5.slowklr

What is the desired Ignition Timing advance of a 2001 Z28 at WOT. I've heard about 22 -23 degrees is this correct? Does ATAP give you an actual reading or an expected reading?

Jadeeglide1550

Advance is good so long as the KR's are not crabbing and pulling things back. Running high test and depending upon the outside conditions, my advance is somewhere between 26 and 30 degrees.
I did the IAT modification and that prevents the advance from being pulled back on a hot day. On the LT style small blocks, 38 to 40 degrees was the desired spark advance. You have to remember that the LS-1 is running 10.5 to 1 compression and even with 93 or 94 octane, GM has a very conservetive advance curve. LS1edit lets you undo this and put more advance in, which you may be able to use with a slightly richer mixture, but it is tuning that will decide how much the engine likes. Things like carbon build up in the cylinders from running an over rich mixture can set off slight detonations that cause the KR's to do their thing. You need to see what Atap says while tuning things in. Possibly you will find different settings for different times of the year, cold days vs very hot days.

cablebandit

iTrader: (37)

while i originally thought like you...i now realize our pcm has a "modifier" for temps. You can (with ls1edit) set your total timing AND how much the pcm is to take away when it sees a certain IAT or coolant temp.

WhynotSS

Mine was at 40 deg. at WOT. Is that too high?

BTW, it was about 80 deg. outside and very dry.

<small>[ July 05, 2002, 07:56 PM: Message edited by: WhynotSS ]</small>

WS6underPRESSURE

</font><blockquote><font size="1" face="Verdana, Helvetica, sans-serif">quote:</font><hr /><font size="2" face="Verdana, Helvetica, sans-serif">Originally posted by WhynotSS:
<strong>Mine was at 40 deg. at WOT. Is that too high?

BTW, it was about 80 deg. outside and very dry.</strong></font><hr /></blockquote><font size="2" face="Verdana, Helvetica, sans-serif">I think 40 is to high, you'll probably see the best power with the timming set around 28-30 at WOT as long as the temp. is not to high and you have enough octane, so you don't get any KR.

CMNTMXR57

</font><blockquote><font size="1" face="Verdana, Helvetica, sans-serif">quote:</font><hr /><font size="2" face="Verdana, Helvetica, sans-serif">Originally posted by Jadeeglide1550:
<strong>Advance is good so long as the KR's are not crabbing and pulling things back. Running high test and depending upon the outside conditions, my advance is somewhere between 26 and 30 degrees.
I did the IAT modification and that prevents the advance from being pulled back on a hot day. On the LT style small blocks, 38 to 40 degrees was the desired spark advance. You have to remember that the LS-1 is running 10.5 to 1 compression and even with 93 or 94 octane, GM has a very conservetive advance curve. LS1edit lets you undo this and put more advance in, which you may be able to use with a slightly richer mixture, but it is tuning that will decide how much the engine likes. Things like carbon build up in the cylinders from running an over rich mixture can set off slight detonations that cause the KR's to do their thing. You need to see what Atap says while tuning things in. Possibly you will find different settings for different times of the year, cold days vs very hot days.</strong></font><hr /></blockquote><font size="2" face="Verdana, Helvetica, sans-serif">FYI, the LS1 is 10.1:1 CR, not 10.5:1. Most LS1's like to overall timing somewhere in the 25-28 degree range whether it be total timing or net of knock retard.

VINCE

iTrader: (1)

When I had my car programmed by Ed Wright for my cam only tuning I was seeing 29 to 31 degrees at WOT with no KR using 93 octane. When I first put my high compression heads on I was still at 29 degrees and autotap never showed any KR. Now I am at 25.5 degrees secondary to Ed thinking that is too high for my compression. I would like to be atleast 28 degrees with my setup.

Jadeeglide1550

I would like to see some hard and fast numbers on maximum advance with no KR's. I stand corrected that the compression ratio is 10:1. Any way, in the past on the SBC, and the BBC, 38 to 40 degrees was the ticket. There were no KR sensors to contend with, and tuning was done so that you would get a slight bit of ping while lugging the engine up a hill on a hot day, and that was ususally the way you would go with the advance. If you were going in the high RPM range, 6,000 RPM and over... you would generally find more HP by retarding the advance at a specific RPM. That was why the electronic units allowed you to plug in both a maximum advance and a retard at a certain RPM.
I am going to do some investigating with my motor, and when you go to O2 or Boost, I am sure you get an entirely different picture than for a NA engine. When I get some hard and fast numbers I will report to the group, unless someone else posts theirs first.

