So over the winter (temps in the 40's) I dialed in my VE table, and set the PE multiplier to a conservative 1.17. I enabled the MAF again and thought things were good. Recently with temps 90+ I was hearing some ping.

I scanned it, and had ~4 degrees of knock throughout the 0.24-0.68 g/cyl area from 1500-5500rpm. To avoid having a huge valley in the table, I flashed it to a stock 2003 zo6 timing table and immediately it felt better at low rpms where it used to bog, along with less knock. I kept logging and tweaking and now have an average of 5 or 6 degrees pulled throughout the entire table.

I know 2000's have the more aggressive stock timing table, and that the ls6 intake will occasionally lead to some knock (better flow needs less timing, etc) but does it sound fishy that I had to modify the majority of the table? Looking at the 2002 timing table it looks like it still has similar timing in areas where I had to pull more.

Car:
2000 Trans Am m6

Mods:
-lid/tb/ls6 intake
-longtubes/catted Y/magnaflow

here's where I was getting knock:


my VE table:


this is what my timing table has ended up looking like (needs smoothing):


stock 2000 timing table:


Attached are my current tune, and a log before the last round of timing changes

 

You might look at what the IAT says, vs what you know
about real air temps. At the lower end where the speed
density air mass is still a big component of dynamic airflow,
IAT affects the calculation a lot. And hot IAT says low air
mass, causing lean fueling.

Now your IAT spark adder might be a better place to do
this spark pulling, if you are convinced that cool air temps
still run right.

Improving the cooling stack (cleaning rad & condenser,
making fans run sooner, etc.) can improve the actual
underhood air temp, if you're pulling from there. The
air path particulars, here, I do not know.

 

Good point jimmyblue, my truck tune start pulling timing above 86* I believe. -1 or 2 at 86, -3 or 4 at 94 and it goes up from there.

 

I was actually just considering relocating my IAT sensor, I think I found a thread of yours about doing the same in my searching. Yesterday I sat with the engine idling and IAT went up to 150+ when it was about 90 outside. I popped the hood and let it sit running and it cooled down to 98 on its own. I was thinking I would just leave it alone because it had been dropping back down once moving though, so I figured it wouldn't throw anything off too much. Also, I'm getting KR not just timing pulled, could that be from the lean condition?

Does relocating it require any changes in itself? The only table I see is the IAT spark table that pulls a few degrees from 100+ over 80 MAP

 

I don't know about it being lean, but pulling hot air will not allow you to run as much timing. I would compare your IAT adder table against a truck table (conservative) and see if you can tweak it to help your issue. I would assume that since you probably maximized the the fuel and timing in cooler weather, you probably don't have the cushion that a stock car would.

 

Well if I were actually getting hot air it would knock and not allow me to, right? I would think that since it is expecting hot air and getting colder air it should already be correcting itself in anticipation of the hot air and therefore not. The only thing I modified was the VE table, and not even by much. The spark was all stock. I tried today with everything stock and still got knock.

Just as a test I put the IAT near the DRL and it stayed just a few degrees above ambient, getting only a little warmer at idle. Still knocking, but I didn't make any tuning changes. Every time I log I hit few cells that get 5ish degrees of knock, not really sure where to go from here or just continue to pull timing.

 

My stock silverado would get some knock retard, how much I can't really remember.

You lost me with your last post, but I think your IAT timing table needs to be a little more aggressive.

 

Hmm okay I think I misunderstood. I think last summer I ran totally stock VE and spark with no issues though which is odd, although it may not have been as hot.

I would think other people would experience the same thing though with how common my mods are, although it is really liking the lower spark off the line.

 

The (falsely) low air mass calculation from (falsely)
high IAT readings gives you both short fuel and long
spark, for the real conditions; both index off air mass.
A double whammy, as it were.

Since you have a condition where you're happy with
the fuel / spark, I'd work with the modifiers based on
that stake-in-the-ground. Though for me, 40F would
be unusually low as a point of refernce.

Another school of thought would be, tune for the
crappiest conditions you normally encounter, and
use the modifiers for "upside" when you find good
air.

But in any case, truth-based tuning is a good idea,
meaning you'd like sensor fidelity (along with better
air, however you can get it). IAT especially is very
subject to location (thermal input, relative weights
of supposed-to-be-sensed and can't-help-sensing).

 

thanks for the help!

I'm going to try running some Techron through the tank, changing plugs and fuel filter, and then starting over with my tune in the heat with the IAT relocated. As the temperature drops I'll see if it's worth modifying the spark vs IAT to run a few degrees extra when I get better air.