Ignition Timing - Lets get technical

[Schmieder]

1996 Grand Prix SE 3100v6 Turbo at 7psi

Ignition timing is something I feel I could spend hours upon hours of tuning for perfection. I am in the beginning stages of tuning the ignition tables.

I am running 93 octane and plan to run nothing less then 91. There aren't to many spark tables in the HP Tuners repository to compare. I tried on for a 3400 turbo 10psi but the higher rpm was retarded so severly it had no power in boost.

So I have stock tables again and plan to advance 2 degrees at a time while correcting any tables that show knock. Also disabling torque management to prevent skewing the spark tables.

Using the PCM to log torque through the transmission I was able to roughly find the most power at idle. I basically set the parking brake and put the car in gear and commanded the spark with HP Scanner while watching the torque adjusting. I found the most power for idle was 22*. Figuring it would also be the most efficient.

Now, I did some research and found these values and would like the advice from the wise members of 60degreev6.com.

Crank 10-20* (15* in my setting)
Idle 15-32* (in my case 22*)
Cruise 35-40* (47* in extreme cases)
WOT w/ turbo 10-22*
Acceleration 8-45*
Over-Run 10-26*

Now, these figures aren't 60*v6 specific.

Any tips and tricks are welcomed and nothing is too technical, I can hang with the best when it comes to math and science.

Specifically if anyone knows the speed of the flame front in a 3x00 at 9.5:1 cr w/ 93 octane I can use that data to start a rough tune and go from there.

If anyone also has a complete map of areas like cruise, wot, over-run, ect. I made my own but it is flawed I'm sure. Mapping WOT is the easy one and I have that down good. But the rest is tricky and I just don't have enough log files yet.

Or even a well tuned ignition table for a 3x00 would be cool so I can compare my tuning down the road.

Lets see what you all got, lol

Thanks

[robertisaar]

Crank 10-20* (15* in my setting)
Idle 15-32* (in my case 22*)
Cruise 35-40* (47* in extreme cases)
WOT w/ turbo 10-22*
Acceleration 8-45*
Over-Run 10-26*

Now, these figures aren't 60*v6 specific.

damn straight they aren't 660 specific! the only time i've EVER seen near 50* commanded was looking at a 3800 spark table. those slugs need that kind of advance to get a full burn.

but it's safe to assume you have a decent table to start with, or even go through some of the latest small-port 3100 BINs from the download section here to see what differences GM made over the years.

and IMO, a better way of getting idle advance: lift the front end with the wheels not touching the ground, drop the tranny in 1st and see what MPH the engine will get to. more MPH = more power for the same amount of fuel. i wouldn't leave it in drive for extended times though since i think it would essentially be a 1 wheel burn-out without all of the weight.

[Schmieder]

damn straight they aren't 660 specific! the only time i've EVER seen near 50* commanded was looking at a 3800 spark table. those slugs need that kind of advance to get a full burn.

but it's safe to assume you have a decent table to start with, or even go through some of the latest small-port 3100 BINs from the download section here to see what differences GM made over the years.

and IMO, a better way of getting idle advance: lift the front end with the wheels not touching the ground, drop the tranny in 1st and see what MPH the engine will get to. more MPH = more power for the same amount of fuel. i wouldn't leave it in drive for extended times though since i think it would essentially be a 1 wheel burn-out without all of the weight.

Putting the car on jack stands is a great idea. See, this is the beauty of this webpage. I only did the in drive w/ E-Brake for a minute or so, not too long at all as I know it is stressing. But your idea rocks cause I can take my time to get it finer and the mph reading is more accurate imho.

Thanks Rob, I'm going to do that later today!

[robertisaar]

i'd wait until someone else says it won't destroy your differential first.

[Joseph Upson]

I intend to combine high compression with moderate boost pressures for combined high mpg and power results. The trend is slowly being recognized as doable successfully now that the benefits of modern technology are becoming more obvious (10.2:1 compression 3.6 DOHC and 87 octane rating).

I don't know that I would bother looking for more advance above a stock non boosted spark table being used with boost, given information that I've gathered in preparation for my own goals. After looking at aluminum head spark tables vs. iron head tables you begin to see the tremendous effect combustion chamber design has. You may also realize that much of the compression vs. boost rules originated with iron head small blocks and those limitations were generalized and applied to aluminum head V6s.

I believe the article below that I looked up today prior to comming across this thread will be very helpful for what you are trying to do.

http://www.popularhotrodding.com/tech/0311_phr_compression_ratio_tech/index.html

What I plan to do in an effort to iron out a good spark table is install a manual cruise control brake-interrupt defeat so that I can set cruise at certain rpm increments and slowly apply the brakes without cruise disengaging until I allow it. That will allow my datalog to see a near constant rpm as the cruise compensates for load all the way through the Kpa range, like a dyno would do holding rpm allowing exposure to the full load range. As long as you don't go over board you can avoid burning up the pads and rotors. 4 second brake loads should be enough to sweep from 35 Kpa to 100 without moving far from the set rpm/speed and get good readings for status along the way.