Jax White TA

You sure there is 0 advance at idle? I thought you needed to add advance at idle to help with a lopey cam.

Jadeeglide1550

What you say CMN is generally true. Having tinkered with the original SBC for years, and working with the Chevy Power Book, they recommended that you have 18 degrees of advance at idle and then have a full mechanical additional of 20 to 22 degrees all in by 2,000 RPM. We had to fiddle with springs and weights to try and get close to the advance in the distributor, and have a good starter to deal with the 18 degrees of initial advance, but that baby would not even crank one revolution before firing up. I had a 76 Vette, and later pulled off the Electronic HEI on my 85 Z-28 in favor of the mechanical advance (did not run any vacuum advance) and then had my 69 Small Block Chevelle and 70 454 BB Chevelle. On the 69 and 70 I bought a Mallory electronic advance box which allowed me to lock out the mechanical advance, set an initial static advance, then tell it when to start advancing, how fast it should advance and how much total advance to bring in and at what RPM. The car really came alive with this advance, and I was running only 9.5:1 Compression in the 69 SBC, but I put aluminum heads on the 454 and pumped the compression to 11:1. The cam I was running had so much overlap that the engine was happy with the initial 18 degree timing, and had only a slight ping under load with the full advance in at and above 2,000 RPM. Anyways... that was what the Chevy Power Books recommended then... would be curious what Chevy would recommend on an all out race engine LS1 style timing wise.

Team ZR-1

</font><blockquote><font size="1" face="Verdana, Helvetica, sans-serif">quote:</font><hr /><font size="2" face="Verdana, Helvetica, sans-serif">Originally posted by VINCE:
<strong>When I had my car programmed by Ed Wright for my cam only tuning I was seeing 29 to 31 degrees at WOT with no KR using 93 octane. When I first put my high compression heads on I was still at 29 degrees and autotap never showed any KR. Now I am at 25.5 degrees secondary to Ed thinking that is too high for my compression. I would like to be atleast 28 degrees with my setup.</strong></font><hr /></blockquote><font size="2" face="Verdana, Helvetica, sans-serif">You did not mention what your engine compression is but my 372 stroker LS1 is 11.3:1 and even with the crappy Ca smog gas I have almost zero knock and no misfire and WOT timing is 28 degrees.

It was not that way when I was using the clunker powerloader PCM calibration, I cured it myself by using Ls1edit and doing the correct tuning, so I suggest you also do a true custom tune for the makeup of your engine/mods and where you live.

CMNTMXR57

Keep in mind though, most older SBC's already had a static timing advance at idle of 6+ or so degree's of timing. The G/F's father and I were setting up timing on the 350 in his '73 Nova and we found it ran the best and strongest at 10-12 degree's of advance at idle. <img border="0" title="" alt="[Eek!]" src="gr_eek2.gif" />

Comparatively, most of our cars (LS1's included) have 0 degrees of advance at idle.

Also, conditions, elevation, weight, etc, etc also factor in (providing you are not doing the IAT mod), mine here in Chicago on a perfect day likes around 28 degrees at WOT, whereas someone below sea level say like down in Houston, may like a little more timing.

At WOT throttle I was getting .4 degrees of KR primarily at the top of gears as I shift so it's not as if I was getting 2, 3, or 4 degree's of KR and scaling it back to 28 degree's.

I also at first had Ed Wrong's programming. After three attempts for him to get it right with numerous dyno sheets, autotap logs (from both Dyno and WOT throttle runs), I went elsewhere. With his programming at WOT throttle I was getting 6-8 degrees KR at WOT and in some cases more. At throttle tip in, he turned off my EGR (even though I told him I DIDN'T have the LS6 intake) which resulted in around 30-40 degrees of KR. <img border="0" title="" alt="[Eek!]" src="gr_eek2.gif" />