ECU pulling timing above 1750 mBar?

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Bigfieroman
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Joined: Wed Mar 11, 2020 11:31 pm

ECU pulling timing above 1750 mBar?

Post by Bigfieroman »

:?: My ECU pulls about 0.5-1 degree of timing from what is specified in the corresponding High Cam Ignition Table cell above 1750 mBar. On a WOT pull, the timing matches my table EXACTLY through 1750, but is a little short at 1875 and 2000 mBar.

The motor is not knocking, my Knock Retard table is completely zeroed out, so KR should not be the cause. My IAT is about 86 degrees, below the threshold at which the IAT compensation table should be pulling spark. Same thing with ECT compensation. Anyone have a clue why it could be pulling timing?
Bigfieroman
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Joined: Wed Mar 11, 2020 11:31 pm

Re: ECU pulling timing above 1750 mBar?

Post by Bigfieroman »

I found that my Knock Limit tables were not set properly.  This could be the cause, I will test it tomorrow morning and report back.
KTuner
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Re: ECU pulling timing above 1750 mBar?

Post by KTuner »

The ECU does many things in the background, but that could be it.
Bigfieroman
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Joined: Wed Mar 11, 2020 11:31 pm

Re: ECU pulling timing above 1750 mBar?

Post by Bigfieroman »

Setting the Knock Limit table high (60 degrees) seemed to help in the 1875mBar range, but it still drops a degree around 1900 mBar and up. I tried everything; KL tables set high with KR set to 0, both set high, I removed my IAT compensation (even though temps were too low to trigger it), and in every datalog it drops 1 degree from commanded at ~1900 and up. KTuner does not export Knock Retard, but watching it in the log in KTuner, the value remains 0 through all of the runs.  I can always just add a degree at 2000 mBar, but I don't want whatever is causing that degree to be AWOL to resolve in some situation and then I have a more aggressive tune than I desire without knowing it.

So, to summarize, I have any high-temp ECT compensation set to 0, IAT compensation set to 0, Knock Retard tables at 0, Knock Limit tables set to 60, Knock Sensitivity unchanged from the Base tune, 0 observed knock retard, and I have exactly the timing commanded in my Ignition tables from idle to 1900, then it drops ~1 degree to redline.
KTuner
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Re: ECU pulling timing above 1750 mBar?

Post by KTuner »

Luckily you have the ability to compensate by adding a degree into the ignition maps if you wish to do so. If it's 100% repeatable that's probably the best way to go.
Bigfieroman
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Re: ECU pulling timing above 1750 mBar?

Post by Bigfieroman »

I absolutely can do that, but as I mentioned, my fear is that this missing degree of timing will come back in at some point because I do not understand why it is being pulled.

I have been through the program and the maps numerous times, and I can find no other setting that should be affecting my timing. Do you know of anything else that I should check?
KTuner
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Re: ECU pulling timing above 1750 mBar?

Post by KTuner »

Then you can always leave it out for safety. Again, the ECU does many things in the background.
Bigfieroman
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Joined: Wed Mar 11, 2020 11:31 pm

Re: ECU pulling timing above 1750 mBar?

Post by Bigfieroman »

Clear timing drop right at 1925 mBar. It is exactly one degree below commanded. Below is a screenshot of the discontinuity.

https://drive.google.com/file/d/1Z2VwUb ... sp=sharing
Bigfieroman
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Re: ECU pulling timing above 1750 mBar?

Post by Bigfieroman »

KTuner wrote:Then you can always leave it out for safety. Again, the ECU does many things in the background.
Ok, I understand that too, BUT the ECU or your program is doing something that I don't want to do, and there is no apparent cause. I find it difficult to believe Honda built in an automatic reduction of 1 degree of timing @ 1925 mBar considering the car was never FI from the factory. Do you know why it is dropping 1 degree of timing at 1925 mBar?
KTuner
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Re: ECU pulling timing above 1750 mBar?

Post by KTuner »

There are thousands of tables in the ECU. It goes without saying that you don't have access to all of them. We won't be making any adjustments to background tables beyond what's already been done.
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