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Timing advance and afrs

blackflag

blackflag

New member
To start off I did a brief search for some answers but I think this might be vehical specific.
Vehicle is a 2001 gtp, pretty much stock at the moment with the exception of a hai and a scangauge. Before i get into real mods im trying to understand a few things.
Right now at wot im running almost kr free ( .7 blip at shifts), but only 12.5 ign advance? and my Afr is 11.5.
I thought stock i was supposed to be running around 15adv area.
If im getting such low kr shouldnt my timing be higher?
Is something else pulling my timing?

Maybe somebody can help me out here
 


There are two timing tables in the pcm. The high octane and low octane. If the pcm thinks you are running low octane, it uses that table.
 
12.5* is about the stock WOT timing advance. I say "about" because the table changes based on RPM, cylinder airmass, and IAT. The car would run 15* stock WOT likely at high elevation from low cyl airmass.

11.5 ish is also the stock AFR after table modifiers. Its still getting KR, so you can't really increase WOT timing.

What octane fuel?
 


BillBoost37 said:
There are two timing tables in the pcm. The high octane and low octane. If the pcm thinks you are running low octane, it uses that table.
Click to expand...
So my pcm thinks im running low octane? I ONLY put 93 in it. Would this be a pcm issue?
Do i even need to worry about it?
 
At what rpm and throttle position are you seeing the 12.5 and how much is it fluctuating? The 11.5 you are seeing for AFR must be your commanded unless you have a wideband, how much is that fluctuating as well? It's hard to tell anything with just 2 numbers but it seems right on par for stock except the part that you only have blips of KR.
 
FoSHO99 said:
At what rpm and throttle position are you seeing the 12.5 and how much is it fluctuating? The 11.5 you are seeing for AFR must be your commanded unless you have a wideband, how much is that fluctuating as well? It's hard to tell anything with just 2 numbers but it seems right on par for stock except the part that you only have blips of KR.
Click to expand...

At wot full range of rpms it stays at 12.5, when i start to let off it hangs at 13.5 for a sec then goes up.
as far as afr goes it starts at 11.5 and fluctuates between that and 11.9

My original question though is if my kr is so low why dont i have higher timing?

Hopefully i can word this in a way you guys can understand what im asking
If I understand Kr correctly- If stock timing at wot is 12.5 and i have lets say zero kr, do i stay at 12.5 or does it advance till right before i reach kr??
Or, If stock wot timing is 12.5 and i have 5-7*kr, do i drop down a few points?
 


If your timing is at say 15* and you have 3* of KR then your actually at 12*. It doesn't advance on it's own you have to have a tune for that.
 
BillBoost37 said:
There are two timing tables in the pcm. The high octane and low octane. If the pcm thinks you are running low octane, it uses that table.
Click to expand...


I could use some clarification on your quote. My understanding is that the PCM defaults to "Bad Fuel Spark Timing" when there is an abundance of knock in some amount of time.


BlackFlag said:
My original question though is if my kr is so low why dont i have higher timing?

Hopefully i can word this in a way you guys can understand what im asking
If I understand Kr correctly- If stock timing at wot is 12.5 and i have lets say zero kr, do i stay at 12.5 or does it advance till right before i reach kr??
Or, If stock wot timing is 12.5 and i have 5-7*kr, do i drop down a few points?
Click to expand...


Spark timing is programmed, not optimized.
 


Nixon said:
11.5 afr commanded, shoots up to 11.9?

12.5 and .7KR, so 13 commanded. stock pcm commanded 14*-16* with commanded AFR of 11.1
Click to expand...


What? No. Look more closely at the stock programming. AFR changes depending on time in PE and RPM, so there are dozens of AFRs.

Also, stock spark goes as low as 9* at high airmass, high RPM.

His car is running the stock tune normally as it should.
 
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