For the past year I have been trying to figure out why my PCM demanded (2-4) more degrees of timing under boost than what the spark advance tables in ls1edit called for (this is obviously pretty dangerous if you don't notice it).

I was able to more or less work around the problem by entering values that were about 4 degrees less than what I wanted, but it was always difficult to figure out exactly how much the PCM would mysteriously add.

Well, I just got a beta/new release of ls1edit (v 1.31H) and it has a new table that completely explains the problem. The table is called "Fuel Ratio vs RPM modifier". It has RPM on the Y axis and Enrichment Ratio on the X axis. In my 2002 PCM the table basically says to add 4 degrees of timing any time the fuel enrichment(PE) goes above 20%. This is obviously not what you want on a FI car.

Anyway, I figured those of you using ls1edit on 2002+ PCMs would want to know about this. I've been told that GM had this table zeroed out until 2002.

I'm sure a few FI cars have detonated into failure because of this.


[Modified by QuickSilver2002, 11:20 AM 12/9/2003]

 

What about year 2000 cars? do they have the problem as well?

 

I don't think anything earlier than 2002 has the same problem. My understanding is that the table is in all the PCMs, but it was zeroed out until 2002.

 

Can you post a pic of the Table???

 

Thanks- sent you a PM. :thumbs:

 

I spent some time with Ken at SEMA and he told me about this. Like you I've found that when I log data there is more timing being logged than what you would expect.

I need to upgrade my Edit so I have this table available.

 

This thread explains part of our Timing table / scanning inconsistencies. FWIW. http://www.efilive.com/forum/viewtopic.php?t=282


[Modified by binksZ06, 9:11 PM 12/11/2003]

 

Wow, nice find QuickSilver... would zeroing out the table again "fix" the problem? Also, would a 2002+ car have this tabled zeroed out already if a tuner dynotuned the car and loaded a predefined base tune on it before doing so? Or is LS1Edit just now starting to read/write these values?

 

Here is what the stock table looked like in my PCM (click to enlarge).




[Modified by QuickSilver2002, 12:15 AM 12/12/2003]

 

Any tuner doing a dyno tune with a scanner hooked up should have discovered this and worked around it for you. On the other hand, everyone thought I was crazy back when I first started seeing this problem and they all just said I was doing something wrong or that it was a problem with my scanner.... Mike Morgan was the only one who was able to tell me that there was a missing table and that I was not missing something obvious. So I guess it really depends on who your tuner is/was.

 

Great Find Quicksilver!

I just looked at that table and sure as sheeaatt! I opened a factory 2002 ZO6 program and the table was zeroed, but the 2002 Blown tahoe I've been tuning shows timing medifications in the stock program. Way to got dude!

John

 

While I don't use LS1Edit for my tuning, my tuning software (DiabloSport ChipMaster-Revolution) has always had this table. It's called the PE table, and even 2001 and 2003 Corvettes utilize this table, so it's not just the 2002 vehicles. Most all the trucks do as well, from 99 and up. Z06's do not use the PE table (0'ed out) from all the different ones I have tuned, or files I have looked at (01, 02, and 03). I'm kindof bewildered that Edit didn't have this table already? Are you sure it didn't have it for the other years, and it was just missing for your 2002, or did it not have it for all of them?

While I haven't done it, I believe you could just zero the table out and write in a timing curve from another LS1 from same year, such as a 2001 Camaro or Firebird with same transmission as you have (A4's have different timing curves in the low end of the table than the M6's), or just copy in a Z06 curve (if you use a Z06 table, be careful on the amount of timing, however, as they are general 3 degrees higher at 0.6 gm/cyl and up from approx. 1400 rpms and up, but lower timing from 0.6 gm/cyl and down, than a comparable Camaro or Firebird of the same year).

I hope this helps!

Sincerely...


[Modified by RWTD, 7:08 AM 1/2/2004]

 

:iagree:

My 2001 convertible PCM has two PE tables. 1) PE vs Temp 2) PE vs RPM both of which have non-zero values. I can see these tables via LS1 Edit. :yesnod:


[Modified by 2k1vert, 6:04 PM 12/22/2003]

 

Ahh, okay, cool. If you're referring to the Spark table, the 2nd one you named, "PE vs Temp", would be "Spark vs IAT adder" in my software.

Thanks!

 

It was missing for all years. I think the term PE is throwing (2k1vert) and others off. We are only talking about timing here. Not PE fuel tables. This new table in ls1edit is a timing table that is only used in PE mode.



[Modified by QuickSilver2002, 3:01 AM 12/24/2003]

 

Wow, I had no clue. That's quite amazing. Well, it's great Ken has included it in there now, and especially safer/better for the end-users.

Yes, you're right, I think it may have been. I hope I didn't confuse anyone.

Thanks!