Spark Advance

[Dawizman]

So I had my new OBS reader hooked up to my car last night and was checking out the live data from the PCM and noticed that the spark advance was different than any other gm ive ever seen.

At idle its at -5 degrees and at WOT it hit -40 degrees.

Is this normal for our cars? If not, what would cause this.

Most new GM's I've seen have a spark advance of around 30-40 degrees at WOT A negeative value that high doesnt make sense to me.

[airattack111]

mine hits like 27 at wot

[Kidcamaro98]

negative would be spark retard, not spark advance. Thats weird its that high tho

[slow6]

So I had my new OBS reader hooked up to my car last night and was checking out the live data from the PCM and noticed that the spark advance was different than any other gm ive ever seen.

At idle its at -5 degrees and at WOT it hit -40 degrees.

Is this normal for our cars? If not, what would cause this.

Most new GM's I've seen have a spark advance of around 30-40 degrees at WOT A negeative value that high doesnt make sense to me.

Your probably just seeing the Torque Management part of the tune. You are probably seeing this when you are shifting and TM decreases timing? Am I right? There are ALOT of tables in the tune that will decrease timing. Its hard to tell from what little description you have given


negative would be spark retard, not spark advance. Thats weird its that high tho
high? you mean that negative?

[RadRacer]

I was reading the HP Tuners write up, and they said that the negative numbers are actually spark advance.

[slow6]

I was reading the HP Tuners write up, and they said that the negative numbers are actually spark advance.
Yes you are right.
There is a Spark Advance Table and a Spark Retard table.
- negative numbers in the Advance table act as retardation though.

If you really wanna be technical:
In the Spark Retard table, if you have - negative spark retard that means it is really advance.

[Kidcamaro98]

yes in the tables you do spark advancement by subtrating the numbers....when your running a scan and pull up the charts it will tell you your advancement.

[slow6]

http://lsx.i8.com/untitled.jpg
you have to copy and paste it
The background is the spark retard tables

the Foreground is the High Octane spark advance, which
will have - negatives, and those are counted as retardation.

[Dawizman]

Well, I dont know how much more dtail I can give. I'm seeing a constant -5 degrees Spark Advance whel at idle, and btween -35 and -40 degrees at WOT in our out of gears (5 speed).

Driving around town casually, I'm seeing around -25 degrees.

[slow6]

....and it lacks power that it used to have?

[Dawizman]

....and it lacks power that it used to have?


I never siad that. I just thought it was odd the according to my computer its retarding the spark by 40 degrees. Just wondering if I had some possible computer problem, or if it was completly normal with these engines.

[slow6]

....and it lacks power that it used to have?
that was a question, hence the ? question mark

If you are not lacking power I find it hard to believe you are actually -40* of timing. Its probably 40*