Total Timing Advance Question

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shawd
Posts: 4
Joined: Sun Feb 19, 2023 12:36 am

Total Timing Advance Question

Post by shawd »

I'm looking at the timing tables for a 2010 Acura TL SH-AWD 6MT. I'm trying to understand the total timing advance that is in place.

Both Factory Base Configuration and Tune 3 (addition of PCDs or HFPCs) show the following on the main layout page:
0 psi (1013 mbar) load @4900 rpm.
19.2 Ignition timing
+ -1.2 knock limit
- 7.6 knock retard
--------------------------
11.6 ignition timing advance

Did I calculate that correctly? The documentation I read says to add the knock limit but the tables @4900RPM show -1.2 so I assume I subtract that out.

I'm assuming the 1013 mbar (0 psi) would be WOT.

So at 4900rpm at WOT the car would have 11.6 degrees of timing advance. Is that correct?

Is the knock retard only invoked if knock is encountered? I'm trying to understand if the actual timing could be closer to the 19.2 ignition timing setting or if the knock limit and knock retard are always in place adjusting the actual ignition timing advance.

Thanks in advance for the help!
KTuner
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Joined: Mon Jul 22, 2013 8:13 pm

Re: Total Timing Advance Question

Post by KTuner »

As explained in the help Knock Control is multiplied by the Knock Retard table to give the final Knock Retard value. If you're trying to calculate this without taking into account your Knock Control value then your value isn't accurate. If you are reviewing your datalogs to see your Knock Control value it's a moot exercise as you can already see Actual Ignition value in logging as well.
shawd
Posts: 4
Joined: Sun Feb 19, 2023 12:36 am

Re: Total Timing Advance Question

Post by shawd »

I understand the actual timing can be seen in the data log. I’m trying to determine how it was derived.

I’m seeing this formula in the help doc:
Ignition Table Value + Knock Ignition Limitation Value - Knock Retard Value = Final Calculated Ignition Timing

I was thinking it used the values I see in the three tables viewable from the main layout page. Reading back through the help documentation on this page, http://ktuner.com/KTunerHelp/ignition_t ... ontrol.htm, it says to multiply the knock control value by the knock retard value to determine the knock retard value to use in the calculation. Okay, I understand knock control is real time and would be fuel dependent as one of the factors.

I see the documentation then says:

It then compares the Final Calculated Ignition Timing and the original Ignition Table Value and chooses the lesser of the two.

In that case the initial timing of 19.2 in my example is compared to the calculated value that factors in the real time knock retard
and compares the two and uses the lessor.

Let me see if I can make another attempt here following your response and the help docs.

These are based on what I’m seeing for 0psi (WOT) @4900rpm
19.2 initial timing + (-1.2 knock limitation) = 18.0. Is it correct to subtract the knock limitation value when it’s negative?

Rather than subtracting the knock retard value directly I first need to multiply that 7.6 times whatever the real time knock control value is as it’s happening, and then take that value and subtract it from the 18 above to come up with the calculated timing advance factoring in knock control. Does that sound correct?

For example, if the knock control value was 1.0 then I’d multiply that by the 7.6 value in the knock retard table and that would come out as 7.6.

18.0 - 7.6 = 10.4 actual degrees of timing advance with a knock control of 1.0. .

The 10.4 calculated is then compared to the 19.2 initial and the lesser would be used so in this example 10.4. Is that correct?

If no knock was being experienced, so let’s say 0 knock control, then the 18.0 - (0 x 7.6) = 18.0. Is that correct?

So with no knock encountered, with the figures I’m seeing in the tables at 4900rpm at WOT, the most timing the car could see is 18.0. Is that correct?

I’m trying to get a firm grasp on how the timing is calculated.

Thank you.
KTuner
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Joined: Mon Jul 22, 2013 8:13 pm

Re: Total Timing Advance Question

Post by KTuner »

You have a pretty good grasp for the overall timing value derived from those tables, just don't forget there are other ignition adjustments applied like ECT and IAT ignition adjustments that may also affect the final output in the end.
shawd
Posts: 4
Joined: Sun Feb 19, 2023 12:36 am

Re: Total Timing Advance Question

Post by shawd »

Thank you for the prompt response. In looking at the base factory configuration as well as tune 3, I see that the IAT Ignition values are broken down into low load and high load.

I also notice in the base factory configuration and tune 3 that the box "Apply IAT Correction to Overall Timing" is not checked. As a result, I understand these IAT values are not being factored into the timing calculations with either of those tunes.

With regards to the ECT corrections, I'm not finding much about this in the help documentation but I think I understand how they work. I see four tables:
ECT Ignition Low
ECT Ignition High
ECT Retard Ignition Low
ECT Retard Ignition High

Each of those four tables show the ECT value and a corresponding correction value.

It looks like at low temps we'd add the corrections values for an advance in timing. I see the ECT Ignition tables in these tunes stop adding any advance at 158 degrees. So at 158 it's considered warm enough that no advance is added at low or high load.

For the ECT Retard tables I see at low loads regardless of temp the factory base configuration and tune 3 aren't making any timing corrections. At high load with warmer temps I see 0 timing taken out at 185, but 2 degrees are taken out at 203 going up to as many as 7 degrees of timing are taken out at 248 degrees.

So if the car is up to operating temp (I believe the thermostats are 167-172) and staying below 203 degrees, the ECT tables would not invoke any timing corrections at least for what I'm seeing defined in the Factory Base Configuration tune as well as Tune 3 (PCDs or HFPCs).

If you could confirm my understanding that would be great.

To finalize the timing calculations in this thread assuming the base configuration or tune 3 values (since they are the same in the timing tables) and that the car is at an operating temperature of let's say 180 degrees, the IAT and ECT have no corrections applied. Timing would be calculated based on:
19.2 initial timing
+ (-1.2) knock limitation
----------------------------
= 18.0 timing
- (7.6 knock retard x real time knock control value)
-----------------------------
= final timing

So with no knock at all (0 knock control) the most timing advance we'd see for this engine on the stock configuration or tune 3 would be 18.0 degrees. Any knock control value would start retarding the timing degrees based on the knock control value times the 7.6 knock retard setting. Does that sound correct?

Thank you for all the assistance.
KTuner
Site Admin
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Joined: Mon Jul 22, 2013 8:13 pm

Re: Total Timing Advance Question

Post by KTuner »

You'll actually notice that checkbox is not available as an option on your platform, so shouldn't be taken into account at all.
shawd
Posts: 4
Joined: Sun Feb 19, 2023 12:36 am

Re: Total Timing Advance Question

Post by shawd »

Thank you. I see the IAT checkbox is grayed out.

Do my other calculations sound correct in that with the data I provided the maximum timing advance the base configuration (or tune 3) should see at 4900rpm at WOT at ECT at 180 (no corrections) is 18.0? That assumes 0 knock control value. I want to make sure my understanding is correct so that I can work from there.
KTuner
Site Admin
Posts: 3745
Joined: Mon Jul 22, 2013 8:13 pm

Re: Total Timing Advance Question

Post by KTuner »

Luckily you have datalogging so you can properly verify any results with your own adjustments. As I previously stated you seem to have a decent understanding of what's described in the help. You can read that again if you need further clarification.
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