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Old 01-05-2008, 11:53 PM   #1
kingtut12
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Default My understanding of the timing calculations

This has always been confusing to me and I just want to get the more seasoned guru's seal of approval or not. I am still green with tuning myself.

In figuring out the total timing - I understand it to be:

an example only -

RPM=5200
Load=1.94

FBKC=0
FLKC=(-2.5)
IAM=12
KCadv=6.0
Prim. Ign=17.0

My thinking and previous examples tells me to use the formula:

KC = (IAM % of 100 x KC adv) + FBKC +FLKC
then, KC + Primary timing value = Total Timing Calculated

In working the math it would be, i think, :

KC = (75% x 6) + 0 -2.5
KC = 4.5 - 2.5
KC = 2

so, 2+17=19 total timing at 5200rpm at a 1.94 load

which means the car is healthy enough to advance timing 2 degrees to 19 at that load, right?

Before I ask any other questions regarding this example - do I properly understand the nature of Timing changes with what you see here?
Thx
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Old 01-06-2008, 12:44 AM   #2
Freon
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That would be 17 base + (6 x 12/16 IAM) - 2.5 feedback = 18.5 total degrees. The 0.5 discrepancy is rounding error with the ignition timing values you are logging. They are all precise to 360/1024 (~0.35) degrees, and your logger may be rounding them off on top of that. But that's not the point.

The problem here is that FLKC is kinda coarse. It might mean at load 1.75 running 23 (or whatever you have there) degrees it tends to knock. It might actually be able to run 20 at 1.94 load. The FLKC values cover a larger area of the timing map. There are maps that define the RPM and load ranges of the FLKC learned map, and they can be rearranged.

The IAM settling on 12/16 could mean you are overall running too much advance.

Try to catch knock with FBKC. It is clearer exactly at what RPM and load you are knocking. FLKC might show you the rough region where you've had knock.
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Old 01-06-2008, 02:39 AM   #3
williaty
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Quote:
Originally Posted by Freon View Post
Try to catch knock with FBKC. It is clearer exactly at what RPM and load you are knocking. FLKC might show you the rough region where you've had knock.
Actually, as long as you're willing to accept that you're going to miss some knock, it's pretty easy to catch _most_ of the knock happening in FLKC eval mode. The first thing you'll need to do is to make a spreadsheet table that mimics your FLKC table. Then print it out. Don't worry, you're not going to fill it in, you're just going to look at it. Now, look at the FLKC column in your log. You're looking for any place FLKC gets more negative (or less positive if your IAM!=1). Once you find a place where FLKC has gotten more negative, look at the line it happened in. Figure out which cell on the FLKC table you printed out the increase in negative FLKC happened in. Then look at the line in the log above that. If the previous line was in the same cell, it was knock. If it was in a different cell, then you just ignore it.

It sounds like a lot of work, but REALLY quickly you'll get a gut feeling for how it works and you'll fly through the log catching knock in both FLKC and FBKC.
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Old 01-06-2008, 09:01 AM   #4
Tea cups
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Quote:
Originally Posted by kingtut12 View Post
RPM=5200
Load=1.94

FBKC=0
FLKC=(-2.5)
IAM=12
KCadv=6.0
Prim. Ign=17.0

My thinking and previous examples tells me to use the formula:

KC = (IAM % of 100 x KC adv) + FBKC +FLKC
then, KC + Primary timing value = Total Timing Calculated

In working the math it would be, i think, :

KC = (75% x 6) + 0 -2.5
KC = 4.5 - 2.5
KC = 2

so, 2+17=19 total timing at 5200rpm at a 1.94 load
"Knock Correction Advance" in Enginuity's logger is the "timing advance max map value" ("ignition timing advance*" logged) with the IAM, feedback correction, and fine learning correction already applied, so you are appyling these corrections twice in your example which is wrong.

Total timing = 'Base Timing' map value + ((timing advance max map value * (IAM/16)) + feedback knock correction + fine learning knock correction) + other timing compensations.

Note: For the 32-bit ECU, replace IAM/16 with IAM. For 16-bit ECU, IAM/16 assumes you are logging the IAM raw value (0-16).

Other timing compensations include those for IAT, ECT, per cylinder, among others.

You should log IAM, feedback knock correction, and fine learning knock correction if you want to determine when knock occured. For your ECU, there is really little downside to logging all three (1 byte each). Keep in mind that the fine learning knock correction table is cleared each time the IAM changes. Also, logging the "Fine Learning Table Offset*" (new to latest logger defs), will allow you to see when you switch to a different cell and therefore know when there are changes being made to the table (and not just the learned value being applied).
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Old 01-06-2008, 11:28 AM   #5
kingtut12
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Quote:
Originally Posted by Tea cups View Post
"Knock Correction Advance" in Enginuity's logger is the "timing advance max map value" ("ignition timing advance*" logged) with the IAM, feedback correction, and fine learning correction already applied, so you are appyling these corrections twice in your example which is wrong.

Total timing = 'Base Timing' map value + ((timing advance max map value * (IAM/16)) + feedback knock correction + fine learning knock correction) + other timing compensations.
Okay - this makes sense. And as I said, it was only "made up" values as an example, not actual data from a log. I am just trying to get a solid grasp on the entire timing spectrum. I am waiting on my tactrix cable to arrive so i can post a log or two. I was tuned several months ago (enginuity) and all is well, but I am wanting to add a few parts along the way and want to tune my own car.

So, when the ECU advances or retards timing, does that new value replace primary ignition value or is it on a separate table/log that you must add or subtract back from the primary?

What happens if ecu is reset?

Sorry for the noob questionaire here, but i feel like I'm right on the verge of understanding.
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Old 01-06-2008, 12:00 PM   #6
rkramer
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Quote:
Originally Posted by kingtut12 View Post
What happens if ecu is reset?
all learned values are reset/zero'ed, and then the base timing and the advanced multipler (initial) take over to give you a default value. depending on your tune, some set the multiplier to the max (16), and let the car work its way down if it knocks, others prefer to set it lower and let the car learn its safe values from the other way.
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Old 01-06-2008, 01:45 PM   #7
mickeyd2005
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I have a spreadsheet that keeps track of FLKC.

http://forums.nasioc.com/forums/show....php?t=1412169

You can get FLKC without ever seeing FC. It happens sometimes. You can also get IAM to drop without ever seeing FLKC.
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Old 01-06-2008, 01:50 PM   #8
Tea cups
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Quote:
Originally Posted by kingtut12 View Post
And as I said, it was only "made up" values as an example, not actual data from a log. I am just trying to get a solid grasp on the entire timing spectrum.
Doesn't matter what the numbers were. You were applying the IAM, FBKC, FLKC to "Knock Correction Advance" which is incorrect as this value already has these corrections applied.

Quote:
So, when the ECU advances or retards timing, does that new value replace primary ignition value or is it on a separate table/log that you must add or subtract back from the primary?
If you are using the latest Enginuity logger definitions, total timing will be called "Ignition Total Timing" (the actual timing).

Quote:
What happens if ecu is reset?
FLKC table is cleared. The IAM is reset to the "advance multiplier (initial)" value and the IAM re-evaluated (Same thing happens at the beginning of the non-reset IAM re-evaluation session so you have to be careful about modifying the initial value).
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