So I've been tuning various things such as fueling, transmission parameters, etc., but when it comes to spark advance, I have no idea what to do. I'll have access to a dyno this Friday, which I plan to do a baseline pull, do some spark tuning (fuel tuning will have already been done on the street; I'm almost done tweaking), and do some dyno drag racing for a somewhat accurate estimate for the track in the spring. I've got the dyno for an hour.
From what I've read around is that you advance the spark timing until knock and/or the power curve begins to drop and then turn it down a bit in those areas. But how should I go about doing this? Just add a certain value to the entire table and see what happens, locate areas where knock and/or power reduction occurs and back off the timing there and continue adding in the other areas and repeat the process? Or do I add values to specific locations on the table to start with..
This is what the stock spark advance tables look like on my LD9 with the MP45 tune:
My other question is why are they jaggy? Timing drops at certain RPMs and then is right back up higher at the next row of RPMs. Should this be smoothed as the first step or should I, as above, add a certain (what number) value to the entire table?
And there are two tables, the Main Spark and the Main Spark (PE), both with nearly the same axes. Should I stick to Main Spark (PE) tuning while on the dyno? (Since my regular driving seems fine, all I want to ensure right now is when wide open it's got decent power)
2001 Olds Alero (LD9)
650 whp / 543 ft-lb
@turboalero
So I just smoothed out the graph, interpolated the dips with the surrounding numbers, per my friend's suggestion. I will flash this after the baseline (jaggy) dyno pull and see what happens and tweak from there I guess...
2001 Olds Alero (LD9)
650 whp / 543 ft-lb
@turboalero
Smoothing is a good idea. I wonder whats up with all those mountains and valleys in the stock HO PE map? It doesn't seem like it would be very smooth to drive, no pun intended.
Dyno time seems to be the best way to get spark maps tuned. Some people think that you can advance until it knocks and than back off a couple degrees, but that just seems dangerous, and ultimately you don't know if there was really an improvement.
Good luck and make sure you post up the dyno results and how the final timing maps look.
A friend who tends to know a lot about GM vehicles said the dips are there to slow the revs, reduce power. When I showed the jaggy timing graph to my dyno shop they were like o_O.
I flashed the interpolated graph, the car feels a lot better, quicker revs, more power, zero knock.
A professional tuner for GM at their proving grounds who has years of experience with spark tuning is going to be helping me tune this on the street and on the dyno this week. He said the tune looks quite conservative as is.
2001 Olds Alero (LD9)
650 whp / 543 ft-lb
@turboalero
altering spark tables will change your AFR
please keep this in mind when tuning.
Mhmm, I'm off to do some fuel tuning right now but my AFRs didn't change much at all..
2001 Olds Alero (LD9)
650 whp / 543 ft-lb
@turboalero
DaFlyinSkwir(LS61) /PJ/ OEM+ wrote:altering spark tables will change your AFR
please keep this in mind when tuning.
What is the general rule for this - more advance leads to leaner AFR's right? Because the charge starts burning earlier and supposedly more completely? Teach me
Quote:
What is the general rule for this - more advance leads to leaner AFR's right? Because the charge starts burning earlier and supposedly more completely?
Other way 'round. Early burn = more complete burn at O2 sensor = less free O2 to register on meter. Less O2 = rich reading. On the opposite side, too little spark advance = artificially lean readings.
Spark and fuel are twin sisters. Can't play with one without the other needing a little attention. The "best" way to tune spark is to watch O2 readings (or a full 4 gas analysis), acceleration times, coolant temp, exhaust temp, and oil temp. Each one has a way of telling you something about the current spark advance compared to what the engine wants. Remember that you're not making the rules... the engine is. All you're doing is trying to listen to what the engine wants and set the tune accordingly. If you're running spark up to the point where the knock sensor trips, or worse yet, the point where you can hear pinging, the engine is literally screaming for help.
-->Slow
Anyone else have any idea why the stock graphs were jaggy?
2001 Olds Alero (LD9)
650 whp / 543 ft-lb
@turboalero
[ion wrote: C2]Anyone else have any idea why the stock graphs were jaggy?
Because they thought nobody would ever notice?? hehe
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[ion wrote: C2]Anyone else have any idea why the stock graphs were jaggy?
