How to advance timing?

[03_Z06_Blue]

Well, I think that I am ready to try to advance the timing? My PE AFR looks good. I shut my COT down. My LTFTs are a bit negative. I am not getting retard. I'd like to advance my timing.
Looks like my Main Spark vs. Airflow vs. RPM table tops out at 22 degrees on the high octane table and 16 degrees on the low octane table. Hits those numbers about 4000 rpm and at .8 g/cyl or higher on my LS6. Sounds a little low.
What is the best way to advance the timing? Should I raise both tables in the full throttle area???
Please share your experience and anything to watch out for. I would like to adjust the timing up a bit, and then check that it moved up on the scanner. Is this how it is done?
Paul

[jimmyblue]

You can probably stand a lot more advance, across the board.

The way I tweaked mine is, I first started with about +6 onto
the stock HO table (this being what I had seen from the Predator
I used before).

Drive around and try to put a good mix of throttle positions
down. Review the spark retard histogram (you would want
to have any TM turned off here or it will obscure the KR-
based spark diddling). Also probably want your KR attack
rate reduced and decay rate increased so the KR is not so
prone to overshoot and persist; that also obscures the true
knock situation.

Anyway, where you see KR pull back a degree and where you
don't, add 2 degrees, lather, rinse, repeat. After a few sessions
of this sort you should have a histogram that's all 0-1 degrees
of max spark retard.

Then subtract 2 degrees across the board and you'll have a
good, safe (for the present mods) tune that is also near MBT.

Then copy HO to LO table and subtract 4 degrees from the LO
just so you have some sort of safety net for bad gas or bad
weather.

[12secSS]

I would like to know what other variables are in play when the VCM selects a certain value for timing (as seen in the histogram). Adjusting just the advance IMHO is not correcting the full picture. You have Base Spark into play, then other features also bump up timing, etc ...

[jimmyblue]

Well, you have the mian table(RPM, CylAir) and then there
are the adders (IAT, ECT, EGR) and the knock learn factor
that interpolates you between high and low octane tables.
That's also a thing that you would want to do is make sure
that is reset for each repeat, or else run with LO=HO copied.
Dunno whether you can force that reset through the scanner
the way you can, fuel trims.

For the most part if you have cold air induction and sane
fan temps you won't be seeing the IAT and ECT adders
mess you around, but they will if given the chance. It only
takes IATs of 86F to start pulling spark out, while ECT only
pulls spark out before warmed up. Though if you have hot
weather ping on a car with proper fueling you may want to
rethink this; I put a roll-off of a few degrees at engine temps
above normal after an unpleasant July road trip.

[gtodoug]

Great info Jimmyblue. I have a question as well. On a stock vehicle I understand where and how to add the timing. I've been adding it slowly (2* at a time) and coming along with some good results. However, you mentioned the KR attack rate and decay rates.

I looked in engine>spark retard and see the "Knock fast attack gain vs." and then it has a couple of tables below it like ect, baro, base retard vs rpm, recovery rate vs rpm. To reduce the attack rate which table is that. And the same for the decay rate, would you be refering to the recovery rate vs rpm table?

Once I'm on the right table what is a good value to be decreasing/increasing this by?

Thanks for helping a newb!!

Dougie

[03_Z06_Blue]

Wow! I appreciate the great response. That is how we all learn.
Anyway, I followed the advice from Jimmy Blue pretty closely.

First of all, I had earlier cut down my retard, and adjusted it to bring it back quicker. In Engine/Spark Retard folder, I went into "Max KR vs. RPM in PE" and changed the limit from 10 down to 5 allowed. On the same screen, I opened "Base Retard vs. RPM" and pretty much cut the speed of KR in half. While still in Engine/Spark Retard folder, I opened "Recovery Rate vs. RPM" and increased the "come back" rate substantially. Up to 2000 rpm, I doubled the recovery rate. 2400 to 3600, I multiplied through by 5. 4000+ I multiplied by 4. You do what you are comfortable in doing. I did lots of full throttle scanning earlier to get it where I felt safe, and yet minimized the KR.

Anyway, after reading Jimmy's input, I basically in 3 steps, added 5 degrees to the Hi table (and the LO), and cut back the sensitive to KR areas (that I detected during lots of scanning) by subtracting 2.

One thing that I found out, that isn't surprising, is that when you look good (no KR) in 3rd gear; you still get plenty in 4th. The problem is that my 3rd gear gets me up to about 105 MPH, so in fourth BE CAREFUL. I think it is close now, so I will rent some dyno time and see if the 4th gear pull is NOK free or just a tad here and there.

I have been working my fuel/air PE ratio to get it somewhat flat. Just a little hump in the max torque area; with the curve close to 13/1.

Lots of fun, but please be careful while scanning.

Paul

[smokinHawk]

are there some areas of the chart you dont want to advace. im not exactly sure when full throttle hits the chart or where /what point ot start mussing with the full throttle timing vrs part throttle timing.

[gtodoug]

Good question. I can tell you if you only want to mess with WOT throttle timing then you should do some scanning. If you set up one of your PID's in the chart display as dyn cyl air you'll be able to monitor at what point to and where to adjust your timing curve.

It's different for every car. My car reads from .80-.88 at WOT. I used to set my timing as a "blanket timing curve". By that I mean setting it at one number for every rpm. In my experience my car likes a little more timing coming up on pk tq and gradually reducing it as I reach peak tq and feeding a little timig up on the top of the rpms. This gives me a "u" shape in my "3D" graph and is very easy to see in the line graph.

I hope what I said makes sense. I'm still a newb so might help if someone else chimes in to help. I'm only speaking of my experiences.

Dougie

[devildog9999]

Good question. I can tell you if you only want to mess with WOT throttle timing then you should do some scanning. If you set up one of your PID's in the chart display as dyn cyl air you'll be able to monitor at what point to and where to adjust your timing curve.

It's different for every car. My car reads from .80-.88 at WOT. I used to set my timing as a "blanket timing curve". By that I mean setting it at one number for every rpm. In my experience my car likes a little more timing coming up on pk tq and gradually reducing it as I reach peak tq and feeding a little timig up on the top of the rpms. This gives me a "u" shape in my "3D" graph and is very easy to see in the line graph.

I hope what I said makes sense. I'm still a newb so might help if someone else chimes in to help. I'm only speaking of my experiences.

Dougie

Any chance you could post a screen shot of your tables for comaprision? I would really like to see what you have done. Reading this thread enduced an epiphany for me, so please post it or email is you can! Thanks,Gary

[MustangEater82]

semi dumb question, but woudl like to clarify...

I shoudl have lno problems playing with advancing the timing even if I have no wideband.


with COT and TM gone I should be able to mess with the tuming until I see knock? Correct. Then adjust the amount of timing according to knock?

[jimmyblue]

Knock is an indication tht you've gone too far.
MBT timing is maybe 2-3 degrees less than what
makes you ping.

But if you go and get the whole map trued up to
the ping limit, then you can end the exercise
by taking out 3 degrees across the board and be
pretty sure you have put it onto peak, with a
little ping margin to boot.

[Runn WS7]

Do you guys tune the whole sparktable or only wot?

[van383]

looking at all these table explained im still unsure what was the purpose or issue trying to resolve moving these tables the way youu did? please explain someone im trying to see if i nned to do the same.. looking at my logs files..

[van383]

looking at all these table explained im still unsure what was the purpose or issue trying to resolve moving these tables the way youu did? please explain someone im trying to see if i nned to do the same.. looking at my logs files..

and explain what disabling your cot does and why, not sure of this?