3800 L67, can't seem to get rid of KR

[n0dih]

Ok, been fussing with this a while, and I just can't lick it. I have a 00 Park Ave Ultra (personal car) with a L67 3800 supercharged.

I get knock (KR) at the point of PE mode enter. PRECISELY, almost EVERYTIME. With stock tune, tuned tune, doesn't really matter. It pings when it goes into PE mode. SO, I raised the point where PE Mode is entered, it tracks. So it is NOT false knock, I get KR at 80% throttle if I set it there, if I set to 100% throttle, I get it there, if at set to stock 45% throttle, I get it there. I have pulled a lot of timing out, and although it helps some, performance suffers heavily and isn't the answer. Same with fuel, adding more PE mode fuel, doesn't cut it either. Performance suffers and it isn't worth it.

I have changed plugs from stock platinums (GM installed NGK platinums) to NGK TR5's (stock heat range), no change. I have changed to a 160 thermostat, no change. I have changed to TR6 plugs (colder, similar to Autolite 103's for heat range), no change. The constant, I get KR when I go into PE mode. I disabled EGR, no change. I went open loop, no change. I disabled the MAF, no change. Cat Converter calc temp stays pretty constant around 450C, it doesn't' dump fuel till 750C or so. No issues there.

I did find a bad injector and swapped, it fixed my P0304 fault, but no change in KR. I still get it at the point of PE mode entry. I was guessing a bad injector causing one cyl lean. I have 5 more (used, but were good takouts for a psychotic 3800 Rivi owner with a Intercooled Whipple on a highly modded 3800 with a 4T80E.

I am at wits end. I just don't know WHY. Everything to me screams something in PE mode makes it go lean momentarily. When I bought the car in May 08, it did not do this, some 23K miles later, it does.

I have not been able to check fuel pump pressure, not sure how to with the 2 speed fuel pump, but that is next, but being fuel trims are good, I don't expect a problem there.

I get the least (almost none) amount of KR when I set PE Mode to 100% and just give up on it. For a SC engine, that is concerning to me.

What am I missing? Gotta be something here. I would expect if FPR that I would not see the precision of the point I enter PE mode that I have this problem (I would expect to see it at many other times).

I attached my latest log file after the new injector and you can notice mid way through the datalog I did up the PE Mode entry point from 45%(ish) to 100%, so you see that heavy application of the throttle does NOT have KR.

Anyone?

[AJxtcman]

Did you get the Case learned yet?

[n0dih]

Nope, not yet, it does this with real time PCM and stock pcm. On the real time I turned off case learn fault. It still is doing everything like it should that I can tell.

Is there anything else at all that is going on when you enter PE mode?

[Kinglt1]

What gas octane gas you runnin?

[n0dih]

93 only, from Mobil or Shell only. In most cases, Shell, same station, but I added Mobil to the mix to see if I could get change, none. Unless all stations here have lower than 93 octane in the tanks....

But E85 gave me same problems. I am running TR6's, cold plugs, similar to 103's from Autolite....

[n0dih]

Oh, forgot to add, gap is set to 0.055" on these (stock 0.060") TR6's. Should I go narrower?

I did a change today, went SD, and my LTFT's jumped up to around 15% lean. Interesting to say the least, I expected to be rich (doesn't GM like to default rich?) This is something.....

[Team ZR-1]

Originally Posted by n0dih

Oh, forgot to add, gap is set to 0.055" on these (stock 0.060") TR6's. Should I go narrower?

I did a change today, went SD, and my LTFT's jumped up to around 15% lean. Interesting to say the least, I expected to be rich (doesn't GM like to default rich?) This is something.....

That is incorrect gap for the TR6.

You should not change from the sparkplugs designed gap by +/= 0.04
The TR6 was designed for .35 thus going to 0.55 that tip is stretched causing a different flame pattern
0.40 is the max I use for that plug but I normally just keep the 0.35

a NGK 55 would be for stock 0.55 gap and step hotter then the TR6

[n0dih]

Hmmm, didn't think changing the gap could make that much of a difference in the flame pattern. But enough to cause a KR problem? Or would it make the temp of the plug hotter than it is "rated" at?

Originally Posted by Team ZR-1

That is incorrect gap for the TR6.

You should not change from the sparkplugs designed gap by +/= 0.04
The TR6 was designed for .35 thus going to 0.55 that tip is stretched causing a different flame pattern
0.40 is the max I use for that plug but I normally just keep the 0.35

a NGK 55 would be for stock 0.55 gap and step hotter then the TR6

[AJxtcman]

NEVER EVER Change the gap on a Platinum plug either. If I get a plug out of spec I get another one. On a platinum plug if you change the angle of the ground electrode it will cause it to wear and that is what a Platinum or Iridium doesn't do.

[AJxtcman]

Call me Tom
We need to get your PCM to Learn #1 TDC and Crank Variance.
I also have a PCM for you to install a socket