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I am making adjustments to my hi/low octane tables to dial in the setup on my sons truck and wanted to ask what some of you might be running. The motor has a 218/227 LS Hotcam and right now I am seeing an average of 35 degrees total at 1800 to 2000 rpm cruising is that close. I have read that re LS likes around 28. I dont have the funds for dyno time so this is all being done on the streets. Any help is appreciated.
You need to be data logging cylinder air in order to see what you are really doing with the spark. Just seeing the average spark on an rpm only chart does not tell you much. You should have the logs formatted to look like your spark tables. Once you see what is really happening with the spark control, you will understand that your question is not as simple as you think.
Street is even better, normal driving conditions. Yup as mentioned need to see the whole chart as you're driving around. Way too many factors. That 28* might be under WOT condition not cruising either.
Last edited by the_merv; Dec 23, 2024 at 08:42 PM.
I am making my adjustments based on my spark advance and spark retard tables from my scans after a solid 30 minute drive. This is the latest scan, but I haven't made anymore changes yet. we were having a knock issue around 2000 rpm that I needed to address first before I made any more adjustments. I have done enough with the VE and MAF tuning that I can get it in just a few scans. I'm not 100 percent positive though on what the LS like for timing though.
The only way to really nail down part throttle spark would be to use the bi-directional controls in the scanner to make real time changes while the car is being driven. It would require being able to hold steady rpm and MAP readings while doing that. As for WOT spark, you would need a dyno or be able to do timed runs in a repeatable manner. A lot of ls based motors will actually take additional spark past what gives them peak power without knocking, so you can't just raise it until it knocks and back off a degree. Also, take any specific timing numbers people tell you with a grain of salt, because there are numerous modifier tables that they may or may not have disabled or otherwise changed.
The only way to really nail down part throttle spark would be to use the bi-directional controls in the scanner to make real time changes while the car is being driven. It would require being able to hold steady rpm and MAP readings while doing that. As for WOT spark, you would need a dyno or be able to do timed runs in a repeatable manner. A lot of ls based motors will actually take additional spark past what gives them peak power without knocking, so you can't just raise it until it knocks and back off a degree. Also, take any specific timing numbers people tell you with a grain of salt, because there are numerous modifier tables that they may or may not have disabled or otherwise changed.
Real world at 2,000-2,500 rpm light throttle cruising conditions not unrealistic to have as much as 40-50° of advance even on a stock engine and stock tune.
Real world at 2,000-2,500 rpm light throttle cruising conditions not unrealistic to have as much as 40-50° of advance even on a stock engine and stock tune.
Quite true. However, it will be extremely difficult to determine what exact number for any given cell really is best with the tools available to him. In the real world a very wide range will work at light cruise anyway, so it only matters as much as you want it to. Most of the LS engines would run "ok" locked out at 20* from idle to WOT, so it really comes down to how much time you want to take to optimize the tables, whether for fuel economy, drivability, or power.
edit-- The wide amount that you can be off on the tune and still have a pretty decent running engine is what keeps a lot of the "professional tooners" in business.
edit-- The wide amount that you can be off on the tune and still have a pretty decent running engine is what keeps a lot of the "professional tooners" in business.
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HPTuners timing adjustment 
