Knock / Ignition adaptations

[sapote]

Very confusing - if I'm so rich that timing is being pulled, then why pull it back so much that the LTFTs are now compensating for being lean?
.

I don't think rich mixture would cause detonation. Lean burned hotter and caused knock, then timing pulled back to avoid knock but it's still lean.

[Tbonem3]

Ya I'm just trying to get all the info I can about this stuff.

My DME is pulling back ignition quite severely (-4/-5) across ALL 6 cyl, but it's resulting in lean LTFTs of 1.07/1.05.

Very confusing - if I'm so rich that timing is being pulled, then why pull it back so much that the LTFTs are now compensating for being lean?

Ughhhh

At least the car runs well, but I'm being anal plus I want to understand. Plus I still want to discover what could cause such retarded ignition on all 6 cyl (not a single plug, coil or injector.

[heinzboehmer]

Ah I see what you mean now.

Sure, if they're close to 0 then that means the DME thinks the AFRs are doing good and there's no need to adjust fueling.

But, the AFRs might also be fine if they're not 0. Actually, unless you have a lean/rich code, then the DME thinks your AFRs are good enough, regardless of it compensating with LTFTs or not.

The key part in the above statements is that the DME thinks the AFRs are fine —i.e. they're below whatever "good enough" threshold is set in the DME. I don't know what the "good enough" threshold is, but I can tell you that when I was running my self-modified CSL tune (basically just changed the VANOS offsets), my AFRs were around 12 (as reported by the dyno sniffer) and the DME wasn't complaining at all about them. Wideband/sniffer is probably the only way to know for sure if your AFRs are where you want them.

[Tbonem3]

I think you answered it though no? If they are 0, then you do have healthy AFRs?

[heinzboehmer]

Another question for anyone - can we trust the LTFT #s as accurate indicators of healthy AFR or must you use a wideband to really know if you're lean/rich overall? I understand a wideband is a great tool, esp when you need more specific data. I'm just wondering if you can confidently say the car's AFR is healthy if the LTFTs are close to zero.

I don't think so. The long term trims are there to compensate for recurring lean/rich conditions. If the trims are not 0, then that means the DME is adding/removing fuel to get the AFRs healthy again..

Imagine your fuel filter is not flowing as much as it should. With the injector duty cycle set to the "normal" value (LTFTs == 0), less fuel than expected will be injected into the cylinders and the car will run lean. The O2s will pick up on this and the DME will increase the LTFTs —causing the injectors to open for longer than normal. The lower fuel flow and longer injector opening times should lead to the same amount of fuel being injected into the cylinders as in a car without the fuel flow issue, thus bringing the AFRs back into the healthy region.

Obviously just a specific example that doesn't apply to every situation, but that would result in LTFTs != 0 and healthy AFRs.

[Tbonem3]

They are stored data, but they must be associated with certain RPM because the ignition timing are quite different at different RPM.

Ya so how do you know which RPM it refers to - or perhaps, it's the rpm where advance/retard is greatest? Or it could be an average?

Another question for anyone - can we trust the LTFT #s as accurate indicators of healthy AFR or must you use a wideband to really know if you're lean/rich overall? I understand a wideband is a great tool, esp when you need more specific data. I'm just wondering if you can confidently say the car's AFR is healthy if the LTFTs are close to zero.

[sapote]

Car is not running. You just turn key to pos 2 for OBD2 readout.

They are stored data, but they must be associated with certain RPM because the ignition timing are quite different at different RPM.

[Tbonem3]

Are all of these values at idle?

Car is not running. You just turn key to pos 2 for OBD2 readout.

[jet_dogg]

Are all of these values at idle?

[lemoose]

With over 4° retard adaption with no tune on it, i would highly recommend to check compression, sparkplugs, coils.



The max ignition retard adaption is defined in a table. So this max value is up to you or the tuner.
I need to double check this, when i´m back home, but from my memory max retard adaption in CSL 0401PD31 is 2,00° cr. And i have seen some tunes from others based on the 0401PD11 with some copied tables from PD31.
On non CSL management i have seen various max retard adaption values.
Most times higher than CSL management. I think this is because of better fuel quality in europe, than NA.

for what its worth- my car is on new plugs and coils and has about -4 across all cylinders still. I need to check compression but i dont shouldn't lower compression lead to less knock anyways?

[S54B32]

If 2.00 deg is max, then why this car has over 4 deg?

With over 4° retard adaption with no tune on it, i would highly recommend to check compression, sparkplugs, coils.



The max ignition retard adaption is defined in a table. So this max value is up to you or the tuner.
I need to double check this, when i´m back home, but from my memory max retard adaption in CSL 0401PD31 is 2,00° cr. And i have seen some tunes from others based on the 0401PD11 with some copied tables from PD31.
On non CSL management i have seen various max retard adaption values.
Most times higher than CSL management. I think this is because of better fuel quality in europe, than NA.

[sapote]

In my opinion that’s not looking very good, if your tune is based on CSL PD31. If I remember correct, the max knock adaption is limited there to 2.00°cr. So it can‘t go any higher than 2.00°..

If 2.00 deg is max, then why this car has over 4 deg?

I just read mine with my Schwaben tool and they read:
Cyl 1: -4.41 deg
Cyl 2: -2.81 deg
Cyl 3: -2.81 deg
Cyl 4: -0.81 deg
Cyl 5: -2.41 deg
Cyl 6: -3.21 deg

[Tbonem3]

Try to reset the adaptions with ecuworx tool or Inpa before next drive and do a long drive with mixed profile (part&full throttle) and read again.

If -2 is not so good, can you comment on my -4 to -5 across all 6 cyl? Maint up to date, can think of much else to do. Stock car, stock tune, just headers cats in sect 1.

[S54B32]

Well, that was base tune, I've since had it dyno tuned and after 1 hour drive the adaptations were the same. I'll have to re-check adaptations again seeing as it had been driven more since the dyno tune and maybe ask the tuner. I am only using premium 91 octane fuel in the vehicle.

Try to reset the adaptions with ecuworx tool or Inpa before next drive and do a long drive with mixed profile (part&full throttle) and read again.

[Cubieman]

In my opinion that’s not looking very good, if your tune is based on CSL PD31. If I remember correct, the max knock adaption is limited there to 2.00°cr. So it can‘t go any higher than 2.00°. So if all knock adaptions are maxed out to max, you have to much ignition advance in your tune for you engine or wrong fuel.

I got similar results with wrong fuel in tank, I mapped my CSL based tune to 102 octan (German premium fuel) and when I put 98 in my tank I also have 2.00° across all cylinders.

Well, that was base tune, I've since had it dyno tuned and after 1 hour drive the adaptations were the same. I'll have to re-check adaptations again seeing as it had been driven more since the dyno tune and maybe ask the tuner. I am only using premium 91 octane fuel in the vehicle.