It's a good question - every table I've seen in HPT - fueling, spark, cam timing, there all jagged and choppy. The cam tables for my GXP would make ya wonder how it can even run smoothly. all i can guess is that there is more happening behind the scenes than the ECU switching from one cell to another. Some of the cam phase switches are 10* or more on the GXP from one load cell to another...
Remember the OE priority list for tuning:
1) Emissions compliance
2) Warranty protection
3) Fuel economy
4) Performance
5) Customer satisfaction
More often than not, the "unexplainable" parts of the tune are due to the first 3 priorities. I like the trans theory. I've seen similar things in other cals.
-->Slow
Seems so. With it smoothed out in the auto calibration you have to up the shift pressure and lower the shift times or else it tends to hit the limiter between shifts. My knowledgeable in all-GM friend said it was likely for VNH. Harder and faster shifting contributes to the vibration/harshness factor. The dips are there to slow down the revs a bit; GM expecting most people to not notice or care thinking most would be slapping this on not intending to get too serious racing it.
2001 Olds Alero (LD9)
650 whp / 543 ft-lb
@turboalero
So my tuner was a no-show last night and can't make it to the dyno appointment.
Need some cliffs on spark tuning. I set up my histograms to record KR in each cell of both spark tables, and set up my filters as they should be. Do I basically just add an arbitrary number to all the cells and then log knock, reduce the advance in each cell that has knock by whatever amount the KR reports (plus 1 or 2 more back) and then add more timing to all the others and repeat?
Meh.
2001 Olds Alero (LD9)
650 whp / 543 ft-lb
@turboalero
[ion wrote: C2]So my tuner was a no-show last night and can't make it to the dyno appointment.
Need some cliffs on spark tuning. I set up my histograms to record KR in each cell of both spark tables, and set up my filters as they should be. Do I basically just add an arbitrary number to all the cells and then log knock, reduce the advance in each cell that has knock by whatever amount the KR reports (plus 1 or 2 more back) and then add more timing to all the others and repeat?
Meh.
I wouldn't add an aribrary number (like one or two for example) because it will skew the high RPM/high MAP values. I'd multiply the all tables by like 1.05 (same as adding 5% ), and go datalog. You can add more if you are brave, but 5% is 1* in a 20* cell or 2* in a 40* cell. As your tune evolves and you begin to tune cells individually where you see KR, remember to smooth with each iteration, or you'll end up with a map similar to the first one you posted.
If you street tune the spark, will you still hit the dyno? it will be interesting to see any discrepancies...
I'm just going to tune on the dyno today at 5PM, I don't feel like streeting it right now. Hoping my tuner friend calls me back, still no answer.. he's awesome at spark.
2001 Olds Alero (LD9)
650 whp / 543 ft-lb
@turboalero
slowolej wrote:Quote:
What is the general rule for this - more advance leads to leaner AFR's right? Because the charge starts burning earlier and supposedly more completely?
Other way 'round. Early burn = more complete burn at O2 sensor = less free O2 to register on meter. Less O2 = rich reading. On the opposite side, too little spark advance = artificially lean readings.
Spark and fuel are twin sisters. Can't play with one without the other needing a little attention. The "best" way to tune spark is to watch O2 readings (or a full 4 gas analysis), acceleration times, coolant temp, exhaust temp, and oil temp. Each one has a way of telling you something about the current spark advance compared to what the engine wants. Remember that you're not making the rules... the engine is. All you're doing is trying to listen to what the engine wants and set the tune accordingly. If you're running spark up to the point where the knock sensor trips, or worse yet, the point where you can hear pinging, the engine is literally screaming for help.
-->Slow
Incorrect.
More timing advance(and assuming a more complete burn) will result in leaner readings. Less timing advance will result in richer readings.
Remember, this is air:fuel ratio. If you burn more fuel there's going to be more air.
