Cell 18 at WOT and 47 degrees of spark advance on launch.
10-30-2008, 08:35 PM
#1
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Cell 18 at WOT and 47 degrees of spark advance on launch.
Two questions.
1. Is it normal for the engine to be in cell 18 at WOT thewhole time during a 1/4 mile run?
2. When reving the motor in preparation to dump the clutch, I am hitting 45-47 degrees of spark advance. As soon as the clutch is dumped, the advance quickly drops (if the RPM's drop some) to what appears to be more desirable. Is this a problem or should I get the timing lower when dumping the clutch?
1. Is it normal for the engine to be in cell 18 at WOT thewhole time during a 1/4 mile run?
2. When reving the motor in preparation to dump the clutch, I am hitting 45-47 degrees of spark advance. As soon as the clutch is dumped, the advance quickly drops (if the RPM's drop some) to what appears to be more desirable. Is this a problem or should I get the timing lower when dumping the clutch?
10-31-2008, 05:24 AM
#2
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The PCM will sometimes default to Cell 18 in power enrichment mode, particularly if the PCM is pulling fuel with the BLM's in Cell 15.
Spark advance is set from a table, with RPM and MAP as the axes. When the engine is free revving, RPM is high (as RPM goes up, advance goes up), and MAP is low, indicating the engine is not under load. So its normal to see more advance when free revving than you will when the engine is under load (high MAP).
Spark advance is set from a table, with RPM and MAP as the axes. When the engine is free revving, RPM is high (as RPM goes up, advance goes up), and MAP is low, indicating the engine is not under load. So its normal to see more advance when free revving than you will when the engine is under load (high MAP).
10-31-2008, 06:31 AM
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Last time you were complaining about bogging at the launch I told you this after you send me a log.
"Take some timing out of it on the launch area, you're sitting there on 48 degrees of timing in the staging beams. No wonder it bogs, you dump 20+ degress of timing as soon as you roll into it. Need to take timing out of the wot cells too 40 degrees of timing at wot is a little much alot of lt1's like about 37, also what you see is not what you get with wot timing, the pcm adds timing in as rpm's increase."
Basicly you dont want a big bunch of spark retard right on tip in or it will fall on its face generally speaking. Cell 18 isnt unusual, dont worry about what cell its in at wot because it doesnt matter at all, even if the cell is out of whack and you have blm locker its going to run the same every time.
"Take some timing out of it on the launch area, you're sitting there on 48 degrees of timing in the staging beams. No wonder it bogs, you dump 20+ degress of timing as soon as you roll into it. Need to take timing out of the wot cells too 40 degrees of timing at wot is a little much alot of lt1's like about 37, also what you see is not what you get with wot timing, the pcm adds timing in as rpm's increase."
Basicly you dont want a big bunch of spark retard right on tip in or it will fall on its face generally speaking. Cell 18 isnt unusual, dont worry about what cell its in at wot because it doesnt matter at all, even if the cell is out of whack and you have blm locker its going to run the same every time.
10-31-2008, 06:56 AM
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Not doubting you at all. Just wanting to completely understand every respect possible regarding the cell 18 and the timing point that you made and what exactly to do about it. I am tweaking my tune right now for new gears and injectors.
What would you change to correct the timing advance at low MAP on launch.
What would you change to correct the timing advance at low MAP on launch.
10-31-2008, 08:58 AM
#6
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You need to take the timing out where its showing 47 degrees. and in the few cells around it rpm map wise. What you want to do is blend it so it matches the timing at wot when you dump the clutch and then the engine will take off much better. Its at very high vacuum and much higher rpm than cruise, it will have no ill effects on drivability or mileage.
Don't need to do anything about it being in cell 18 or any cell its in for that matter. Cells are just arbitrarily defined boundaries for long term fuel trims and behaviors. The only one thats really special at all is 16 and it is not very special in any case, it merely uses a different timing table and iac scheme. What you're doing with various cells is making an integer to store fuel trims for very similar rpm/load conditions so the computer has a better guess on fuel requirements and makes it more effective at controlling smog and giving you better mileage.
As long as your blms show 128 at wot theres no problem.
Don't need to do anything about it being in cell 18 or any cell its in for that matter. Cells are just arbitrarily defined boundaries for long term fuel trims and behaviors. The only one thats really special at all is 16 and it is not very special in any case, it merely uses a different timing table and iac scheme. What you're doing with various cells is making an integer to store fuel trims for very similar rpm/load conditions so the computer has a better guess on fuel requirements and makes it more effective at controlling smog and giving you better mileage.
As long as your blms show 128 at wot theres no problem.
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