Octane Adjust Ratio, Decrease Global Timing

[DSMtuned]

At this point I'm tweaking E-tunes on my SCT Livewire to the extent possible for my 3.5 Ecoboost F-150.

I noticed my octane adjust ratio was at -.30 with a new tune. Would I be correct to assume that decreasing global timing a couple degrees would bring that OAR closer to -1?

My understanding is that the OAR is a multiplier that is used to figure total timing. So if all other variables equaled 18* BTDC timing, and the OAR is -.30, then -18*x-.30=5.4* BTDC as the final timing. If the OAR is -1 then -18*x-1=18*.

It seems like you want your OAR as close to -1 as possible for the most timing and best power. Am I on the right track here?

 

[J-Will]

'gas quality' impacts OAR, not timing.

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[DSMtuned]

'gas quality' impacts OAR, not timing.

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In a way, yes.  But too much timing can increase knock, so if it's knocking then decreasing knock by lowering timing  will increase the OAR.  I just don't know if this is the proper way to do it.

 

[StealBlueSHO]

'gas quality' impacts OAR, not timing.

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In a way, yes.  But too much timing can increase knock, so if it's knocking then decreasing knock by lowering timing  will increase the OAR.  I just don't know if this is the proper way to do it.

So I have been tuned by several tuners.. They all seem to approach it the same way. Get the OAR to max out and tune the spark so there is minimal to no KR. That way if you get a bad tank of gas there is plenty of room for the ECU to pull timing.. of course if you are running the ragged edge of power, the knock sensor may not be able to respond fast enough to save your motor.. IE... your meth pump fails in the middle of a track or dyno run.

From what I understand, and someone correct me if I am wrong. The knock sensor will pulling timing obviously if it needs it, but after consistently pulling timing, it will pull back the OAR which scales back on spark as a whole....

If your tuner is cranking up the spark to the point where you never reach peak OAR then I would re-evaluate the entire tune.

 

[TopherSho]

AJP needs to chime in ..

 

[8nutz8]

'gas quality' impacts OAR, not timing.

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yes but oar directly affects timing so through a second hand process gas quality does impact timing.
IMHO I wouldnt decrease timing to improve OAR unless you're getting positive knock values.
to the op- i would drive around under light/moderate boost and watch your knock sensor activity. if it's always in the negative it will further drop your oar into the negative which will ultimately increase timing. if you're getting positive knock values during those conditions THEN I would look at scaling back your base timing tables.
ultimately- adjust timing based on knock, not oar.
but yes we need to hear from brad on this.


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[DSMtuned]

For one thing, I was thinking about OAR and how it's used in final timing calculation.  Here's how member sc544x4f150 corrected me on the HPTuners forum.

"You do want it as close to -1 as possible but it functions a lot different that what you suggested. It is a multiplier against the octane adjustment table then added to the borderline knock calculation. For example if the borderline knock tables output is 18*, octane adjustment tables output is -5, and the OAR is -.30 then your math would look like this: 18+(-.3X-5)=19.5* or 18+1.5=19.5*. So in that scenario the ECM adds 1.5 degrees to the borderline knock calculation. The other function of the OAR is to determine the LSPI limits. There is three LSPI tables: Low, Nominal, and High. These tables have the maximum air load the engine is allowed to reach based on RPM and manifold charge temperature. The Low table has lower load limits for lower octane fuels and the high has higher load limits for higher octane fuels. At an OAR of -1 the high table is weighted 100%, at an OAR of 0 the Nominal table is weighted 100%, and at an OAR of 1 the low table is weighted 100%. If your OAR is in between those numbers the ECM blends the tables together. Correct LSPI load limits is crucial to avoiding engine damage. I wouldn't trick the OAR just to get to -1. The correct way would be to increase your octane. Now for me I had OAR values all the way to -1 on 87 octane which would not support the load limits in my high LSPI table without preignition. To fix this I datalogged the areas of the borderline knock tables that had negative knock retard and added in timing to get my OAR to positive values and decreasing my load limits. When I'm injecting water-meth or have higher octane fuel in the tank the OAR goes more negative adding timing and increasing the load limits."

There's some really good insight there.  Makes me rethink decreasing global timing.

 

[8nutz8]

DSM- keep in mind that the vast majority of people on this forum are using SCT instead of HP tuners. (this includes resident tuner AJP turbo) and that there may be different functionalities among the 2 different softwares in the way specific tables are layed out and perform. not to mention most people here have transverse ecoboost engines which could present differences as well.

just something to keep in mind when gathering info here.


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[DSMtuned]

Fair enough.  This is just the best community I've found for discussion.

It seems like the underlying Ford logic will be the same regardless of the interface, so the OAR should interact with other tables in the way same. 

 

[8nutz8]

Fair enough.  This is just the best community I've found for discussion.

It seems like the underlying Ford logic will be the same regardless of the interface, so the OAR should interact with other tables in the way same.

For the most part i think you're right. The ford logic is universal but approaches to how it is modified are different. At the very least i'm sure tables that serve the same function have different names and i'm not sure as many tables have been mapped out through HP as have SCT. At least this holds true for the SHO and transverse ecoboost applications. Not sure about F150

Are you tuning yourself or going through a vendor?

 

[DSMtuned]

A vendor is tuning for me, but this is unnatural for me since I've always tuned my own cars.  This is why I wanted to see how much I could change with my SCT tuner without relying on someone else. 

When looking at the various tables in the free version of HPTuners, these ECUs are tremendously complicated when compared to the platforms I'm used to tuning.  I'd like a full understanding of their intricacies before buying the full version.

 

[SHOdded]

https://thetuningschool.com/fordtuning/
https://www.sctflash.com/support/tune-training