Thread: Timing advance and afrs

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

do you still have the 3.8" pulley on?

Yes, stock with the exception of Hai and i guess 606s but those are stock heat range.

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?

FWIW the fact that you get only 0.7* KR without flow mods is good.

Originally Posted by BillBoost37

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.

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?

Originally Posted by mechguy

FWIW the fact that you get only 0.7* KR without flow mods is good.

its a shame ill prob never go past a 3.4 setup

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.

Originally Posted by FoSHO99

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.

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.

Originally Posted by BillBoost37

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.

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.

Originally Posted by BlackFlag

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?

Spark timing is programmed, not optimized.

lol your car doesn't sound right.

Originally Posted by Nixon

lol your car doesn't sound right.

Explain.

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

Originally Posted by Nixon

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

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.

9* -- + AFR modifiers.

Look closer my friend.

You just confirmed what I said.

Meaning the timing goes up with more fuel being pushed. -- His AFR doesn't seem correct.