JDM model, which apparently has the EVAP pin installed. As it's on A01G I'd assume that the purge function is no longer working, since Australian models don't have that pin; in the same way it likely means the tune also does not have the evaporative purge function.

To install the switch, do I just unpin the existing pin and repin from my own connector?

correct standard A01G formware doesnt look at evap pressure input on A35 pin 20, but the modified fles A01G rom looks to that for flex fuel ethanol content