Well a more complete burn means more of both combustible gases are burned, no? So it wouldn't make it leaner or richer. Why would "a more complete burn" affect the burning of only oxygen or fuel? (I don't know, curious)
2001 Olds Alero (LD9)
650 whp / 543 ft-lb
@turboalero
when you used the interpolate function, did you use it on the whole table or just a few cells? i never used it only smooth so i dont know how well it would work. i tried it on my table to see what it would do and it made it a flat slope so it looks like linear interpolation.. which doesnt seem to be very precise, as it changed some values by over 5, and in this case it was the spark table so it was at least 5* O.O
my spark tables are a nice curve, do you think its better to have a good curve or a straight linear line?
12.33 @ 111.67 mph [Oct 2009]
Dyno'd on 08/02/09 - Mustang Dyno:
327.6 WHP 333.6 WTQ [10.1 AFR]
ion C2 wrote:Well a more complete burn means more of both combustible gases are burned, no? So it wouldn't make it leaner or richer. Why would "a more complete burn" affect the burning of only oxygen or fuel? (I don't know, curious)
You're right, except that fuel is not a gas, nor is it measured directly in determining AFR. In closed loop, you wont notice a small change in timing. Its under WOT/PE mode where it will make a difference. There is a set amount of fuel going in at a given TPS/RPM cell, and changing the timing in that cell will affect the AFR measured at a WBO2. I just can't wrap my head around which way it will affect it.
People always say more fuel and more timing = more power to an extent, so that would imply more timing is making the system leaner. However if you're burning more completely, there will be less oxygen and this would give a rich reading on the WBO2...
oldskool wrote:ion C2 wrote:Well a more complete burn means more of both combustible gases are burned, no? So it wouldn't make it leaner or richer. Why would "a more complete burn" affect the burning of only oxygen or fuel? (I don't know, curious)
You're right, except that fuel is not a gas, nor is it measured directly in determining AFR. In closed loop, you wont notice a small change in timing. Its under WOT/PE mode where it will make a difference. There is a set amount of fuel going in at a given TPS/RPM cell, and changing the timing in that cell will affect the AFR measured at a WBO2. I just can't wrap my head around which way it will affect it.
People always say more fuel and more timing = more power to an extent, so that would imply more timing is making the system leaner. However if you're burning more completely, there will be less oxygen and this would give a rich reading on the WBO2...
not sure im following what you are saying, so i may be wrong in this next statement. it sounds like you are assuming the fuel isnt burned along with the oxygen that is getting burned from having a more complete burn, if that makes sense..
12.33 @ 111.67 mph [Oct 2009]
Dyno'd on 08/02/09 - Mustang Dyno:
327.6 WHP 333.6 WTQ [10.1 AFR]
evilmonkitar wrote:when you used the interpolate function, did you use it on the whole table or just a few cells? i never used it only smooth so i dont know how well it would work. i tried it on my table to see what it would do and it made it a flat slope so it looks like linear interpolation.. which doesnt seem to be very precise, as it changed some values by over 5, and in this case it was the spark table so it was at least 5* O.O
my spark tables are a nice curve, do you think its better to have a good curve or a straight linear line?
I smoothed between each row of high points. I wouldn't change the overall shape of the advance curve too much, there is some logic into what each number is.
2001 Olds Alero (LD9)
650 whp / 543 ft-lb
@turboalero
evilmonkitar wrote:oldskool wrote:ion C2 wrote:Well a more complete burn means more of both combustible gases are burned, no? So it wouldn't make it leaner or richer. Why would "a more complete burn" affect the burning of only oxygen or fuel? (I don't know, curious)
You're right, except that fuel is not a gas, nor is it measured directly in determining AFR. In closed loop, you wont notice a small change in timing. Its under WOT/PE mode where it will make a difference. There is a set amount of fuel going in at a given TPS/RPM cell, and changing the timing in that cell will affect the AFR measured at a WBO2. I just can't wrap my head around which way it will affect it.
People always say more fuel and more timing = more power to an extent, so that would imply more timing is making the system leaner. However if you're burning more completely, there will be less oxygen and this would give a rich reading on the WBO2...
not sure im following what you are saying, so i may be wrong in this next statement. it sounds like you are assuming the fuel isnt burned along with the oxygen that is getting burned from having a more complete burn, if that makes sense..
No I'm saying the amount of fuel spent is not measured directly - the remaining oxygen is measured and the AFR is calculated from that. I'm trying to rationalize definitively how spark advance affects AFR when advanced/retarded and all else is equal...
