timing questions

[ringram]

Hi all,
I think I have my VE fairly good now. It swings a little day to day as is apparently usual. High pressure and RPM its slightly -ve and the bottom end around 0 or thereabouts.
I turned PE back on and with high TP O2's are around 920mv or so. Im going to wait till I get my LC-1 installed before messing with commanded or going open loop only.
Anyway Ive been having to pull timing out of the highoctane table almost constantly. My run spark is around 26deg so perhaps is about right. But I get some horrible hesitations and the log shows timing at 2deg! Yuk.
You will see in the dash where this happens, its usually when I put some throttle in. O2's look pretty crazy so Im not sure if they have something to do with it. Does anyone have any ideas why this might be happening?
DFCO and LeanCruise are disabled at present.

Rich

[SSpdDmon]

How is your tune currently different from stock? Are you running with/without the MAF, DFCO, LTFTs, closed-loop, etc.?

[BowlingSS]

Hi all,
I think I have my VE fairly good now. It swings a little day to day as is apparently usual. High pressure and RPM its slightly -ve and the bottom end around 0 or thereabouts.
I turned PE back on and with high TP O2's are around 920mv or so. Im going to wait till I get my LC-1 installed before messing with commanded or going open loop only.
Anyway Ive been having to pull timing out of the highoctane table almost constantly. My run spark is around 26deg so perhaps is about right. But I get some horrible hesitations and the log shows timing at 2deg! Yuk.
You will see in the dash where this happens, its usually when I put some throttle in. O2's look pretty crazy so Im not sure if they have something to do with it. Does anyone have any ideas why this might be happening?
DFCO and LeanCruise are disabled at present.
Rich

How did you set your VE Table since you do not have a WD yet?

Bill

[ringram]

Tune has a little more VE, not much, but more timing, maybe 4deg. (Based on 02 camaro).
dfco set to 140C, leancruise disabled (set to very high speed).
ltft enabled, closed loop as stock, no maf.
Timing and ve below. PE MAP set to 15 (stock)
AFR vs RPM all at 12.80

BowlingSS I set VE with 100+ mile trip to set ltft's and used factor scaling to multiply average of left and right banks as a percentage to current ve table.
Most changes were minor. All under 10%
(eg) ((Left+right/2)/100)+1

Timing basically create a map of dyn_cyl_dma vs rpm vs KR and pull max values from spark table and smooth to lowest values.

Thanks guys, not looking for a detailed breakdown just a pointer in the right direction. Im learning more every day.

Low RPM and high rpm seem ok, its midrange 2000-3500 with open throttle that seems the problem area. Something looks like its pulling spark..

[SSpdDmon]

If your car came with a MAF from the factory and you're running with it turned off, you need to make spark corrections to the low-octane spark map. It reverts to this map in SD....at least, it does in my Camaro. What seemed to work best for me when I added timing was to blend it in from about 4000rpms on up. So, I may have added .5*, then 1.0*, then 1.5* and so on to the WOT portion of the stock table.

[ringram]

Yeah sorry SSpd, another thing I didnt mention. Im running custom OS 3 with Octane scaling enabled and set to 100% to run off the High Octane table exclusively.

So you think Im on the right track? What about when it drops to only 2 deg advance with no knock?

[Blacky]

To answer the comment about the O2s, they are operating correctly, the stock narrow band O2 sensors should flip from rich to lean a few times per second. They will stay high (rich) during wide open throttle (open loop), because PE causes the engine to run richer than stoich. The PCM ignores the O2 sensors in PE mode. If they do stay high or low for too long in closed loop mode you would get an "insufficient activity" trouble code.

Try logging as many of the {GM_EST_xxx_DMA} PIDs as you can, one of them should show timing being pulled. Right click on the culprit PID in the [PIDs (F8)] tab page and select "More info..." that will tell you which tables in the tuning tool are related to the PID.

Regards
Paul

[caver]

Seems to me you are running way to little adv.Will look at one of my tuns tommorow at work.
If you dont have a wide band you have no idea what the mixtures are doing could be horribly lean in pE mode and that will certainly cause knock.
Suggest you put it all back to std untill you get a wide band.

[zrx1200]

in your ve table 3200 rpm colum 55-105 map theese values look low ..07 way lean. prob should be 70.................spark .n the .48-1.20 1800-4000rpm also looks low..as mentioned above wideband and logging are your friends..

[caver]

Timing table from a stock 2005 that I tuned.Timing works for me at 5000ft u might find otherwise.

[ringram]

Thanks guys, turned out lots of "burst knock" pulled in anticipation.
I reverted the ve back towards stock and the hesitation is gone. Knock is also much reduced. Have ordered a O2 sensor socket to get the mutha off because its fairly well seized in there. So will progress again once thats in.

