Dan_the_C5_Man

Two tabs - SCR and DCR http://drummerforhire.myownsiteonlin...CR_and_DCR.xls

Here's the deal -

Stock LS1 block and pistons, stock LS6 heads (02 - ZO6), LPE GT2-3, Cometic .040 MLS gaskets.

I've had to pull timing from about 3K on up, stock was around 28, I can only run around 26 w/o measurable detonation during a 4th gear run from 2K to 6500 (HP Tuners scan). I have AFR "perfect" (12.8), so I do not believe it is AFR issue, still pinged when I bumped it up to 11.8.

I have a feeling I should have not wasted extra cash on the Cometic gaskets, should have used the thicker (and cheaper and more reliable!) stock MLS.

Am I high? Do I have another issue? Are my calcs wrong? Do I have shitty gas? (93 - or so the pump sticker says)? If I back the timing down across the board to 25 - 26 degrees, how much Tq am I giving up? Less than if I switched gaskets?

During a recent track day (road racing not drag racing – air temp 40 degrees, coolant 190, oil 280) I could hear it rattle / measured it pinging on the throttle blips to down-shift!

Any help would be appreciated. Thanks guys.

on2

iTrader: (4)

If that 10.0 in green is your DCR then hell yeah it is too high. 9 is considered high.

1BADAIR

iTrader: (1)

I don't think that is right. in the "advertised intake dur in use" at the top it says 207. 207 is the duration at .050 not advertised.
I can only see part of that calc for some reason

dca1042

im backing bad fuel,take a sample somewhere and get it tested,before going any further.
just my 2cents worth,but we see it time and again over here in australia.
cheers dave. let us know how it ends up.

on2

iTrader: (4)

Or try a different calculator like the Piano Prodigy calculator.

1BADAIR

iTrader: (1)

is it pulling oil through the pcv? that will cause detonation
https://ls1tech.com/forums/generatio...sier-than.html

405HP_Z06

iTrader: (11)

Do you have the cam card for the LPE cam? What is the LSA and ICL?

vettenuts

iTrader: (4)

I re-checked with the GM MLS gasket and the DCR is still too high. This cam and those heads are used very frequently without issue so I am thinking the calulcation has some bad inputs. I used the numbers in your file in my own calculator and came up with the same numbers.

LS1-450

iTrader: (33)

Regardless of the DCR calculator issue. I would expect that timing from 24 to 26 is reasonable. There is no definate setting as to whether or not you're losing torque/power by reducing from 28. More importantly, get an oil cooler for road racing track days. The oil temperature is a greater culprit for the ping than anything else. When not in use, cover it so that your oil gets warm enough under normal driving conditions. Make sure & check your oil pressure after installing the cooler to see whether or not an oil pump spring shim is required due to a pressure drop from adding the cooler. You may not need one, but it's good to check. Did your power steering reservoir overheat & bubble out of the reservoir as well? If so, a look @ the ps cooler isn't a bad idea.

Hope you were using 15W-50 racing oil while @ 280* oil temps.

405HP_Z06

iTrader: (11)

When calculating DCR you must use cam specs at .006 or 'advertised'. I don't know for sure that the ICL on the LPE GT2-3 is 118.5, ie 'straight up', but based on the specs here and from what I can gather the IVC @ .006 on this cam is 66 degrees.

All that said, here are my calculations:



A stock 02-04 Z06 only has 22 degrees of timing in the high octane table from 4000 RPM and up so I wouldn't be surprised that running 28 degrees results in detonation. From my own tuning experience on my 03 Z06, 28 degrees on the top end always results in detonation. IN MY HUMBLE OPINION, I would start with a stock Z06 HO and LO timing tables and add incrementally from there.

Heres the stock 03 Z06 High Octane timing table:



Bottom line, it appears you have too much timing. I don't put much into DCR, so don't get hung up on that. Your combination should run quite well, just needs a little tweaking. Don't waste your time and money swapping head gaskets.

Can you post your .hpt file?

Dan_the_C5_Man

Well hell Aaron, I think you've basically answered the question, and I am embarrassed that I didn't think of it. A stock LS1 would have (or should I say could have) more timing than a stock LS6, simply based on the .5 point lower SCR.

So it sounds like my high-octane table is simply too high for the combo, but still higher than what GM uses as a base setting for this combo (sans the .040 gaskets of course). Excellent!!

I am aware of the .006" list rating vs. .050" - I got the .006" angles from a guy that used to work at LPE (a post from a few years ago on LS1Tech). But I'll be damned if you folks didn't catch my mistake (thanks!) I should have used 255/281 in the calcs.. I will re-do the numbers tonight. And yes, I do not know if there is advance ground into a GT2-3, so I am guessing that ICL and LSA are identical.

At any rate, a sigh of relief on my part. Thanks!!

On a similar note, does anyone understand how the PCM determines when to switch from the high to low octane tables?

405HP_Z06

iTrader: (11)

I guarantee the SCR numbers I posted are spot on based on your data. Concerning timing and the LS6, the LS6 has a more efficient combustion chamber so less timing is needed for MBT. Also, keep in mind that cam advance will affect DCR, but don't worry about your combo. Fix the timing and you're good. Make sure you adjust your low octane table to maintain adaptive spark.

The PCM ALWAYS tries to run the high octane table values; however, if a MAF or Knock DTC is set it defaults to the low octane table only. A vehicle that has neither of these faults interpolates equally between the two tables based on the octane scalar value; it does not totally switch between one and the other. The PCM uses a counter based on engine knock to increment or decrement the scalar that determines the exclusive table value or distance between the high and low octane timing table values at a particular engine load point.

For example, at the same engine load point, the high octane table has a value of 20 degrees and the low octane table has 10 degrees; the octane scalar is 50% (EFILive) or .5 (HPTuners). The final timing value at that specific load point would be 15 degrees. If the octane scalar were 75% (EFILive) or .75 (HPTuners) it would result in 17.5 degrees, etc. This is a simplified example that does not take into account the many spark multipliers and adders in the PCM.

In EFILive log the High/Low Adaptive Spark PID (ASPARK) to see what the scalar is and where the PCM is interpolating the timing values. The PID value is a percentage where 100% is the high octane table exclusively and 0% is the low octane table exclusively.

In HPTuners log the Knock Learn Factor PID. For Gen III PCM's the PID value starts at 1 (high octane table) and decreases to 0 (low octane table) as knock is encountered.

I've got some timing tables you may be interested in. Let me know if you want them.

1BADAIR

iTrader: (1)

what do the plugs look like? if your using 55's switch to tr6's

405HP_Z06

iTrader: (11)

Dan_the_C5_Man, let us know how this works out. It's always good to hear the final outcome for future reference.