Octane/Timing relationships

[WildHorse]

I'm saying to watch the actual knock sensor sine wave, not if it is adding or subtracting spark.

Right, so I seen nothing unusual.

Anyways running through the gears @ moderate throttle I see -1 to -5 KR,
No WOT runs yet.

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[WildHorse]

No WOT runs yet.

Did quite a few last night. No issues.
@engineermike & @K4fxd I was wondering, do you guys ever try what yer typing on the keyboard ?

I'm curious cause I did some serious WOT pulls last night. Nothing unusual, LOGS showed zero knock.

 

[engineermike]

I was wondering, do you guys ever try what yer typing on the keyboard ?

Only a few times…..per week for the last 5 years or so.

What exactly did you post that refutes anything I posted?

 

[WildHorse]

Only a few times…..per week for the last 5 years or so.

What exactly did you post that refutes anything I posted?

Well that's great. Carry on.

 

[K4fxd]

Yes I do test.

 

[markmurfie]

Yeah I just threw the timing in the lambda borderline knock modifier table instead of the 25 MP borderline tables.

That is the usual go to, easy tuning, instead of global. I think global is what the SCT X4 used to allow users some timing control.

 

[WildHorse]

Yes I do test.

you specifically try what I did ?

 

[ice445]

The problem with what you're doing is that it assumes things, which is bad. Every tank of gas can be slightly different. Sure, you have no knock now, but let's say you have a bad tank of gas or it's a hot day and you hit it after sitting in traffic. Now because all the tables are +2 you can run into a situation where the car goes deep into knock and can suffer damage or at least go into limp mode.

As the other guys are saying (who are basically experts on this matter and have written and tested their own tunes for years), you also mess up the torque calculations and various other parameters the ecu relies on being correct. Since the ecu is always trying to select the lowest/safest value of the 4, having them all cranked up the same amount is fine until it's not.

The car will probably be even faster if you add the 2 degrees the right way

 

[WildHorse]

The problem with what you're doing is that it assumes things, which is bad. Every tank of gas can be slightly different. Sure, you have no knock now, but let's say you have a bad tank of gas or it's a hot day and you hit it after sitting in traffic. Now because all the tables are +2 you can run into a situation where the car goes deep into knock and can suffer damage or at least go into limp mode.

As the other guys are saying (who are basically experts on this matter and have written and tested their own tunes for years), you also mess up the torque calculations and various other parameters the ecu relies on being correct. Since the ecu is always trying to select the lowest/safest value of the 4, having them all cranked up the same amount is fine until it's not.

The car will probably be even faster if you add the 2 degrees the right way

Fair enough.
I reverted the global back to 0 and added +2° to the borderline @ WOT.
Odd though cause when you use say nitrous, you want a GLOBAL reduction in timing.

 

[engineermike]

I reverted the global back to 0 and added +2° to the borderline @ WOT.

That's the right choice. Now your other 4 spark sources will be preserved with less chance of unintended consequences.

Odd though cause when you use say nitrous, you want a GLOBAL reduction in timing.

Eh, not really. Where to remove timing depends on why you are removing timing, but global is not the right answer. If you believe MBT is lower then you would remove it from the highest-load row of the MBT tables. If you are worried about knock, then you would remove it from the bottom row of the borderline tables. If you are worried about engine mechanical stresses then you would remove it from the bottom row of the cylinder pressure timing table. Global would take timing from all of these tables at all loads, so you would lose timing at all times part-throttle and potentially lose idle stability. Did you really want to take 3 deg timing away when cruising or tipping-in the throttle, when it will hurt efficiency and make the engine more sluggish?

Ford built these calibrations with over-rides in many places, like cam timing, DI blend, even burble mode. These features are for development purposes. It's a lot easier for a calibration engineer to add 2 deg timing quick-n-dirty using global on the dyno to see if it fixes some odd problem, that they can then drill down and further develop a permanent fix for if the issue improves.

 

[K4fxd]

you specifically try what I did ?

I've only used global timing when testing.

 

[Pistol_91]

I've only ever used global to pull timing. Never add. Add timing in borderline for specific MPs for that load/rpm. It's very simple. Make a histogram and filter it by mapped point. Copy and add to the MP. You aren't going to notice a whole lot top end N/A, but you will notice it alot mid range if your timing is more accurate in the borderline tables. Especially if the timing is that of the stock tune.

Tuning for timing is one of the easiest things to do (for me at least) with the coyote. There should be no reason to be lazy while doing it. That's my opinion.

 

[WildHorse]

I've only used global timing when testing.

Right. I tested it, worked fine, nothing catastrophic, no p-codes, put it back to 0, and moved on.

 

[WildHorse]

So I compared logs GLOBAL vs BORDERLINE ... I can't find anything wonky when comparing the two with my little experiment.

w/ 93 OCTANE
both had zero knock.
both added the same timing cruising / WOT
both added the same timing Idle / cruising / WOT
both had the same fueling
nothing unusual whatsoever.

 

[engineermike]

So I compared logs GLOBAL vs BORDERLINE ... I can't find anything wonky when comparing the two with my little experiment.

w/ 93 OCTANE
both had zero knock.
both added the same timing cruising / WOT
both added the same timing Idle / cruising / WOT
both had the same fueling
nothing unusual whatsoever.

All this really points to is that you're running below the knock limit...if you're reading the logs properly. Adding timing does not equate to zero knock. I'd have to look at a proper log to know for sure. Did you log MBT, borderline, and timing? All 8 knock advances if per-cyl, or are you in global mode? Maybe post some logs up so folks experienced in data analysis can draw their own conclusions.

That said, none of what is posted above speaks to all the unintended consequences that I've tried informing you about regarding MBT, torque calculations, cylinder pressure limits, preignition limits, spark torque ratio, etc. It would take some pretty detailed logging and analysis to really understand all the effects, many of which might not be apparent.

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