[caver]

Why bother your WB is going to be in and out lots.
Just weld a bung in the exhaust ahead of the cats.

[Delco]

Timing table from a stock 2005 that I tuned.Timing works for me at 5000ft u might find otherwise.

YOUCH , you must have some real good fuel in your area to be able to run that much timing OR you are having a lot pulled out from other area's.

Final spark on a stock LS1 will rarely go over 22 deg without detonation

[Black02SS]

Timing table from a stock 2005 that I tuned.Timing works for me at 5000ft u might find otherwise.

YOUCH , you must have some real good fuel in your area to be able to run that much timing OR you are having a lot pulled out from other area's.

Final spark on a stock LS1 will rarely go over 22 deg without detonation
So are you recommending that max timing at WOT never go above 22*?

[Delco]

Timing table from a stock 2005 that I tuned.Timing works for me at 5000ft u might find otherwise.

YOUCH , you must have some real good fuel in your area to be able to run that much timing OR you are having a lot pulled out from other area's.

Final spark on a stock LS1 will rarely go over 22 deg without detonation
So are you recommending that max timing at WOT never go above 22*?

On the fuel we get here in Aust on a stock engine that is the max WOT timing we find for best power and torque at the AFR we run.

On a car with a cam in it we can sneak the timing up to a max of 26 deg at wot .

One thing the novice needs to remember is that we tune on a dyno with the principal of minimium timing to make the power is the best point to be at , adding more timing doesnt make more power it just brings you closer to the detonation threshold ( this can be seen clearly with in cylinder pressure transducers) with no gains in power at all. From there it only takes a little bit of extra combustion pressure to put the engine into full on detonation .

So often I see guys ( especially blown combo's) running way too much timing , they even get to the point that detonation happens before TDC and the factory knock sensors wont pick it up , you back a little timing out of it ( and in this case we are normally going from the 14-15 deg back to 12 deg so the order of magnitude is not high ) and all of a sudden you can see the detonation , take another degree out and the engine is back in the sweet spot.

[GMPX]

On a car with a cam in it we can sneak the timing up to a max of 26 deg at wot .

I like reading expert opinions, that's about where I am at.
I must admit I am in :shock: when I see timing figures over 30deg on stock LS1's.
Delco, a 50 state tuning tour is in order :wink:

Cheers,
Ross

[dfe1]

Timing table from a stock 2005 that I tuned.Timing works for me at 5000ft u might find otherwise.

YOUCH , you must have some real good fuel in your area to be able to run that much timing OR you are having a lot pulled out from other area's.

Final spark on a stock LS1 will rarely go over 22 deg without detonation
In my experience, you can run a bunch more spark and get by with lower octane gas at 5000 feet than you can at sea level. With relatively low ambient air pressure (barometer) and oxygen, an engine makes considerably less power than it does at low altitude. Consequently, internal pressures are lower so the engine will tolerate more spark and lower octane fuel. As people who tune at altitude often say, "don't try this at sea level".

[caver]

In my experience, you can run a bunch more spark and get by with lower octane gas at 5000 feet than you can at sea level.

You beat me to it. Thats exactly what happens I rarely go over .68g/s in the timing table.
My atmospheric pressure runs from 84.7 to 86.2 kpa depending on temp etc.

Depending on airtemp my final timing figures run bween 22 and 25 degrees. I find that part throttle and between 1600 and 4600rpm it likes huge amounts of advance.

[GMPX]

Caver,

Please change your sig to read, I am up with the clouds, I keep forgetting you a barometrically challenged :)

Cheers,
Ross

[Delco]

Caver,

Please change your sig to read, I am up with the clouds, I keep forgetting you a barometrically challenged :)

Cheers,
Ross

being barometrically challanged means it can safely run more boost to compensate :)

[caver]

Yep I have to run .15 bar boost just to get to where you guys start.

The upside is if I go to the coast for a holiday my car feels like a monster.

[dfe1]

Caver,

Please change your sig to read, I am up with the clouds, I keep forgetting you a barometrically challenged :)


At 3,000 feet, you're barometrically challenged, at 5,000 feet you're barometrically deprived. I once did a bunch of dyno testing at SuperFlow's facility in Colorado Springs (5,000+ feet) and the correction factor was staggering- Correcting observed power readings to standard corrected added about 100 horsepower to a 350-400 sea level horsepower engine. Perhaps we should take up a "charity" collection for Caver and send him a huge fan so he can pressurize his dyno cell.

[caver]

Perhaps we should take up a "charity" collection for Caver and send him a huge fan so he can pressurize his dyno cell.
LOL :o