ervin

On a stock $8d,the advance tables not including pe,ae advances or any retards from knocks,is spark timing.Is this total timing,or do we add initial to this for total timing.The wide open seems low at 19 degrees,at 100 kpa.THAT would make this only 25 degrees at wot.Hardly enough time for combustion to take place .It looks to me that you would take the value on spark table,add the initial to it for a total.Not counting adds or subtracts for pe or knock.Is this right,tuner studio,with mega squirt dosen't do it this way.Theres has total in the ve tables.You set base on engine,and learn or adjust tables to where you set base.What you see on VE tables is what you see on the crank.

RBob

iTrader: (1)

The main SA table is WYSIWYG. Ignore the initial timing, it is subtracted out by the ECM, and added back in by the physical position of the distributor. Just make sure that those two settings match.

RBob.

C409

iTrader: (5)

.......... Soooo ... is the base timing included in ... or added to ... the SA table for total advance timing settings ? ... you really didn't say it ...

Ronny

iTrader: (1)

base timing included in main table. What is in the table is what engine sees.

For kicks you could let engine idle , run data log, attach timing light, and see if they match up.

xch3no2

As long as the distributor position matches the base setting in the bin, thats the important part. I use 0* and build SA tables from scratch.

The distributor position can also be used for injector timing, it provides the reference pulse.

C409

iTrader: (5)

.......... Thanks for the clarification ........ something so simple but with the potential to do so much harm to the internals ... I've kept the advance tables on the conservative side in the event that the base was added in ... Sooo , that means that I've been leaving power OFF the " table " ..........

RBob

iTrader: (1)

Well, the other side of the story is that one should tune for best power, not to a number.

Case in point is one of my older TBI cars. It is a SBC with the aluminum '113 heads on it. I found best power at 36* BTDC at WOT (for most of the RPM range). When others that also tuned engines with those heads stated that it was too much SA. It should be closer to 28* BTDC.

The issue was that the at-crank SA wasn't what it seemed to be. The ICM latency was actually reducing the SA by 8*. So the SA was at the 28* that others said it should be at. Not the 36* BTDC that was being commanded.

There is a good thread here on ICM latency and the corrections for it in the ECM.

RBob.

xch3no2

Similar ICM latency would exist for the injectors reference pulse then, would it not?

RBob

iTrader: (1)

It may, I never checked if the latency was from the trigger to the ref-high to the ECM. Or if the latency is from the EST (from ECM) to the coil trigger. Or, it may be from latency in both signals.

Although, from my research it does appear that the latency is in the trigger to ref-high signal. Which would then affect the injector firing point.

RBob.