Timing gradually dropping as RPMs rise at full throttle.

[Mingus]

If you look on the log at 2:06 in, he goes full throttle and the timing starts dropping. Up through the 1-2 shift it pulls pretty good, but as soon as it shifts into second, the timing slopes down as the RPMs go up. It makes for a long acceleration through 2nd gear. I see the injectors getting over 90% duty cycle at 5200 RPM, but I don't think the injector duty cycle is linked to timing is it? I've looked through everything I could think of and can't find what is pulling the timing.

5.3 DBW Iron Block
Z06 cam
LS6 intake and injectors.

[blindsquirrel]

Taking one point in the log as an example: 4400 RPM, 0.80g/s, 221* ECT, & 163* IAT...

Spark table is only asking for 11.5 degrees at that RPM & cylinder airmass. Then the sky-high IAT is pulling 8-9*, and the ECT is pulling another 3*.

The IAT is most of it. Do you have it installed in the exhaust pipe or something?

The factory timing tables mostly ignore the regions above where the stock engine is able to reach, so up around 0.80g/s can honestly be 22 to 24, maybe 25 degrees. No need for it to fall off to 10 or 11 starting around the 0.70-ish range like that.

[blindsquirrel]

This is my HO spark from a 5.3 that makes about the same power (low-mid 0.80s cylinder airmass). I have not spent a lot of time on the spark but I get no knock with this. ECT & IAT tables are also adjusted so that they are not pulling timing at normal operating temps.

screenshot.11-07-2022 11.41.58.png

[Mingus]

It was a brutal 104F that day. It's running a stock MAF with the air coming from beside the radiator. The radiator in a 1950 Fleetline is on the smaller side of marginal, and he could only fit a fan on the front side of the radiator. At one point the water temp got up to 137F so I called it a day. I told him he needs to push the radiator forward and add a "puller" fan with a shroud.

I'll look at the AIT and ECT tables. That you for your time.

[blindsquirrel]

As far as the IAT goes, it's probably not bad that it pulls 8* or whatever when temps are that high, but that should be 8* pulled from 25*, not 8 from 10.

If the air really is in the 160s it needs a better location to draw from, obviously. But the other possibility is that the IAT is reporting higher than actual. That can be checked with a temp probe snaked into the airstream somewhere right before the MAF.

Check that the IAT, ECT, & trans temps all read within a few degrees when it's sat overnight and everything is at ambient.

[Mingus]

I'll get back with him when he gets the fan location and CFM fixed. He knows he has to move the air filter. I'll most definitely verify the temps next time I hook up. Thanks for your help.

[Life is an Enigma]

If you're running LS6 injectors why is your injector data wrong? The injector data looks like it's for the stock 5.3 lm7 injectors. LS6 injectors P/N (12482704 or 12561462)
2004 LS6 injectors
Screenshot (771).png

Yours
Screenshot (772).png

[Mingus]

I'll recheck the numbers. I usually start out by referencing the injector part number and inputting the flow rate. They might not specifically be LS6 injectors but they are the long EV1 style.

[Alvin]

If you look on the log at 2:06 in, he goes full throttle and the timing starts dropping. Up through the 1-2 shift it pulls pretty good, but as soon as it shifts into second, the timing slopes down as the RPMs go up. It makes for a long acceleration through 2nd gear. I see the injectors getting over 90% duty cycle at 5200 RPM, but I don't think the injector duty cycle is linked to timing is it? I've looked through everything I could think of and can't find what is pulling the timing.

5.3 DBW Iron Block
Z06 cam
LS6 intake and injectors.

It's got like 12 degrees in the main table and -8 in the IAT table at those temps.. I think someone already said that.

Why is the main spark table so low? You might be creating heat being that far off.

Its also rich at WOT so fixing that will bring the IDC down. I've made 500 rwhp (barely) on stock LS6 injectors. NA FYI