do you guys adjust the entire map of timing, or just the wot stuff? like idle and low rpm for cruising, do you focus on that, or just the higher rpm and wot timing?

 

I have adjusted the whole table by +6 degrees and then made my adjustments depending on KR. It seems to be the fastest way to add timing.
But one thing to keep in mind, When adding timing to the Main Spark Advance, you only want to make adjustments to the grade of gas you are running. For example. If you running 87octane and making adjustments to the High Octane table, you won’t see any improvements. What will happen is, your High Octane Table will be all out of wack.

 

You would think that gm would have set the low load regions at the best timing. For the most part it looks like they did based on the optimal timing table that the computer uses to calculate delievered torque but as loads increase they drop it a lot.

 

The High octane table is the primary table used regaurdless of the fuel you put in the tank. Depending on knock activity the PCM will interpolate between the high octane table and the low octane table.

When tuning for timing, set the low octane table the same as the high octane. Make simultaneous changes in both tables, then once you are satisfied and experience no knock, reduce the entire low octane table by 4-6 degrees. This will give the PCM some room to remove timing in case you get a bad tank of gas and have frequent knock occuring.

One more tip, more timing is not always better. My experience has shown a loss of power running more than 25 degrees at WOT. The same can be true running too much timing at partial throttle.

 

Does anybody have any dyno experience with timing on a relatively stock motor? Anybody ever use the optimal timing table to base timing on?

With the stock compression ratio did gm get away with running the best timing or did that have to sacrifice it so you can run 87 octane?

 

Optimal timing table is too much timing across the board on a relatively stock 5.3L

 

If the LS6, LS2 run at 26-29 degrees of timing and has more compression than why dosent the 5.3 need more timing especially with a lower compression ratio? I guess the LS6 might have a little more timing in the low end as the 5.3 probably has a little more torque in the low end than a LS6.

The LS4 which I think has 10-1 compression(im not sure if it has LS6 stlye heads or 5.3 style heads) runs 30 degrees stock. I don't guess the lower weight of the car or something has anything to do with that.

It just seems like the 5.3 could use a little more timing past 5200+ as the power drops off so much.

 

 

Your goal with spark timing is to initiate the burn in the cylinder at the correct time.
If the timing is too advanced power will be lost due to the mixture burning too much before the piston reaches TDC. This makes ecsessive heat and fights the piston as it comes up the bore.
If the timing is too retarded the piston will have moved away from TDC before the burn comes up to speed. This does not create enough pressure in the cylinder to make good power.
If the timing is just right it will exert maximum engergy on the piston to put your crankshaft stroke to best use.
The degrees of advance that yield best power will differ from vehicle to vehicle depending on heads, cam, bore, stroke, compression ect. These things affect the rate of burn, which you want to happen fast.

 

Does the pcm use the optimal timing table to determine how far away your spark advance is from it so it can calculate torque.

To get that spark advance from a stock compression 5.3 I have to run 93 without knock. But dosent the higher octane increase burn rate?

So if you could tune it as close to the optimal timing as you could running 87 octane you would be more efficient with 87 octane?