Is this normal? I would think so, but what does the ECM use for spark advance while in a WOT condition? The table I see in TC is "spark advance in WOT vs RPM", but only has 5 rpm levels and the advance numbers are less than 10. I recorded some data during a run down the 1/4 mile, and am wondering about this advance stuff. Here are some numbers:

speed=50.1 mph
engine=3400rpm
filtered load variable=233 LV8
spark advance relative to TDC=34.8 deg
knock retard=12.7 deg
spark control counts= 72

All numbers taken at the same point in time at WOT. Is my "effective advance"= to 22.1?
I am using most all values from the ARAP bin, except for the main spark advance vs RPM table.

Thanks for any support.


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Best ET 14.413 @95.57 without
pulling valve covers or manifolds.
Also with stock 2.77 rear end!!!

 

If your hitting the K/S that is a bad thing, since the ecm will make every effort to dtop the *Knock*, meaning it adds more then enough retard to stop it.

Sounds like your looking at a Spark adder for PE/WOT.

Remember the less timing you use the better (per given performance level). The old nonsesne about running the max possible is exactly that, nonsense). tune to what the engine wants, not what you feel it needs.

 

The PE (WOT) Spark is summed with the values in the main spark advance table to give the commanded advance when in Power Enrichment.

You're correctly interpreting the effective commanded advance.

The knock counter increments each time the sensor detects a knock event (not 100% sure but that's the basic idea). The range of values is 0-255. Once it reaches 255 it starts over at zero. The value of 72 means nothing by itself. You have to see how the values change over time. For instance, a value of 72 in the next data frame means no knock was detected, 110 means it detected a lot of knock, 73 equals one knock event.

The ECM will retard the timing if the knock counter is incrementing. The rate at which timing is pulled out depends on the knock sensor attack rate in the PROM. The maximum timing it can pull out is also dictated by data in the PROM. The knock recovery rate in the PROM defines how quickly the timing will be added back. Stock values are very conservative. Many seconds are required to remove the knock retard even if no knock events reoccur.

My latest PROM is ARAP based. The PE spark is zeroed out and I also removed additional timing from the 2800-4800 RPM range of the 160-208 LV8 columns in the main spark advance table. The knock sensor is happier and the car is quicker than ever based on the stopwatch FWIW.

 

Good info, fellas, thanks. My knock counts never got above 82 during the run. It varied quite a bit until I got to 3rd gear, and then the load settled down at 230LV8 for several frames. The knock counts stayed around 75, knock retard around 12deg, and SA rel to TDC was at 33-34. I understand what this sensor does, but I didn't realize that if the counter was not incrementing, IE staying the same, there was NO new knock. But when does the counter reset? I never got to 255.

Also, what values does the ECM use when you are over LV8 values of 208? I was above that in WOT. Same question when you are above 4800rpm? I did put more timing in those areas you mentioned above, but I didn't think it was alot. I left the "rate" tables as is per the ARAP bin. When you say you 0'out the PE adder table, would that be the little table that has only 5 rpm levels of advance?

This is important info, since I don't want to inflict pain on my lovely L98!!!

 

The counter resets on startup (I think, never bothered to check). Don't get hung up on the specific value; look at the change in value over time.

It will use the data in the last column (LV8=208) when at or above that load value. Similarly, the values in the 4800 rpm row will be used when at or above that engine speed.

Back it out. All it is doing is causing your knock sensor to pull out 12 degs of timing.

[QUOTE]When you say you 0'out the PE adder table, would that be the little table that has only 5 rpm levels of advance?[QUOTE}

That's correct. You won't hurt your engine as long as you wisely use the most effective knock control devices, your ears and right foot.

 

Thanks Mark, that really clears things up for me. I just like to learn as much as I can about how TC softare works. The help files don't really say much. I did take some timing out last night, mostly just at the 192 and 208 load levels, from 1600RPM on up. I also set the WOT advance values to 1.1 from 1200 to 4800. There was one value in there at 2000 that had 9.1deg of advance!!! Kind of odd don't you think? Now I just need to do some WOT data runs and see what is happening. Don't need the 1/4 mile strip for that!!

As far as the knock sensor, the spark control counts went to 0 (as well the retard) once I backed off the throttle at the end of the 1/4 mile. I am sure this is normal.