Timing adjustments

[JASON11LS1]

I'm looking to play with the timing on my G8. I am a newbie and haven't played with timing yet. I figure I have to adjust the main high octane table. At full thorttle I was at about 22-25 degrees of timing. That seems like I have some room to play with. I spray the car occasionally but I'm pretty sure I can still advance it some. Any ideas on how much?? Also, I have no clue on how adjust it. I see that it's in grams/cylinder? How do I figure that out to accurately change the table?

[eficalibrator]

Just because you CAN advance the timing doesn't mean you always should. Many of these newer engines make better power with less timing due to their more efficient combustion systems (chambers, ports, cooling, etc...) so advancing the timing may do nothing more than reduce your safety margin before knock. Since you plan to spray it, I'd recommend going with the lowest timing necessary to make the desired power and keep a bigger safety margin.

The best way to test this is on a loaded chassis dyno where you can perform back to back tests with various timing curves and overlay the resulting torque curves. If adding timing showed less than 1% increase in torque, there's no real reason to keep it in there. The guys tuning these engines from the factory are no dummies, and they know where both MBT and the knock limits are; so it's hard to outsmart them on a stock car anymore.

[JASON11LS1]

I understand what your saying 100%. But these cars were tuned to run on 87 octane and I'm sure they left a few ponies under the hood. Anyone care to explain how to adjust the timing properly? I've also got a blown Camaro I'm looking to adjust as well.

[eficalibrator]

But these cars were tuned to run on 87 octane and I'm sure they left a few ponies under the hood.

If the engine is not knock limited, then increasing octane (and timing) is not going to pick up any power. The only way to know for sure is to do the homework and test on a load bearing dyno with consistent temps and AFR as you try different timing curves and compare the resulting torque output. Don't be surprised if a stock vehicle doesn't pick up too much from this.

[5.7ute]

I'm looking to play with the timing on my G8. I am a newbie and haven't played with timing yet. I figure I have to adjust the main high octane table. At full thorttle I was at about 22-25 degrees of timing. That seems like I have some room to play with. I spray the car occasionally but I'm pretty sure I can still advance it some. Any ideas on how much?? Also, I have no clue on how adjust it. I see that it's in grams/cylinder? How do I figure that out to accurately change the table?

You need to log the pids that the spark table references to see which cell may need adjusting. These are RPM & one of the following GM.DYNCYLAIR_DMA,GM.CYLAIR_DMA,GM.DYNCYLAIR,CALC.C YLAIR depending on whether you are running maf or mafless. In all honesty, if you do not fully understand how to use the scan & tune tool properly I wouldnt be messing around with spark. Familiarise yourself in how it all works before playing.
Greg also states a valid point in relation to Octane & MBT. Dont be fooled by the more timing/ higher octane is more power that seems to be the norm on the internet. Just give the engine what it wants, and the only way to find that is with quality dyno time.

[dfe1]

I understand what your saying 100%. But these cars were tuned to run on 87 octane and I'm sure they left a few ponies under the hood. Anyone care to explain how to adjust the timing properly? I've also got a blown Camaro I'm looking to adjust as well.

These systems have high and low octane tables so although they CAN run on 87 octane fuel, they will typically produce more power when 93 octane gas is in the tank. Keep in mind that actual timing is determined by the high octane/low octane fuel table bias, which changes according to the amount of knock detected. When 87 octane fuel is on tap, spark will be heavily biased towards the values in the low octane table values. When the good stuff is in the tank, spark will be heavily biased towards the values in the high octane table. This arrangement allows engines to be calibrated for cheap skates, while maintaining optimum performance for car owners who are intelligent enough to realize that you don't purchase a vehicle with a high performance engine if you can't afford or don't want to purchase fuel of sufficient quality.