Pulling massive timing with higher IATs
11-19-2019, 12:00 PM
#21
Drifting
Thread Starter
i personally would spend more effort lowering the charge temperatures, and a lot less effort on your opinion of spark.
you don't have in-cylinder pressure transducers, you don't have "knock ears", you dont know your cylinder pressures (or the cylinder pressures that the LS3 pistons can support), you just have an opinion that the spark is not advanced enough; based on other peoples experience on other engines. soooooo you're either the ultimate engine whisperer or you're risking the health of your engine on a guess.
I did it too (completely different engines), thinking spark was too retarded, tried advancing it 1 degree or 2, and it went from absolutely no knock to a little knock here and there. backed off, tried it in a different operating zone, advanced a degree or 2, started knocking again. Over time i learned more about engines, eventually i got some real education on combustion theory then things started making more sense.
Point is just because spark is low while IATs are high, doesn't necessarily mean the spark is incorrect. sure you can test adding spark, and it might work, but you are reducing your safety margin. For instance, if you get it tuned in december, make sure you log data at the drag strip in the summer, it may very well knock, even though it never knocked on the dyno.
you don't have in-cylinder pressure transducers, you don't have "knock ears", you dont know your cylinder pressures (or the cylinder pressures that the LS3 pistons can support), you just have an opinion that the spark is not advanced enough; based on other peoples experience on other engines. soooooo you're either the ultimate engine whisperer or you're risking the health of your engine on a guess.
I did it too (completely different engines), thinking spark was too retarded, tried advancing it 1 degree or 2, and it went from absolutely no knock to a little knock here and there. backed off, tried it in a different operating zone, advanced a degree or 2, started knocking again. Over time i learned more about engines, eventually i got some real education on combustion theory then things started making more sense.
Point is just because spark is low while IATs are high, doesn't necessarily mean the spark is incorrect. sure you can test adding spark, and it might work, but you are reducing your safety margin. For instance, if you get it tuned in december, make sure you log data at the drag strip in the summer, it may very well knock, even though it never knocked on the dyno.
agreed and I am. I’m set on doing the meth injection after talking with Julio the last two days. Not sure if it will be a mix or 100% yet.
Say I was able To incrementally add 5 -6 degrees of timing and still get zero knock /kr it would prove that the tune is very conservative. Pretty much every one who have had put these kits on agree they are very conservative. I don’t think I’m making wild guesses.🤷♂️
using other people who have the same exact car and blower as a general guide seems like an educated guess at the very least. If it was one freak car I’d also be more worried but it’s multiple identical setups. If we want Safe we would never mod our cars at all......
Last edited by dllhg; 11-19-2019 at 12:10 PM.
11-19-2019, 01:09 PM
#22
Race Director
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St. Jude Donor '15
The issue might be that your base timing is too conservative to begin with.. so you'd want to start there, not by dumbing down the advance vs. IAT table.
Or even better would be getting your IAT's down
11-19-2019, 02:17 PM
#23
Drifting
Thread Starter
Nobody has argued this... the point is the amount that ignition timing needs to change based on IAT is accurate... so, it makes sense to pull however many degrees of timing when going from say 80* to 140* IAT's. That isn't the issue
The issue might be that your base timing is too conservative to begin with.. so you'd want to start there, not by dumbing down the advance vs. IAT table.
Or even better would be getting your IAT's down
The issue might be that your base timing is too conservative to begin with.. so you'd want to start there, not by dumbing down the advance vs. IAT table.
Or even better would be getting your IAT's down
We are 100% in agreement on the IATs . I’m getting a colder T-Stat and adjusting my fan temperatures. I’m also looking into a bigger heat exchanger. I was considering a Vararam intake or the halltech heat shield too.
i have also decided to cough up the dough to do the methanol injection. Not sure if it will be a 50/50 or 100% yet. That alone should take care of the problems. I’ll add the 3.0 pulley at that point. Might bet a blower cam since I’ll be paying $700 for the tune anyway. 🤔
Last edited by dllhg; 11-19-2019 at 02:21 PM.