Spark advance *NEW datalog pic*

[StealthyWeasel]

Data Point 1) Spark advance is 37* , RPM is 4400

Data Point 2) Spark advance is 9* , RPM is 2020 (Ignore the values on the side, thats at a little lower RPM)

Data Point 3) Spark advance is 8.5* , RPM is 2953

My questions.

What is going on in those areas? I think point 1 is easily explainable, but what is happening at point 2 and 3? Warmonger and I have ideas on what might be happening, but don't say anything yet. I want to see what everyone else thinks first.



NEW PIC:

[96blackse]

Show the graph with TP

BTW why does you bank 2 rear o2 has reading while the bank 1 doesn't???

[warmonger]

Datapoint #1 is a spike that happens when you tip into the throttle and can usually be discarded.

#2 - Assuming your cam/crank sensors are working then you had a sudden change in timing that could have been caused by a simple misfire, or it could have been engine knock. I can't think of too many other reasons.

#3 - same as #2.

There are many things that can affect timing, poor fuel quality, combustion temps, etc. You have to realize also that back-to-back runs heat up the combustion chamber a lot and where a car was running fine on a certain type of fuel and tune in the beginning, it could later be susceptible to ping/knock once conditions in the block/heads heat up.
Also you can have changes in intake air temp that can be just enough to put the intake charge a bit too hot and more susceptible.

I suggest you pull your plugs and look at the electrodes. See if they are pitted burnt or broken. If they look fine then you probably didn't have any knock.
Knock can be powerfull enough to damage pistons, rods, etc. but if it is that powerful it likely will damage the plugs which are pretty weak by comparison.

[StealthyWeasel]

new pic with TP

[warmonger]

Originally Posted by StealthyWeasel

new pic with TP

Holy crap! I wish I'd seen that before. Your TP is dropping so that would explain the spikes.

When your throttleposition goes less than full throttle the PCM will attempt to advance the timing to clean up the fuel after a full throttle run.
Timing will always spike when the pcm sees a deceleration.
So you get spikes like that if you press the thottle and let off.

When you go full throttle your timing will drop down and then slowly climb as rpm climbs. If you mash the throttle and then let off a little bit, you will get a quick drop and then a spike before the timing will drop again and level out.

[StealthyWeasel]

thanks again, that makes me feel alot better about the potential knock situation. You're the best.