[pocket-rocket]

i'd wait until someone else says it won't destroy your differential first.

As long as both tires are turning in the same direction I don't think it would do anything to your diff. It would be more like it's just going down the road with virtually no load.

[robertisaar]

that's the thing: i'm not sure if when i did it if both tires spun, or just one did...

[pocket-rocket]

Initially one might and the other would start because of drag on the spiders, but I would think both would start right off the bat, unless you had brakes dragging.

Edit: Here you go, watch this video. It's an old vintage GM video on how a differential works and still applies to today's cars:

http://www.youtube.com/watch?v=yYAw79386WI

[Schmieder]

Well, I still won't run it on jacks for a long time, just enough to tune idle spark for maximum power.

Doing so will also give me the data I need to determine the speed of the flame front running 93 octane.

I should be able to tweak the rest of the timing values, but not much, just the right amount to bring it into efficient power.

Tell me guys, if I log only torque delivery to trans, rpm and spark degree I could get a more detailed log that I can review. Each WOT run I could adjust the timing ever so slightly to see how it reacts and adjust. Working eventually to a max power capable spark degree.

Do you guys have any tricks, advice tuning the spark for max power/efficiency w/o a dyno tune?

I know nothing beats a dyno but I'de like to do my best first even if it means going extreme. Then one day using a dyno to see how good I am and to tweak the rest.

[robertisaar]

i don't trust PCM torque calculations too much...

rely too much on the MAF being perfect.

[pocket-rocket]

Do you guys have any tricks, advice tuning the spark for max power/efficiency w/o a dyno tune?

Little by little and keep backups of your original and changes. Also I would find a spot of ground and take a baseline run to see what kind of speed you get from point A to point B, be it from a bridge to a sign, a specific tree to a driveway, or whatever.

[Schmieder]

i don't trust PCM torque calculations too much...

rely too much on the MAF being perfect.

And if the MAF is tuned right? Would you know the degree of error if the MAF was tuned perfect? It's cool if not, just curious.

EDIT: Hmm, what about torque calcs from the PCM when the MAF is disabled? I still get measurements with the MAF unplugged during VE Tuning. Would those calcs be more accurate?

Little by little and keep backups of your original and changes. Also I would find a spot of ground and take a baseline run to see what kind of speed you get from point A to point B, be it from a bridge to a sign, a specific tree to a driveway, or whatever.

Yeah, that I figured. I was hoping for a slick trick to surface. Maybe still.

I thought about logging my runs in a specific spot and looking at time from beginning of WOT to a specified speed. I could do several runs, each with a tuning 2 degrees off either direction to see where the power curve goes. And then work that direction until spark knock or power starts to drop off. Then log several runs with finer spark differences and start looking at velocity changes through out the rpm band where the WOT run rests.

I have a solid plan working up. And honestly, this is a LOT of fun. It is an excuse to get away from the wife when she is in a mood, lol.

Yet still, any advice or slick tricks are welcomed.

I know I keep saying it but videos are coming. I'm a busy man so I tend to blow off videos easily. But I WILL get them going before too long.

[robertisaar]

And if the MAF is tuned right? Would you know the degree of error if the MAF was tuned perfect? It's cool if not, just curious.

someone mentioned not too long ago that even with the same MAF and motors, there were differences in the MAF tables... like GM half-assed it and used other tables to compensate for it...

that's why i'm hesitant. if you can get a decent flowbench set up and calibrate a MAF from that, then it's more believeable...

[Schmieder]

someone mentioned not too long ago that even with the same MAF and motors, there were differences in the MAF tables... like GM half-assed it and used other tables to compensate for it...

that's why i'm hesitant. if you can get a decent flowbench set up and calibrate a MAF from that, then it's more believeable...

It's so ghetto when a manufacturer with such revenue as GM half-asses something. Uughh...GM, what were you thinking?

What about tuning the VE tables w/o the MAF (unplugged) until LTFT/STFT are all within 0-1% then plugging in the MAF and scaling the MAF tables until the Fuel Trims equal what they were before the MAF was plugged back in?

Also, what about the PCM measuring torque throught the trans when the MAF is unplugged? How accurate is that method?

[robertisaar]

i've had people tell me the PCM won't use torque calcs when the MAF is unplugged and burns the tranny... but i have no idea personally.

tuning the MAF to meet the VE SHOULD be a good method.